Extracting band structure characteristics of GaSb/InAs core-shell nanowires from thermoelectric properties

TL;DR

This paper models the band structure of GaSb/InAs core-shell nanowires using advanced theoretical methods and links these structures to thermoelectric measurements, aiding experimental identification of electronic properties.

Contribution

It introduces a comprehensive theoretical framework combining band structure calculations with thermoelectric modeling for core-shell nanowires, highlighting how to distinguish different band gap regimes experimentally.

Findings

Band structure varies from metallic to semiconducting with shell thickness.

Hybridization-induced band gaps can be identified through thermoelectric signatures.

Guides for experimental thermoelectric measurements to probe electronic regimes.

Abstract

Nanowires with a GaSb core and an InAs shell (and the inverted structure) are interesting for studies of electron-hole hybridization and interaction effects due to the bulk broken band-gap alignment at the material interface. We have used eight-band $\mathbf{k\cdot p}$ theory together with the envelope function approximation to calculate the band structure of such nanowires. For a fixed core radius, as a function of shell thickness the band structure changes from metallic (for a thick shell) to semiconducting (for a thin shell) with a gap induced by quantum confinement. For intermediate shell thickness, a different gapped band structure can appear, where the gap is induced by hybridization between the valence band in GaSb and the conduction band in InAs. To establish a relationship between the nanowire band structures and signatures in thermoelectrical measurements, we use the calculated energy dispersions as input to the Boltzmann equation and to ballistic transport equations to study the diffusive limit and the ballistic limit, respectively. Our theoretical results provide a guide for experiments, showing how thermoelectric measurements in a gated setup can be used to distinguish between different types of band gaps, or tune the system into a regime with few electrons and few holes, which can be of interest for studies of exciton physics.