Invited: Limiting factors of inversion layer mobility in Si-face 4H-SiC MOSFETs

Abstract

We propose a method to experimentally evaluate the carrier transport properties in the inversion layer of SiC metal-oxide-semiconductor field effect transistors (MOSFETs). Intrinsic phonon-limited mobility $(\mu_{\mathrm{phonon}})$ in the SiC MOSFETs was successfully observed owing to the suppression of severe impact of Coulomb scattering on the SiC MOS inversion layer by lowing the acceptor concentration to the order of $1\times 10^{14}$ cm−3, Additionally, the $\mu_{\mathrm{phonon}}$ was found not to be affected by nitridation, representing a fundamental feature of thermally oxidized SiO 2 /4H-SiC systems. On the basis of this finding, Coulomb-and surface roughness-limited mobility were evaluated by using their dependences on surface carrier density or effective normal electric field $(E_{\mathrm{eff}})$ . Dominant limiting factors of inversion layer mobility in Si-face 4H-SiC MOSFETs were found to be phonon and Coulomb scatterings, and not surface roughness scattering even at high $E_{\mathrm{eff}}$ region. These results represent that conventional understanding of carrier scattering in the SiC MOS inversion layer should be modified, especially in the high $E_{\mathrm{eff}}$ region.