Afterpulsing suppression in 4H-SiC avalanche photodiodes by sub-bandgap photoexcitation

Dark counts in silicon carbide avalanche photodiodes (SiC APDs) significantly limit their signal-to-noise ratio and overall performance, with afterpulsing being a major contributing factor. However, the specific correlation mechanisms between afterpulsing and trap states in SiC remain unclear, posing challenges for effective suppression. This work elucidates the influence mechanisms of shallow-level and deep-level traps on the temporal characteristics of afterpulsing in 4H-SiC APD. Based on these findings, we develop an innovative sub-bandgap optical excitation method that facilitates rapid carrier release from trap states, effectively reducing afterpulsing. This approach achieves a 37% reduction in afterpulsing probability without increasing the primary dark count rate. The proposed technique optimizes overall device performance by reducing dark count rate by 22% while maintaining high photon detection efficiency of 29% at 285 nm, ultimately improving the signal-to-noise ratio of the APDs.