Trap-Mediated Avalanche in Large-Area 1.2 kV Vertical GaN p-n Diodes
Jingcun Liu, Ming Xiao, Ruizhe Zhang, Subhash Pidaparthi, Cliff Drowley, Lek Baubutr, Andrew Edwards, Hao Cui, Charles Coles, Yuhao Zhang
Abstract
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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVA</sub> ), 51 A maximum avalanche current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVA</sub> ), and 63 mJ maximum avalanche energy (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVA</sub> ). The I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVA</sub> and E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVA</sub> are the highest reported in high-voltage GaN power devices. A lower BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVA</sub> is observed in the I-V curves and a trap mediated avalanche model is proposed to explain it. The BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVA</sub> in I-V curves is believed to be induced by avalanche-assisted trap-filling in the edge termination region, while the BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVA</sub> 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.