Experimental Validation of Robust Hybrid Edge Termination Structures in Vertical GaN p-i-n Diodes with Avalanche Capability

Vertical gallium nitride (GaN) p-i-n diodes with a planar hybrid edge termination (HET) experimentally demonstrate avalanche capability. The HET consists of a nitrogen ion implanted, single-zone junction termination extension (JTE) modulated by rings of increased implant depth/dose for higher breakdown voltage (BV), process latitude, and robustness. Structures with only isolation implantation (ISO), JTE, and variations in the HET were investigated. The BV of ISO/JTE structures increased from 928 V/1039 V to 1383 V by implementing the HET design. Increasing the number of modulation rings monotonically increases the BV, thereby validating computational models and providing straightforward process modifications for highly efficient termination. Increasing temperature increases BV, verifying avalanche breakdown in the diodes. Electroluminescence (EL) measurements show the location of emission varies with device structure. Technology computer aided design (TCAD) simulation accurately modeled the significant increase in breakdown strength for the HET design, and furthermore, the location of the simulated peak electric field replicated the observed EL signature. The HET approach offers a solution for dramatic improvements in breakdown strength with minimal added complexity to device processing and fabrication while simultaneously widening process latitudes and robustness for GaN devices.