Performance enhancement of a p-Si/n-ZnGa2O4 heterojunction solar-blind UV photodetector through interface engineering

Abstract

Interface engineering is an effective way to improve the performance of heterojunction photodetectors (PDs). We have constructed p-Si/n-ZnGa₂O₄ heterojunction solar-blind ultraviolet (UV) PDs with and without an SiO₂ interfacial layer and studied the effect of the SiO₂ interfacial layer on device performance in detail. At −1 V bias, the dark current of the device from 3.8 × 10⁻⁸ A to 5.7 × 10⁻¹² A was greatly reduced, specifically 6.7 × 10³ fold, attributed to the high barrier induced by the insertion of the SiO₂ interfacial layer. With the introduction of the SiO₂ interfacial layer, the photo-to-dark current ratio and the detectivity of the device were greatly improved due to the substantial reduction of dark current. Owing to the insertion of the SiO₂ layer reducing the carrier trapping at the interface defects, the rise and decay times of the device were significantly reduced from 0.96 s/0.88 s to 0.12 s/0.08 s, i.e. 8 fold and 11 fold, respectively. Moreover, the large conduction band offset of Si/SiO₂ could effectively block visible-light-generated electrons in Si, thereby suppressing the visible-light response and enhancing the UV-visible rejection ratio of the Si/SiO₂/ZnGa₂O₄ PD. Our work has provided a feasible approach for enhancing the performance of Si/wide-bandgap semiconductor heterojunction solar-blind UV PDs.