Model and data of optically controlled tunable capacitor in silicon single-photon avalanche diode

Abstract

This paper reports the photocapacitance effect of silicon-based single-photon avalanche diodes (SPADs), and the frequency scattering phenomenon of capacitance. The test results of the small-signal C-V method show that the light can cause the capacitance of the SPAD device to increase under low-frequency conditions, and the photocapacitance exhibits frequency-dependent characteristics. Since the devices are fabricated based on the standard Bipolar-CMOS-DMOS (BCD) process, this study attributes the above results to the interfacial traps formed by Si-SiO2, and the illumination could effectively reduce the interfacial trap lifetime, leading to changing the junction capacitance inside the SPAD. Accordingly, an equivalent circuit model considering the photocapacitance effect is also proposed in this paper. Accurate analysis of the capacitance characteristics of SPAD has important scientific significance and application value for studying the energy level distribution of device interface defect states and improving the interface quality.