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In this work, fast sweeping characterization with an extremely short relaxation time was used to probe the V TH instability of p-GaN gate HEMTs. As the I D -V G sweeping time deceases from 5 ms to 5 µs, the V 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 TH features a very fast shifting process but a slower recovering process. D-mode HEMTs counterpart without Mg contamination demonstrates a negligible V TH shift and hysteresis, proving the V TH instability is probably due to the ionization of acceptor-like traps in the p-GaN depletion region. Finally, the V TH instability is verified by a GaN circuit under switching stress. The V TH instability under different sweeping speed uncovers the fact that the high V TH by conventionally slow DC measurements is probably artificial. The DC V TH should be high enough to avoid HEMT faulty turn-on. Index Termsp-GaN gate HEMT, fast sweeping, V TH shift, PBTI.

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