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
_TH
instability of p-GaN gate HEMTs. As the ID-VG 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.