COMPARISON OF 6H-SIC, 3C-SIC, AND SI FOR POWER DEVICES

This paper defines the drift region properties of 6H- and 3C-SiC-based Schottky rectifiers and power MOSFET's to achieve breakdown voltages ranging from 50 to 5000 V. Using these values, the output characteristics of the devices have been calculated and these are compared with the characteristics of Si devices. It is found that due to very low drift region resistance, 5000-V SiC Schottky rectifiers and power MOSFET's can deliver on-state current density of 100 A/cm2 at room temperature with a forward drop of only 3.85 and 2.95 V, respectively. These values are superior to even that for silicon P-i-N rectifiers and gate turn-off thyristors. Both these SiC devices are expected to have excellent switching characteristics and ruggedness due to the absence of minority-carrier injection. Additionally, a thermal analysis based upon a peak junction temperature limit, as determined by packaging considerations, is presented. Using this analysis, ft is found that 5000-V, 6H-, and 3C-SiC MOSFET's and Schottky rectifiers would be approximately 20 and 18 times smaller than corresponding Si devices. This thermal analysis for the SiC indicates that these devices would allow operation at higher temperatures and at higher breakdown voltages than conventional Si devices. Also, a significant reduction in the die size is expected. This reduction in the die size would offset the higher cost of the material. The results of the analysis presented in this paper provide a strong impetus to embarking upon the fabrication of SiC power devices.