Performance optimization of self-powered ultraviolet and short-wavelength blue photodetectors based on ZnO/SrTiO3 heterojunctions by annealing treatment

Abstract

In this study, self-powered photodetectors (PDs) sensitive to ultraviolet (UV) and short-wavelength blue (SWB) light were developed using a ZnO/SrTiO₃ heterojunction, created through the magnetron sputtering technique. The photoresponse of the ZnO/SrTiO₃ PDs showed significant enhancement following an annealing process. Post-annealing, the response (R) value of the ZnO/SrTiO₃ PDs was recorded at 0.7 mA W⁻¹, indicating an increase of 3.5 times compared to the pre-annealed state. Additionally, the rejection ratio between 390 nm and 450 nm (R₃₉₀ nm/R₄₅₀ nm) improved markedly from 6.21 to 38.16, demonstrating enhanced UV-SWB spectral discrimination. The rise and decay times for the annealed devices were measured at 35 μs and 3.5 ms, respectively. The observed enhancements in the performance of ZnO/SrTiO₃ PDs are primarily attributed to the improved crystal quality of ZnO and the optimized intrinsic defect structures within the ZnO films due to annealing. This led to a strengthened internal electric field, facilitating the efficient separation and movement of photogenerated charge carriers. The outcomes of this study offer significant insights for the design and production of self-powered UV-SWB photodetectors.