Real-time dark count compensation and temperature monitoring using dual SPADs on the same chip

Abstract

Dual single-photon avalanche photodiodes (SPADs) integrated on the same chip enable the effective compensation of dark count rate (DCR) in the SPAD and also the real-time monitoring of the chip temperature. In the design, two identical SPA Ds are fabricated on the same chip. one operating normally and the other one covered by a metal layer to be kept in the dark. The two SPADs are identically biased and connected to identical active quench and reset integrated circuits. As both detectors are identical in structure. the dark count is expected to be similar for both. Experimental measurements show that the two SPADs exhibit similar DCR performance over a range of bias voltages and temperatures. By measuring the DCR from the covered SPAD, the DCR from the normally operated SPAD can be accounted for directly. This can he particularly useful for SPADs, where the DCR is high. Experiments under illumination show that the shaded SPAD is immune to illumination over a wide range of incident light power. This enables the real-time monitoring of the temperature on the sensor chip using the counting rate from the dark operated avalanche photodiode (APD).