Conference Agenda

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.