Observation of Dynamic VTH of p-GaN Gate HEMTs by Fast Sweeping Characterization

In this work, fast sweeping characterization with an extremely short relaxation time was used to probe the ${V}_{\text {TH}}$ instability of p-GaN gate HEMTs. As the ${I}_{\text {D}}$ - ${V}_{\text {G}}$ sweeping time deceases from 5 ms to $5~\mu \text{s}$ , the ${V}_{\text {TH}}$ dramatically degenerates from 3.13 V to 1.76 V, meanwhile the hysteresis deteriorates from 22.6 mV to 1.37 V. Positive bias temperature instability (PBTI) measurement by fast sweeping shows the ${V}_{\text {TH}}$ features a very fast shifting process but a slower recovering process. D-mode HEMTs counterpart without Mg contamination demonstrates a negligible ${V}_{\text {TH}}$ shift and hysteresis, proving the ${V}_{\text {TH}}$ instability is probably due to the ionization of acceptor-like traps in the p-GaN depletion region. Finally, the ${V}_{\text {TH}}$ instability is verified by a GaN circuit under switching stress. The ${V}_{\text {TH}}$ instability under different sweeping speed uncovers the fact that the high ${V}_{\text {TH}}$ by conventionally slow DC measurements is probably artificial. The DC ${V}_{\text {TH}}$ should be high enough to avoid HEMT faulty turn-on.