Design, Fabrication, and Verification of Blue-Extended Single-Photon Avalanche Diode with Low Dark Count Rate and High Photon Detection Efficiency

Single-photon avalanche diodes (SPADs) can detect extremely weak optical signals and are mostly used in single-photon imaging, quantum communication, medical detection, and other fields. In this paper, a low dark count rate (DCR) single-photon avalanche diode device is designed based on the 180 nm standard BCD process. The device has a good response in the 450~750 nm spectral range. The active area of the device adopts a P+/N-Well structure with a diameter of 20 µm. The low-doped N-Well increases the thickness of the depletion region and can effectively improve the detection sensitivity; the P-Well acts as a guard ring to prevent premature breakdown of the PN junction edge; the isolation effect of the deep N-Well reduces the noise coupling of the substrate. Use the TCAD simulation tool to verify the SPAD’s basic principles. The experimental test results show that the avalanche breakdown voltage of the device is 11.7 V. The dark count rate is only 123 Hz when the over-bias voltage is 1 V, and the peak photon detection efficiency (PDE) reaches 37.5% at the wavelength of 500 nm under the 0.5 V over-bias voltage. PDE exceeds 30% in the range of 460~640 nm spectral range, which has a good response in the blue band. The SPAD device provides certain design ideas for the research of fluorescence detectors.