Performance of Waveguide-Integrated SPAD With a CMOS Fast Gating Circuit

A monolithically SiN-waveguide-integrated silicon single-photon avalanche diode (SPAD) for application in a photonic quantum simulator is presented. An array of SPADs was connected to a 9-channel gating circuit using wire bonding. The gating circuits, fabricated in 0.18 μ m CMOS, exploit double cascoded quenching and resetting switches to obtain 9.9 V gating pulses. Characterization at room temperature and with 635 nm light showed an intrinsic photon detection probability under direct illumination from 65 % to 75 % at 9.5 V excess bias voltage and a dark count rate between 10 and 100 counts/s at 7.5 V excess bias voltage and 40 MHz gating frequency. The estimated total waveguide-coupled photon detection probability is about 56 %. The afterpulsing probability was 0.24 % at 20 MHz gating frequency and 7.5 V excess bias. Rise and fall times of 160 ps and 215 ps, respectively, of the 9.9 V gating pulses were measured with a picoprobe. A minimum gating pulse width of 0.83 ns was achieved at a pulse height of 8.0 V.