Electronic structure, vibrational spectrum, and thermal properties of yttrium nitride: a first - principles study

Abstract

Yttrium nitride (YN) is a promising semiconductor for use in metal/semiconductor superlattices for thermoelectric applications. We determine its electronic structure, vibrational spectrum, and thermal properties using first-principles density functional theory (DFT) based simulations with a generalized gradient approximation (GGA) of the exchange correlation energy. We employ GGA+U and GW approximations in our calculations to (a) improve the accuracy of the calculation of bandgaps and (b) determine specific features of its electronic structure relevant to transport properties, such as transverse (m_t^∗) and longitudinal (m₁^∗) conduction band effective mass. To evaluate consequences of forming alloys of YN with other materials to its electronic properties, we have determined the volume deformation potentials. Our results for phonons show a large longitudinal optical (LO) and transverse optical (TO) splitting at the Γ point in the vibrational spectrum with a gap of 325 cm^-1 arising from long- range dipole-dipole interactions. We estimate temperature dependent lattice specific heat and lattice thermal conductivity based on Boltzmann transport theory to assess YN's potential for thermoelectric applications.