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

Accumulation-layer electron mobility in n-channel depletion-mode metal oxide semiconductor field effect transistors (MOSFETs) fabricated in 4H-SiC was investigated using Hall-measurements. The accumulation-layer mobility showed a smooth transition from the bulk value (/spl sim/350 cm/sup 2//V-s) in the depletion regime into accumulation (/spl sim/200 cm/sup 2//V-s). In contrast, the field-effect mobility, extracted from the transconductance, was found to be much lower (/spl sim/27 cm/sup 2//V-s), due to the trapping of the field-induced carriers by interface states. Though the current in depletion/accumulation-mode MOSFETs can be high due to the contribution of bulk conduction resulting in low on-resistance, carrier trapping will cause the transconductance to be low in the accumulation regime.