Impact of c- and m- sapphire plane orientations on the structural and electrical properties of β-Ga₂O₃ thin films grown by metal-organic chemical vapor deposition

This work presents a comprehensive investigation into the structural and electrical properties of Ga₂O₃ thin films grown via metal-organic chemical vapor deposition on both c- and m-plane sapphire substrates. Structural characterization revealed the β-Ga₂O₃ phase formation in both substrate orientations, with strong epitaxial ( 2 ¯ 01 ) preferential growth on c-plane substrates and polycrystalline films on m-plane substrates. Results show that Ga₂O₃/m-sapphire exhibits the lower electrical resistivity than its counterpart grown on c-sapphire. Activation energies of acceptor levels were estimated at ~1.4 eV and ~0.7 eV , for Ga₂O₃ films grown on c- and m-plane, respectively. This result shows that growing Ga₂O₃ on m-plane sapphire is beneficial to reach a weakly compensated sample. Cathodoluminescence analysis suggests that the additional low activation energy of ~0.18 eV observed in Ga₂O₃ grown with the highest oxygen flow on m-plane sapphire can be associated to thermally-induced migration of self-trapped hole states.