Design and Measurement of Ring-Gate Single Photon Avalanche Diode With Low Dark Count Rate

Single photon avalanche diodes (SPAD) based on avalanche effect have been widely used in the detection of extremely weak light signals. Conventional SPAD devices manufactured with silicon-based CMOS technology have a high dark count rate (DCR), making it difficult to accurately detect single photon signals. This paper proposes a low dark count rate ring-gate SPAD (RG-SPAD) to solve above problems, and compares RG-SPAD with conventional SPAD (C-SPAD) and conventional dummy-gate SPAD (CDG-SPAD). Slivaco-Technology Computer Aided Design (TCAD) performs two-dimensional simulation of the device to verify the basic principles of SPAD. Three types of SPAD device are manufactured by standard BCD process. The passive quenching circuit is built to obtain the DCR of SPAD devices. The avalanche breakdown voltages of C-SPAD, CDG-SPAD and RG-SPAD are 11.55 V, 11.85 V and 11.4 V respectively. In order to test the dark count rate of SPAD devices, an over-bias voltage of 1 V was applied to three types of SPAD device under the same size condition (temperature: 22 degrees C). The DCR of RG-SPAD (186 Hz) with ring-gate structure is significantly lower than CDG-SPAD (378 Hz) with conventional dummy-gate structure and C-SPAD (498 Hz) with conventional structure. When the room temperature dropped to 18 degrees C, RG-SPAD still maintained the lowest DCR (148 Hz) among three types of device structure.