Hgcdte Saphira Arrays: Individual Pixel Measurement Of Charge Gain And Node Capacitance Utilizing A Stable Ir Led

We have relayed an extremely stable 1.7 mu m LED through a cryogenic integrating sphere to uniformly illuminate Leonardo SAPHIRA 320x256 arrays. This has enabled us to determine parameters such as charge gain, voltage gain, and node capacitance as a function of avalanche gain for individual pixels in a centered 64 x 64 pixel sub-array, and our results are reported here. We collected multiple sequences of one hundred 320-frame ramps over a variety of timescales and used them for several analyses. These measurements demonstrate that the intensity of the IR LED source is linear with current and stable to 0.1% over periods of an hour and from day to day, while the data cubes additionally allow determination of charge gain (in e(-)/ADU for each pixel. We have separately determined voltage gain (in mu V/ADU), and together these yield node capacitance for each pixel. We have repeated these measurements at bias voltages ranging from 1 V (corresponding to unity gain, i.e. negligible avalanche gain) to 10.5 V (corresponding to an avalanche gain of 12.43 and the full onset of tunnel-tunnel current). These measurements are used to determine avalanche gain as a function of avalanche bias voltage, which becomes critical at bias voltages up to 10.5 V bias as dark current is low and junction capacitance varies.