Thermopower of a 2D electron gas in suspended AlGaAs/GaAs heterostructures

TL;DR

This study investigates thermopower in a suspended 2D electron gas, revealing how micro patterning and reduced thermal conductivity influence thermoelectric behavior and electron-phonon interactions.

Contribution

It demonstrates the impact of micro patterning and membrane dimensions on thermopower and uncovers the dominant electron diffusion contribution up to 7 K in suspended structures.

Findings

Reduced thermal conductivity in suspended membranes enhances thermal gradients.

Diffusion thermopower remains dominant up to 7 K, unlike in bulk materials.

Electron-phonon coupling is via screened deformation potentials, not piezoelectric effects.

Abstract

We present thermopower measurements on a high electron mobility two-dimensional electron gas (2DEG) in a thin suspended membrane.We show that the small dimension of the membrane substantially reduces the thermal conductivity compared to bulk material so that it is possible to establish a strong thermal gradient along the 2DEG even at a distance of few micrometers. We find that the zero-field thermopower is significantly affected by the micro patterning. In contrast to 2DEGs incorporated in a bulk material, the diffusion contribution to the thermopower stays dominant up to a temperature of 7 K until the phonon-drag becomes strong and governs the run of the thermopower. We also find that the coupling between electrons and phonons in the phonon-drag regime is due to screened deformation potentials, in contrast to piezoelectric coupling found with bulk phonons.