Avalanche Gain in Metal–Semiconductor–Metal Ga2O3 Solar-Blind Photodiodes

Metal–semiconductor–metal structured photodetectors based on β-Ga2O3 thin films were fabricated. Because of the high dark-resistance and considerable photoconduction, extremely uneven distribution of electric field is formed in the device under solar-blind UV light-illumination when a bias is added. Avalanche multiplication takes place in the high-field area near the electrode edges. Responsivity up to 46 A/W and the corresponding external quantum efficiency of 23 000% are observed. The photodetector shows a peak response at 248 nm, a sharp cut off edge at 262 nm (at −20 dB), and a fast response speed with a fall time of about 26.7 μs. Because of the ultralow response out of band, the rejection ratio R 254/365nm is larger than 7 orders of magnitude, where the illumination intensity at 254 and 365 nm are 0.5 and 1.2 mW/cm2, respectively.