Conference Agenda

The incorporation of Bi into GaAs has demonstrated significant potential for reducing excess noise in avalanche photodiodes (APDs) by lowering the hole ionization coefficient. It has been proposed that the incorporation of group III elements in GaAsBi alloys, such as Al, could facilitate the development of a novel class of ultra-low noise APDs utilizing GaAs substrates. This study investigates the growth dynamics, surface morphology, and optical properties of AlGaAsBi alloys epitaxially grown on GaAs substrates. By systematically varying the Bi flux and III/V ratio, we identify two distinct types of superficial nanomotifs: "caldera volcanoes" and "dome volcanoes," associated with Bi-rich and Ga-Al-Bi droplets, respectively. The results reveal that higher Bi flux improves interface quality but can lead to droplet formation, while the presence of Al modifies droplet dynamics. These findings provide critical insights into optimizing AlGaAsBi growth for low-noise APDs operating in the near-infrared range.

The results of a throughout investigation of β‐Ga2O3/4H-SiC heterostructures are presented, with particular attention to the nucleation of Ga2O3 islands on the stepped 4H-SiC surface. The formation of domains resulting from the deposition of a monoclinic material on a hexagonal substrate is also presented and discussed. This study opens new perspectives for the preparation of heterostructures with improved properties.

Opposite to planar heterostructures, nanowires (NWs) allow heterostructures to overcome the limits regarding lattice mismatch and strain relief. However, the structural characterization of heterostructured NWs is typically done by means of transmission electron microscopy (TEM), costly and time consuming. In this work, an angular multi-segment detector in backscatter electron (BSE) configuration is employed to analyse III/V semiconductor NWs. We analyse three different sets of NWs: 1.- InGaN/GaN; 2.- GaInP/InP based tandem solar cells; and 3.- triangular GaAs/InAs core/shell. First, we carry out a comprehensive study of the beam conditions (acceleration voltage and beam current) to achieve the highest contrast between the core and the shell. In this work, we demonstrate that by properly adjusting contrast and brightness, either the topography or the compositional contrast can be enhanced. Finally, we show preliminary results in the characterization of defects such as stacking faults and twin-plane superlattices in axially heterostructured NWs.

ULTRARAM is a low-voltage, ultrafast memory that merges the speed of dynamic random-access memory (DRAM) with the data retention capabilities of a flash memory. The performance of the device relies on a triple barrier resonant tunneling (TBRT) structure, based on a InAs/AlSb heterostructure. Hoever, achieving atomically sharp interfaces within this structure poses a significant challenge due to unintended atomic intermixing and segregation. This lead to the formation of the quaternary alloy Al(x)In(1-x)As(y)Sb(1-y) near the interfaces, that could expand to most of the layer.

In this study, we quantitatively analyze atomic-resolution annular dark field (ADF) scanning transmission electron microscopy (STEM) images by comparing experimental ADF-STEM intensities with image simulations of the quaternary alloy. This analysis is completed by atomic-resolution energy dispersive X-ray (EDX) spectroscopy maps, providing a comprehensive understanding of elemental distribution and interface quality. The resulting Sb composition is modeled using Muraki's segregation model.

The semiconductor sector has an important need of characterization of materials, in particular, crystalline defects that can be detrimental for devices performance. To this aim, electron channelling contrast imaging (ECCI) has emerged as fast and a non-destructive technique for defect characterization. In this work we established a protocol to easily achieve ECCI measurement conditions in a scanning electron microscope (SEM). By using a retractable back scattered electron detector, we achieve direct observation of dislocation without any sample preparation and with small tilt angles. We have applied it for the characterization of Ga(In)As and GaSb thin films grown on Si. We study different measurement conditions to optimize the observation of defects. We demonstrate direct observation of threading and misfit dislocations in thin films while reducing preparation time, cost and labour compared to other characterization techniques such as transmission electron microscopy (TEM).

This lecture provides a comprehensive overview of bulk GaN crystallization,

tracing its evolution, key milestones, recent advancements, and future

prospects. Various growth techniques will be examined, including halide

vapor phase epitaxy (HVPE) and the ammonothermal method, the latter

being the most promising. A comparative analysis of acidic and basic

ammonothermal growth will highlight their advantages, limitations, and

technological challenges. The integration of ammonothermal and HVPE

technologies presents significant potential for further advancements.

However, scaling GaN crystal growth for commercial applications remains

a critical challenge. This lecture will explore current progress and realistic

development timelines. Additionally, the transition from bulk crystal

growth to usable substrates requires precise processing techniques, such

as wafer cutting and surface treatment. The discussion will conclude with

key applications of GaN substrates in optoelectronic and electronic devices.

InGaN Multiple Quantum Wells (MQWs) were examined in situ during annealing in the KARA synchrotron. The high brightness of the X-ray beam enabled us to measure the reciprocal space maps fast enough to monitor the changes in the InGaN lattice. At moderate temperatures, we observed homogenization of the QWs. At temperatures close to 1000oC, the wells got decomposed. Still, this phenomenon depended not only on In-content in InGaN and temperature but also on the microstructure (defect density) layers below the QWs.

This work aims to find a correlation between the high-value Young’s modulus of silicon carbide and the high frequencies and quality (Q) factors in resonant devices built with 3C-SiC Double-Clamped (DC) beams grown on (111) silicon substrates. The study is important for understanding the sensitivity of the device’s eigenfrequencies with respect to variations in length and thickness. We aim to verify if our data[1], along with results from the literature, confirm the Quality factor model proposed by Romero et al. [2], extending the range of film thickness to about 1 µm.

Thermal annealing plays a crucial role in the optimization of 4H-SiC electronic devices, particularly in passivating interface defects. In this work, we investigate the effects of high-pressure (800 PSI) thermal annealing in Oxygen and Helium atmospheres of 4H-SiC at 400 °C by studying the exciton lifetime. We studied three different wafer types representing different stages of the fabrication process: a bare epitaxial layer A(epi), an oxide-covered sample B(epi+ox), and a sample subjected to post-deposition annealing in NO C(epi+ox+NO). Photoluminescence decay measurements reveal a significant decrease in exciton lifetime for the bare epitaxial sample after annealing, while the oxide-covered sample exhibits an increase in lifetime in oxygen-rich conditions. Comparisons with helium treatments highlight the role of oxygen in defects passivation, suggesting that O₂-based annealing could be a cost-effective alternative to NO treatments.

This study presents an innovative approach for fabricating monoclinic gallium oxide (β-Ga2O3) microtubes and nanomembranes by ion-beam-induced exfoliation. Using Cr ion implantation as a case-study, the evolution of the defects, strain and stress profiles are assessed by a combination of X-ray Diffraction, Rutherford Backscattering Spectrometry in Channelling mode and Molecular Dynamics. The developed strain engineering method is shown to lead to a self-rolling of the surface layers of (100)-oriented single-crystals, yielding microtubes. A subsequent thermal annealing leads to strain relaxation, and these structures unroll, forming nanomembranes with bulk-like crystalline quality. This novel technique has the potential of becoming a scalable and reproducible method compared to conventional exfoliation techniques, while also enabling the simultaneous doping of the membranes, which can be customised in terms of their optical, electrical, and magnetic properties. This work thus contributes to better understand the elastic properties of this material under ion irradiation, as well as enhanced its potential for applications in power electronics, photonics, and sensors.

The 200 meV band gap difference between wurtzite (WZ) and zinc blende (ZB) GaN and InGaN opens the possibility of realizing homoepitaxial WZ/ZB heterostructures for light emitting devices in the visible and UV wavelength range. However, the realization of such devices requires a controlled conversion at the monolayer scale from WZ to ZB and vice-versa, which has not been achieved to date. In this work, we demonstrate that plasma-assisted MBE grown GaN nanowires (NWs) are offering a new paradigm to control WZ/ZB selection, in particular when grown in the mononuclear growth regime.

In the case of catalyst-grown NWs, the formation of ZB and WZ sections is achieved by controlling the size and the wetting angle of the catalyst droplet. This approach does not hold in the case of GaN NWs, which are grown catalyst-free in plasma-assisted MBE. However, we found that by taking advantage of the mononuclear growth regime of GaN NWs, it is possible to kinetically control the crystallographic variant and to realize ZB insertions of controlled thickness in WZ GaN NWs.

The substrates consist of in-plane organized, MOCVD-grown GaN pedestals [1]. After introduction in the MBE chamber, a ZB GaN section was grown at low temperature and high Ga/N flux ratio. In these conditions, a ZB nucleus of a new layer on top of the GaN pedestal is more stable than its WZ counterpart [2]. Following this nucleation event, the layer is next rapidly completed, before repetition of this process after an incubation time. Once completed the ZB section, growth was interrupted while temperature was increased and Ga/N flux ratio reduced, to switch to conditions favorable to growth of a WZ upper GaN section. The samples were characterized by hyperspectral cathodoluminescence and photoluminescence spectroscopy. These results assess the kinetically controlled crystallographic WZ/ZB phase selection in NWs, opening the path to the realization of full homoepitaxial, carrier confining heterostructures.

