Scattering mechanisms in state-of-the-art GaAs/AlGaAs quantum wells

TL;DR

This paper investigates the various scattering mechanisms affecting electron mobility in GaAs/AlGaAs quantum wells, highlighting impurity and interface roughness contributions and their dependence on electron density.

Contribution

It provides a detailed analysis of scattering mechanisms in state-of-the-art GaAs/AlGaAs quantum wells and compares theoretical predictions with experimental data.

Findings

Mobility limited by background impurities at low densities

Power law dependence of mobility on electron density with exponent ~0.85

Interface roughness likely limits mobility at higher densities

Abstract

Motivated by recent breakthrough in molecular beam epitaxy of GaAs/AlGaAs quantum wells [Y. J. Chung \textit{et al.}, Nature Materials \textbf{20}, 632 (2021)], we examine contributions to mobility and quantum mobility from various scattering mechanisms and their dependencies on the electron density. We find that at lower electron densities, $n_e \lesssim 1 \times 10^{11}$ cm$^{-2}$, both transport and quantum mobility are limited by unintentional background impurities and follow a power law dependence, $\propto n_e^{\alpha}$, with $\alpha \approx 0.85$. Our predictions for quantum mobility are in reasonable agreement with an estimate obtained from the resistivity at filling factor $\nu= 1/2$ in a sample of Y. J. Chung \textit{et al.} with $n_e = 1 \times 10^{11}$ cm$^{-2}$. Consideration of other scattering mechanisms indicates that interface roughness (remote donors) is a likely limiting factor of transport (quantum) mobility at higher electron densities. Future measurements of quantum mobility should yield information on the distribution of background impurities in GaAs and AlGaAs.