Structural, Electronic, Optical, Elastic and Thermal Properties of Gallium Arsenide (GaAs): A Density Functional Theory Study

Abstract

Gallium Arsenide (GaAs), an outstanding member of the III-V semiconductor family with larger and direct band gap enable transistors made of GaAs preferred compared to silicon. The problem of computationally understanding properties of such materials goes down to solving Schrödinger equation of a collection of mobile nuclei and electrons. Thus, DFT the most successful method that forms the basis for advanced ab initio calculations was employed. Being motivated by the promising role of GaAs in future technology and the DFT contribution in computational material science, the researcher was determined to study the structural, electronic, optical, mechanical and thermal properties of GaAs using DFT. In selecting suitable DFT software, the researcher opted for open-source plane-wave DFT code – Quantum ESPRESSO. The lattice parameter of GaAs was calculated using GGA-PBE and LDA, both are in a better agreement to the experimental value. The band gap of GaAs calculated using LDA is much better than GGA in approaching the experimental value. From the DOS and PDOS calculation, a strong covalent bonding between Ga and As is observed. The optical properties of GaAs have been investigated in the photon energy range 0 to 25eV. Maximum values of real and imaginary part dielectric constant, refractive index, extinction coefficient, absorption coefficient have been observed; and are all in good agreement with theoretical values. The calculated elastic constants indicate GaAs is mechanically stable at ambient condition. The phonon DOS and the corresponding phonon dispersion relation were calculated within temperature range of 0K to 300K. The maximum numbers of branches is six and are displayed at K point. The temperature dependencies of vibrational energy, free energy, entropy and heat capacity of GaAs were calculated within room temperature and all are fairly in good agreement with experimental values.