Arrays of InP-based Avalanche Photodiodes for Photon Counting

Arrays of InP-based avalanche photodiodes (APDs) with InGaAsP absorber regions have been fabricated and characterized in the Geiger mode for photon-counting applications. Measurements of APDs with InGaAsP absorbers optimized for 1.06 mum wavelength show dark count rates (DCRs) <20 kHz for room-temperature operation with photon detection efficiency (PDE) up to 50% and a reset or dead time of 1s. APDs with InGaAs absorbers optimized for 1.55 μm wavelength and 240 K temperature have DCRs <20 kHz, PDE up to 45%, and a reset time of ~6 mus. Arrays for both wavelengths have been fabricated and packaged with GaP microlenses (of 100 and 50 μm pitch) and CMOS readout integrated circuits (ROICs). Comparisons are made between ROICs that operate in the framed-readout mode as well as those that operate in continuous-readout mode.