Technical Field
The present application is generally related to single photon avalanche diode (SPAD) sensors, and in particular, but not exclusively to, SPAD arrays for time-of-flight (TOF) image sensing.
Description of the Related Art
Single Photon Avalanche Diodes (SPADs) are semiconductor photon detection devices based on a p-n junction reverse-biased at a voltage that exceeds a breakdown voltage VB of the junction. At this bias, the electric field is so high that a single charge carrier injected into the depletion layer can trigger a self-sustaining avalanche. The current rises swiftly to a steady level. If the primary carrier is photo-generated, the leading edge of the avalanche pulse marks the arrival time of the detected photon. The current continues until the avalanche is quenched by lowering the bias voltage until the current ceases. In order to detect another photon, the bias voltage must be raised again above breakdown.
SPAD arrays can provide single-photon imaging, which is useful in a variety of applications. However, such arrays typically require readout and enable circuitry, and corresponding signal paths, which may be a limiting factor in the overall size or number of SPADs in such arrays.