Characteristics and mechanisms of subthreshold voltage hysteresis in 4H-SiC MOSFETs.

In order to investigate the characteristics and mechanisms of subthreshold voltage hysteresis (ΔVth,sub) of 4H-SiC metal–oxide–semiconductor field-effect transistors (MOSFETs), 4H-SiC planar and trench MOSFETs and corresponding P-type planar and trench metal–oxide-semiconductor (MOS) capacitors are fabricated and characterized. Compared with planar MOSFEF, the trench MOSFET shows hardly larger ΔVth,sub in wide temperature range from 25 °C to 300 °C. When operating temperature range is from 25 °C to 300 °C, the off-state negative Vgs of planar and trench MOSFETs should be safely above –4 V and –2 V, respectively, to alleviate the effect of ΔVth,sub on the normal operation. With the help of P-type planar and trench MOS capacitors, it is confirmed that the obvious ΔVth,sub of 4H-SiC MOSFET originates from the high density of the hole interface traps between intrinsic Fermi energy level (Ei) and valence band (Ev). The maximum ΔVth,sub of trench MOSFET is about twelve times larger than that of planar MOSFET, owing to higher density of interface states (Dit) between Ei and Ev. These research results will be very helpful for the application of 4H-SiC MOSFET and the improvement of ΔVth,sub of 4H-SiC MOSFET, especially in 4H-SiC trench MOSFET. [ABSTRACT FROM AUTHOR]