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 studi ed. 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] parallel to GaAs[111]B; when an AlN buffer layer is introduced, the single hexagonal GaN crystal is obtained with the growth direction of GaN[0001] p arallel to GaAs[001]. X-ray diffraction and photoluminescence measurements are used to analyze the phase structure and orientation of the two epilayer s. Atomic force microscopy is used to analyze the surface characteristics a nd it is revealed that the morphologies of the two samples differ The resul ts reveal different nucleation mechanisms of GaN on the GaN buffer layer an d AlN buffer layer.