Abstract
In this study, the threshold voltage instability of the Schottky gate HEMT, the p-GaN gate HEMT, and the recessed MIS gate HEMT is investigated. The annealed p-GaN gate HEMT and Schottky gate HEMT are relatively stable. The threshold voltage shift of the recessed MIS gate HEMT, which is attributed to the trapping of electrons in the gate dielectric, can be as large as 2.5 V depending on the stress conditions. The activation energies of the trapping and de-trapping are extracted from the time constant spectra for the recessed MIS gate HEMT.