High-performance solar-blind Al_0.6Ga_0.4N/Al_0.5Ga_0.5N MSM type photodetector

An Al_0.6Ga_0.4N/Al_0.5Ga_0.5N metal–semiconductor–metal (MSM) deep-ultraviolet (DUV) photodetector was developed. It possesses both high photosensitivity and high rejection ratios in comparison to photomultiplier tubes (PMTs). The photodetector was designed to have a two-dimensional electron gas layer at the Al_0.6Ga_0.4N/Al_0.5Ga_0.5N hetero-interface, which plays an important role in increasing the photosensitivity. Additionally, for reducing the dark current, a V/Al/Mo/Au electrode was employed as a Schottky electrode with an appropriate barrier height. Upon irradiation with 10 μW/cm², an extremely low dark current (10⁻¹¹A) and high photocurrent (5 × 10⁻⁵A) were achieved at a bias voltage of 5 V. The photodetector was true solar-blind with a cut-off wavelength of 280 nm. A high photosensitivity of 10⁶ A/W and a rejection ratio of 10⁶ were realized under the irradiation of 10 nW/cm² DUV photons. The present results revealed that the AlGaN/AlGaN MSM DUV photodetector is one of the most suitable candidates for an all solid-state photodetector with a performance superior to PMTs.