Wide bandgap semiconductors, particularly silicon carbide (SiC) based electronic devices and circuits, are presently being developed for use in high-temperature, high-power, and high-radiation conditions under which conventional semiconductors cannot adequately perform. Silicon carbide's ability to function under extreme conditions is expected to enable significant improvements to a far-ranging variety of applications and systems. These range from improved high-voltage switching in public electric power distribution to sensors and controls for jet aircraft and automobile engines. Aside from tremendous theoretical advantages yet to be realized in SiC devices, the need for numerical simulation based on accurate models for the design and optimization of these devices is indispensable to further the success of modern electronics.

A comprehensive and systematic model development based on the recent research findings and published data was performed. Due to the anisotropic nature of the SiC crystal structure, the mobility, the dielectric permittivity, and the conductivity are tensors along the crystallographic axes of the semiconductor lattice. These tensors are diagonal with only two independent components parallel and perpendicular to the c-axis, respectively. A tensorial formulation of Poisson's equation and the current equations are adapted to make it feasible for use in the general-purpose device simulator Minimos-NT, applying the same discretization scheme as in the case of conventional current transport equations.

The most common doping impurities in SiC have activation energies larger than the thermal energy even at room temperature. Inequivalent sites of SiC, one with cubic surrounding and the other with hexagonal surrounding, cause site-dependent impurity levels. Therefore, an appropriate incomplete ionization model which accounts for ionization level dependence on polytype and lattice sites is implemented. A variety of other SiC-specific models, including band structure and bandgap narrowing; Shockley-Read-Hall and Auger recombination, temperature- and field-dependent impact ionization; and mobility dependencies on impurity concentration, lattice temperature, carrier concentration, carrier energy, parallel and perpendicular electric fields have been implemented.

The models are tested on state-of-the-art SiC rectifiers, switches, and RF transistors. Three classes of SiC rectifiers were investigated: the Schottky barrier diodes which offer extremely high switching speed but suffer from high leakage current; the PiN diodes which offer low leakage current but show reverse recovery charge during switching and have a large junction forward voltage drop due to the wide bandgap of SiC; and the merged PiN Schottky diodes which offer Schottky-like on-state and switching characteristics and PiN-like off-state characteristics.

Three types of unipolar transistors were simulated. UMOSFET devices, which were the first unipolar transistors realized in SiC, have shown good on- and off-state characteristics but suffered from problems including lower inversion layer mobility and high electric field crowding at its trench corners. The DMOSFET structure formed by using a double ion implantation has avoided the trench problems occurred in UMOSFET, but still has low inversion layer mobility. An ACCUFET structure is proposed by incorporating an n-type counter-doped layer along the oxide/semiconductor interface to restore the low inversion layer mobility observed at both UMOSFET and DMOSFET.

The implemented models were further tested on RF transistors. A microwave MESFET fabricated using epitaxial layers on semi-insulating SiC substrates was investigated for both DC and high frequency characteristics. The results of the simulation were compared to measurements, and excellent agreement was obtained.