Ge–Si separate absorption and multiplication avalanche photodiode for Geiger mode single photon detection

Abstract

A Ge–Si separate absorption and multiplication avalanche photodiode (SAM-APD) is reported. The structure is grown using a low temperature in situ clean and epitaxy process, Tinsitu and Tepitaxy<∼460°C, resulting in a Ge layer with a dislocation density of ∼5×1010cm−2. The SAM-APD has a responsivity of 3.2×10−4A∕W (1310nm) and a dark current density at punch-through of 0.2mA∕cm2. In Geiger mode (GM) at 206K, the dark count rates (DCRs) are ∼280kHz, which is within an order of magnitude of DCR reported for InGaAs∕InP GM APDs despite the high defect density in the Ge.