Electronic and optical properties of SiC polytypes using a transferable semi‐empirical tight‐binding model

Abstract

The semi‐empirical tight‐binding (TB) method within the sp3s* basis has been used to investigate the electronic structure and optical properties of silicon carbide (SiC) polytypes. A TB model for the electronic structure calculations of the (4H, 6H and 8H) SiC polytypes is presented. The procedure involves the construction of the TB Hamiltonian of the (4H, 6H and 8H) SiC polytypes from the wurtzite one. The set of TB parameters is transferable to all hexagonal structures, which overcomes the need for extensive experimental data. The band structures for different SiC polytypes are used to determine the electron effective masses. The results are shown to be consistent with available experimental data and other theoretical calculations. Furthermore, the joint densities of states are calculated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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

“…Having established the geometric structure for the polytypes, the electronic band structure was calculated along the symmetry directions (62). Figure 3 shows the BZs of cubic, and hexagonal polytypes with high symmetry points marked.…”

“…The values vary depending on the experimental techniques or model used, especially for the hexagonal polytypes. Results for the lowest conduction band minima in K, M points, or at the LM line near M point are calculated (62). For electrons we give the full inverse effective-mass tensor along the principal axis determined by the c axis of the structure and the position of the minimum in k space.…”

“…The DOS was determined by the tetrahedron integration over a mesh that was generated by six cuts in the Γ-M direction of the BZ and included 112, 84, 78 and 56 points in the irreducible part of 2H, 4H, 6H and 8H BZ, respectively. In Figure 5 total densities of states of SiC polytypes (62) are shown which can be used for the interpretation of photoemission spectra of SiC. The lowest valence band in 6H SiC between -19.0 and -13.0 eV is dominated by s-electrons of C atom.…”

“…The intra-material elements in the Hamiltonian can be formed uniquely by using the corresponding bulk parameters. Our TB parameters (62) give the correct indirect and direct gap in comparison with Ref. (73) and are checked for their transferability to all considered structures by calculating the optoelectronic properties of different polytypes of SiC.…”

Photoluminescence of 8H-SiC

“…Considering the hexagonality [3] the excitonic bandgap of 8H polytype was evaluated to be E gx = 2.80 ± 0.015 eV. The indirect bandgap was reported in the literature to be 2.86 eV [4,5], however the experimental data are unclear. Here PL results on epitaxial layers of the 8H SiC polytype are presented and analyzed to allow determination of E gx as well as the binding energy of the nitrogen bound excitons.…”