Accumulation-layer electron mobility in n-channel 4H-SiC MOSFETs

Accumulation-layer electron mobility in n-channel depletion-mode metal oxid e semiconductor field effect transistors (MOSFETs) fabricated in 4H-SiC was investigated using Hall-measurements. The accumulation-layer mobility show ed a smooth transition from the bulk value (similar to 350 cm(2)/V-s) in th e depletion regime into accumulation (similar to 200 cm(2)/V-s), In contras t, the held-effect mobility, extracted from the transconductance, was found to be much lower (similar to 27 cm(2)/V-s), due to the trapping of the hel d-induced carriers by interface states. Though the current in depletion/acc umulation-mode MOSFETs can be high due to the contribution of bulk conducti on resulting in low on-resistance, carrier trapping will cause the transcon ductance to be low in the accumulation regime.