Monte Carlo Study Of Channel Mobility In SiC MOSFET

Silicon carbide(SIC) is a very promising material in the fields of high temperature, radiation resistant,high frequency and high power devices due to its excellent properties,such as wide band-gap,high critical breakdown electric field,high thermal conductivity,high saturated cartier drift velocity.It's also the only compound,which can grow natural oxide dielectric.Nowadays,the main course of SiC application is the research power devices,especially the MOSFET power devices.But the low channel mobility that caused by high interface states density is still the biggest problem.How to reduce the density and how the interface states effect the channel mobility is the first job to do in the study of SiC MOS devices.The main work of the paper is to analysis of channel mobility of 4H-SiC MOSFET by the full-band and different scattering mechanism simulation method.The effect of lattice,ionized impurities,surface phonon,interface charges and surface roughness scatterings on the mobility is considered in this model.And further,electrically shielded effect of carriers is also considered in the interface-charge scattering mechanism.Then the relationship between gate voltages with channel mobility is calculated.According to the above-mentioned one,the mechanism of acceptor-like interface state at upper half forbidden band and donor-like one at lower half part is used, 9.3 cm~2/V·s of maximum channel mobility is got by considering interface-charge and surface roughness scattering,which is closed to actual measured result..Of course, when only considering the surface roughness scattering,35 cm~2/V·s of maximum channel mobility which is closed to the real one that is got by the Nitrogen Plasmas treatment.By analysising the extent of effecting the mobility which is simulated by different scattering mechanism,it indicates that the interface charge in the Coulomb scattering is the main factor for the impact of channel electron mobility,which determines the most value of channel electron mobility.At the same time,comparison of varied processes which can enhance high channel mobility,the Nitrogen Plasmas treatment obviously improves the device performance.As a result of the study in the paper,Monte Carlo methods have been proved that the reasons that the channel mobility of SiC MOSFET devices can be improved significantly,at the time,the mechanism of Nitrogen Plasmas treatment can be interpretated.The result is significative to the further research.It provides necessary theory basises for improving techincs and performances of SiC MOS devices.