Low-temperature transport properties of a two-dimensional electron gas with additional impurities

TL;DR

This study examines how background impurities affect the magnetotransport properties of high-quality GaAs/AlGaAs two-dimensional electron gases, revealing complex temperature-dependent behaviors and limitations of existing theoretical models.

Contribution

It demonstrates the impact of homogeneously incorporated Si impurities on low-temperature mobility and electron density, highlighting phenomena not explained by current electron-electron interaction theories.

Findings

Mobility decreases monotonically with impurity density at low temperatures.

A temperature-dependent transition in scattering mechanisms is observed.

Impurities cause non-monotonic temperature dependence of electron density.

Abstract

We investigate the effect due to background impurities embedded in the region of two-dimensional electron gases to the magnetotransport. These impurities are achieved by homogeneously incorporating Si atoms in single quantum wells of high quality GaAs/AlGaAs heterostructures. Several materials were grown this way with different densities of Si atoms. At low temperature the mobility decreases monotonically with increasing impurity density. In materials with incorporated impurities, effects are observed with increasing temperatures. On the one hand, a minimum in mobility appears, marking a transition between scattering enhancement due to acoustic phonon and mobility enhancement due to impurity driven conductivity. The temperature at which the transition takes place decreases with increasing impurity density. On the other hand, the incorporated impurities induce a non-monotonic temperature dependence of the electron density. The magnitude of this variation rises with increasing impurity density. The theory of electron-electron interaction correction to the conductivity alone fails to explain our results.