A self-powered and broadband UV PIN photodiode employing a NiOx layer and a -Ga₂O₃ heterojunction

Crucial commercial and space applications require the detection of broadband ultraviolet (UV) rays spanning from UV-A to UV-C. In this study, the authors demonstrate a broadband UV photodetector employing a p-type NiOx layer and an n-type beta-Ga2O3 heterostructure in PIN configuration for the first time. Simulations are conducted to optimize the doping concentration and thickness of the NiOx layer, ensuring that (a) a reasonable depletion width is maintained within the NiOx layer for UV-A and UV-B light absorption; (b) anode ohmic contacts are formed on the nondepleted NiOx film, and (c) > 70% of the UV-C light is absorbed by beta-Ga2O3. The optimized NiOx/beta-Ga2O3 PIN photodiode exhibits good responsivity to incident light wavelengths in the UV-A, UV-B, and UV-C regions. While the NiOx layer is considered to be responsible for providing good photoresponsivity in the UV-A and UV-B regions, a highly resistive (near-intrinsic) beta-Ga2O3 layer is required for the absorption of incident UV-C light. A record detectivity of > 10(11) cm Hz(0.5) W-1 for the UV-B and UV-C regions and > 10(10) cm Hz(0.5) W-1 for the UV-A region is observed in the NiOx/beta-Ga2O3 heterostructure PIN photodiode during the self-powered operation. The results presented in this study are promising and instigate device design strategies for (ultra)wide bandgap semiconductor-based broadband UV PIN photodetectors.