Understanding limits to mobility in ultra-high-mobility GaAs two-dimensional electron systems: The quest for 100 million cm$^2$/Vs and beyond

TL;DR

This paper reviews the current state of ultra-high-mobility GaAs 2DESs, presents new record mobility data, analyzes scattering mechanisms, and discusses future prospects for surpassing 100 million cm$^2$/Vs.

Contribution

It provides the latest mobility measurements, comprehensive analysis of scattering mechanisms, and explores potential pathways to achieve even higher mobility in GaAs 2DESs.

Findings

Record mobility of ~57 million cm$^2$/Vs at 0.3 K.

Analysis of dominant scattering mechanisms.

Discussion of scenarios to exceed 100 million cm$^2$/Vs.

Abstract

For several decades now, ultra-high-mobility GaAs two-dimensional electron systems (2DESs) have served as the hallmark platform for various branches of research in condensed matter physics. Fundamental to this long-standing history of success for GaAs 2DESs was continuous sample quality improvement, which enabled scattering-free transport over macroscopic length scales as well as the emergence of a diverse range of exotic many-body phenomena. While the recent breakthrough in the quality of GaAs 2DESs grown by molecular beam epitaxy is highly commendable in this context, it is also important and timely to establish an up-to-date understanding of what obstructs us from pushing the mobility limit even further. Here, we present mobility data taken at a temperature of 0.3 K for a wide variety of state-of-the-art GaAs 2DESs, exhibiting a maximum, world-record mobility of $\mu\simeq57\times10^6$ cm$^2$/Vs at a 2DES density of $n=1.55\times10^{11}$ /cm$^2$. We also provide comprehensive analyses of the collective scattering mechanisms that can explain the results. Furthermore, based on our study, we discuss potential scenarios where GaAs 2DES mobility values exceeding $100\times10^6$ cm$^2$/Vs could be achieved.