  We present an InGaAs/InP avalanche photodiode with an active quenching
circuit on an ASIC (application specific integrated circuit) that is capable of
operating in both gated and free-running modes. The 1.6mm2 ASIC chip is
fabricated using CMOS (complementary metal oxide semiconductor) technology
guaranteeing long-term stability, reliability and compactness. In the
free-running mode we find a single photon detection efficiency of 10% with
<2kHz of noise.
