Integrated readout electronics for Geiger mode avalanche photodiodes

Geiger mode avalanche photodiodes are devices that count single optical photons. Two disadvantages of these devices, afterpulsing and cross talk in arrays, would be significantly reduced if readout electronics is integrated with the avalanche photodiode. The different methods that exist for biasing the diodes are reviewed with special attention towards their application in integrated circuits. So far, these methods have only been implemented in discrete circuits. It is determined, that the active recharge method will give the best results. The compatibility issues involved with the combined integration of Geiger mode avalanche photodiodes and CMOS electronics are discussed. Combined integration presents no problems in p-well or twin well CMOS processes which use an n-type substrate. An integrated active recharge circuit is described. The basic building blocks of this circuit are a recharge transistor, a comparator with a common mode input range that includes the positive rail, and a schmitt trigger input NAND gate. Simulation results on this circuit are presented. A hybrid system, consisting of a Geiger mode avalanche photodiode, an integrated circuit realization of the comparator with the recharge transistor and a separate NAND gate was created. Measurement results on this system are presented.