Scattering Mechanism in Modulation-Doped Shallow Two-Dimensional Electron Gases

TL;DR

This study investigates the dominant scattering mechanisms in shallow 2DEGs in GaAs/AlGaAs heterostructures, revealing a transition from background impurity scattering to remote dopant scattering as the depth decreases.

Contribution

It provides a systematic analysis of how the scattering mechanism in shallow 2DEGs changes with depth, supported by experimental data on mobility and density dependence.

Findings

Mobility versus density follows a power-law with exponent ~1.65 at 130 nm depth.

Exponent drops to ~1.3 when the 2DEG is shallower than 130 nm.

Results align with remote dopant scattering theory for shallow 2DEGs.

Abstract

We report on a systematic investigation of the dominant scattering mechanism in shallow two-dimensional electron gases (2DEGs) formed in modulation-doped GaAs/Al_{x}Ga_{1-x}As heterostructures. The power-law exponent of the electron mobility versus density, mu \propto n^{alpha}, is extracted as a function of the 2DEG's depth. When shallower than 130 nm from the surface, the power-law exponent of the 2DEG, as well as the mobility, drops from alpha \simeq 1.65 (130 nm deep) to alpha \simeq 1.3 (60 nm deep). Our results for shallow 2DEGs are consistent with theoretical expectations for scattering by remote dopants, in contrast to the mobility-limiting background charged impurities of deeper heterostructures.