Optimization of Guard Ring Structures for Superior Dark Current Reduction and Improved Quantum Efficiency in InGaAs/InP APDs

Avalanche photodiodes (APDs) based on InGaAs/InP are pivotal for applications in low-light detection, yet their performance is often hindered by edge breakdown and high dark currents. This study systematically optimizes guard ring structures to address these challenges, focusing on attached guard rings (AGRs) and floating guard rings (FGRs) through a synergistic approach combining simulation-guided design, fabrication, and experimental validation. We analyze the impact of Zn diffusion depth, AGR/FGR geometries, and electric field distribution on device performance. Experimental results demonstrate that optimized AGR structures reduce dark currents by 70% and enhance quantum efficiency (QE) by 43%, while FGR structures achieve an order-of-magnitude reduction in dark current and a 90% QE improvement compared to non-guarded devices. The breakdown voltage increases by 2.5 V (AGR) and 4 V (FGR), leading to enhanced gain. These advancements highlight the critical role of guard ring optimization in effectively mitigating edge breakdown, offering a pathway to high-sensitivity InGaAs/InP APDs for photon detection technologies.