At present, nearly all SiC devices have utilized epitaxial SiC for at least part of the active
device structure. The primary reasons are the relatively low purity and electrical quality of
substrate material. Ion implantation is often utilized for doping profiles in semiconductors,
but epitaxy is required for the starting material. Implants directly into substrates have
generally been of poor electrical quality [41]. Dopant diffusion is also not feasible because
of the high temperatures required.
For these reasons most SiC electronic devices
are not fabricated directly in sublimation-grown wafers, but are instead fabricated in much
higher quality epitaxial SiC layers that are grown on top of the initial sublimation-grown
wafer. Well-grown SiC epilayers have superior electrical properties and are more controllable
and reproducible than bulk sublimation-grown SiC wafer material. Therefore, the controlled
growth of high-quality epilayers is highly important in the realization of useful SiC
devices. Epitaxial SiC has been successfully grown on many substrates, including SiC,
sapphire, AlN and Si [58,59,60]. Of these substrates, only SiC has been
utilized as a substrate for high-performance devices [1].
