Differential Resistance Lowering Effect in High-Speed Ge Photodetectors During Nanosecond ESD Events

An electrothermally induced resistance modulation in advanced high-speed Ge photodetectors under nanosecond electrostatic discharge (ESD) events is investigated through measurements and physics-based models. By employing a very-fast transmission line pulsing (VF-TLP) test system, the measured I-V characteristics reveal that the differential resistance-lowering (DRL) effect is triggered under a 1-ns pulse duration, consistent with temperature-dependent intrinsic carrier density behavior and TCAD simulation results. Among the evaluated devices, the vertical Ge photodetector (VPIN) exhibits the most pronounced DRL behavior, attributed to its device geometry. Understanding these mechanisms can help improve ESD robustness and enhance the reliability of next-generation high-speed silicon photonic technologies.