DARK CURRENT AND NOISE FACTOR OF STAIRCASE AVALANCHE PHOTODIODES

The dark current and the noise factor are calculated for a "staircase" avalanche photodiode allowing for thermal generation of carriers from the states at heterojunctions. When the dark current in such a photodiode is governed by thermal release from the surface states at the junctions, the noise factor of the device is less than unity and it falls on increase in the multiplication coefficient. Numerical estimates are obtained of the various components of the dark current through a photodiode made of CdxHg1-xTe. It is shown that the main source of the dark current and noise in a photodiode made of this material and characterized by a red sensitivity edge at lambda(c) less than or similar to 2 mu m is the thermal release of carriers from the surface states.