Opto-Electronic Study of SiC Polytypes: Simulation with Semi-Empirical Tight-Binding Approach

Abstract

The recent growing scientific and technological interest on silicon carbide (SiC) arises from its peculiar physical properties, i.e., its mechanical, and chemical stability. Moreover, SiC is considered to be a promising material for electronic and optical devices. Microelectronic devices made of SiC can be used in high-power, high-speed, high temperature, high-frequency, and even hard-radiation application (1)-(4). The strong bonding between Si and C atoms in SiC makes this material very resistant to high temperature and radiation damage. In view of this extraordinary application potential a thorough knowledge of the structural and electronic properties of SiC is a matter of both ionic interest and technological importance. In addition to its traditional use as an abrasive (carborundum) there is currently much interest in materials made from SiC fibres, which compare well with their carbon fibre counterparts. Over a two hundred chemically stable semiconducting polytypes of SiC exist, they have a high bulk modulus and generally wide band gap. From such difference in stacking order it is possible to get almost 200 different crystal structures (1)-(10) of which the two extremes are the pure cubic polytype (with zinc blende structure) and the pure hexagonal one (with wurtzite structure). SiC is the most prominent of a family of close packed materials which exhibit a one dimensional polymorphism called polytypism. In addition, numerous hexagonal and rhombohedral structures (11)-(19) of SiC have been identified in addition to the common cubic form. In fact, SiC is one of the few compounds which form many stable and long-range ordered modifications, so-called polytypes (11)-(17). Previously, SiC has been subject to many theoretical studies. With this respect, a variety of structural, electronic and optical properties in SiC have been investigated by many theoretical groups (12)-(15) and the results can be related to the experimental works (7)-(10). In the last years, first-principle calculations have been applied to determine the ground-state properties of cubic and hexagonal polytypes of SiC (19)-(53). Based on previous theoretical works, the high-pressure behavior (18)-(33), and the effect of atomic relaxation on structural properties 16