Calculated and measured uv reflectivity of SiC polytypes

1994; American Physical Society; Volume: 50; Issue: 15 Linguagem: Inglês

10.1103/physrevb.50.10722

ISSN

1095-3795

Autores

Walter R. L. Lambrecht, B. Segall, M. Yoganathan, W. Suttrop, Robert P. Devaty, W. J. Choyke, J. A. Edmond, J. A. Powell, M. Alouani,

Tópico(s)

Semiconductor materials and devices

Resumo

A systematic study of the vacuum uv reflectivity (4--10 eV) for an electric field perpendicular to the c-axis is presented for SiC polytypes. Experimental results for the 4H, 15R, 6H, and 3C SiC polytypes are compared to theoretical calculations within the local-density approximation in conjunction with a muffin-tin-orbital basis set for the 2H, 4H, 6H, and 3C polytypes. Agreement to \ensuremath{\sim}0.2 eV is obtained between theoretical and experimental peak positions assuming a single, k-point-, energy-, and polytype-independent gap correction, the value of which agrees well with recent calculations based on Hedin's GW approximation. The main features and their trends with degree of hexagonality of the polytype are interpreted in terms of interband transitions involving extended regions in the Brillouin zone where valence and conduction bands are nearly parallel.

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