Avalanche multiplication in AlGaN-based heterostructures for the ultraviolet spectral range

Al(x)Ga(1-x)N based avalanche photodiodes grown on sapphire substrate with Al-contents of x=0.65 and x=0.60 have been examined under back- and frontside illumination with respect to their avalanche gain properties. The photodetectors suitable for the solar-blind ultraviolet spectral regime show avalanche gain for voltages in excess of 30V reverse bias in the linear gain mode. Devices with a mesa diameter of 100 lm exhibit stable avalanche gain below the break through threshold voltage, exceeding a multiplication gain of 5500 at 84V reverse bias. A dark current below 1 pA can be found for reverse voltages up to 60 V.