Ab initio calculation of structural, electronic, and optical properties of TlxGa1-xAs ternary alloys

Abstract

In this study, first-principles calculations are performed to study the structural, electronic, and optical properties of the ternary TlxGa1-xAs alloys in the cubic structure. It is argued that, among four investigated density functionals, the SOGGA functional gives more accurate structural properties and predicts a linear volume expansion by increasing the thallium concentration. The new mBJ exchange correction method is applied to obtain more reliable electronic properties including energy band gap, band structure, and density of states. It is observed that alloys with x < 0.75 are direct band gap semiconductors, while, at concentrations x = 0.75 and above, are semi-metallic. The obtained results in the presence of the relativistic spin-orbit effect indicate that the energy band gap of ternary alloys decreases with increasing Tl content. We applied several methods to calculate the electron effective mass of the TlxGa1-xAs alloys in the [100] direction and observed a minimum effective mass at x = 0.375. Optical properties, including absorption coefficient, reflectivity, refractive index and extinction coefficient of the TlxGa1-xAs alloys, are also calculated within the SOGGA and TB-mBJ + SOC exchange correction schemes. The results confirm considerable potential of the investigated ternary alloys for optoelectronic applications, especially infrared detectors.