Influence of AlN Buffer on Phase Structure of GaN on GaAs (001) Grown by Radio-Frequency Molecular Beam Epitaxy

The influence of an AlN buffer layer on the phase structure of GaN is studied. Cubic GaN grown on a GaN buffer layer present on a GaAs (001) substrate, and secondary hexagonal GaN in the sample is grown according to GaN[0001]∥GaAs[111]B; when an AlN buffer layer is introduced, the single hexagonal GaN crystal is obtained with the growth direction of GaN[0001]∥GaAs[001]. X-ray diffraction and photoluminescence measurements are used to analyze the phase structure and orientation of the two epilayers. Atomic force microscopy is used to analyze the surface characteristics and it is revealed that the morphologies of the two samples differ. The results reveal different nucleation mechanisms of GaN on the GaN buffer layer and AlN buffer layer.