Phase Formation And Strain Relaxation Of Ga2o3 On C-Plane And A-Plane Sapphire Substrates As Studied By Synchrotron-Based X-Ray Diffraction

Heteroepitaxial Ga2O3 was deposited on c-plane and a-plane oriented sapphire by plasma-assisted molecular beam epitaxy and probed by ex-situ and in-situ synchrotron-based x-ray diffraction. The investigation on c-plane sapphire determined a critical thickness of around 33 angstrom, at which the monoclinic beta-phase forms on top of the hexagonal alpha-phase. A 143 angstrom thick single phase alpha-Ga2O3 was observed on a-plane sapphire, much thicker than the alpha-Ga2O3 on c-plane sapphire. The alpha-Ga2O3 relaxed very fast in the first 30 angstrom in both out-of-plane and in-plane directions as measured by the in-situ study. Published by AIP Publishing.