Arrays of 128x32 InP-based Geiger-mode avalanche photodiodes

Arrays of InP-based avalanche photodiodes operating at 1.06-µm wavelength in the Geiger mode have been fabricated in the 128x32 format. The arrays have been hermetically packaged with precision-aligned lenslet arrays, bump-bonded read-out integrated circuits, and thermoelectric coolers. With the array cooled to -20C and voltage biased so that optical cross-talk is small, the median photon detection efficiency is 23-25% and the median dark count rate is 2 kHz. With slightly higher voltage overbias, optical cross-talk increases but the photon detection efficiency increases to almost 30%. These values of photon detection efficiency include the optical coupling losses of the microlens array and package window