A Comparative Study on G-to-S ESD Robustness of the Ohmic-Gate and Schottky-Gate p-GaN HEMTs

In this work, we have comprehensively studied the forward/reverse G-to-S electrostatic discharge (ESD) robustness for Ohmic-gate p-GaN HEMT. It is found that Ohmic-gate p-GaN HEMT exhibits superior G-to-S ESD robustness than Schottky-gate p-GaN HEMT with similar current capacity. First, Ohmic-gate p-GaN HEMT possesses a high forward/reverse second breakdown current ( ${I}_{\text {SF}}/I_{\text {SR}}$ ) of 9.3/2.7 A, while the value is 2.0/0.1 A for Schottky-gate p-GaN HEMT. Correspondingly, the equivalent forward/reverse human body model (HBM) failure voltages ( ${V}_{\text {HBM-F}}/{V}_{\text {HBM-R}} = {1500} \Omega \times {I}_{\text {SF}}/{I}_{\text {SR}}$ ) are 14/4.05 kV and 3/0.15 kV for Ohmic-gate and Schottky-gate p-GaN HEMTs, respectively. In addition, Schottky-gate p-GaN HEMT exhibits obvious changes in its ON-state current ( $\Delta {I}_{ \mathrm{\scriptscriptstyle ON}}$ = 0.8/0.7 A), threshold voltage ( $\Delta {V}_{\text {TH}}$ = 0.23/0.35 V), G-to-S leakage after the forward/reverse repetitive G-to-S ESD stress. While there is no obvious change ( $\Delta {I}_{ \mathrm{ON}}$ = 0 A and $\Delta {V}_{\text {TH}}$ = 0 V) in Ohmic-gate p-GaN HEMT, which may be attributed to that there are numerous holes to recombine the electrons trapped at the recombination center. But for Schottky-gate p-GaN HEMT, there is no enough holes to recombine the electrons trapped at the recombination center, due to the Schottky barrier at gate region.