Hall effect mobility in inversion layer of 4H-SiC MOSFETs with a thermally grown gate oxide

Abstract

The inversion layer mobility of 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) with a thermally grown gate oxide was investigated using Hall effect measurements. To clarify the fundamental scattering properties of inversion layer mobility in SiO2/4H-SiC systems, we examined the effects of nitridation treatment after thermal oxidation and the gate oxide thickness on Hall effect mobility (μHall) in the inversion layer of 4H-SiC MOSFETs. The effect of nitridation treatment after thermal oxidation on phonon-limited mobility (μphonon) was investigated by using a p-type well region with an epitaxial layer with extremely low acceptor concentration (NA). It was found that nitridation treatment had little effect on μphonon for gate oxide thicknesses of 5 nm and 50 nm. The carrier transport properties were experimentally evaluated from the viewpoint of the effects of gate oxide thickness and nitridation treatment after thermal oxidation. Here, we used samples with a moderate NA of 1 × 1016 cm−3, which enabled us to distinguish μphonon, Coulomb-limited mobility (μCoulomb) and surface roughness-limited mobility (μSR). It was found that thermally grown SiO2/4H-SiC systems have the common feature that the dominant scattering components in the inversion layer are phonon scattering and Coulomb scattering and not surface roughness scattering at room temperature within the measured effective normal field (Eeff).