Incorporating the Dynamic Threshold Voltage Into the SPICE Model of Schottky-Type p-GaN Gate Power HEMTs

The threshold voltage (V-TH) of an enhancement-mode Schottky-type p-GaN gate high-electron-mobility transistor (HEMT) is found to have a special dependence on the drain bias. The device commonly requires higher gate voltage to switch on the transistor from a high-drain-voltage off-state than what is expected from the static device characteristics. The reason behind the dynamic V-TH has been proved to be the floating p-GaN layer, where charges could be stored and further influence V-TH under different drain bias. In this article, a SPICE-compatible equivalent circuit model is presented according to the structure of Schottky-type p-GaN gate HEMTs. It features a floating node to imitate the charge storage process within the gate stack. Compared to conventional models, the proposed model could accurately predict the dynamic V-TH characteristics and switching behaviors of power electronics circuits, where Schottky-type p-GaN gate HEMTs are deployed as power transistors. The phenomena related to the dynamic V-TH, including the disappearance of Miller plateau, the overestimated false-turn-on problem, and the higher reverse conduction loss are evaluated with a half-bridge circuit and the merits of the proposed model are verified.