Owing to the differing arrangement of Si and C atoms within the SiC crystal lattice, each SiC polytype
exhibits unique fundamental electrical and optical properties. Some of the more important semiconductor
electrical properties of the 3C, 4H, and 6H SiC polytypes are given in Table 5.1. Much more
detailed electrical properties can be found in References 11–13 and references therein. Even within a
given polytype, some important electrical properties are nonisotropic, in that they are strong functions
of crystallographic direction of current flow and applied electric field (for example, electron mobility
for 6H-SiC). Dopant impurities in SiC can incorporate into energetically inequivalent sites. While all
dopant ionization energies associated with various dopant incorporation sites should normally be
considered for utmost accuracy, Table 5.1 lists only the shallowest reported ionization energies of each
impurity.
TABLE 5.1Comparison of Selected Important Semiconductor Electronic Properties of Major SiC Polytypes
with Silicon, GaAs, and 2H-GaN at 300 K
For comparison, Table 5.1 also includes comparable properties of silicon, GaAs, and GaN. Because
silicon is the semiconductor employed in most commercial solid-state electronics, it is the standard
against which other semiconductor materials must be evaluated. To varying degrees the major SiC
polytypes exhibit advantages and disadvantages in basic material properties compared to silicon. The
most beneficial inherent material superiorities of SiC over silicon listed in Table 5.1 are its exceptionally
high breakdown electric field, wide bandgap energy, high thermal conductivity, and high carrier saturation
velocity. The electrical device performance benefits that each of these properties enables are discussed
in the next section, as are system-level benefits enabled by improved SiC devices.