Dynamic $V_{\mathrm{th}}$ in $p$-GaN Gate Power HEMTs and Its Impacts upon Power Switching Circuits

The p-GaN gate power HEMT exhibits a dynamic threshold voltage $(V_{\mathrm{th}})$ during device operation, i.e. its $V_{\mathrm{th}}$ is a mathematical function of the terminal bias. The dynamic $V_{\mathrm{th}}$ phenomenon can be accurately predicted by a charge storage mechanism. The floating p-GaN layer stores negative charges during switching operating, and requires an additional gate bias to counteract these charges. The dynamic $V_{\mathrm{th}}$ has profound impacts upon power switching circuits. It affects the dynamic on-state characteristics and reverse conduction characteristics, presents restriction on the design of gate driving circuit design, and influences the switching waveforms of the circuits. Detailed analysis of these effects will be presented.