Silicon carbide (SiC) is the one of the most attractive materials for electronic devices in high-power and high frequency operations due to its outstanding electrical properties. The high breakdown field and high thermal conductivity of SiC coupled with high operational junction temperature theoretically permit extremely high power densities and efficiencies to be realized in SiC devices. The wide bandgap energy and low intrinsic carrier concentration allow SiC based semiconductor electronic devices and circuits to operate in high-temperature high-radiation conditions under which conventional semiconductors cannot adequately perform.

Over the last several years, significant effort has been made to develop commercially viable SiC-based bipolar technology. At present, the main obstacle on the road to commercialization of high voltage SiC diodes is degradation of the forward I–V characteristics. This phenomenon was observed in p-i-n diodes formed by both ion implantation and epitaxial growth. This research focuses on the development of the diffusion technique to prevent degradation of 4H-SiC p-i-n diodes.

Numerous experiments have been performed in our laboratory with intent to determine the effect of acceptor impurity in the anode region on the degradation behavior of 4H-SiC p-i-n diodes. Degradation tests, current-voltage (IV) measurements, electroluminescence (EL) spectra measurements, electron beam induced current (EBIC) analysis and EL imaging were performed in order to characterize the p-i-n diodes produced under different processing conditions. Results allow us to conclude that diodes, formed using Al as diffusion dopant for p+-region in the p-i-n structure, have very high yield of degraded devices; while utilizing of cooperative diffusion of Al and B makes it possible to fabricate devices that do not exhibit degradation of the forward voltage drop.

With use of selective codiffusion of Al and B, it was possible to fabricate small area nondegrading p-i-n diodes with breakdown voltage of 1.8kV, which is 85% of the theoretically obtainable value for the given device design. As well, nondegrading large area (4mm²) diodes, which carry a current of 6A with low forward voltage drop, are fabricated.