Buried-channel silicon carbide MOSFETs

Silicon carbide (SiC) is a wide bandgap semiconductor that has a high thermal conductivity and large saturation velocity for electrons. It has been proposed for power devices and high temperature applications. SiC is similar to silicon in certain aspects, but the deep energy level of the dopants requires new models to be developed to fully model the device behavior.; This dissertation focuses on the characterization of buried-channel SiC transistors that were fabricated with epitaxial structures. Both enhancement and depletion mode devices were fabricated on the same substrate. The buried-channel lowers the noise in the transistors that is due to interface traps and the rough SiC surface. The incomplete ionization effects were incorporated into a new model. This model allows the device parameters to be extracted with only a few simple electrical measurements which then can be used to predicate the device behavior. Tests were performed over a range of temperatures from room to {dollar}325spcircrm C.{dollar} The bulk mobility was found to be 200 cm{dollar}sp2{dollar}/Vs at room temperature, which was 4 times the surface mobility. The {dollar}rm(W/L = 100mu m/4mu m){dollar} maximum transconductance of 2 mS/mm at room temperature which increased about twice at {dollar}325spcircrm C.{dollar} These structures lack a source of minority carriers so the surfaces cannot be inverted. A memory effect was noted due to hole injection from the substrate.; To further improve the transistor behavior a series of experiments were conducted to study and improve the oxide quality. Samples on p-type substrates exhibited a large fixed oxide charge {dollar}(6times10sp{lcub}11{rcub}rm cmsp{lcub}-2{rcub}){dollar} and an interface trap density of {dollar}2times10sp{lcub}11{rcub}rm cmsp{lcub}-2{rcub}eVsp{lcub}-1{rcub}.{dollar} N-type samples also had the large density of interface traps but an order of magnitude lower fixed oxide charge. The wet oxidation had an unexpected dependency on the carrier gas used for the oxidation. Deposited oxides were also characterized. A series of tests was also performed to determine if SiC would contaminate the tubes that were used for Si processing. No signs of mobile ion, heavy metal ions or a loss of oxide quality was observed.