Potential performance of SiC and GaN based metal semiconductor field effect transistors

A Monte Carlo simulation has been used to model steady-state electron transport in SiC and GaN field effect transistor. The simulated device geometries and doping are matched to the nominal parameters described for the experimental structures as closely as possible. Simulations of SiC MESFETs of lengths 2, 2.6 and 3.2 µm have been carried out and compared these results with those on GaN MESFETs of the same dimensions. The direct current IV characteristics of the two materials were found to be similar, though the GaN characteristics were on the whole superior, reaching their operating point at higher drain voltages and possessing higher gains. However, oscillations in the drain current caused by changes in drain voltage in the GaN devices were not present to the same degree in the SiC devices. This difference is caused partially by the onset of the negative differential regime in SiC at a higher electric field than in GaN but the primary cause is the longer ballistic transport times in SiC. This suggests that GaN MESFETs may prove to have superior frequency response characteristics than SiC MESFETs.