Common Wearout Mechanism of pGaN Gate in GaN HEMTs under DC and Inductive Switching Test Methods

In this work, time-dependent gate reliability studies were carried out on GaN high-electron-mobilitytransistors (HEMTs) under continuous DC gate bias ($\mathrm{V}_{\mathrm{GS}}$) and repetitive transient gate overvoltage stress conditions. The high frequency gate overvoltage ringing stress is realized by an inductive switching test circuit. Weibull distribution analyses find the Weibull slope parameter from the DC test $\left(\mathrm{V}_{\mathrm{GS}}=10 \mathrm{~V}\right)$ is consistent with the slope parameter of the inductive switching test with a peak gate voltage of 10 V. Failure analyses were conducted on failures from both test methods, revealing consistent electrical and physical failure characteristics. By correlating the key failure characteristics from two different tests, this work establishes that impact ionization is the common wearout mechanism responsible for $\mathrm{p G a N}$ breakdown under DC and inductive switching test methods.