The nature and impact of ZNO buffer layers on the initial stages of the hydride vapor phase epitaxy of GAN

The nature and impact of ZnO buffer layers on the initial stages of the hyd ride vapor phase epitaxy (HVPE) of GaN have been studied by xray photoelect ron spectroscopy (XPS), atomic force microscopy (AFM), xray diffraction (XR D) and photoluminescence (PL). During pre-growth heating, the surface ZnO l ayer was found to both desorb from ZnO-coated sapphire and react with the u nderlying sapphire surface forming a thin ZnAl2O4 alloy layer between ZnO a nd sapphire surface. This ZnO-derived surface promotes the initial nucleati on of the GaN and markedly improves material surface morphology, quality an d growth reproducibility.