Nitride-based ultraviolet Schottky barrier photodetectors with LT-AlN cap layers

We present the characteristics of novel GaN-based ultraviolet (UV) Schottky barrier photodetectors (PDs) with a low-temperature (LT-)AlN cap layer. Comparing them with conventional Schottky barrier PDs, it was found that we achieved smaller dark current and larger UV to visible rejection ratio from the PDs with the LT-AlN cap layer. The dark leakage current for the Schottky barrier PDs with the LT-AlN cap layer was shown to be about four orders of magnitude smaller than that for the conventional Schottky barrier PDs. With −5 V applied bias, the measured responsivity and UV to visible rejection ratio are 0.16 A /W and 7.74×102 for the Schottky barrier PDs with the LT-AlN cap layer, respectively. This result can be attributed to the thicker and higher potential barrier when the LT-AlN cap layer was inserted.