GaN ceramics obtained by fusing of nanocrystalline GaN powder at high pressures and temperatures as substrate for growth of GaN epilayers

Abstract In this paper, we have grown GaN films by metalorganic chemical vapor-phase epitaxy (MOVPE) on GaN ceramics obtained from nanocrystalline powder of different initial grain sizes. The samples have been investigated by X-ray diffraction (XRD) and photoluminescence (PL). XRD reveals that the MOVPE GaN films are of single-phase wurtzite structure. Also, it has been observed that the PL spectrum is different for the GaN films compared to that for the GaN powder and also depends on the initial grain sizes.

Gallium oxide buffer layers for gallium nitride epitaxy

Gallium nitride (GaN) is very attractive semiconductor material because of its unique properties. The serious matter is a lack of easy access to bulk crystals of GaN. Synthesized crystals are precious and rather small. For these reasons almost all device manufacturers and researchers apply alternative substrates for gallium nitride devices epitaxy and it causes that the technology is intricate. Alternative substrates need buffer layers – their technology is usually complex and expensive. We have proposed a simple method to avoid large costs: applying gallium oxide – monoclinic β-Ga2O3, as the buffer layer, which has structural properties quite good matched to GaN. As the substrates made from single crystal gallium oxide are still hardly available on the market, we have used hydride vapour phase epitaxy (HVPE) GaN epilayers as a starting material. It can be GaN layer under good quality – middle or low. The oxidation process converts top GaN to β-Ga2O3 layer which can release or absorb the strain. Applying such structure in another, second, epitaxy of GaN allows to obtain good quality epitaxial structures using HVPE technique

Influence of AlN Buffer Layer Deposition Temperature οn Properties of GaN HVPE Layers

Gallium nitride layers were deposited on AlN and double layer (AlN/AlGaN) buffers grown at various temperatures on $Al_{2}O_{3}$. Stress in layers was evaluated based on the Raman scattering and photoluminescence measurements. The obtained values were less than 1 GPa

Interface and Surface Subsignals in Photoreflectance Spectra for GaAs/SI-GaAs Structures

Photoreflectance spectra were measured at room temperature for energies in the vicinity of the E$\text{}_{0}$ critical point for p-type as well as n-type doped GaAs/SI-GaAs structures. Depending on the doping concentration the existence of two photoreflectance subsignals was observed; the first one arises from the surface space charge region while the second one from the interface region. The decomposition of photoreflectance spectrum into surface and interface subsignals was based on the photoreflectance measurements carried out for different wavelengths of the laser pump beam