[1] C. Guérin et al, ACS Appl. Nano Mater. 2024, 7, 20301−20307 https://doi.org/10.1021/acsanm.4c03276

[2] Hang Zang et al, Phys. Rev. B 107, 165308 (2023), DOI: 10.1103/PhysRevB.107.165308

The synthesis of α-Fe2O3 nanowires with tensile strained structure has aroused the interest of researchers due to the enhancement of the physical properties advantageous for different applications such as photocatalysis or water splitting. In this work, a synthesis method based on the Joule-Heating effect has been used to synthesize a high density of α-Fe2O3 nanowires grown along the edges of the ribbon used as precursor. The morphology, composition and anisotropic nanostructure growth has been analysed by diverse electron microscopy and spectroscopy techniques, indicating that the nanostructures possess high crystalline quality. The role played by the induced current on the growth mechanisms and the characteristic strain-induced superstructure achieved are discussed. The fast and energy-saving synthesis method employed in this work, along with the potential scalability, reveals a great advantage as compared to conventional thermal oxidation routes making it highly attractive.

Hybrid semiconductor nanowire architectures are promising building blocks for next-generation optoelectronic devices due to their flexible integration, high surface-to-volume ratio, and quantum confinement effects. However, their performance is highly sensitive to clusters, secondary phases, and local structural variations, making it essential to perform a correlative investigation of their elemental composition, structural order, and optical response. While electron microscopies are commonly employed, recent advances in synchrotron-based techniques—offering increased brightness, rapid acquisition, and superior spatial resolution—enable unprecedented insights into these systems.

Here, we apply X-ray nanoprobes at the European Synchrotron Radiation Facility (ESRF) beamlines ID01 and ID16B for spatially resolved nano-analysis of wide-bandgap oxide semiconductor systems, specifically Zn2GeO4/SnxGe1-xO2 and β-Ga2O3/SnO2. By combining X-ray fluorescence (XRF), scanning X-ray diffraction microscopy (SXDM), X-ray absorption near-edge structure (XANES), and X-ray excited optical luminescence (XEOL), we correlate chemical composition, structural order, and optical properties with nanometer resolution. This multi-technique approach establishes a robust methodology for characterizing complex nanostructures and provides valuable insights for the design of advanced optoelectronic devices.

Resistive Joule heating is a fast, simple, low-cost and effective method to obtain micro- and nanostructured metal oxides, such as MoO3. Its growth mechanism is based on the electromigration processes that takes place due to the electric current flowing through the material, promoting ion diffusion associated with the thermal gradient in the wire, a characteristic process of the Joule heating. The growth of layered α-MoO3 microplates on the surface of Mo wires during Joule heating has been studied by applying an external electric field to the current carrying wire. The rapid formation of the structures is further enhanced by the external field, leading to a near instantaneous formation of MoO3 plates. Additionally, other MoO3 nanostructures have been found to grow by a thermally assisted electric-field-driven process from the Mo wire on the electrodes. To gain deeper insight into the synthesis of MoO3 by this resistive heating method, a macroscale Multiphysics approach is presented, simulating the effects of high electric currents passing through Mo wire.

This work explores the influence of bismuth incorpora-tion into the GaAs capping layer (CL) on the structural and compositional properties of InAs quantum dots (QDs). To accommodate the distinct growth tempera-tures of InAs QDs (510 °C) and GaAsBi layers (370 °C), three Time Temperature Routes (TTRs) involving growth interruptions were implemented. Two of these routes exhibited defective regions characterized by bismuth-depleted nanotracks within the GaAsBi layer, associated with the surface segregation of Bi-rich droplets. Remark-ably, one specific TTR led to the formation of embedded icosahedral-like nanoparticles (NPs) at the initial inter-face, accompanied by elongated trails. Structural and compositional analyses revealed that these NPs com-prise three distinct phases: rhombohedral Bi, elemental Ga, and a previously unreported In₄Bi intermetallic phase. The long particle trajectories and low growth temperatures suggest that the NPs stayed liquid during growth, solidifying only upon cooling. This reveals a new method for integrating non-noble metal plasmonic NPs into buried semiconductor structures.

Nanomaterials and nanocomposites are revolutionizing science and industry by offering unique properties that surpass those of conventional materials. Their applications range from electronics and medicine to energy and aerospace, driving key advances in sustainability, energy storage and smart materials, and paving the way to a new era of technological innovation. However, high production cost and low production rate hinder in numerous cases their industrial implementation. In this work, a graphene-nanoparticles nanocomposite synthesis method via plasmas at atmospheric pressure is presented. This approach enables the production of different nanocomposites based on graphene, such as the graphene-TiO2 nanocomposite reported in this work, yielding a material of high quality and purity. The process is simple, environmentally friendly, economical and scalable, thus providing an opportunity for the implementation of this and other graphene-based nanocomposites into novel applications.

Semiconductor spintronics holds the potential for opto-spintronics that will allow integration of spin-based information processing and storage with photon-based information transfer. Unfortunately, progresses of semiconductor spintronics have during the last three decades been severely hampered by the failure to generate nearly fully spin-polarized charge carriers at and above room temperature (RT). Here, by exploring a new approach of defect-engineered remote spin filtering, we demonstrate that dilute-nitride III-V nanostructures based on coupled GaNAs and InAs quantum dots can be tailor-made for RT opto-spintronics - achieving the highest RT electron spin polarization (exceeding 90%) ever reported in any semiconductor by any approach! This is accompanied by an array of extraordinary spin functionality including spin filtering, spin amplification, dynamic nuclear spin polarization, non-linear spin dynamics and polarized spin-photon conversion, making this material system attractive for a range of potential spintronic and opto-spintronic applications exploiting the state-of-the-art GaAs technology platform, such as spin-LEDs, spin lasers, spin-polarized single-photon sources, spin-photon interfaces, spin qubits.

Transmission electron microscopy (TEM) was employed to investigate the micromorphological properties of subsurface lattice damage (SLD) in ground and rough polished InAs substrates. We show that the types and distributions of SLD defects in ground substrates and rough polished substrates are different obviously, which are more complex compared to those in other hard-brittle materials. Remarkably, the depth of SLD layer containing severely damaged regions, abnormal contrasts and moiré fringes in rough polished substrates, is three times deeper than that of SLD layer composed of dislocations, stacking faults and subsurface cracks in ground substrates. SLD in the rough polished substrate exhibits defect characteristics of lattice glide caused by the force applied during the polishing process.

GaAsBi nanowires (NWs) are promising materials for optoelectronic applications, e.g. as solid-state light emitters within the near-infrared spectral range. In this work, we employ photoluminescence (PL) and PL excitation spectroscopies to examine recombination processes in these novel materials and their dependence on growth conditions during the NW fabrication. We show that radiative recombination in GaAsBi-based NWs is dominated by excitons bound to Bi-related clusters. The formation of these clusters is affected by Bi beam equivalent pressure (BEP) during the growth so that larger Bi clusters, which introduce deep states within the bandgap, are formed under conditions of high Bi BEP.

A novel broadband p-n UV photodiode that integrates a n-type Si-doped k-Ga₂O₃ epitaxial film and a p-type NiO polycrystalline film is presented. The proposed device, based on the planar NiO/k-Ga₂O₃ p-n heterojunction, can work in self-powered mode for UV detection. The p-n photodiode exhibits fast response (<0.8 s), very good sensitivity to UV-C light, and appreciable response to UV-B and UV-A wavelengths.

In this work, a 7 nm ScAlN barrier GaN High Electron Mobility Transistor (HEMT) structure is grown on silicon (111) substrate by ammonia-source molecular beam epitaxy (NH3-MBE). On 75 nm T-shaped gate transistor, a saturated current density of 1.35 A/mm at a gate bias of 0V and a transconductance peak higher to 280 mS/mm are reached. Transition frequencies fT/fmax of 82 / 112 GHz are reported. At VDS = 8 V, continuous-wave (CW) output power density of 1 W/mm is achieved at 10 GHz with 16 % associated Power-Added Efficiency (PAE) and a linear power gain of 10 dB. These preliminary results demonstrate the potential of ScAlN/GaN-based HEMTs on low-cost silicon substrates.

Recently, Ga₂O₃-based photodetectors have attracted much interest due to their potential applications in space exploration, environmental monitoring, and security systems. Self-powered and efficient devices of this kind will enable significant advancements for the next generation of photodetection applications. In this work, we present a selective UV-C photodiode prototype based on planar p-n NiO/β-Ga₂O₃ heterojunction with circular geometry. β-Ga₂O₃ epilayers are grown using metal-organic vapor phase epitaxy (MOVPE), while the NiO polycrystalline film is deposited by sputtering at room temperature. The photodiode operates in self-powered mode and exhibits high responsivity and selectivity to UV-C light, with fast response and recovery times of 0.28 s and 0.18 s, respectively. Notably, no persistent photocurrent is observed during the on-off illumination cycles; the photocurrent rapidly returns to baseline after each UV-C illumination. This prototype shows great potential for high-performance UV-C detection applications.

Gallium oxynitride thin films were deposited by reactive radio frequency sputtering. A high throughput combinatorial material synthesis method was used to study a wide range of compositions. Structural (X-ray diffraction) and optical (spectroscopic ellipsometry) characterizations were performed to investigate their dependence on the chemical composition of the layers. A correlation between the optical bandgap and the oxygen concentration of the films was found.

The performance and reliability of GaN high-electron-mobility transistors (HEMTs) are strongly influenced by self-heating effects. Electrothermal Monte Carlo (MC) simulations provide accurate modelling but require substantial computational resources. This work introduces a hybrid AI-thermal model that integrates MC-generated training data with an artificial neural network (ANN) to predict self-heating effects efficiently. The ANN, coupled with thermal models, iteratively estimates current density and lattice temperature (T_latt). Compared to full electrothermal MC simulations, the proposed model maintains high accuracy while drastically reducing computational costs, providing a fast and effective tool for GaN HEMT optimization.

