Low dark current GaN p-i-n photodetectors with a low-temperature AlN interlayer

GaN p-i-n ultraviolet (UV) photodetectors (PDs) with a low-temperature (LT)-AlN interlayer were proposed and fabricated. It was found that the dark current of such detectors is as small as 28pA even at a high reverse bias of 40 V. Although the high potential barrier at the AlN-GaN interface would slightly reduce the responsivity of PD under low reverse biases, the high UV-to-visible rejection ratio of the PD with an LT-AlN interlayer could be achieved under high reverse biases due to its very lowdark current. The rejection ratio of the PD with the LT-AlN interlayer is as large as 735 at the reverse bias of 40 V.