Epitaxial stabilization of pseudomorphic alpha-Ga2O3 on sapphire (0001)

Heteroepitaxial Ga2O3 was grown on c-plane sapphire by molecular beam epitaxy, pulsed-laser deposition, and metalorganic Chemical vapor deposition. Investigation by scanning transmission electron microscopy (STEM) revealed the presence of a three-monolayer-thick pseudomorphically grown layer of trigonal alpha-Ga2O3 at the interface between the c-plane sapphire substrate and the beta-Ga2O3 independent of the growth method. On top of this pseudomorphically grown layer, plastically relaxed monoclinic beta-Ga2O3 grew in the form of rotational domains. We rationalize the stable growth of the high-pressure trigonal alpha-phase of Ga2O3 in terms of the stabilization of the alpha-Ga2O3 phase by the latticemismatch-induced strain. (C) 2015 The Japan Society of Applied Physics