This study investigates the structural and compositional transformation of gallium selenide (GaSe) into gallium oxide (Ga₂O₃) via thermal oxidation, a process that enhances environmental stability and widens the bandgap beyond 3 eV, which are key attributes of ultraviolet photodetectors and insulating layers in electronic applications. Thin GaSe layers were grown on sapphire substrates using molecular beam epitaxy (MBE) and subjected to controlled thermal annealing in an oxygen-rich atmosphere at temperatures ranging from 400 to 900 °C. STEM-related techniques were employed to analyse the crystallographic structure and chemical composition. The results indicate a full transformation of GaSe into β-Ga₂O₃ at temperatures exceeding 600 °C, as evidenced by the [Ga]:[O] ratio of 2:3 and the disappearance of elemental selenium. The oxide layer exhibits high crystallinity with nanoscale voids, which compensates the expected lattice contraction during oxidation. These findings contribute to the fundamental understanding of GaSe oxidation processes and highlight the potential of thermally grown Ga₂O₃ layers in optoelectronic applications.

Gallium Nitride (GaN) transistors have become a key technology in high-frequency and high-power applications. N++GaN/InAlN/GaN heterostructure is a promising platform for realizing enhancement (E-mode) and depletion (D-mode) mode devices on the same wafer. In this work we explore digital etching as a precise method for tuning n++GaN cap thickness in D-mode transistors. By implementing a cyclic oxidation and etching process, we achieve controlled treatment of the cap surface, enabling transistor operation without compromising high current or introducing current collapse.

The increasing reliance on efficient power-switching technologies necessitates advancements in semiconductor materials to reduce energy losses. This study investigates the potential of beta-gallium oxide (β-Ga₂O₃) for power electronic converters, leveraging its ultra-wide bandgap and high breakdown field strength. Homoepitaxial β-Ga₂O₃ films up to 4µm thick were grown via metal-organic vapor phase epitaxy (MOVPE) on (100) 4° off-oriented substrates. The research explores growth mechanisms, including step-flow growth optimization, and addresses challenges in vertical device architectures requiring thick, low-doped layers. The growth approach used in this work enabled for the (100) orientation record mobilities above 160 cm²/Vs and improved growth rates, enhancing the material’s viability for next-generation power electronics.

Monoclinic β-Ga₂O₃ is an ultra-wide bandgap semiconductor with a pronounced anisotropy in its optical, electronic, and thermal properties, emerging from the coexistence of two different Ga coordination environments. In this work, we study the anisotropic optical response of mechanically exfoliated (100)-oriented β-Ga₂O₃ nanomembranes using synchrotron radiation-based techniques. The correlative study of polarization-resolved X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) spectroscopy was used to investigate the orientation-dependent luminescence and absorption, as well as the site-specific contribution of Ga ions to the luminescence process. These oriented-dependent optical properties reveal its potential for a wide range of advanced applications.

In this work, the molecular beam epitaxy with ammonia source (NH3-MBE) has been developed to grow AlScN/GaN high electron mobility transistor (HEMT) heterostructures on sapphire and silicon substrates. The capping of AlScN surface with AlN and or GaN thin layers has been studied as well as the insertion of an AlN interlayer between the barrier and the GaN channel.

A three-layered diamond/AlN/diamond structure has been grown. Firstly, the AlN deposition on free-standing boron-doped diamond (BDD) has been optimized by using two different temperatures (400 ℃ and 600 ℃) to obtain a c-axis oriented film. Once the deposition temperature has been analysed, the effect of different deposition times on the film crystallinity has been also studied. Finally, a BDD layer has been grown on top of the AlN/diamond heterostructure to obtain the three-layered structure.

We present a novel inter-die Cu/diamond microbump bonding to reduce inter-die thermal resistance in 3D heterogeneous packaging systems. The fabrication process began with the chemical vapour deposition (CVD) of a 8 um-thick polycrystalline diamond film on Si. An array of cylindrical vias was etched through the diamond surface using oxygen plasma. Cu/Sn microbumps were fabricated within the etched volume using electroplating. Finally, two diamond-coated dies were bonded through thermocompression hybrid flip-chip bonding.

In this work this presentation will focus on a newly developed tool for

measuring carrier mobility in thick diamond crystals: Time of Flight

Electron Beam Induced Current (ToF-EBIC)1. This technique has been

initially proposed in 1970 for silicon2. Following a brief description of the

experimental method, we will illustrate how this technique can be used to

evaluate the purity and quality of diamond crystals. Various crystals will be

examined, including electronic-grade substrates from Element Six Ltd. and

heteroepitaxial diamond substrates synthesized using the CVD method

(KENZAN diamond process) provided by Orbray Co., Ltd. Carrier mobility

values will be determined using this technique and limitations of the

experimental technique will be discussed. The carrier mobility in intrinsic

diamond will be compared with other methods such as photo-excited ToF

or cyclotron resonance measurements6. For hetero-epitaxial diamond

substrates, we will demonstrate that this technique is highly effective in

assessing the suitability of different crystals for use as substrates in

electronic devices.

References

1 A. Portier, et al, Phys. Rev. Appl. 20, 024037 (2023).

2 A. A. Quaranta, et al, Review of Scientific Instruments 41, 1205 (1970)

3 K. Konishi, et al. Phys. Rev. Applied 17, L031001 (2022).

CVD Diamond is an exceptional material known for its superlative properties, such as thermal conductivity, hardness, biocompatibility, radiation resistance, optical transparency etc. These advantages motivated numerous studies towards its use for a broad range of applications, the most stimulating ones being in electronic devices or quantum properties (the latter with almost one paper published every 20 min!). But at the end of the day, are those technologies ready to enter the semiconductor industry? While academia still explores the latest novelties, the CVD diamond industry around the planet is unfortunately still essentially limited to production lines dedicated to gem fabrication! This has most likely prevented the progress CVD diamond materials deserve! It’s only recently, with the recent significant downturn of the lab grown diamond business, that we can hope an inflection point has been reached where CVD diamond is not just a gemstone… What is the next opportunity for diamond then? Is it exotic power or quantum devices? Or rather packaging applications?

Indeed, to enter electronic production lines, the most realistic opportunity for diamond is for it to be used as a heat spreader for electronic packaging applications. For this community, academic teams developed prototype devices exploring several approaches such as wafer bonding, 3D embedded vias, and buried channels, all very challenging technical approaches where diamond integration, sometimes over 3D architectures, enabled other WBG components to reach better performances. That said, is the CVD diamond technology now ready to enter the semiconductor industry? What about synthesis flexibility, but also production costs, repeatability, substrate size, and compatibility of the processes with fab plants? We really need to move forward and raise the CVD diamond manufacturing technology towards higher TRLs to enter such industrial application domains. In this context, how can machine manufacturers facilitate this progress? Drawing from typical cases where diamond-based devices are used for specific applications, examples will be used to illustrate material opportunities and challenges for diamond to meet device fabrication standards for packaging and standard device applications.

Recently, there has been a large interest in the ScAlN alloy, thanks to its various applications in high-frequency high-power, acoustoelectric, and ferroelectric devices. Nonetheless, these applications could be impaired by the presence of oxygen in the ScAlN alloy due to the high affinity of scandium with such impurity. Recent trends in ScAlN growth such as lowering growth temperature and increasing Sc content could have an effect in the incorporation of impurities. Considering this, we have studied the influence of growth temperature and Sc content in the surface oxide and oxygen content of ScAlN films grown by ammonia source molecular beam epitaxy and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and angle resolved- X-ray photoelectron spectroscopy.

This study investigates the effects of post-deposition rapid thermal annealing (RTA) on aluminium nitride (AlN) thin films for the fabrication of microelectromechanical (MEMS) resonators. RTA was performed in a controlled nitrogen atmosphere at temperatures ranging from 200 to 1000°C on AlN thin films deposited via DC reactive sputtering with no applied heating. The effects of RTA temperature on the crystalline structure, residual strain, and piezoelectric coefficient (d₃₃) were systematically analysed. This abstract covers the preliminary results of an optimisation experiment of AlN piezoelectric properties in a CMOS-compatible process.

We present growth and fabrication of fully vertical FinFET device with a 5 μm Al0.025Ga0.975N drift layer. The stack of GaN-AlGaN layers were pseudomorfically grown on an ammonothermal-GaN bulk substrate by using MOVPE technique. This is a novel fabrication and represents a significant advancement over GaN drift layer devices.

We present a theoretical investigation of a previously

unexplored dilute nitride III-V-N short-period superlattice

system, GaPN/GaAsP, designed as a potential top-cell

absorber for monolithic III-V/Si tandem solar cells. This

system exhibits a type-II band alignment. Through

multiband k·p calculations and the envelope function

approximation, we show that an optimal bandgap of 1.7

eV can be achieved while satisfying the strain-balanced,

zero-stress condition over a broad range of dilute

nitrogen compositions. The thicknesses of individual

layers remain well below the critical threshold for plastic

relaxation. We also discuss the experimental feasibility of

realizing such structures, supported by recent progress in

the growth of high-quality GaP buffer layers and precise,

monolayer-controlled incorporation of nitrogen in dilute

nitrides on silicon via molecular beam epitaxy.

