(In_xGa_1−x)₂O₃ Thin Film Based Solar‐Blind Deep UV Photodetectors with Ultra‐High Detectivity and On/Off Current Ratio

Abstract This work reports the fabrication of high performance solar‐blind deep‐UV photodetectors using (In_xGa_1−x)₂O₃ thin films grown on Al₂O₃ (0001) substrates. The In contents in (In_xGa_1−x)₂O₃ are controlled at x = 0, 0.1 and 0.2, whereas a higher In content leads to phase segregation of Ga₂O₃ and In₂O₃. The bandgaps of (In_xGa_1−x)₂O₃ films are tuned from 4.93 eV for Ga₂O₃ to 4.67 eV for (In_0.2Ga_0.8)₂O₃. Schottky‐type photodetectors based on metal−semiconductor−metal structure were fabricated. The (In_0.1Ga_0.9)₂O₃ photodetector is highly sensitive to solar‐blind UV spectrum and achieves a large on/off current ratio of over 10⁸, a remarkable specific detectivity of 4.5 × 10¹⁶ Jones with a prominent responsivity of 23.3 A W⁻¹. Such enhanced performance compared to Ga₂O₃ is associated with In modulated optical and electronic properties. High‐resolution X‐ray photoemission spectroscopy was used to study the interfacial electronic structure at the semiconductor−metal interface. A large Schottky barrier height of 1.31 eV was found for (In_0.1Ga_0.9)₂O₃ devices, accounting for the low dark current. More importantly, the incorporation of In introduces In 4d states hybridizing with O 2p at top of the valence band of (In_0.1Ga_0.9)₂O₃, which increases the optical absorption to generate a higher density of photocarriers, and therefore results in greater photocurrents.