Optoelectronic and mechanical properties of gallium arsenide alloys: Based on density functional theory.

Abstract

First principles calculations based on density functional theory (DFT) were performed to investigate the structural, electronic, optical and mechanical properties of pristine GaAs compound and its alloy; Ga0.75Al0.25As, Ga0.75In0.25As, Ga0.75Sn0.25As, Ga0.75Ti0.25As. WIEN2K and Quantum expresso (QE) codes were adopted for calculations using generalized gradient approximation (GGA) in Perdew-Burke Erzenhoff (PBE) as exchange correlation function for both codes. Full potential linear augmented plane wave (FPLAPW) with the local orbital method was adopted as implement in WIEN2K code. In QE code, norm-conserving pseudopotentials were employed on a plane-wave expansion of the wave functions. Structural and electronic properties were elaborated since their result gives information about the optical and mechanical performance. Electronic band structure and optical parameters were performed using WIEN2K code. Underestimation of band gap observed from DFT calculations were corrected by using Modified Becke and Johnson (mBJ). Mechanical components were determined using QE with thermo_pw package. Lattice constant, volume, bulk modulus and other physical parameters were calculated for structural properties. Discrepancy in these parameters as observed in crystal structure is associated to difference in ionic radius of host and substituted atom. The results of band structure and density of states were calculated for electronic properties. All the studied compounds were semiconductors in nature except Ga0.75Sn0.25As which displayed metallic character. Optical parameters including extinction coefficient, absorption coefficient, refractive index, optical conductivity, optical reflectivity and energy loss function have been computed from the dielectric function at energy range of 0 to 25 eV using the Kramers-Kronig transformations. Calculated elastic function were used to compute the mechanical properties such as anisotropic, brittle characteristics, stiffness and many others. All the results were compared with available theoretical and experimental records.