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-mu m-diameter active area and a double-mesa structure exhibit a low dark current density of 1.06 x 10(-8) A/cm(2) 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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772984]