Patent ID: 10847563

Abstract:
A wearable system includes a stacked photodetector assembly including a first wafer including a single photon avalanche diode (SPAD), the first wafer having a thickness T1 configured to minimize absorption by the first wafer of photons included in light incident upon the first wafer while the SPAD is in a disarmed state, and a second wafer having a thickness T2 including a fast gating circuit electrically coupled to the SPAD and configured to arm and disarm the SPAD, the second wafer bonded to the first wafer in a stacked configuration. The fast gating circuit includes a capacitor configured to be charged, while the SPAD is in the disarmed state, with a bias voltage by a voltage source, and supply, while the SPAD is in an armed state, the bias voltage to the SPAD such that a voltage across the SPAD is greater than a breakdown voltage of the SPAD.