Crystal orientations of β‐Ga 2 O 3 thin films formed on m ‐plane and r ‐plane sapphire substrates

We have used X‐ray pole figure analyses to study crystal orientations of β‐Ga 2 O 3 thin films formed on (100) m ‐plane or (102) r ‐plane sapphire substrates prepared by gallium evaporation in oxygen plasma. The (−201) plane of β‐Ga 2 O 3 on the (100) m ‐plane was inclined to be along two (110) a ‐planes. Crystals of (−201)‐oriented β‐Ga 2 O 3 exhibit six‐fold symmetry in which a β‐Ga 2 O 3 crystal is rotated every 60° from [001] for each a ‐plane. In all, twelve kinds of β‐Ga 2 O 3 crystals formed on m ‐plane sapphire substrate. Similarly, the (−201) plane of β‐Ga 2 O 3 on the (102) r ‐plane was inclined to be along to two (113) n ‐plane. Crystals of (−201)‐oriented β‐Ga 2 O 3 exhibit three‐fold symmetry with a β‐Ga 2 O 3 crystal rotated every 120° from the opposite direction of projection of the c ‐axis of each n ‐plane. In all, six kinds of β‐Ga 2 O 3 crystals formed on the r ‐plane sapphire substrate. These observations can be explained by comparing oxygen atomic arrangements on the β‐Ga 2 O 3 (−201) plane with those on the sapphire (110) a ‐plane and (113) n ‐plane.