InGaAsP avalanche photodetectors for non-gated 1.06 μm photon-counting receivers

For the detection of single photons at 1.06 pm, silicon-based single photon avalanche diodes (SPADs) used at shorter wavelengths have very low single photon detection efficiency (similar to 1-2%), while InP/InGaAs SPADs designed for telecommunications wavelengths near 1.5 mu m exhibit dark count rates that generally inhibit non-gated (free-running) operation. To bridge this "single photon detection gap" for wavelengths just beyond I pm, we have developed high performance, large area (80-200 pm diameter) InP-based InGaAsP quaternary absorber SPADs optimized for operation at 1.06 gin. We demonstrate dark count rates that are sufficiently low to allow for non-gated operation while achieving detection efficiencies far surpassing those found for Si SPADs. At a detection efficiency of 10%, 80 Pin diameter devices exhibit dark count rates below 1000 Hz and photon counting rates exceeding I MHz when operated at -40 degrees C.