Gate-Induced Threshold Voltage Instabilities in p-Gate GaN HEMTs.

In this study, we investigate the threshold voltage (${V} _{{{ \text {th}}}}$) instability of p-gate GaN HEMTs induced by gate bias. Experimental results are acquired by a custom pulse setup for two commercially available devices with an ohmic gate and a Schottky gate. A transient drain current change is observed, which corresponds to a shift of ${V} _{{{ \text {th}}}}$. A negative ${V} _{{{ \text {th}}}}$ instability is identified for the ohmic gate, a mostly positive for the Schottky gate that can also become negative depending on the gate bias voltage and duration. The impact of the gate-bias-induced ${V} _{{{ \text {th}}}}$ instability on the Schottky-gate device is significantly higher compared to the ohmic-gate device, but clearly noticeable at the nominal rated ON-state gate voltage for both devices. Electron depletion and trapping as well as hole accumulation and trapping are identified to cause this transient ${V} _{{{ \text {th}}}}$ instability. [ABSTRACT FROM AUTHOR]