Low-noise and high-detectivity GaN UV photodiodes with a low-temperature AlN cap layer

Here, we present the characteristics of a novel GaNbased ultraviolet (UV) photodiode (PD) with a low-temperature (LT) AlN cap layer. The dark leakage current for the PD with the LT-AlN cap layer was shown to be about four orders of magnitude smaller than that for the conventional PDs. It was found that we could achieve larger UV to visible rejection ratio by inserting an LT-AlN cap layer. It was also found that we could improve minimum noise equivalent power and maximum normalized detectivity of the PD by inserting an LT-AlN cap layer.