Surge Current and Avalanche Ruggedness of 1.2 kV Vertical GaN p-n Diodes

This letter reports the avalanche and surge current ruggedness of the industry's first 1.2-kV-class vertical GaN p-n diodes fabricated on 100-mm GaN substrates. The 1.2-kV vertical GaN p-n diodes with a 1.39-mm2 device area and an avalanche breakdown voltage of 1589 V show a critical avalanche energy density of 7.6 J/cm2 in unclamped inductive switching tests, as well as a critical surge current of 54 A and a critical surge energy density of 180 J/cm2 in 10-ms surge current tests. All these values are the highest reported in vertical GaN devices and comparable to those of commercial SiC p-n diodes and merged p-n Schottky diodes. These GaN p-n diodes show significantly smaller reverse recovery compared to SiC p-n diodes, revealing less conductivity modulation in n-GaN. The negative temperature coefficient of differential on-resistance and the anti-clockwise surge I-V locus are believed to be due to the increased acceptor ionization in p-GaN and the decreased contact resistance at high temperatures. These results suggest the high ruggedness of GaN p-n junctions with fast switching capabilities. As the first electrothermal ruggedness data for industry's vertical GaN devices, these results provide key new insights for their development and application spaces.