Novel Silicon Epitaxy-Based Avalanche Photodetectors With Parameter-Sensitivity Engineering for Enhanced Fabrication Robustness

Avalanche photodetectors (APDs) are prized for their high gain, fast response, excellent sensitivity, and cost-effectiveness. However, the conventional fabrication methods that rely on complex and expensive high-energy ion implantation introduce lattice defects, leading to increased dark current. This study presents a novel silicon epitaxy-based APD structure and fabrication approach that employs thin silicon epitaxy combined with low-energy ion implantation to form the multiplication region. This method avoids the need for expensive high-energy ion implantation equipment. The prototype for the first trial achieved a 20 V breakdown voltage ( $V_{b}$ ), 0.43 A/W responsivity (830 nm, ${M} =1$ ), and 64% quantum efficiency (QE). Secondary ion mass spectrometry (SIMS) analysis and simulations revealed that deviations in p-well junction depth and variations in doping concentration significantly affect both breakdown voltage and gain characteristics. To mitigate the sensitivity of implantation fluctuations, the study proposes a structural optimization approach focusing on lower p-well doping concentrations and deeper junction depths. Simulation results indicate that this structure can achieve a p-well junction depth variation of $0.7~\mu $ m, corresponding to a breakdown voltage variation within 100 V, while maintaining a high gain. Combined with a silicon epitaxy-based fabrication process, this approach significantly enhances the robustness of APD fabrication. By adjusting the p-well ion implantation energy, APDs with breakdown voltages of 90, 125, and 175 V were successfully achieved.