Crystal orientations of beta-Ga2O3 thin films formed on m-plane and r-plane sapphire substrates

摘要

We have used X-ray pole figure analyses to study crystal orientations of -Ga2O3 thin films formed on (100) m-plane or (102) r-plane sapphire substrates prepared by gallium evaporation in oxygen plasma. The (-201) plane of -Ga2O3 on the (100) m-plane was inclined to be along two (110) a-planes. Crystals of (-201)-oriented -Ga2O3 exhibit six-fold symmetry in which a -Ga2O3 crystal is rotated every 60 degrees from [001] for each a-plane. In all, twelve kinds of -Ga2O3 crystals formed on m-plane sapphire substrate. Similarly, the (-201) plane of -Ga2O3 on the (102) r-plane was inclined to be along to two (113) n-plane. Crystals of (-201)-oriented -Ga2O3 exhibit three-fold symmetry with a -Ga2O3 crystal rotated every 120 degrees from the opposite direction of projection of the c-axis of each n-plane. In all, six kinds of -Ga2O3 crystals formed on the r-plane sapphire substrate. These observations can be explained by comparing oxygen atomic arrangements on the -Ga2O3 (-201) plane with those on the sapphire (110) a-plane and (113) n-plane.