A Near-Infrared Single-Photon Detector for Direct Time-of-Flight Measurement Using Time-to-Amplitude-Digital Hybrid Conversion Method

A near-infrared (NIR) single-photon detector for direct time-of-flight (dTOF) measurement is proposed based on 0.18 ~\mu \text{m} BCD technology. The integrated single-photon avalanche diode (SPAD) adopts a high-voltage p-well (HVPW)/high-voltage buried n+ (HVBN) layer as a deep-junction multiplication region to significantly enhance the NIR photon detection probability (PDP). Meanwhile, a virtual guard ring formed by the low doping p-type epitaxial layer is used to effectively minimize dark count noise. In particular, a compact time-to-amplitude converter (TAC) combined with an asynchronous counter is employed to realize a time-to-amplitude-digital hybrid conversion for gaining higher time resolution and larger dynamic range, simultaneously. The experimental results demonstrate that at 5 V excess bias voltage, the NIR PDP at 905 nm wavelength is up to 7.9%, and the dark count rate (DCR) is below 10 Hz at room temperature. Furthermore, the detector obtains a time resolution of 39 ps and a time full-scale range (FSR) of 2.56 ~\mu \text{s} , with a differential nonlinearity (DNL) and integral nonlinearity (INL) less than ±1 LSB, respectively. The proposed single-photon dTOF detector exhibits the significant advantages of high sensitivity, low noise, high time resolution, and large FSR, which is very fit for low-cost and high-precision dTOF measurement systems.