Zero-field thermopower of a thin heterostructure membrane with a 2D electron gas

TL;DR

This study investigates the low-temperature thermopower of free-standing GaAs/AlGaAs heterostructure membranes with a 2D electron gas, revealing suppressed phonon-drag effects due to low thermal conductivity at temperatures up to 7 K.

Contribution

It provides experimental measurements of zero-field thermopower in suspended 2D electron systems, highlighting the impact of low thermal conductivity on thermoelectric effects at low temperatures.

Findings

Strong thermal gradients observed due to low thermal conductivity.

Phonon-drag contribution to thermopower is suppressed up to 7 K.

Demonstrates feasibility of thermopower measurements in micron-sized membranes.

Abstract

We study the low-temperature thermopower of micron sized, free-standing membranes containing a two-dimensional electron system. Suspended membranes of 320 nm thickness including a high electron mobility structure in Hall bar geometry of 34 {\mu}m length are prepared from GaAs/AlGaAs heterostructures grown by molecular beam epitaxy. Joule heating on the central region of the membrane generates a thermal gradient with respect to the suspension points where the membrane is attached to cold reservoirs. Temperature measurements on the membrane reveal strong thermal gradients due to the low thermal conductivity. We measure the zero-field thermopower and find that the phonon-drag contribution is suppressed at low temperatures up to 7 K.