Dynamic Gate Stress-Induced VTH Shift and Its Impact on Dynamic RON in GaN MIS-HEMTs

Very fast transients ofV_ THshift and their impact onRONunder dynamic AC (1 k–1 MHz) positive gate stress in depletion-mode (D-mode) metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) are revealed. We achieve data acquisition within 120 ns right after each stress pulse throughout the entire stress time range from10^ -7up to10^ 3s, by virtue of a short stress-to-sense delay of~ 100ns and high sampling rate up to 50 MSa/s. Despite the considerableV_ THshift, its impact onRONin D-mode MIS-HEMT is modest, if the device is under sufficient gate overdrive. Furthermore,V_ THshift and the consequentRONincrease under dynamic stress, which are more relevant to high-frequency switching operation, exhibits frequency dependence within 1 k–1 MHz and is always smaller than that under conventionally used static (constant) stress.