Deep-Level-Free SiC Semi-Insulating Buffer Layers for High-Power RF Transistors 02-014A

"SemiSouth proposes a proprietary technology involving the passivation of one type of shallow acceptor impurity to achieve precision compensation of the opposite type of shallow donor impurity. This Phase I feasibility demonstration represents aninnovative breakthrough in deep-level-free semi-insulating (SI) buffer layers for high-performance, economical silicon carbide radio-frequency (RF) MEtal Semiconductor Field Effect Transistors (MESFET). Semi-insulating materials are widely used inelectronics, which is especially so in RF applications. SI materials are now commercially available in SiC as substrates with very high bulk resistivity. However, RF MESFET's are known to be susceptible to electrical instabilities arising from the deepenergy levels intentionally introduced into all currently practical SI material. The deep energy levels are necessary to compensate, meaning to electrically offset, the shallow doping impurities to produce very high electrical resistance. These same deeplevels produce trapping effects that are responsible for the electrical instabilities. Until now, it was not practical to create semi-insulating buffer layers by using "shallow" dopants of one type (say aluminum acceptors in SiC) to compensate shallowdopants of another type (say nitrogen donors in SiC) with sufficient precision to produce deep-level-free SI buffer layers. The approach developed by SemiSouth reduces or eliminates the electrical inst