We present large-signal load-pull measurements of a transferred InP/GaAsSb double heterojunction bipolar transistor fabricated on a high-resistivity silicon substrate. The tested devices feature an emitter area of 0.44 × 3.9 µm². When biased for highest power, an output power of 13.42 dBm was achieved corresponding to a power density of 12.92 mW/µm² (5.68 W/mm). A peak value of 23.7% was obtained along with a power gain of 5.35 dB when the load impedance was optimized for maximum power-added efficiency (P.A.E). These results highlight the benefits of thermal dissipation improvement in overcoming self-heating effects to achieve high output power.

This study investigates the effects of Ni and O vacancies on the electronic and optoelectronic properties of NiO using density functional theory (DFT) alongside cathodoluminescence experiments. Computational results obtained with the B3LYP hybrid functional closely match experimental band gaps, validating the reliability of our simulations. Specifically, the introduction of Ni vacancies produces intra-gap states that align well with experimentally observed emission peaks. In contrast, O vacancies demonstrate donor-like behavior, aligning with experimental reports of enhanced n-type conductivity. These findings provide critical insights for defect engineering strategies, bridging theoretical predictions with experimental data to optimize NiO for advanced optoelectronic applications.

Control elements based on III-V semiconductors are widely used in radiofrequency circuits, especially in the GHz range, as they offer superior high-frequency performance, easy integration, high reliability and compact size. In this context, PIN diodes are one of the most popular choices for limiter and switch applications. However, there is little literature connecting their structure and physical configuration with their circuit response, which hinders further understanding of these devices. In this regard, we present an analysis of the performance of GaAs and AlGaAs/GaAs PIN diodes as possible switches/limiters in X-Band applications, where we have conducted simulations on their high frequency behaviour, employing the Silvaco ATLAS numerical simulation software. Variations in the physical structure of the PIN diodes have been explored, and the resulting changes in their high frequency response have been evaluated. In this communication, we present a sample of the most relevant metrics explored for X-band operation (8-12 GHz), such as as R-I characteristics under forward bias, insertion losses and band structures for all PIN designs.

Single-photon emitters (SPEs) in wide-bandgap materials, like group III-nitrides, are promising for room-temperature single-photon sources. Recent studies have shown antibunched emission from colour centres in gallium nitride and aluminum nitride (AlN). However, the nature of these defects and optimal formation conditions are still unclear.

In this work, we investigated the effect of aluminum implantation on AlN epilayers, followed by thermal annealing and confocal microscopy. The results showed that the SPEs density increased with fluence, with ensembles forming at the highest implantation fluence and that the use of thermal annealing at 600°C increases the number of individual colour centres for the highest fluences. A second study tracked native and created SPEs in a patterned sample, revealing that both native and fabricated ones were present near the sapphire interface. These findings highlight the importance of vacancy formation for SPEs creation and offer new possibilities for defect engineering in solid-state SPEs.

Deterministic single-ion implantation has become a critical focus in the semiconductor field, particularly for its applications in solid-state quantum technologies. The ability to precisely position single dopants in nanostructures is essential for developing quantum devices, driving significant advancements in implantation techniques. Among these, single-ion lithographic methods utilizing scanning probes achieve exceptional nanometer-scale accuracy but are limited by slow processing speeds. Direct ion implantation, by contrast, offers a more rapid and scalable solution, though at the cost of reduced spatial precision and constraints imposed by device architecture.

In this study, a novel approach utilizing an ultra-thin 4H-SiC membrane sensor for single-ion detection is presented. The membrane design enables ion detection by monitoring the energy deposited by the ions as they pass through the active layer of the sensor. With this experimental setup, a 96.5% ion counting confidence was achieved, underlining the potential of SiC membranes as high-fidelity in-beam ion sensors. However, the introduction of the SiC membrane impacts the ion beam trajectory, resulting in ion straggling and increased uncertainty in the dopant’s final position within the target. Using a scanning knife-edge technique and SRIM simulations, we quantified the ion straggling, observing an increase in the beam size from 3.43 µm to 8.15 µm. These findings highlight the trade-off between detection accuracy and spatial resolution, emphasizing the need for further optimization to minimize beam perturbations while maintaining high detection efficiency.

With the rise of 6G and growing data demands, high-performance materials for RF components are essential. Scandium-doped aluminum nitride (ScAlN) offers a promising barrier layer for next-generation high electron mobility transistors (HEMTs), providing enhanced carrier density. This piezoelectric material, with high electromechanical coupling coefficients (K²), is also a strong candidate for surface acoustic wave (SAW) filtering applications, particularly in the 1-10 GHz range, due to high SAW velocities. We demonstrate the monolithic integration of ScAlN/GaN HEMTs with interdigital transducers (IDTs), highlighting the potential of this material system for high-performance RF applications.

Ga₂O₃ is a wide-bandgap semiconductor which has been steadily growing in popularity. This work focuses on RF Sputtering, which stands out among possible deposition techniques of Ga₂O₃ thin films as it combines high quality with low costs. The use of sapphire substrates and post-deposition thermal annealing promotes the crystallisation of the thin films, which are amorphous as-deposited, but also the interdiffusion of Al and Ga, which directly affects their opto-electronic properties. In particular, through the formation of an (AlₓGa₁₋ₓ)₂O₃ compound, we can tune the bandgap from 4.85 to 5.30 eV by shifting the Al₂O₃ molar fraction up to 43.8%. This is leveraged to produce metal-semiconductor-metal interdigitated solar-blind photodetector prototypes with a very fast response time and competitive responsivities. We also evaluate the potential of ion implantation for photodetectors and similar systems, namely using Sn ions.

The combined properties of wide band gap semiconductors and metallic nanoparticles have captured the interest of many in the scientific community due to their vast potential for device applications.

This study probes the formation of Ag and Au nanoparticles in RF-sputtered Ga₂O₃ thin films, implanted with various fluences of Ag and Au ions and submitted to thermal treatment at different temperatures. Optical transmission measurements revealed absorption bands at 400–600 nm and 500–700 nm, corresponding to the localized surface plasmon resonance (LSPR) of Ag and Au nanoparticles, respectively, as well as a significant red-shift of the bands with the increase of the annealing temperature.

Additionally, the impact of heavy ion irradiation on Ag and Au ion distributions was analyzed. The implanted Ga₂O₃ films on sapphire were irradiated with Si, Cu, and I ions and, simultaneously, characterized with Rutherford backscattering spectrometry (RBS). RBS analysis showed that I irradiation led to peak broadening to higher energies, indicating ion redistribution towards the surface. Optical transmission measurements exposed a red-shift of the Ag LSPR peak in the as-implanted samples and a blue-shift in the annealed sample.

This study investigates the effects of 0.9 GeV Uranium-238 Swift Heavy Ion (SHI) irradiation on AlxGa1-xN thin films (with x between 0 and 1). High-resolution X-ray diffraction (HRXRD) revealed the formation of lattice strain in the irradiated samples which was considerably larger in GaN than in Al-containing compounds. Furthermore, irradiation in GaN induces a prominent optical absorption band in the visible region. Conversely, in AlₓGa₁₋ₓN samples with x = 0.18 and 0.77, although an increase in optical absorption is observed in the same spectral region, this enhancement is significantly lower than that seen in GaN. Notably, the AlN sample behaves differently from AlGaN samples, displaying the emergence of an absorption band centred at approximately 4.73 eV.

This work gives an overview of the performances of GaN p-i-n and Schottky structures used for proton detection. Their ability to efficiently and accurately monitor proton beam profile have been demonstrated. In addition, first 2D image of the proton beam shape has been obtained. These results represent a significant step toward the use of GaN detector array for the daily beam quality assurance routine mandatory by proton therapy.

The effect of a sulfurization treatment carried out at 800 °C on silicon carbide (4H-SiC) surface was studied by detailed chemical, morphological, and electrical analyses. X-ray photoelectron spectroscopy confirmed sulfur (S) incorporation in the 4H-SiC surface at 800 °C, while atomic force microscopy showed that 4H-SiC surface topography is not affected by this process. The electrical characterization of Ni/4H-SiC Schottky contacts fabricated on sulfurized 4H-SiC surfaces revealed a significant reduction (∼0.3 eV) and a narrower distribution of the average Schottky barrier height with respect to the reference untreated sample. This effect was explained in terms of a Fermi level pinning effect induced by surface S incorporation. In fact, an increase in the 4H-SiC electron affinity was revealed by Kelvin Probe Force Microscopy in the sulfurized sample with respect to the untreated surface to corroborate this hypothesis.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) ternary alloys, such as MoxW1-xS2, are very appealing for the possibility of continuously tuning their excitonic bandgap by the composition. In this work, we demonstrated the growth of highly uniform Mo0.5W0.5S2 bi-layers on cm2 size SiO2/Si substrates by employing a simple and scalable approach, i.e. the sulfurization of a pre-deposited ultra-thin Mo/W stack at a temperature of 700°C. Comparison of Mo(1.2 nm)/SiO2, W(1.2 nm)/SiO2, and Mo(1.2 nm)/W(1.2 nm)/SiO2 samples after identical sulfurization conditions revealed very different results, i.e. (i) a uniform monolayer (1L) MoS2 film, (ii) separated multilayer WS2 islands, and (iii) a uniform bilayer (2L) Mo0.5W0.5S2 film. This indicates how W surface diffusion and coalescence on SiO2 surface plays a main role in WS2 islands formation, whereas the reaction between S vapour with Mo films or Mo/W stacks represents the dominant mechanism for the formation of MoS2 and the MoWS2 alloy. Micro-photoluminescence (PL) mapping of the obtained 2L-Mo0.5W0.5S2 film showed an excellent uniformity of light emission on large area with an exciton peak at 1.97 eV, significantly blue-shifted with respect to PL emission of 1L-MoS2 at 1.86 eV. Such highly uniform optical properties make the grown MoWS2 alloy very promising for optoelectronic applications.

