Growth and characterization of α-, β-, and ϵ-phases of Ga₂O₃ using MOCVD and HVPE techniques

Heteroepitaxial films of Ga ₂ O ₃ were grown on c-plane sapphire (0001). The stable phase β-Ga ₂ O ₃ was grown using the metalorganic chemical vapor deposition technique, regardless of precursor flow rates, at temperatures between 500 ^∘ C and 850 ^∘ C. Metastable α- and ϵ-phases were grown when using the halide vapor phase epitaxy (HVPE) technique, at growth temperatures between 650 ^∘ C and 850 ^∘ C, both separately and in combination. XTEM revealed the better lattice-matched α-phase growing semi-coherently on the substrate, followed by ϵ-Ga ₂ O ₃ . The epitaxial relationship was determined to be [ 1̄100 ] ϵ-Ga ₂ O ₃ $ \| $ [ 112̄0 ] α-Ga ₂ O ₃ $ \| $ [ 112̄0 ] α-Al ₂ O ₃ . SIMS revealed that epilayers forming the ϵ-phase contain higher concentrations of Cl introduced during HVPE growth.