VTH Instability of ${p}$ -GaN Gate HEMTs Under Static and Dynamic Gate Stress

The impacts of static and dynamic gate stress on the threshold voltage (
${V}_{\text {TH}}$
) instability in Schottky-type
${p}$
-GaN gate AlGaN/GaN heterojunction field-effect transistors are experimentally investigated.
${V}_{\text {TH}}$
shifts negatively under large positive bias static stress (
${V}_{\text {G}}\_ {\text {stress}} > 5$
V) by adopting conventional quasi-static characterization techniques. In contrast,
${V}_{\text {TH}}$
under fast-dynamic-stress exhibits positive shift, and a positive frequency dependence occurs within a wide range of frequency from 10 Hz to 1 MHz. The different
${V}_{\text {TH}}$
instability behavior under static and dynamic stress mainly originates from the time-dependent charges (electrons and holes) storage/release mechanisms in the
${p}$
-GaN layer, which is floating in the Schottky-type
${p}$
-GaN gate HEMT.