First-principles investigations of thermoelectric properties of novel polytypes of Indium phosphide

Abstract

In this work, we report the thermoelectric properties of indium phosphide (InP) in ground state Zinc-Blende (zb) structure and the pressure-driven Beryllium Oxide (β-BeO)-, wurtzite (wz)-, and Silicon Carbide (SiC)-phases using the first-principles approach. Their electrical and thermal conductivities, Seebeck coefficient (S), thermoelectric power factor (PF), and the figure-of-merit (zT) have been evaluated in detail. The S values of InP polytypes have been found typically larger than 230 μV/K when the Fermi-level is fixed inside the band gap edges, however, shifting the Fermi-level to the middle of the band gap has evolved S larger than 2000 μV/K. These polytypes of InP exhibited high electrical conductivities and significant S values that have induced substantial PFs. The maximal PFs have been recorded as 18.73 × 1010 W/mK2s for zb-InP, 14.04 × 1010 W/mK2s for wz-InP, 10.30 × 1010 W/mK2s for β-BeO-InP, and 11.14 × 1010 for SiC-InP. Our analysis shows that the recorded substantial PFs go through further improvement with an increase in temperature. The optimized electrons and holes dopings that resulted in the maximal PFs have been recognized as − 0.72, 1.75, 1.56, and 1.72 eV for zb-, wz-, β-BeO-, and SiC-type of InP. The zT values exhibited by these polytypes of InP approach to unity at moderate p-type doping level specifies their potential for applications in thermoelectric devices.