Limit to 2D mobility in modulation-doped GaAs quantum structures: How to achieve a mobility of 100 millions

TL;DR

This paper theoretically analyzes the limits of carrier mobility in modulation-doped GaAs quantum structures, identifying conditions to reach 100 million cm²/Vs and highlighting phonon scattering as a fundamental limit at higher temperatures.

Contribution

It provides a detailed theoretical framework and numerical results for achieving ultra-high 2D mobility in GaAs structures by optimizing impurity levels and doping separation.

Findings

Achieving 100 million cm²/Vs at 1K with low impurity density and large doping separation.

Phonon scattering limits mobility to about 22 million cm²/Vs at 4K and 5 million at 10K.

Numerical results guide experimental efforts for ultra-high mobility in 2D GaAs structures.

Abstract

Considering scattering by unintentional background charged impurities and by charged dopants in the modulation doping layer as well as by GaAs acoustic phonons, we theoretically consider the practical intrinsic (phonons) and extrinsic (background and dopants) limits to carrier mobility in modulation doped AlGaAs-GaAs 2D semiconductor structures. We find that reducing background impurity density to $10^{12}$ cm$^{-3}$ along with a modulation doping separation of 1000 \AA or above will achieve a mobility of $100 \times 10^6$ cm$^2$/Vs at a carrier density of $3\times 10^{11}$ cm$^{-2}$ for T=1K. At T=4 (10)K, however, the hard limit to the 2D mobility would be set by acoustic phonon scattering with the maximum intrinsic mobility being no higher than 22 $(5) \times 10^6$ cm$^2$/Vs. Detailed numerical results are presented as a function of carrier density, modulation doping distance, and temperature to provide a quantitative guide to experimental efforts for achieving ultra-high 2D mobilities.