Back-illuminated separate absorption and multiplication AlGaN solar-blind avalanche photodiodes

This letter reports the fabrication and performance of back-illuminated separate absorption and multiplication AlGaN solar-blind avalanche photodiodes. Devices with a 60-μm-diameter active area and a double-mesa structure exhibit a low dark current density of 1.06 × 10−8 A/cm2 at the reverse bias of 20 V and a maximum multiplication gain up to 3000 at the reverse bias of 91 V. The temperature dependence of avalanche voltage shows a large positive temperature coefficient of 0.05 V/K, confirming that avalanche multiplication is the dominant gain mechanism in the photodiodes.