A Study On The Effct Of Interface Properties Of SiO₂/SiC On Performances Of N-Channel SiC Mosfet

In this paper, the effect of interface properties of SiO2/SiC on performances of n-channel SiC MOFET are studied systematically:Incomplete ionization of impurity in SiC is analyzed based on the crystal structure of SiC materials. The effect of incomplete ionization of impurity on C-V characteristics of p-type 6H-SiC MOS is researched based on Charge-Sheet model for SiC MOS inversion layers. The results of the analysis show that the impact of incomplete ionization on SiC MOSFET is more notable in subthreshold region than in strong inversion region.The effect of interface state charges on the threshold voltage, drain current, transconductance and field-effect mobility of n-channel SiC MOSFET is analyzed with numerical method by establishing the model of the interface state density exponential distribution. The study shows that interface state charges not only increase the threshold voltage, but also lower the MOSFET transconductance, drain current and field-effect mobility, which can well explain the results of experiment. It is pointed that inversion-layer mobility is different from field-effect mobility for SiC MOSFET. And a relationship has been established between the ratio of the experimentally-determined field-effect mobility to the actual inversion-layer carrier mobility and interface states.In this paper, it has been attempted how to improve interface properties. It is expected that the SiOj layer grown on SiC wafer by means of 3UCVD can improve interface properties. But the definite conclusions have not still been obtained.