Electric contacts made on an n-type diamond layer through FIB structure modification have been studied. First, the characterization of a conduction channel was carried out, revealing an ohmic behaviour of the transformed area although it remains highly resistive. Then, a circular TLM was conducted on the surface of the sample. The specific contact resistivity, obtained from the cTLM (circular Transfer Length Method) analysis, is 4,42·10^4 Ωcm^2, which is comparable to traditional contacts.

This study utilizes transmission electron microscopy (TEM), specifically high-resolution TEM (HREM), to analyze zinc oxide (ZnO) thin films sputtered onto Si (001) substrates, with a focus on correlating their crystalline structure to the observed piezoelectric properties. Studies confirm that all the samples exhibit wurtzite (HCP) structure, with highly c-axis oriented grains. In HREM observations, predominant [2-1-10] zone axis, with a smaller and variable proportion of [0001]-oriented zone axis is found, depending on the growing parameters.It is observed that the more homogeneously [2-1-10] orientation extends, the more enhance in piezoelectric behaviour is found. Features as nonc-oriented grains or more complex crystalline structures seem to negatively affect piezoelectricity.

Graphene has long been considered a paradigm-shifting material due to its outstanding electronic, thermal, and mechanical properties. However, exploiting its full potential in real-world devices remains a challenge due to limitations in synthesis methods, scalability, and material consistency. In this work, we present a scalable, single-step approach for the synthesis of high-quality, few-layer powdered graphene using microwave plasma torch at atmospheric pressure. The resulting material exhibits high quality and purity and a low defect density, maintaining high electrical conductivity and structural integrity while enabling excellent dispersibility in common solvents. The versatility of this synthesis technique is further evidenced by the one-step production of graphene-based nanocomposites such as G-TiO₂ and G-Cu. The demonstrated capabilities of the material highlight its strong potential for integration into compound semiconductor applications such as printable electronics, electromagnetic interference shielding, and functional contacts, among others.

Recently, hexagonal boron nitride (hBN) has attracted significant interest

as a promising material for a wide range of applications related to van der

Waals heterostructures. Due to its wide bandgap, hBN can host defect

centers that emit light across a broad spectral range, from infrared to

ultraviolet. Some of these defects can serve as single photon emitters (SPE)

or optically active spin defects with the prime example being the

negatively charged boron vacancy (VB-) making hBN an excellent platform

for sensing applications. However, a key bottleneck for the industrial

application of hBN in quantum technologies is the fabrication of highquality, large-area layers with controlled defect properties, enabling their

integration into specialized applications. In this context, one of the most

promising growth techniques for hBN is Metal-Organic Chemical Vapor

Epitaxy (MOVPE).

At the University of Warsaw, we explore homoepitaxial [1] and

heteroepitaxial growth of hBN [2, 3] for various applications, including

hydrogen barriers [4], spin defects, single-photon emitters [5, 6], and as a

useful substrate for the growth and gating of other 2D materials [7] as well

as leading to polarization-dependent Raman enhancement [8]. Notably,

MOVPE enables the optimization of defect emissions within the desired

spectral range [9], including the deep UV region, where controlling carbonrelated defects is of utmost importance [10, 11].

In this presentation, I will discuss how modifications in MOVPE growth

influence the properties of epitaxial hBN, which is crucial for different

optoelectronic applications.

[1] J. Binder et al. Nano Letters 24, 6990 (2024)

[2] A. K. Dabrowska et al. 2D Materials 8, 015017 (2021)

[3] M. Tokarczyk et. Al. 2D Materials 10, 025010 (2023)

[4] J. Binder et al. Nano Letters 23, 1267−1272 (2023)

[5] M. Koperski et al. Scientific Reports 11:15506 (2021)

[6] I. Niehues et al. Nanophotonics, 14, 335 (2025)

[7] K. Ludwiczak et al. ACS AMI, 16, 49701 (2024)

[8] J. Rogoża et al. Nanoscale 17, 3053 (2025)

[9] A. Dabrowska et al. Journal of Luminescence 269, 120486 (2024)

[10] K. P. Korona et al. Nanoscale 15, 9864 (2023)

[11] J. Iwanski et al. npj 2D Materials and Applications 8:72 (2024)

The oxidation behavior of 4H-SiC is critical for the fabrication of reliable SiC-based devices, especially in high-voltage and high-temperature applications. However, the oxidation process of 4H-SiC is challenging due to the presence of carbon in the lattice, which results in lower oxidation velocity and higher defect formation at the SiO2/SiC interface, negatively impacting the electrical properties of the device. This study investigates the effect of silicon and oxygen pre-implantation on the oxidation behavior of 4H-SiC. High-dose implantation of silicon and oxygen ions was performed on 4H-SiC wafers before thermal oxidation at 1100 °C. The results show that both implanted samples exhibited higher oxidation rates compared to non-implanted samples, leading to thicker oxide layers. The silicon-implanted sample displayed increased surface roughness and deeper crystal damage, attributed to the higher energy transferred by silicon ions. The presence of these defects suggests that the oxidation process was not sufficient to fully oxidize the damaged region. In contrast, the oxygen-implanted sample exhibited a smoother surface and no visible crystal damage, indicating more complete oxidation of the damaged area. These findings underscore the significant impact of implantation species on oxidation kinetics and surface morphology, offering valuable insights for optimizing oxidation processes in SiC-based devices for power and high-temperature applications.

In this work we study the formation of VGa and their complexes and clusters in the thin nitride films prepared by MOVPE using variable energy positron annihilation spectroscopy (VEPAS). Our preliminary results suggest that vacancies are always present in the form of complexes with other atoms, or they are agglomerated in clusters consisting of several vacancies of both types nVGa+mVN. We show the correlation of different defect types with PL properties. Surprisingly, vacancy concentration and even clustering is usually positively correlated with high PL efficiency, implying that these defects must be inefficient recombination centres. The possible explanation is that they are multiply charged and at the same time their formation is anticorrelated with the formation of some other non-radiative defects. We show that one such non-radiative defect could be the nitrogen vacancy VN and that it can be deactivated by the formation of nVGa+mVN clusters during annealing.

In this work, we studied building blocks for the selective area growth of low n-type doped GaN layers in view of fabricating the thick crack-free drift layer of a high breakdown voltage pseudo-vertical diode on Silicon substrate. For this purpose, we first analysed the influence of growth parameters on the incorporation of impurities within films grown by metal organic vapor phase epitaxy on planar substrates. We then study the influence of different mask materials on the selectivity of the growth as well as on the electrical conductivity of the GaN regrown films. Finally, we use micro-Raman and micro-Photoluminescence spectroscopies to provide evidence of the elastic strain relaxation within the regrown patterns.

This study presents cathodoluminescence (CL) mapping as a novel, high-resolution technique for quantifying silicon doping in GaN layers. Doping levels are quantitatively mapped by correlating energy shifts and linewidth broadening of the near-band-edge (NBE) emission. Calibration with Secondary Ion Mass Spectrometry (SIMS) validates the doping quantification method. Discrepancies between energy shift and half-width at half-maximum (HWHM) estimations are attributed to strain effects. CL mapping effectively decouples doping and strain, enabling precise visualization of strain relaxation at mesa edges, demonstrating its potential for optimizing GaN-based devices.

Light-emitting diodes (LEDs) are widely used in modern displays, but achieving a Achieving efficient red emission in monolithic white LEDs using nitride semiconductors remains challenging due to intrinsic limitations like big lattice mismatch difference between GaN and InN and the Quantum Confined Stark Effect. This study explores an alternative approach using Europium (Eu)-doped GaN nanowires (NWs) grown by molecular beam epitaxy. NWs offer improved dopant solubility, defect reduction, and enhanced light extraction, characteristics that can be exploited for the fabrication of LEDs. Electroluminescence measurements confirm stable red emission at 621 nm from Eu-doped GaN NWs, demonstrating their potential for efficient red-light integration in LED devices.

The spontaneous polarization Pspont is a key property of the wurtzite III-N

semiconductors AlN, GaN and InN and a unique feature compared to

alternative semiconductor classes like Si, SiC or GaAs. While previously, the

direction and magnitude of Pspont in III-Ns was exclusively determined

during film growth, ferroelectricity now allows to select and measure

direction and net-magnitude of Pspont through the application of external

bias. Intense research on adding non-volatile memory functionality,

tailored excitation of higher acoustic modes and functional domain walls to

III-N technology has therefore commenced and is in the process of

extending to optoelectronics. At the same time, chances are that the ability

to measure Pspont will reverberate strongly to established III-N technology,

as it provided experimental evidence that Pspont of GaN, AlN and InN

surpasses conventional wisdom by more than one order of magnitude. This

development should lead to new design paradigm for e.g. the polarization

based GaN high electron mobility transistor (HEMT).

