(higher) sample qualities. We discuss experimental implications of our theoretical results and comment on possible strategies for future improvement of 2D sample quality.'
address: |
    $^1$Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111\
    $^2$SKKU Advanced Institute of Nanotechnology and Department of Physics, Sungkyunkwan University, Suwon, 440-746, Korea
author:
- 'S. Das Sarma$^1$ and E. H. Hwang$^{1,2}$'
title: Mobility versus quality in 2D semiconductor structures
---

introduction
============

One of the most significant materials developments in the fundamental quantum condensed matter physics, which is not universally known outside the 2D community, has been the astonishing 3,000-fold increase in the low temperature electron mobility of GaAs-based 2D confined quantum systems from $ \sim 10^4$ cm$^2$/Vs in the first modulation-doped GaAs-AlGaAs 2D heterostructures [@stormer] in 1978 to the current world-record mobility of $\sim 3-4 \times 10^7$ cm$^2$/Vs in the best available modulation doped GaAs-AlGaAs quantum wells of today. [@heiblum] This represents a truly remarkable more than three orders of magnitude enhancement in the low temperature ($\sim 1$K) electron mean free path from a rather short microscopic length $\sim 50$ nm in 1978 to the essentially macroscopic length scale of $\sim 0.2$ mm in 2010. This incredible 3,000-fold 