An advanced physical model for the Coulombic scattering mobility in 4H-SiC inversion layers

摘要

In this work, a new model for the mobility due to Coulombic scattering by interface charges (juc) in 4H-SiC MOS structures, which is suitable for device study via finite element (FE)-based simulations, is proposed. Unlike popular expressions based on the classical Sah-Lombardi model which lead to major inconsistencies in μ_C's variation with the semiconductor depth z, the proposed model combines previous experimental data with established theoretical results on μ_C's depth dependence. The evolution of the components of the channel drift mobility (μ_(ch)) with z and the gate bias V_(gs) is then examined using this model by means of FE analysis. It is found that while μ_C is the dominant component at the surface, at larger depths μ_(ch) is determined by the mobility due to acoustic phonon scattering (μ_(SA)). Moreover, at low channel dopings (N_A) or temperatures above approximately 425 K, μ_(SA) replaces μ_C as the key limitation. Conversely, the roughness scattering mobility μ_(SR) becomes important only at very high V_(gs) and N_A.