Enhancing the responsivity of UV to visible by inserting a SiO2 layer between p-Si and i-ZnO for the heterojunction photodiode with p-Si/SiO2/i-ZnO/n-ZnO structure

Silicon dioxide (SiO₂) was inserted between p-Si and intrinsic zinc-oxide (i-ZnO) to improve the photo responsivity of p-i-n heterojunction photodiodes (HPDs) with a structure of p-Si/SiO₂/i-ZnO/n-ZnO. The i-ZnO and n-ZnO layers were grown on the p-Si substrate by radio-frequency (RF) magnetron sputtering system. Observations found that the p-i-n HPDs with SiO₂ insertion can reduce the leakage current and hence increase the rectification ratio from 12.8 to 8.7×10³ at ± 2 V. The insertion of SiO₂ also decreases visible response and enhance ultraviolet (UV) response, resulting in a higher ratio of UV to visible.