In addition to highlighting how ferroelectricity can thus shape a new

perspective on III-N semiconductors, this contribution will discuss recent

progress towards understanding and harnessing the implications of

ferroelectric domains in III-Ns: electric field induced polarization

discontinuities are apparently able to concentrate massive bound charge

(~ 200 µC/cm²) in atomically sharp interfaces. This bound charge in turn

induces conductive sheets that can e.g. directly serve for the purpose of

resistive memories. On/off ratios and operating voltages attractive for inmemory computing are demonstrated.

Vertical GaN devices typically suffer from high reverse leakage currents and premature breakdown due to the etch damage caused by chlorine-based reactive ion etching (RIE) during fabrication. This study examines the impact of such etch damage and evaluates the effectiveness of various post-etch treatments on regrown GaN pn diodes. A single low-power CF₄ plasma treatment proves highly effective in reducing etch damage and removing contaminations from the surface before regrowth, significantly lowering reverse leakage currents. However, it also increases the diode on-resistance, likely due to fluorine passivation. To address this, an in-situ trimethylgallium (TMGa) flushing step at 400 °C following the ex-situ CF₄ plasma treatment successfully removes such fluorine species, reducing on-resistance and further enhancing electrical performance to a level comparable to that of continuously grown pn diodes.

The thermal enhancement and the behavior of GaN Schottky diodes grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrates has been investigated. Pt/Au anodes annealed at 500 °C and 600 °C show an improvement of the electrical characteristics and a breakdown voltage as high as 130 V for a drift layer thickness of 1 μm and a doping of 1016 cm-3.

The performance of GaN Schottky barrier diodes and high electron mobility transistors as mm-wave power detectors is measured and interpreted in terms of analytical and equivalent circuit models. The dependence of the results on the device geometry, bias, frequency and temperature is analyzed.

In this work, we propose a model to discern between the perimeter and area contributes of the p-GaN HEMTs gate current density. The perimeter and area contributes of the gate current density were evaluated on HEMTs of different geometry. Then, temperature dependent electrical measurements allowed to extrapolate the Schottky barrier height (1.18 eV) and the p-GaN doping level (4.1×1018 cm-3) of the p-GaN layer.

Nowadays, Raman spectroscopy is crucial in studying semiconductors by

providing insights into their structural, vibrational, and electronic

properties and stability under light exposition. This presentation focuses on

studies we conducted on III-Nitride heterostructures for solid-state light

emitters and chalcogenide thin films for photovoltaic applications.

For III-Nitrides, Raman spectroscopy helps analyze crystalline phase, strain,

composition, and defect density, particularly in ion-implanted materials. It

detects disorder-induced vibrational changes and enables the study of

phonon lifetimes, anharmonic effects, and size-dependent phonon

behavior, crucial for optimizing optoelectronic and high-power devices.

In chalcogenide thin films, particularly Sb₂(S, Se)₃, Raman is widely used

but can be affected by in situ surface reactions. These reactions may lead to

phase transformations, resulting in misinterpretation of Raman spectra,

highlighting the need for careful experimental conditions.

Silicon carbide (SiC) diodes are crucial in high-power applications due to their excellent electrical and thermal properties. However, the nonlinear nature of SiC diodes is rarely represented by conventional calibration methods. This paper proposes a neural network-based calibration methodology using simulation data for extracting the ideality factor (n), saturation current (Is), series resistance (Rs), and leakage resistance (Rl), of a diode directly from V–I curves. Implemented as a feedforward network with two hidden layers and optimized hyperparameters, the network takes advantage of the logarithmically scaled training data to enhance the performance in the low-current region. The method shows low mean squared error and mean percentage deviation below 5% for a large operating range and hence can be considered a computationally efficient approach compared to the traditional curve-fitting techniques in SiC diode modelling.

In this work, a novel technique used to create β-Ga2O3 microtubes and nanomembranes, ion-beam-assisted exfoliation, was employed in the fabrication of simple metal-semiconductor-metal (MSM) devices to be tested as field-effect transistors (FET) and UV photodetectors, as MSM photodetectors and as phototransistors. Electrical characterisation showed that these devices can reach very high responsivities and detectivities, up to 4.7×10^4 A/W and 2.7×10^17 Jones, respectively. A rejection ratio above 10^6 between 5.08 eV and 3.4 eV light was also obtained. However, some of these devices exhibit high persistent photoconductivity. In order to better weigh the different mechanisms that are responsible for the high and persistent photoresponses, ion beam induced current (IBIC) measurements were performed on the two metal junctions and on the semiconductor channel using a 2 MeV proton microbeam.

This work describes a stacked diode CMOS sensor using a 0.18 µm process for energy-resolved electron imaging. Inspired by optical sensors that use these devices to detect color based on light absorption depth, this sensor applies the analogous principle to electrons, whose energy deposition also varies with depth in silicon. Optical tests confirmed distinct spectral responses separable via a correction algorithm. Electron beam tests using a 10 keV SEM showed sensitivity dependent on beam current and diode depth. This approach shows promise for integrated, lower-cost energy discrimination in SEM.

Electro-optical modulators, operating via linear and non-linear electro-optical effects are well-established; however, typically, this modulation is performed using high-power grid-supply electricity. In this research, a green, environmentally friendly alternative is investigated, combining the field of triboelectric nanogenerators (TENG) with photonics to produce a precise tribophotonic device, capable of stimulating standard electro-optical modulators (EOMs) at the lower frequency range. Varying levels of TENG hand-tapping stimulation (corresponding to output voltage) evidenced a successful non-linear EOM response resulting from electric field exposure. EOM transmission amplitude reduction at 993 nm by 17.5 % at 154 V applied via the TENG and by 64.7 % at 348 V was observed. Furthermore, this investigation characterizes the developed zinc oxide (ZnO) - polyethylene terephthalate (PET) based TENG, further optimizing base conditions for integration with photonics.

In this work, the electrical characteristics of Mo Schottky contact on n-GaN were investigated post-metal annealing at 850 °C. Barrier Height ΦB and ideality factor η were extracted from the measured forward current-voltage linear fit using the thermionic emission (TE) theory and C-V measurements. The leakage current is directly given by the reverse bias I-V measurements. Results indicate dependency of the electrical characteristics upon annealing. The Mo/n-GaN junctions showed ideal electrical characteristics after annealing at 850 °C with an ideality factor of 1.07, a hard breakdown voltage of 118 V/µm and a leakage current of 6.57mA.cm-2 at -10 V. The specific on resistance RON is very low with a value of 0.1 mΩ.cm². SEM images showed no post-annealing physical degradation of the device.

As dopant energy ionisation is relatively high in diamond (EA,B=0,37eV) a diamond FET using the concept of optical activation of the channel is here demonstrated. The IR laser (473nm) irradiation allows to activate exclusively dopants in the channel inducing current across the channel while it remains closed without irradiation. By varying the applied laser power, the current intensities can be modified. Based on that dependence, the carrier activations versus laser power have been estimated.

This study introduces the preparation of a future transferred InP double heterojunction bipolar transistor (DHBT) on a high-resistivity silicon substrate. Our approach employs copper (Cu) as a thermal heat sink and chosen for its excellent thermal conductivity, which will make possible efficient heat dissipation in electronic devices. This ensures superior compatibility with industry standards and improves performance in high power applications and ultra-low-cost material bonding. The development includes the first instance of heatsink bonding using a Si-Fab copper layer, together with a method for removing InP substrate [1]. This process involves also a mechanical thinning down to 10 µm, followed by etching with HCl. These advancements are expected to significantly improve power amplification performance at high frequency, paving the way for 6G-compatible CMOS integration.

In this work, measured DC characteristics of an AlGaN/GaN on silicon carbide (SiC) high electron mobility transistor (HEMT) are numerically simulated accounting for self-heating effects (SHEs). Dirichlet boundary conditions for room temperature (25°C) and proper surface thermal resistances of 0.9°C-mm2/W were used at all terminals. Most SiC substrate (96% in depth) was replaced by an additional equivalent surface thermal resistance of 0.6°C‑mm2/W. To facilitate hot spot removal at the device level, which is often a source of premature breakdown, an all-around heat spreader is implemented. It is integrated with polycrystalline (isotropic) diamond, which is grown on top of the active device region, as well as the sidewalls, and the SiC substrate. The device thermal resistance is reduced from 9.0°C-mm/W originally to 6.7°C-mm/W when the all-around heat spreader is used, which is in agreement with experimental measurements already published in literature. Additionally, when SiC is substituted with polycrystalline diamond, the device thermal resistance is as low as 3.2°C-mm/W.

This work is a cathodoluminescence study on homoepitaxial diamond samples grown at University of Cádiz where the success in introducing three different doping elements in the layers is shown. At the University of Cádiz, we started developing our diamond growth methodology during 2024. At this point, we can grow high-quality nitrogen-doped and phosphorus-doped diamond layers in a SEKI Diamond Systems vertical reactor. In addition, we can also produce high-quality boron-doped diamond layers in a NIRIM-type homemade reactor.

