The self-powered photodetector of n-Si/n-ZnO heterojunction with enhanced temperature adaptability via transient current response

Abstract

Self-powered photodetectors (PDs) have great application potential in distributed sensor networks, imaging systems and Internet of Things (IoT) due to their simple structure and long-term mobile detection without external power supply. However, the steady-state current response of PD decreases sharply with the increase of temperature, which restricts its application in high temperature environment. Here, a self-powered PD of n-Si/n-ZnO heterojunction with transient current response has been prepared, and the current generation mechanism and response characteristics under various temperature have been studied as being excited by periodic light pulses. The results show that the transient current response can not only improve the photocurrent responsivity and specific detectivity of PD, but also improve the performance of PD at high temperature. When the temperature rises to 340 K, the transient current holding factor η t (η t′) of device excited by 127 μW cm−2, 365 nm light are increased by 115% (315%) compared with steady state current holding factor η s. The corresponding transient current enhancement factor α tt′ (α t′) of PD increase monotonically with the temperature, and the maximum values α tt′ (α t′) of PD excited by 365 nm light are 12.5 (5.0). As the temperature increases, the t r and t f of PD excited by 365 nm (287 μW cm−2) light decrease from 0.16 and 0.15 ms to 0.11 and 0.11 ms, respectively. The transient current response is caused by the transport of excess photo-generated carriers in the PD at the moment of light on and off. The transient current increases significantly with decrease resistance and is less affected by decreasing built-in electric field that make PD has high holding factor under high temperature conditions. This work provides a new avenue for designing high-performance self-powered PDs capable of operating in higher temperature environments, and promotes the wide application of transient-response self-powered PDs in the fields of IoT, fast detecting, and imaging.