Optical Absorption and Refractive Index of SiC

This Datareview outlines the data on optical absorption and refractive index in the various polytypes of SiC. The optical transitions give rise to the characteristic colour of each polytype. Values for both the ordinary and extraordinary refractive indices versus wavelength are given. 

The absorption edges of the seven poly types of SiC have been studied by Choyke [4]. Solangi and Chaudhry [6] and Nishino et al [7] have measured the absorption coefficient of p-SiC. The shapes of the absorption curves are characteristic of indirect transitions. In FIGURE 1, the square root of the absorption coefficient is plotted vs. photon energy. These actual curves were supplied by [5]. In this case, EXc, the stronger absorption curves were used at liquid nitrogen temperature. 

FIGURE 1 Absorption edge of several polytypes at 4.2 K light polarised E Lc [5]. 

The arrows on FIGURE 1 mark the principal phonons and a detailed discussion is provided in the later sections of this book. These indirect interband transitions reflect on the simultaneous absorption or emission of phonons. The mechanism of exciton transition for an indirect semiconductor may involve a bound exciton which may recombine without phonon emission during the transition. This is explained in detail in [4,5]. 

The absorption coefficient as a function of wavelength in p-SiC grown on Si is also provided in [5,6]. 

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Optical absorption and refractive index of SiC TABLE 3 Refractive index of SiC polytypes. 

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