Trap-Mediated Avalanche in Large-Area 1.2 kV Vertical GaN p-n Diodes

This work studies the avalanche characteristics of the 1.2 kV vertical GaN p-n diodes with implanted edge termination, based on quasi-static current-voltage ( I-V ) sweeps and unclamped inductive switching (UIS) tests. The UIS tests reveal a ~1.7 kV avalanche breakdown voltage ( $BV_{{\text {AVA}}}{)}$ , 51 A maximum avalanche current ( ${I}_{{\text {AVA}}}{)}$ , and 63 mJ maximum avalanche energy ( ${E}_{{\text {AVA}}}$ ). The ${I}_{{\text {AVA}}}$ and ${E}_{{\text {AVA}}}$ are the highest reported in high-voltage GaN power devices. A lower $BV_{{\text {AVA}}}$ is observed in the I-V curves and a trap mediated avalanche model is proposed to explain it. The $BV_{{\text {AVA}}}$ in I-V curves is believed to be induced by avalanche-assisted trap-filling in the edge termination region, while the $BV_{{\text {AVA}}}$ in the UIS test reflects the robust avalanche at the main p-n junction. These results provide important new insights on the avalanche breakdown in GaN devices and address some seemingly contrary observations of vertical GaN p-n diodes published recently.