Crystal-Face-Dependent Electron Mobility Due to Distinct Interface Trap Distributions in SiC n-Channel MOSFETs

Abstract

In this study, we investigated the electron trapping and scattering mechanisms in SiC ( $\boldsymbol {\mathsf {11\overline {2}0}}$ ) and ( $\boldsymbol {\mathsf {1\overline {1}00}}$ ) n-channel MOSFETs. Body-bias measurements revealed that the interface trap density distributions in these non-polar devices do not exhibit an energetic shift with increasing effective normal field near the interface, in contrast to the behavior observed in the (0001) devices. It was found that the fixed charge density near non-polar MOS interfaces is on the order of $\boldsymbol {\mathsf {\textbf {10}^{\textbf {12}} \ \textbf {cm}^{-\textbf {2}}}}$ and increases with increasing p-body doping concentration, while its absolute value is smaller than that observed in (0001) devices. Numerical calculation of free electron mobility ( $\boldsymbol {{\mathsf {\mu _{free}}}}$ ) was performed using the physical model we recently developed. The calculated results successfully reproduced the experimental Hall mobilities over 200–400 K. It was revealed that Coulomb scattering due to fixed charges is the dominant mobility-limiting factor in non-polar devices. The higher $\boldsymbol {{\mathsf {\mu_{free}}}}$ in ( $\boldsymbol {\mathsf {11\overline {2}0}}$ ) and ( $\boldsymbol {\mathsf {1\overline {1}00}}$ ) MOSFETs is mainly attributed to the reduced impact of scattering by trapped electrons and surface roughness, as a result of the distinct distributions of interface traps in polar and non-polar devices.