Analysis of threshold voltage in GaN MOSFETs on homoepitaxial p-type GaN layers

In this study, we investigate the sources of unintentional threshold voltage
$(V_{\mathrm{TH}})$
lowering in GaN MOSFETs by analyzing a dependence of
$V_{\mathrm{TH}}$
on body voltage
$(V_{\mathrm{B}})$
. Through the
$V_{\mathrm{TH}}-V_{\mathrm{B}}$
characteristics of the MOSFETs, we concluded that the
$V_{\mathrm{TH}}$
lowering results from the relatively large amount of positive charge at the MOS interface rather than the donor in the p-type GaN layer.