High-Detectivity GaN MSM Photodetectors with Low-Temperature GaN Cap Layers and Ir∕Pt Contact Electrodes

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GaN-based metal-semiconductor-metal (MSM) UV photodetectors (PDs) with a low-temperature (LT) GaN cap layer and Ir/Pt contact electrodes were fabricated. Compared with the conventional Ni/Au contacts, we found that Ir/Pt contacts can reduce the dark current. Further, a smaller dark current and larger UV-to-visible rejection ratio obtained from the PD with LT GaN cap layer and Ir/Pt contact electrodes were determined. Furthermore, the noise equivalent power and detectivity (D*) were respectively obtained as 2.75 X 10 -13 W and 1.76 X 10 12 cm Hz 0.5 W -1 for the aforementioned PDs.