Structural and optical characterizations of cubic GaN layers grown by MOVPE on GaAs(114) substrate

Abstract

GaN-based structures have been employed in a range of electronic and optoelectronic applications. Despite the extensive utilization of hexagonal GaN (h-GaN), certain devices, such as green-emitting lasers, face limitations. Conversely, cubic GaN (c-GaN) proves advantageous in addressing challenges associated with h-GaN, thanks to its reduced bandgap and being free of the strong polarization fields resulting in enhanced radiative recombination rate. Yet, c-GaN possesses a metastable phase during growth, which can negatively impact the structure of the films. Optimizing the growth conditions can significantly improve material quality and, hence, device performance. In our present work, we report the growth of cubic GaN on GaAs (114) substrates using metal-organic vapor phase epitaxy (MOVPE) with various thicknesses. Morphological analyses demonstrated a grain structure with increased surface roughness versus layer thickness. Such measurements enabled us to study the texture and growth mode evolutions. High-resolution X-ray diffraction 2 θ-ω scans showed a (002) c-GaN preferred orientation with hexagonal inclusions. The optical characteristics of the investigated layers were explored using cathodoluminescence measurements, revealing a correlation between the stress state and layer thickness.