Doping Concentration Influenced Pyro-Phototronic Effect in Self-Powered Photodetector Based on Ga-Incorporated ZnO Microwire/p~+-GaN Heterojunction

摘要

Pyro-phototronic effect, a coupling of pyroelectric and photovoltaic effect, provides an effective method to improve the performance of self-powered photodetectors (PDs). Developing high-performance PDs, the influence of pyroelectric effect on photoelectric characteristics and coupling mechanism deserves further study. Herein, a self-powered PD made of Ga-incorporated ZnO microwire (ZnO:Ga MW) and p(+)-GaN layer is fabricated, and the performance influenced by pyro-phototronic effect is investigated systematically. Through varying Ga concentration in ZnO:Ga MWs, the pyroelectric current gradually dominates the photocurrent of PDs under ultraviolet illumination; while the photovoltaic current deteriorates rapidly. The enhanced pyroelectric responsivity can compensate the decreased photovoltaic responsivity, maintaining their high total responsivities (5 mA W-1) under self-biased conditions. Furthermore, the decay time of pyroelectric current, representing the duration of pyroelectric effect, decreases markedly from 0.313 to 0.044 s by increasing Ga concentration. Associated with theoretical analysis, incorporating Ga dopant can not only increase the rate of photogenerated temperature variation, but also narrow depletion layer at ZnO:Ga/GaN heterojunction. Besides, the temperature variation can lead to a significant reduction of decay time. These findings give a deeper insight into the influence of pyroelectric effect on photoresponse and its coupling mechanism, providing a scheme to develop high-performance self-powered PDs.