High-Sensitivity Silicon Avalanche Photodiodes through Edge Electric-Field Management

Abstract Traditional avalanche photodiodes (APDs) typically necessitate a compromise between the gain and dark current to achieve high sensitivity. In this work, we report an edge electric-field management strategy based on a virtual guard ring structure that simultaneously suppresses dark current and enhances gain. By adjusting the lateral spacing between the p-well multiplication region and the p-epi absorption region, the electric field profile at the edge of the virtual guard ring can be precisely tailored. Simulations were also performed to evaluate the influence of different lateral spacings on the electric field distribution and detector sensitivity. APDs with various lateral spacings were fabricated using a standard complementary metal–oxide–semiconductor (CMOS) process. Experimental results show that the device achieves an optimal balance between gain and noise at a lateral spacing of 26 μm, delivering a noise equivalent power (NEP) of 1.13 × 10–14 W·Hz-1/2, a responsivity of 21.7 A/W, and a specific detectivity (D*) of 2.63 × 1013 Jones. These findings demonstrate that the edge electric-field management strategy provides a pathway toward high-sensitivity APDs, enabling improved detection capabilities for low-light environments.