HOMOEPITAXIAL GROWTH OF CUBIC GAN BY HYDRIDE VAPOR-PHASE EPITAXY ON CUBIC GAN/GAAS SUBSTRATES PREPARED WITH GAS-SOURCE MOLECULAR-BEAM EPITAXY

Thick cubic GaN (c-GaN) layers were homoepitaxially grown on c-GaN/(100)GaAs by hydride vapor phase epitaxy (HVPE). The c-GaN crystals used as substrates in this work were prepared by gas source molecular beam epitaxy (GSMBE). When the growth temperature was too low (approximately 700-degrees-C) or too high (approximately 1000-degrees-C), hexagonal GaN (h-GaN) was included in the grown layer, but pure c-GaN was obtained at 900-degrees-C. The growth rate of c-GaN by HVPE in this work was about 1.6 mum/h, which was 4-10 times higher than that of GSMBE or metalorganic vapor phase epitaxy (MOVPE), and an about 5 mum thick c-GaN film was obtained by 3-h growth. The X-ray diffraction (XRD) patterns showed only the (200) and (400) c-GaN peaks but no h-GaN one. The cathodoluminescence (CL) spectra exhibited a strong peak at about 365 nm, which corresponds to the band edge emission. No emission due to deep levels was observed.