Yellow luminescence band defect related photocurrent instability of GaN p-i-n ultraviolet photodetectors

Abstract

In this work, a low leakage current and high responsivity GaN p-i-n ultraviolet (UV) photodetector (PD) is fabricated for a photocurrent instability study. When the illumination condition shifts from dark to constant UV illumination, the PD’s photocurrent is found first to increase sharply and then go through a slow rising process until reaching its saturation value in tens of seconds. The degree of photocurrent instability lessens as UV illumination intensity increases. Meanwhile, when the PD is illuminated by periodic square-wave UV light, its transient response time is measured to be ∼1–2 μs. The observed photocurrent instability behavior is likely due to photocarrier trapping by yellow luminescence band related defects in GaN, which is supported by multiwavelength light illumination and photocurrent decay measurements.