Enhanced Gate Reliability of p-GaN/AlGaN/GaN HEMTs Due to Gate Hole Injection and Recombination

This letter substantially improves the understanding on the degradation of normally-OFF GaN HEMTs with p-GaN gate subject to forward gate stress, and demonstrates that a significant reliability enhancement can be obtained at high bias through hole injection from the gate terminal. Key results are: (i) for the first time we adopt an experimental setup capable of investigating the threshold voltage shift of the devices during time-dependent breakdown tests in a wide time window (from μs to failure). (ii) Remarkably, we demonstrate that the acceleration factor for gate breakdown is substantially lower at high stress voltage. (iii) The lower acceleration factor of degradation at high voltages is correlated to the number of holes which are injected and trapped in the gate stack. The results give strong experimental evidence that the injection of holes from the p-GaN contact can have a beneficial effect on device robustness, by reducing - through recombination - the amount of hot electrons responsible for degradation.