Tight-binding calculations of the band structure and total energies of the various polytypes of silicon carbide

Abstract

We present electronic structure and total energy calculations for SiC in a variety of polytype structures using the NRL nonorthogonal tight-binding method. We develop one set of parameters optimized for a combination of electronic and energetic properties using a sp basis, and one optimized for electronic properties using a spd basis. We compute the energies of polytypes with up to 62 atoms per unit cell, and find that the hexagonal wurtzite structure is highest in energy, the 4H structure is lowest in energy, and the cubic zinc-blende structure is in between, in agreement with our linear augmented plane-wave and other calculations. For the sp model we find that the electronic structure of the cubic and hexagonal structures are in good agreement with densityfunctional theory calculations only for the occupied bands. The spd parametrization optimized for the electronic structure of the zinc-blende and wurtzite structures at the equilibrium volume reproduces nearly perfectly both the valence and conduction bands. The sp tight-binding model also yields elastic constants, phonon frequencies, stacking fault energies, and vacancy formation energies for the cubic structure in good agreement with available experimental and theoretical calculations. Using molecular dynamics simulations we compute the finite-temperature thermal expansion coefficient and atomic mean-square displacements in good agreement with available first-principles calculations.

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

“…Our energy gap for 3C SiC agrees within 3.72% with the empirical pseudopotential method (EPM) value. In contrast, the indirect energy gap obtained by nonorthogonal tight binding (NTB) [50] is smaller than our TB value of 1.06 eV. Thus, the variation of our calculated energy gap and the NTB result is about 40%.…”

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

“…The results show that SiC is an indirect gap semiconductor. In addition, the calculated energy gaps of SiC are in good agreement with the other results (73), (74), (75), (77). Values of lowest indirect forbidden gaps (E g ) are listed in Table 1 (77) which agree with other calculations (22), (25), (73), (75), (76), (77), (78), (79) and experimental data (74).…”

Thermal evolution of the band edges of 6H-SiC: X-ray methods compared to the optical band gap

“…Silicon is the workhorse for information technologies and photovoltaic photon harvesting, while SiC is a promising material for high power, high temperature and high frequency applications, because of its extreme thermal and chemical stability together with the large electron saturation velocity and mobility [3,4] and SiC has applications in light-emitting diodes [2][3][4], temperature sensors [5] and as neutron detectors [6,7]. The most stable of about 100 different SiC polytypes, the hexagonal 6H-SiC containing six SiC pairs per unit cell with the stacking sequence ABCACB [8] is the subject of this study.…”