Dielectric Substrate Dependence of Thermoelectric Transport in BLG-GaAs-BLG Heterostructures

TL;DR

This study theoretically investigates how dielectric substrates affect thermoelectric transport in bilayer graphene-GaAs heterostructures, revealing substrate dielectric constant and interlayer distance as key factors influencing thermopower and device optimization.

Contribution

It provides a detailed theoretical analysis of substrate effects on thermoelectric transport in BLG-GaAs-BLG systems, highlighting the dominance of piezoelectric scattering and substrate-dependent thermopower trends.

Findings

Piezoelectric scattering dominates thermoelectric transport, especially at low densities.

Thermopower order: HfO2 > Al2O3 > h-BN.

Interlayer distance increase enhances thermopower.

Abstract

We theoretically study the thermoelectric transport S in a double-layer bilayer graphene (BLG-GaAs-BLG) system on dielectric substrates (h-BN, Al2O3, HfO2). Electrons interact with GaAs acoustic phonons via both the deformation potential (acDP) and piezoelectric (acPE) scattering. Results show that piezoelectric scattering dominates the total transport, especially at low carrier density and high dielectric constant. Substrate dielectric constant significantly influences thermopower S, and the thermopower of the materials is in the order of HfO2 > Al2O3 > h-BN. When densities on two BLG layers are unequal, the contribution from acDP scattering Sd decreases (increases) at low (high) densities versus equal densities, while acPE scattering Sg remains stable, making S largely Sg-dependent. Increasing interlayer distance d enhances S, while higher temperature boosts Sd (notably at low densities) with minimal effect on Sg. These insights and substrate-dependent trends demonstrate substrate engineering as a key parameter for optimizing BLG thermoelectric devices