4H-SiC and Si Based IGBTs/VDMOSFETs Characters Comparison

In order to compare the performance differences of IGBTs/VDMOSFETs based on wide bandgap material 4H-SiC and silicon(Si), the basic theory of semiconductor physics for 4H-SiC and Si was used to describe the quantitative relationship of carrier mobility with doping concentration, output I-V curves with devices design and fabrication parameters, switching characteristics with material properties and devices rating voltage. MATLAB software was used to calculate those above characteristics, the calculation results show that, for given doping concentration, the carrier mobility of 4H-SiC is lower than that of silicon, so its conducting output currents are also smaller than that of silicon in the same design rule of same chip area and same devices terminal bias conditions, for example, when 4H-SiC and Si with same doping concentration of 10¹⁵cm^-3 and same bias conditions of gate-source voltage 18V/drain-source voltage 2V, the carrier mobility and conducting current are 990.9cm²/V/s and 6.686mA for 4H-SiC, which is only about 74.4% and 55.9% that of silicon with value of 1332.0cm²/V/s and 11.950mA, respectively. However, for devices breakdown voltage of 4000V, the turn-on time for 4H-SiC, 27.88ns, is shorter than that of silicon, 110.30ns, this is because the wide bandgap material 4H-SiC will have higher epilayer doping concentration and thinner epilayer thickness when compared with silicon for given devices blocking voltage, this will lead the more fast turn-on and switching characteristics of 4H-SiC devices than that of Si devices.