Linear- and Geiger-Mode Characteristics of Al0.8Ga0.2As Avalanche Photodiodes

We report Al
_0.8
Ga
_0.2
As avalanche photodiodes with low dark current and low excess noise. In linear mode when biased to a photocurrent gain of 200, a 150-μm diameter device exhibits dark current of 32 pA (180 nA/cm
²
). The external quantum efficiency is 31% at 490 nm and the excess noise factor corresponds to k ~ 0.15. In Geiger mode operation, low dark count probability of 10-5 at room temperature is reported.