First-principles study of optoelectronic and thermoelectric properties of LiCaX (X=N, P and As) half-Heusler semiconductors

Abstract

In this paper, we have investigated the LiCaX (X ​= ​N, P and As) half-Heusler semiconductor by using density functional theory (DFT) implemented in QUANTUM ESPRESSO and semi-classical Boltzmann transport theory in order to find more suitable materials for optoelectronic and thermoelectric applications. The obtained results of the ground state show that all compounds are semiconductors with an indirect band gap. The optical properties, such as the imaginary and real parts of dielectric complex function, refractive index and absorption coefficient are calculated and discussed in detail. The reflectivity is found less than 40% and the refractivity index is about 2-3.5 in the visible light region. The thermoelectric properties are evaluated in the range of temperature of 50K–1000K. The lattice thermal conductivity decreases with the increase of temperature and the figure of merit is found to increase with temperature and reaches the maximum value of 0.73, 0.497 and 0.57 ​at 1000K for LiCaN, LiCaP and LiCaAs, respectively. These properties make LiCaX promising materials for thermoelectric and optoelectronic applications.