Self-Protection Mechanism of Schottky-Type p-GaN Gate HEMTs Under Forward Gate ESD Stress

The gate-side HBM (human body model) ESD robustness of Schottky-type p-GaN gate HEMTs is investigated. The maximum reverse gate current and gate breakdown voltage in the quasi-static I-
$V$
tests are higher than the forward cases, whereas the forward gate ESD robustness is much stronger than the reverse case. Such contradiction is caused by a self-protection mechanism under forward gate ESD stress. The capacitive division of the forward gate voltage in the two junctions of the p-GaN gate stack induces high transient electron thermionic emission current through the p-GaN/ AlGaN/GaN p-i-n junction. This current dominates the forward gate current and enables substantial charge leakage from the HBM capacitance. The self-protection mechanism analysis is facilitated by a custom-designed pulsed
$I$
-
$V$
test system based on SiC MOSFETs, which can generate high current (up to 26 A) pulses with short pulse width
$(\leq 90\ \text{ns})$
.