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.