Experimental investigation and modeling of inversion carrier effective mobility in 4H-SiC trench MOSFETs

Abstract

The effective mobility in 4H-SiC trench metal-oxidesemiconductor field-effect transistors (MOSFETs) with an n-channel region on the 11-00 face, corresponding to the trench sidewalls, is investigated. Using a previously proposed mobility model, which includes Coulomb scattering mobility (μC), surface roughness scattering mobility (μSR) and optical phonon scattering mobility (μOP), the dependence of the effective field (Eeff) on μOP is studied experimentally. It is found that for the trench MOSFETs with a drift layer, μOP is proportional to Eeff−1, whereas for trench MOSFET without a drift layer, it is proportional to Eeff−0.3, which is consistent with reports on phonon scattering mobility in SiC lateral MOSFETs fabricated on 0001 and 0001- faces. The results suggest that the proposed mobility model is effective, and that the dependence of Eeff on μOP is not affected by the plane orientation of SiC and needs to be evaluated with the drift layer resistance removed. A method for evaluating the carrier transport properties of trench MOSFETs with a drift layer is also proposed.