InGaN/GaN multiquantum-well metal-semiconductor-metal photodetectors with beta-Ga₂O₃ cap layerslayers

InGaN/GaN multiquantum-well (MQW) metalsemiconductor- metal photodetectors with a beta-Ga₂O₃ cap layer formed by the furnace oxidation of a GaN epitaxial layer are fabricated and characterized. The beta-Ga₂O₃ cap layer is found to suppress the reverse leakage current by at least about two orders of magnitude with a 5-V applied bias because it creates a thicker and higher potential barrier. The reverse leakage current can be further reduced and a 90-fold larger ultraviolet-to- visible rejection ratio can be achieved by using InGaN/GaN MQW layers, which confine the electron-hole pairs generated by lower-energy photons. In addition, the noise level is reduced and detectivity is increased. With a 5-V applied bias, the noise-equivalent power and normalized detectivity are 8.4×10^-13 W and 7.9×10¹² cm Hz^0.5 W^-1, respectively.