Anderson disorder related p-type conductivity and metal-insulator transition in β-Ga₂O₃

The p-type doping is one of the main challenges of the emerging semiconductor β-Ga₂O₃ technology. Phosphorus (P) implantation has been recently reported as a novel route to achieve p-type conduction on Ga₂O₃ at room temperature. Here, P-implanted epilayers, grown onto c-plane sapphire revealed a pseudo-metallic behavior (ρ = 1.3–0.3 Ω cm) in the 300–600 K range with a hole carrier concentration of p ⁓ 4–6 × 10¹⁸ cm⁻³ and hole mobility of μ = 1.2–2.1 cm²/(V·s). At sufficiently low temperature, a metal-insulator transition arises together with an increase in the positive magnetoresistance, reaching up to 200 % (9 T) large positive magneto resistance effect at 2 K. It is suggested that an Anderson delocalization model explains the room temperature conduction, and the transition to an insulator state caused by random variation of potential related to the incorporated phosphorous in Ga₂O₃. We believe that the lack of shallow acceptors can be mitigated by promoting Anderson disorder through the incorporation of a high level of acceptor impurities.