Characterization of Dynamic Threshold Voltage in Schottky-Type p-GaN Gate HEMT Under High-Frequency Switching

The dynamics of the intrinsic threshold voltage (
${V}_{{\text {TH}}}{)}$
shift in 650-V Schottky-type p-GaN gate HEMT under high-frequency switching is investigated by a bootstrap voltage clamping circuit in which the GaN HEMT serves as the key bootstrapping device. This new testing setup covers a wide range of OFF-state drain bias (
${V}_{{\text {DSQ}}}{)}$
up to 400V, a short OFF-to-ON (or stress-to-sense) delay (
${T}_{{\text {delay}}}{)}$
of 60ns, and a high switching frequency (
${f}_{{\text {sw}}}{)}$
up to 2MHz. The dynamic
${V}_{{\text {TH}}}$
’s dependences on
${V}_{{\text {DSQ}}}$
and
${f}_{{\text {sw}}}$
are characterized by this testing setup. A higher V
_DSQ
(up to 400V) results in a larger dynamic
${V}_{{\text {TH}}}$
shift (
$\Delta {V}_{{\text {TH}}}{)}$
. The
$\Delta {V}_{{\text {TH}}}$
exhibits a gradually increasing trend under the continuous high-frequency switching mode. In addition, after continuous switching operation for
$200\mu \text{s}$
, the maximum
$\Delta {V}_{{\text {TH}}}$
shows no
${f}_{{\text {sw}}}$
dependence with a wide range of frequency from 50kHz to 2MHz.