CHARGE PROPERTIES OF AN AL-SIO2-N-6H-SIC((0001)SI) MOS STRUCTURE

The charge properties of an MOS structure based on n-type 6H-SiC have been studied at room temperature. An insulating layer 30 nm thick was grown under the gate by thermal oxidation of epitaxial 6H-SiC with a ( 0001)Si orientation (the concentration of uncompensated donors was 2.8 X 10(16) cm(-3)) in a flow of dry oxygen with an admixture of trichlo roethylene vapor. The breakdown voltage of the oxide measured under el ectron-accumulation conditions ranges up to 25 V. The breakdown field is 8 x 10(6) V/cm. Under conditions of a pronounced nonequilibrium dep letion, the MOS structures withstand voltages up to 300-350 V. This re sult indicates that a layer with an inverted p-type conductivity forms at an extremely low rate at the SiO2/SiC interface. The small-signal admittance of the MOS structure is analyzed at frequencies of 1 kHz an d 1 MHz. The density of surface states is found to have an exponential energy distribution within the 6H-SiC band gap near the conduction ba nd. The total density of states is N-t similar or equal to 2 x 10(11) cm(-2). The surface charge density fixed in the oxide is N-f similar o r equal to 10(11) cm(-2). Surface traps with levels near the conductio n band are classified as acceptor-like (the cross section for electron capture is -similar to 10(-18) cm(-2)).