First-principles analysis of ZrN/ScN metal/semiconductor superlattices for thermoelectric energy conversion

We present a first-principles density functional theory-based analysis of the electronic structure, vibrational spectra, and transport properties of ZrN/ScN metal/semiconductor superlattices aiming to understand its potential and suitability for thermoelectric applications. We demonstrate (a) the presence of Schottky barriers of 0.34 eV at the metal/semiconductor interface and (b) a large asymmetry in the electronic densities of states and flattening of electronic bands along the cross-plane directions near the Fermi energy of these superlattices, desirable for high Seebeck coefficient. The vibrational spectra of these superlattices show softening of transverse acoustic phonon modes along the growth direction and localization of ScN phonons in the vibrational energy gap between metal and semiconductor layers. Boltzmann transport theory-based analysis suggests a reduction of lattice thermal conductivity by an order of magnitude compared to its individual bulk components, which makes these materials suitable for thermoelectric applications.