Planar Implantation Edge Termination for Vertical GaN Power Devices

Edge termination plays a crucial role in achieving near-ideal avalanche breakdown in power semiconductor devices. In this paper, two edge termination designs, one GR (guard ring) [1], the other USAB-JTE (ultra-small-angle bevel junction termination extension) [2] that utilize planar ion implantation are developed and studied. The fabrication process only has a single implantation step that does not need precise control over the depth. Isolation is also done by the same process, avoiding the need of etching and possible etch-induced damages to the devices. Comprehensive characterization, including static I-V test and avalanche circuit test are conducted to confirm the avalanche breakdown capability of both devices. It is found both the GR design and the JTE design achieved an efficiency over 83% and a positive temperature coefficient of breakdown voltage, suggesting avalanche breakdown capability. The JTE design specifically shows robust avalanche breakdown behavior to pass high avalanche current under UIS (unclamped inductive switching) test. Finally, a comprehensive comparison between these two designs and other vertical GaN device edge terminations is performed, showing that these two designs are promising as the building blocks for vertical GaN devices.