Reverse-bias step-stress of normally-off GaN power FETs at different temperatures

We show results of temperature-dependent reverse-bias step-stressing of normally-off high-power GaN FETs. In the range 250 – 400 K, the stress voltage at which the FETs fail catastrophically does not show a clear temperature dependence, while some correlation is observed with the initial leakage current value. We consistently observe gradual breakdown walkout and threshold voltage decrease. In terms of degradation modes, our results are consistent with previous observations from another group, pointing to reversible trapping followed by permanent changes due to defect percolation.