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 capacitance–voltage method show that light can cause the capacitance of a 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 process, this study attributes the above results to the interfacial traps formed by Si–SiO2, and the illumination can effectively reduce the interfacial trap lifetime, leading to changes in 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.