Simulation of Dark Count in Geiger Mode Avalanche Photodiodes

Silicon avalanche photodiodes operated above breakdown, in Geiger mode, can be sensitive enough to allow single photon detection. An inherent limit to GMAPD sensitivity is the noise caused by thermally generated carriers. This noise manifests itself as extraneous counts in the absence of light and is termed the dark count. The presence of the dark count in GM-APD detectors reduces the signal to noise ratio and increases the integration times that are necessary for photon detection. A 1-Dimensional model of the dark count in GM-APD detectors was developed and dark count was found to depend predominantly on carrier generation through Shockley-Read-Hall (SRH) generation centres and secondly on thermal diffusion of minority carriers in the bulk. Simulations performed show that minimisation of the dark count is limited by bulk diffusion of minority carriers. The reduction of process induced damage minimises the dark count and allows theoretically minimum dark counts to be achieved.