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 I-D-V-G sweeping time deceases from 5 ms to 5 mu s, the V-TH dramatically degenerates from 3.13 V to 1.76 V, meanwhile the hysteresis deteriorates from 22.6mV 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.