Nanocrystalline diamonds are emerging as promising materials for luminescent nanothermometry due to their ability to host a range of luminescent point defects, such as nitrogen-vacancies (NV-) and silicon-vacancies (SiV-) [1]. These diamonds exhibit low cytotoxicity and good biocompatibility, alongside the benefits of carbon chemistry, allowing for versatile surface functionalization with target molecules. In this study, N/Si co-doped nanocrystalline diamonds were synthesized using microwave plasma-enhanced chemical vapor deposition (MWPECVD), varying methane flow and temperature conditions to optimize photoluminescence intensity. The results reveal a thermal coupling between the NV- and SiV- emitting point defects, enabling ratiometric thermometry that enhances temperature measurement sensitivity. A maximum thermal relative sensitivity of 5.5 % K⁻¹ was achieved, making these diamonds particularly suitable for in vitro temperature sensing of biological tissues.

Shifting the emission wavelength of InAs quantum dots

grown on GaAs to the telecom C band is a major challenge.

While the lattice parameter can be adapted using InGaAs

metamorphic buffers to obtain C-band emission,

embedding the quantum dots in a λ-cavity to exploit

Purcell effect requires thinning the graded layer below

λ/2n, while preserving a large relaxation and twodimensional

growth. Nonlinear compositional gradings,

particularly jump-convex-inverse, were recently proven a

successful strategy, but detailed structural information and

its effect on emission properties is still limited. In this

contribution, we study InAs(Sb) quantum dots grown on

jump-convex-inverse InGaAs(Sb) buffer layers by molecular

beam epitaxy. The structures are theoretically predicted to

be superior to linear or superlinear gradings in terms of

larger misfit dislocation-free zones and lower residual

strain. However, the large dislocation densities needed to

reach equilibrium in thin films with high grading rates are

experimentally challenging. Our approach is based on the

addition of Sb as (i) a surfactant during metamorphic

growth to preserve a smooth surface at increased grading

rates and (ii) as an alloying element soaked in the quantum

dots to increase quantum dot size. We will discuss a series of samples

with varying In gradings, currently being studied at each

step of the growth to determine the maximum admissible

In content and the effect of Sb.

AlGaN/GaN high-electron-mobility-transistors on semi-insulating substrates are promising for not only high-frequency devices but also power devices. Semi-insulating substrates made of GaN are now available. Therefore, we evaluated the static characteristics and breakdown voltage of AlGaN/GaN HEMTs on semi-insulating GaN substrates containing Mn or C as impurities were formed on conductive GaN substrates by the HVPE method. We confirmed that the breakdown voltage of AlGaN/GaN depends on the type of impurity in the semi-insulating substrates.

High-quality (100)-oriented 4-inch InAs single crystals with low dislocation density were successfully grown using the vertical gradient freeze (VGF) method and subsequently processed into substrates with superior surface quality through chemical mechanical polishing (CMP) for infrared detection applications. Comprehensive characterization of the InAs substrates was performed to evaluate the crystalline quality, optical/electrical properties, and surface characteristics. XRD mapping analysis revealed exceptional crystalline uniformity with rocking curve full width at half maximum (FWHM) values consistently below 20 arcsec across most regions of the 4-inch InAs substrate. The crystal demonstrated excellent crystalline integrity, as evidenced by dislocation etch pit density (EPD) measurements of 526.52 cm-2 and 648.26 cm-2 at the head and tail positions, respectively. In addition, the substrates exhibited remarkable electrical uniformity and achieved an average infrared transmittance of approximately 50% across the spectral range of 760-2300 cm⁻¹. Post-CMP processing yielded wafers with both low defect density and an atomically smooth surface with RMS surface roughness below 0.5 nm. These optimized 4-inch InAs substrates provide a robust foundation for developing infrared detectors with higher pixel density.

In this work, we have used two-photon polymerization (2PP) to incorporate CsPbBr₃ perovskite quantum dots (QDs) into a photosensitive resin. Initially, the optimal ratio of QD solution to resin for high quality printing has been determined as 0.02. Backscattered electrons (BSE) imaging confirms the presence of the QDs in the printed objects, although showing some degree of agglomeration. Confocal microscopy demonstrates the fluorescence of the QDs in the printed structures. This method holds promise for fabricating micro-optical components.

This presentation will discuss recent advancements and emerging

technologies based on III-Nitride semiconductors that aim to address

some of the challenges in power electronics. We will highlight the

significant improvements in device performance achieved through the use

of multi-channel structures, resulting in figures of merit that far exceed

current standards. To address the challenge of managing high heat fluxes

in compact devices, we will explore recent advancements in the thermal

management of GaN devices. This includes the co-design of microfluidics

and electronics within the same semiconductor substrate, a technology

that offers significantly greater cooling capabilities than currently available

and enables denser integration of GaN devices on a single chip. These

emerging technologies present exciting opportunities for the future

development of III-nitride electronic devices.

In this work, we present the electrical performance of quasi-vertical Schottky barrier diodes (SBDs) featuring a 500 nm n-GaN layer grown on a silicon carbide (SiC) substrate. The effect of rapid thermal annealing (RTA) on the Schottky contact was examined by comparing two annealing temperatures. The fabricated diodes demonstrate a low specific ON-resistance (RON,sp) of 1.23 mΩ·cm², a high forward current density of 543 A/cm², and a breakdown voltage of 78 V/μm, highlighting the potential of GaN-on-SiC SBDs for high-power and high-frequency applications.

Power switching devices are the key drivers for innovation in energy systems, ranging from the power utility grid, wind and solar power generation, and EVs, but also IT, servers and AI data centers.

4H-SiC MOSFETs have already become the preferred switches for EV drives and chargers, with commercial devices being available with blocking voltages of 1200V, 900V and 600V. More recently, Infineon announced a 400V 4H-SiC MOSFET, aimed at providing an alternate device to GaN HEMTs and silicon superjunction (SJ) MOSFETs for lower voltage applications. The latter two have typically been considered preferable at lower voltage because of their higher channel mobility and lower substrate cost. However, 8” 4H-SiC substrates are now available with ever lower cost per wafer and 4H-SiC trench MOSFETs with submicron channel length have led to lower channel resistance. This warrants a closer look.

This presentation provides a detailed analysis of the switching behavior of 4H-SIC MOSFETs as well as 3C-SiC MOSFETs. The analysis shows that the specific on-resistance can be as low as 1.1 mOhm-cm^2 and 0.25 mOHm-cm^2 respectively for quarter-micron gate-length 400V trench MOSFETs, where the difference is attributed to the higher channel mobility and lower substrate resistivity of the 3C-SiC MOSFET.

The low specific on-resistance combined with the higher thermal conductivity of SIC substrates enables operation at 400 A/cm^2 and 600 A/cm^2 for the 4H-SiC and 3C-SiC MOSFETs respectively. This enables smaller area devices with lower capacitance. Switching times shorter than 1.4ns and 0.46ns have been obtained with a switching energy less than 2.08uJ and 0.69 uJ for 10A, 400V, 4H-SiC and 3C-SiC MOSFETs respectively.

Detailed graphs showing the device performance as a function of key design parameters, including channel length, substrate thickness, junction temperature and operating frequency will be presented.

Finally, the performance of the SiC MOSFETs will be compared with that of equivalent GaN HEMTs and silicon SJ MOSFETs, highlighting advantages and trade-offs of each technology.

We report the successful development of Schottky barrier diodes (SBDs) that exhibit both a high breakdown voltage and the ability to withstand extreme temperatures. By utilizing a GaN epitaxial structure on sapphire substrate with a 5 µm thick drift layer and depositing a molybdenum-GaN Schottky contact annealed at 700 °C for 60 seconds. We have fabricated functional SBDs that deliver excellent performances including an ideality factor of 1.33, a breakdown voltage of 363 V and a very low on-resistance of 1.8 mΩ.cm².

Vertical GaN Nanowire (NW) Field Emitters (FE) are promising candidates for next generation devices. GaN NWs were grown selectively on SiO2 masked GaN/Al2O3 substrates for FE applications. Arrays of ~4 mm2 each with varied NW diameters and pitches were fabricated on a single GaN-based sample. A custom-made vacuum test system with an integrated micromanipulator High-Voltage setup was used for device characterization. The devices exhibited the expected Fowler-Nordheim (FN) tunneling behavior. Increased pitch from 1 μm to 3 μm, for given diameter of 100 nm, leads in lower current, possibly due to the decreased number of GaN NWs. Moreover, an increased diameter from 300 to 400 nm for given pitch of 5 μm, leads in higher current due to a larger emitting surface.

Surface-trap effects play a crucial role in understanding the operating principle of two-terminal devices based on AlGaN/GaN nanochannels. The trapping and de-trapping of carriers at the boundary surfaces are particularly significant, not only due to their influence on the current levels within the nanochannels but also because of their impact on the saturation of the current-voltage (I-V) curve. In this study, Monte Carlo simulations, incorporating traps through two different models, are done to replicate the experimental behaviour of the I-V curve and to identify the surface charge location under forward and reverse bias.

Active implantable medical devices have experienced enormous

development over the past years. However, one limiting factor remains a

challenge, its reliance on external batteries. Furthermore, in the case of

neural interfaces, the use of bulky batteries limits the advance of our

understanding of the nervous system, since the presence, on the

head/body of a moving animal under study, of a bulky head-stage

originates the large variability found in the existing results on this regard. In

an ideal scenario, medical implants should be powered using long-lasting

power suppliers that pose no mechanical or chemical danger to the body.

We work towards the development of an energy autonomous neural

stimulation technology by exploring the coupling of triboelectric

nanogenerators and our neural graphene-based microelectronics.

