DC characterization of 4H-SiC depletion mode MOS field effect transistor

A depletion mode metal–oxide–semiconductor field effect transistor (MOSFET) has been fabricated using 4H-SiC. The basic structure is the same as that of a conventional metal–semiconductor FET (MESFET), except that the Schottky barrier gate is replaced by a MOS gate that comprises a 50 nm silicon oxide (SiO2). The device has a pinch-off voltage of −1.0 V and a flat band voltage of 4.0 V. The drain current of the device can be substantially increased compared to the case of MESFET when a large positive gate voltage is applied, resulting in strong accumulation of electrons in the n-channel. Specifically, at a drain voltage of 25 V, the drain current is found to increase by 3.3 times when VGS is increased from 4.0 V (flat band condition) to 11.0 V (strong accumulation). Such gate bias condition, which is not possible in MESFETs, renders such devices ideal for high power applications. The electron mobility in the accumulation layer was found to be about 17.5 cm2/V s.