Inserting an i-ZnO layer to increase the performance of p-Si/n-ZnO heterojunction photodetectors

By inserting an intrinsic-zinc oxide (i-ZnO) layer into conventional p-Si/n-ZnO (p-n) heterojunction photodetectors (HPDs), the structure of p-Si/i-ZnO/n-ZnO (p-i-n) was prepared. It is evident that the i-ZnO layer could effectively reduce leakage current by about three orders, which leads to rectification ratio increasing from 70 to 6.6×104 for p-n and p-i-n HPDs, respectively, at +2 V bias-voltage. With bias-voltages, the responsivity of p-n HPDs shows less variation. In contrast, the p-i-n HPDs demonstrate a greatly increasing in ultraviolet (UV) response. Such a result causes the UV (350 nm)-to-visible (550 nm) rejection ratio is enhanced from 14.1 to 39.7 for p-n and p-i-n HPDs, respectively. The UV response of p-i-n HPDs is roughly proportional to bias-voltages, however the p-n HPDs has less responsivity dependence on bias-voltages. Related mechanisms are studied here.