Mechanisms of Low Noise and High Detectivity of p-GaN/i-ZnO/n-ZnO : Al-Heterostructured Ultraviolet Photodetectors

The i-ZnO film and n-ZnO : Al film were deposited on n-GaN layer using vapor cooling condensation system and sputter, respectively. The dark current of the resulting p-GaN/i-ZnO/n-ZnO : Al-heterostructured photodetectors was 4.11 pA. The rejection ratio between ultraviolet wavelength at 360 nm and visible wavelength at 420 nm was 3.0 103at a zero bias voltage. The low frequency noise exhibited the flicker noise (1/ f) behaviors. With a reverse bias of -5 V, the flicker noise power density was about 2.51 10-25A2, which corresponded to the high detectivity of 1.71 1011cmHz1/2W-1. The flicker noise was the dominant noise source of the photodetectors.