Abstract

The study of two-dimensional (2D) materials, particularly molybdenum disulfide (MoS2), is crucial for future electronic and optoelectronic devices. Single-layer MoS2 (1L-MoS2) exhibits a 1.8 eV bandgap, making it ideal for such applications. However, achieving large-scale synthesis with consistent properties remains a challenge. The synthesis method and substrate choice significantly affect the material’s electronic and optical properties, influencing strain and doping. To address this, controlled post-synthesis treatments are explored. Previous studies showed that 1L-MoS2 thermal treatments on gold substrates can effectively tune strain-doping properties and fluorescence without altering morphology, though the effects depend on synthesis routes. This work systematically compares 1L-MoS2 samples obtained via Chemical Vapor Deposition (CVD), deposited on an insulating substrate of SiO2, and Gold-Assisted Exfoliation (GAE). Thermal treatments in O2 and Ar atmospheres were applied to refine strain, doping, and fluorescence, showing potential for defect remediation, doping control, and luminescence enhancement.

Introduction

The study of two-dimensional (2D) materials has a huge interest and influence on the future electronic and optoelectronic devices based on nanostructures[1]. One of the most promising and studied 2D structures is molybdenum disulfide (MoS2), due to its interesting electronic and optical properties[2, 3]. Single layer MoS2 (1L-MoS2) presents semiconductive properties with a bandgap of 1.8 eV from which a fluorescence emission is obtained by direct exciton recombination[4]. These features make 1L-MoS2 an ideal candidate as material for optoelectronic devices. However, to reach this step an industrial-scale synthesis with homogeneity in structural and physical properties is required but not yet achieved. Several methods of synthesis exist to produce this kind of material and each of them has a different impact on the electronic and optical MoS2 features[5].

Furthermore, the nature and the superficial features of the substrate on which 1L-MoS2 is placed influence significantly the initial strain and doping of the nanostructure, highlighting that the choice of the substrate is crucial according to the application or the heterostructure needed[6]. For this reason, finding a controlled procedure after synthesis to remediate and tune the MoS2 properties is nowadays a challenge.

As shown in our previous work[7], thermal treatments of 1L-MoS2 on gold substrates are promising for tailoring the strain-doping properties and properly tuning the optical features. The best condition found underlines that there is a critical temperature over which the physical properties have been changed without ruining the morphology of the sample. However, all these advantages cannot be extendible automatically for each kind of sample independently of the route of synthesis.

In this work, we present a systematic study of 1L-MoS2 obtained by CVD on SiO2 comparing the results with the samples made by GAE[6] in our previous work, exploring the physical differences raised from the different procedures and substrates. We applied thermal treatments in a controlled atmosphere (O2 and Ar) to fine-tune strain, doping and fluorescence properties after synthesis. These treatments seem to be promising in remediating defects occurring naturally, controlling the doping type and enhancing the luminescence of 1L-MoS2.

Experimental Details

Several flakes of 1L-MoS2 have been prepared by CVD using liquid molybdenum precursors, at a temperature of 820 °C, under an ambient pressure, nitrogen atmosphere and grown on a SiO2/Si substrate (silicon with native silicon oxide on top)[8]. All the samples were treated in a Linkam cell from the temperature of 100 °C up to 300 °C, for 2 hours with 2 atm of O2 or Ar atmosphere.

We performed non-destructive techniques such as Raman spectroscopy and steady-state micro-photoluminescence using a Horiba LabRaman HR-Evolution with a 532 nm laser source, to study initial strain and doping conditions and the effects of the thermal treatments. A Bruker FastScan Dimension Atomic Force Microscope (AFM) was employed for observing the structure and morphology of the flakes in tapping mode.

Results and discussion

The E12g (in-plane) and A1g (out-of-plane) vibrational modes of MoS2 are detectable through Raman spectroscopy. As known in the literature, the frequency of vibration of these two Raman modes is connected to the strain and doping of the MoS2 flakes[9]. Figure 1 shows a strain-doping map of two different samples, the first one thermally treated in Ar (Figure 1a) and the second one in O2 (Figure 1b), studying the effect as a function of the temperature.

In general, both pristine samples characterized at room temperature (20°C) show a compressive strain condition and an initial n-type doping. Thermal treatments in Ar (figure 1a) at 100°C do not affect the flake. The first significant change appears at 150°C and 200°C, in which is possible to observe an increase of n-type doping and a small reduction of the compressive strain. Over these two temperatures, the 1L-MoS2 maintains the same doping of the pristine sample, but with a smaller compressive strain than untreated flake. A similar behaviour has been observed in the sample treated in O2. Increasing the temperature above 200°C there is a significant and systematic decrease of the n-doping. Strain variations are the same in both experiments, as this is probably only affected by temperature. Otherwise, except at the lowest temperatures, variations in doping seem to be accelerated by the presence of an active atmosphere like O2.

Additional effects of thermal treatments in the optical properties have been recorded through the acquisition of micro-photoluminescence steady-state spectra (data not shown), in which modifications in intensity and band position have been recorded. In detail, a significant variation of the photoluminescence has been observed treating the flake in the presence of O2. By contrast, under an Ar atmosphere, no significant enhancement of the intensity of luminescence is observed. Instead, in the O2 environment an increase from 2 up to 7 times the intensity has been measured, notably improving the luminescence of the 1L-MoS2. AFM and optical images (data not shown) have been used to observe the sample morphology before and after the thermal treatments.

We have found that temperatures higher than 225°C showed some variations in the structure of the flake. These findings allowed us to set the best conditions of treatment at 225°C with 2 atm, finding a controlled protocol to tailor the strain-doping properties (Ar, or O2 treatment) and/or the luminescence properties (only O2 treatment).

Conclusions

In conclusion, we have performed a systematic study on single-layer Molybdenum Disulfide prepared by CVD on an insulating SiO2 substrate, in which a controlled process aimed at modifying the strain, doping and luminescence properties has been optimized. This study can open a path towards the improvement of the features of two-dimensional materials regardless of the synthesis route chosen.

Acknowledgements

This research was funded by the Italian MUR PNRR project SAMOTHRACE (ECS00000022) and Funded by the European Union - Next Generation EU, Mission 4 Component 1 CUP B53D23004460006 (Finanziato dall’Unione europea- Next Generation EU, Missione 4 Componente 1 CUP B53D23004460006).

References

[1] Huang, X. et al., NPJ 2D Mater Appl, vol. 6, no. 1, 2022.

[2] Serron, J. et al., ACS Appl Mater Interfaces, vol. 15, no. 21, pp. 26175–26189, May 2023.

[3] Scheuschner, N. et al., Phys Rev B Condens Matter Mater Phys, vol. 89, no. 12, p. 125406, Mar. 2014.

[4] Splendiani, A. et al., Nano Lett, vol. 10, no. 4, 2010.

[5] Samy, O. et al., Crystals 11, no. 4: 355. 2021.

[6] Panasci S.E. et al., Appl Phys Lett, vol. 119, no. 9, Aug. 2021.

[7] Sangiorgi, E. et al., Nanomaterials, 15, 160, 2025.

[8] Esposito, F. et al., Appl Surf Sci, vol. 639, 2023.

[9] Michail, A. et al., Appl. Phys. Lett., 108, 173102, 2016.

This paper reports on the large area growth of ultrathin monolayer (1L) MoS2 onto homoepitaxial n--GaN on n+-GaN substrates by sulfurization of a pre-deposited MoOx film. A highly uniform and conformal MoS2 coverage and a nearly ideal van der Waals interface between MoS2 and Ga terminated GaN crystal was demonstrated by the combination of several high-resolution analyses. Finally, the vertical current-voltage characteristics showed a highly rectifying behaviour with an average turn-on voltage Von=1.7 V under forward bias, indicating the formation of p+/n heterojunction diode at 1L-MoS2/GaN interface.

In this paper, the growth of uniform few layers MoS2 on single crystalline diamond substrates has been obtained by sulfurization of a pre-deposited ultra-thin Mo film at an optimal temperature of 750°C. The MoS2 thickness uniformity, interface structural, and electrical behaviour of the MoS2/diamond heterostructures has been investigated by the combination of TEM, micro-Raman, AFM and several electrical scanning probe techniques (C-AFM, KPFM). The obtained results indicate the formation of a n-MoS2/p-diamond heterostructure.

In this work, we report on the fabrication of an ultrathin superabsorber in the visible spectral range based on transition metal dichalcogenide (TMDC) nanostructures. We designed and patterned a periodic nanohole arrays on MoSe₂ thin films deposited on metallic foils. Our results show broadband absorption above 90% over the visible range, attributed to multiple optical resonances such as diffraction, guided modes, Fabry–Pérot interference, and plasmonic excitations. The overall approach demonstrates a simple, scalable method to produce efficient light-trapping photonic structures suitable for optoelectronic devices. As a proof of concept, we employed a fast, clean-room-free laser ablation.

The exceptional properties of graphene promised a candidate to overcome the fundamental limitations of silicon technologies in photonics and optoelectronics. Especially when data transferring is at stake, novel graphene devices have been reported. These hybrid structures exploit the integration of graphene on a CMOS compatible process. In this work, the simulation of a mode filter based on SiN photonics is presented together with the developments carried out to achieve yield and control of the fabrication process. Finally, we present the characterization of the power transmitted in the TE0 mode through the graphene-on-silicon nitride (SiN) integrated waveguides. Our devices can potentially boost the development of efficient Mode Division Multiplexing systems for ultra-fast on-chip interconnections.