(In<i><sub>x</sub></i>Ga<sub>1−</sub><i><sub>x</sub></i>)<sub>2</sub>O<sub>3</sub> Thin Film Based Solar‐Blind Deep UV Photodetectors with Ultra‐High Detectivity and On/Off Current Ratio
Wen-Shan Chen, Xiangyu Xu, Jiaye Zhang, Jiaye Zhang, Jueli Shi, Jiawei Zhang, Jiawei Zhang, Wen‐Cheng Chen, Qijin Cheng, Yuzheng Guo, Kelvin H. L. Zhang
Abstract
Abstract This work reports the fabrication of high performance solar‐blind deep‐UV photodetectors using (In x Ga 1 − x ) 2 O 3 thin films grown on Al 2 O 3 (0001) substrates. The In contents in (In x Ga 1 − x ) 2 O 3 are controlled at x = 0, 0.1 and 0.2, whereas a higher In content leads to phase segregation of Ga 2 O 3 and In 2 O 3 . The bandgaps of (In x Ga 1 − x ) 2 O 3 films are tuned from 4.93 eV for Ga 2 O 3 to 4.67 eV for (In 0.2 Ga 0.8 ) 2 O 3 . Schottky‐type photodetectors based on metal−semiconductor−metal structure were fabricated. The (In 0.1 Ga 0.9 ) 2 O 3 photodetector is highly sensitive to solar‐blind UV spectrum and achieves a large on/off current ratio of over 10 8 , a remarkable specific detectivity of 4.5 × 10 16 Jones with a prominent responsivity of 23.3 A W − 1 . Such enhanced performance compared to Ga 2 O 3 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 0.1 Ga 0.9 ) 2 O 3 devices, accounting for the low dark current. More importantly, the incorporation of In introduces In 4 d states hybridizing with O 2 p at top of the valence band of (In 0.1 Ga 0.9 ) 2 O 3 , which increases the optical absorption to generate a higher density of photocarriers, and therefore results in greater photocurrents.