Role of background impurities in the single-particle relaxation lifetime of a two-dimensional electron gas

Abstract

We re-examine the quantum τq and transport τt scattering lifetimes due to background impurities in two-dimensional systems. We show that the well-known logarithmic divergence in the quantum lifetime is due to the non-physical assumption of an infinitely thick heterostructure, and demonstrate that the existing non-divergent multiple scattering theory can lead to unphysical quantum scattering lifetimes in high quality heterostructures. We derive a non-divergent scattering lifetime for finite thickness structures, which can be used both with lowest order perturbation theory and the multiple scattering theory. We calculate the quantum and transport lifetimes for electrons in generic GaAsAlGaAs heterostructures, and find that the correct 'rule of thumb' to distinguish the dominant scattering mechanisms in GaAs heterostructures should be τt/τq 10 for background impurities and τt/τq 10 for remote impurities. Finally we present the first comparison of theoretical results for τq and τt with experimental data from a GaAs 2DEG in which only background impurity scattering is present. We obtain excellent agreement between the calculations and experimental data, and are able to extract the background impurity density in both the GaAs and AlGaAs regions.

Alloy disorder modulated electron transport at MgxZn1-xO/ZnO heterointerface

“…The ratio τ tr /τ q is about ∼10 for background impurities and τ tr /τ q > 10 for remote surface charges. 26 Contrary to Ref. 9 (where the carrier density varies by an order of magnitude), at a nearly constant carrier density (corresponding to the highest mobilities) we find that the alloy disorder which apparently reduces µ (τ tr ) is not a dominant scattering mechanism in limiting τ q .…”

Quantum lifetime of two-dimensional electrons in a magnetic field

“…The electron quantum lifetime τ q has been measured in many experiments [1] and is an important property of two dimensional systems [50]. The standard transport method to measure the electron lifetime is based on an extraction of the Dingle factor from temperature or magnetic field dependences of the amplitude of Shubnikov-deHaas (SdH) oscillations.…”

Chiral wave-packet scattering in Weyl semimetals

“…In contrast, the transport lifetime τ t measures the collision events in one particular direction, which can be obtained from the conductivity. 47 Conventionally, the quantum lifetime and the transport lifetime are usually of the same order. However, in Ref.…”

“…Conventionally, τ t is regarded as the same order as the quantum lifetime (or single particle scattering time) τ q . 47,48 In the case of twodimensional electron gas (2DEG) in GaAs/AlGaAs, the ratio R τ = τ t /τ q can be large (10−100) because the scattering centers are separated from the carriers. [48][49][50][51] The charge fluctuations in the dopant layer lead only to smallangle scatterings, which strongly limit τ q but hardly affect τ t .…”