Scattering Mechanisms in a High Mobility Low Density Carbon-Doped (100) GaAs Two-Dimensional Hole System

TL;DR

This study investigates how scattering mechanisms affect mobility in a high-quality, low-density 2D hole system in GaAs, revealing a transition from background impurity to remote impurity scattering as density decreases.

Contribution

First observation of a carrier density-induced transition in scattering mechanisms within a single high-mobility 2D GaAs hole system.

Findings

Mobility reaches 2.6 x 10^6 cm^2/Vs at low temperature and high density.

The mobility's dependence on density varies continuously, not following a simple power law.

A crossover from background impurity to remote impurity scattering is identified.

Abstract

We report on a systematic study of the density dependence of mobility in a low-density Carbon-doped (100) GaAs two-dimensional hole system (2DHS). At T= 50 mK, a mobility of 2.6 x 10^6 cm^2/Vs at a density p=6.2 x 10^10 cm^- was measured. This is the highest mobility reported for a 2DHS to date. Using a back-gated sample geometry, the density dependence of mobility was studied from 2.8 x 10^10 cm^-2 to 1 x 10^11 cm^-2. The mobility vs. density cannot be fit to a power law dependence of the form mu ~ p^alpha using a single exponent alpha. Our data indicate a continuous evolution of the power law with alpha ranging from ~ 0.7 at high density and increasing to ~ 1.7 at the lowest densities measured. Calculations specific to our structure indicate a crossover of the dominant scattering mechanism from uniform background impurity scattering at high density to remote ionized impurity scattering at low densities. This is the first observation of a carrier density-induced transition from background impurity dominated to remote dopant dominated transport in a single sample.