Study of phase transition in mocvd grown ga2 o3 from κ to β phase by ex situ and in situ annealing

Abstract

We report the post-growth thermal annealing and the subsequent phase transition of Ga2 O3 grown on c-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD). We demonstrated the post-growth thermal annealing at temperatures higher than 900◦ C under N2 ambience, by either in situ or ex situ thermal annealing, can induce phase transition from nominally metastable κ-to thermodynamically stable β-phase. This was analyzed by structural characterizations such as high-resolution scanning transmission electron microscopy and x-ray diffraction. The highly resistive as-grown Ga2 O3 epitaxial layer becomes conductive after annealing at 1000◦ C. Furthermore, we demonstrate that in situ annealing can lead to a crack-free β-Ga2 O3.