Design And Simulation Of The Novel4H-SiC MESFET With Stepped Channel

4H-SiC MESFET is one of the most widely applied devices in L, S, X band, this isbecause MESFET structure is better than other structures in the high frequencyapplication field. At present, the most advanced solid microwave communicationsystem and radar use GaAs or InP semiconductor devices. But, the military aircraftelectronic system for solid microwave devices in high power, high temperature of thedemands have already exceeded GaAs semiconductor devices limit theory, and hightemperature resistant and high power density of SiC MESFETs microwave powercomponents can satisfy these requirements completely.This paper fully absorbs SOI power components design ideas, combining4H-SiCMESFET existing design thought and practice based on the effect of electric fieldcrowding and electric field modulating, through the change of the drain-source drift areadoping distribution, innovative presents a stepped channel （stepped spacer）4H-SiCMESFET of new structure, which adopts a series of models and algorithms about4H-SiC MESFET, and uses the ISE TCAD with fully detailed simulation. Optimizationin the simulation contains of the depth of the buried gate, stepped spacer thickness anddoping concentration of the spacer, in addition we analysed electric field modulationeffect of different step positions. We found that the trans-conductance of the steppedchannel structure compared with the traditional gate field plate structure is smaller, andfor the same frequency, Cgsand Cgdof the stepped channel structure is also smaller thanthe gate field plate structure’s. It is because that the introduction of a board, which addsadditional gate-drain or gate-source feedback capacitor （Cgsand Cgd）, leading to the fTand fmaxreduced. Relative to the gate field plate structure, stepped channel increases66.7%and186.7%respectively.We analyzed DC breakdown voltage with different a, b length of4H-SiC MESFETdevice, for a, b length ratio of1:1, we obtain the biggest breakdown voltage175V,which is the value that we obtained by the simulation an optimized. Step in differentposition of the drain-gate area can improve the breakdown voltage of the4H-SiCMESFET microwave power device. From our simulation results can be seen, improvedegree is about40%.