Impact of Inadequate Mg Activation on Dynamic Threshold Voltage of Schottky-type $p$-GaN Gate HEMTs

To further reduce the forward gate current of Schottky-type
$p$
-GaN gate HEMTs, inadequate Mg activation in
$p$
-GaN is deployed in this work, which tends to convert the conventional
$p$
-GaN into insulating GaN with high concentration of Mg passivated by hydrogens. The free hole concentration in
$p$
-GaN is reduced, and so is the hole deficiency effect that is the main cause of dynamic threshold voltage (
$V_{\text{TH}}$
) in commercial Schottky-type
$p$
-GaN gate HEMTs. However, plenty of electron traps left in
$p$
-GaN lead to more significant dynamic
$V_{\text{TH}}$
shift (up to 6 V) under reverse gate bias (
$V_{\text{GSQ}}$
, up to -13 V), as revealed by the
$V_{\text{TH}}$
recovery processes under different conditions of light illumination and forward gate bias. Fortunately, under forward
$V_{\text{GSQ}}$
, the fully depleted
$p$
-GaN layer facilitates electron acceleration by the electric field, suppressing the electron trapping and consequent dynamic
$V_{\text{TH}}$
shift. Besides, deeper-level electron trapping in AlGaN may account for the slight dynamic
$V_{\text{TH}}$
shift under
$V_{\text{GSQ}}\geq 7\mathrm{V}$
.