Diffusion in Silicon Carbide (Carborundum)

Abstract

In this chapter α-SiC is the main consideration, which is a very hard ceramic and therefore is extensively used as abrasive, but also in applications requiring high endurance. Related to these characteristics SiC is commonly used as automobile breaks and clutches. However, the main property is its being a semiconductor, and therefore it is commonly used in high-temperature/high-voltage semiconductor electronics. In high temperature applications diffusion problems are of great concern requiring an understanding of all types of diffusion that may occur. In single crystal applications only lattice diffusion occurs. Doping to change the semiconductor characteristics to obtain either an n-type or p-type SiC semiconductor means that solute (impurity) diffusion is important, in particular of N (for an n-type) and Al (for a p-type). In polycrystalline SiC short-circuit diffusion often contributes to the overall diffusion. Therefore it is important to measure and evaluate diffusion in grain boundaries and dislocations. Diffusion in these locations is enhanced which commonly should be avoided. Understanding enhanced diffusion and its magnitude is a prerequisite for tailoring the proper conditions permitting safe use of SiC. Diffusion data (self, solute, grain boundary and dislocation) are compiled at the end of the chapter.