Thermal stability of HVPE-grown (0001) alpha-Ga2O3 on sapphire template under vacuum and atmospheric environments

In the present study, thermal stability of alpha-Ga2O3 under vacuum and ambient pressure conditions was investigated in situ by x-ray diffraction and transmission electron microscopy (TEM). It was observed that the thermal stability of alpha-Ga2O3 increased by 200 degrees C when pressure was lowered from an atmospheric to a vacuum level. This finding can be explained by oxygen diffusion under different oxygen partial pressures. In addition, in situ TEM imaging revealed that, once past the decomposition temperature, the onset of phase change propagates from the top crystal surface and accumulates strain, eventually resulting in a fractural film. The mechanism of alpha-Ga2O3 to beta-Ga2O3 transition is evaluated through experiments and is discussed in this manuscript. Published under an exclusive license by the AVS.