The Discovery of Polytypism

When Acheson found the hexagonal crystals in the voids, he sent some to B.W. Frazier, a professor at Lehigh University. Professor Frazier found that although the crystals were all silicon carbide, they differed in their crystalline structure. He had discovered the polytypism of SiC [18]. Polytypism will be explained in Section 1.3.2. 

The electronic properties of SiC were investigated shortly afterward and in 1907 the first LED was produced from SiC [19]. However, the extraction of crystals was a cumbersome process that required patience, and the purity of the crystals was not controllable. As a consequence, in 1955 another crystal growth invention of significant proportions was made by J. A. Lely [20]. 

C—Intergrown and twinned mass of SiC platelets with cubic overgrowth D—Hexagonal and cubic whiskers on radiation shields and further furnace parts 

In 1958, the first SiC conference was held in Boston, Massachusetts. However, after this, the interest in SiC rapidly declined and the 1960s and 1970s are characterized by a low interest in SiC. Research was still ongoing, mainly in the former Soviet Union. In the United States, the work done by Westinghouse and the University of Pittsburgh is primarily notable. Indeed, the photoluminescence studies made by Choyke, Patrick, and Hamilton are still very relevant and often cited [21]. 

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