Large Active Area AlGaN Solar-Blind Schottky Avalanche Photodiodes with High Multiplication Gain

We report the fabrication and performance of solar-blind AlGaN Schottky avalanche photodiodes grown on sapphire substrates. An increased active donor density is found near the surface, leading to an enhanced electric field adjacent to the Schottky electrode. Multiplication gain over 2000 has been achieved in the fabricated devices with a mesa diameter of 200 μm. The measured dark I–V curves at different temperatures show strong temperature dependence, suggesting that the gain mechanism in our devices is primarily due to impact ionization. Peak responsivity of 66.3 mA/W is obtained at 260 nm and at zero bias, corresponding to an external quantum efficiency of 31.6%.