Improved Channel Mobility in 4H-SiC MOSFETs by Boron Passivation

We propose another process for fabricating 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) with high channel mobility. The B atoms were introduced into a SiO₂/4H-SiC interface by thermal annealing with a BN planar diffusion source. The interface state density near the conduction band edge of 4H-SiC was effectively reduced by the B diffusion and the fabricated 4H-SiC MOSFETs showed a peak field-effect mobility of 102 cm²/Vs. The obtained high channel mobility cannot be explained by counter doping because B atoms act as acceptors in 4H-SiC. We suggest that the interfacial structural change of SiO₂ may be responsible for the reduced trap density and enhanced channel mobility.