Conference Agenda

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.