High Vth Ferroelectric Gate Stack GaN HEMT for Power Switching Applications

Abstract

AlGaN/GaN high-electron-mobility transistors (HEMTs) have high saturation velocity, high mobility, and high current density with high breakdown electric field, which make them promising for next-generation high power and high frequency device applications. However, AlGaN/GaN HEMTs always demonstrate normally-on operation, which is not desirable for Electrical Vehicle applications due to safety concerns. To achieve normally-off operation for GaN HEMT devices, several methods have been proposed to achieve high positive threshold voltage. For example, p-GaN, recessed-gate, and fluorine treated AlGaN technologies have been demonstrated. In this work, a new charge storage structure with hybrid ferroelectric charge-trapping gate stack is proposed to realize the GaN E-mode MIS-HEMT for power switching applications. This gate stack structure combines ferroelectric film with charge-trapping layer and current blocking film, resulting in a polarization charge field against the applied gate voltage, and thus achieves a large positive shift of the threshold voltage. As a result, the device has a high Vth, meanwhile maintains low on Resistance, high saturation current, and high breakdown voltage, perfect for EV applications.