Optimization of Step-Etched Junction Termination Extensions for Vertical GaN Devices

This work provides the first demonstration of a multipoint fit from theory to experiment for step-etched junction terminations on vertical gallium nitride (GaN) devices. Viable edge termination methods in GaN are limited due to challenges with selective-area doping. We report on a study that determines the optimal charge in the junction termination extension (JTE) of a GaN-based p-n diode to aid in the design of multizone JTEs. Experimental results show a step-thickness offset compared to theoretical prediction, which is attributed to plasma-induced etch damage, as well as variation in passivation-related charge, surface charge, and doping profile variations. Results are supported by electroluminescence imaging, which confirms the match from theory to experiment.