Variation of elastic scattering across a quantum well

TL;DR

This study investigates how elastic scattering times of electrons in a quantum well vary with electron position and scatterer location, revealing insights into scattering mechanisms and impurity segregation during growth.

Contribution

It provides new understanding of the dependence of scattering times on electron position and scatterer location in a two-subband quantum well system.

Findings

Scattering times decrease as electrons move towards well edges.

Scatterer location influences scattering times significantly.

Evidence of impurity segregation during quantum well growth.

Abstract

The Drude scattering times of electrons in two subbands of a parabolic quantum well have been studied at constant electron sheet density and different positions of the electron distribution along the growth direction. The scattering times obtained by magnetotransport measurements decrease as the electrons are displaced towards the well edges, although the lowest-subband density increases. By comparing the measurements with calculations of the scattering times of a two-subband system, new information on the location of the relevant scatterers and the anisotropy of intersubband scattering is obtained. It is found that the scattering time of electrons in the lower subband depends sensitively on the position of the scatterers, which also explains the measured dependence of the scattering on the carrier density. The measurements indicate segregation of scatterers from the substrate side towards the quantum well during growth.