(InxGa1−x)2O3 Thin Film Based Solar‐Blind Deep UV Photodetectors with Ultra‐High Detectivity and On/Off Current Ratio

Abstract

AbstractThis work reports the fabrication of high performance solar‐blind deep‐UV photodetectors using (InxGa1−x)2O3 thin films grown on Al2O3 (0001) substrates. The In contents in (InxGa1−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 (InxGa1−x)2O3 films are tuned from 4.93 eV for Ga2O3 to 4.67 eV for (In0.2Ga0.8)2O3. Schottky‐type photodetectors based on metal−semiconductor−metal structure were fabricated. The (In0.1Ga0.9)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 (In0.1Ga0.9)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 (In0.1Ga0.9)2O3, which increases the optical absorption to generate a higher density of photocarriers, and therefore results in greater photocurrents.