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 ~1.7kV avalanche breakdown voltage (BV
_AVA
), 51 A maximum avalanche current (I
_AVA
), and 63 mJ maximum avalanche energy (E
_AVA
). The I
_AVA
and E
_AVA
are the highest reported in high-voltage GaN power devices. A lower BV
_AVA
is observed in the I-V curves and a trap mediated avalanche model is proposed to explain it. The BV
_AVA
in I-V curves is believed to be induced by avalanche-assisted trap-filling in the edge termination region, while the BV
_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.