Electron transport and optical properties of shallow GaAs/InGaAs/GaAs quantum wells with a thin central AlAs barrier

TL;DR

This study investigates how inserting a thin AlAs barrier in GaAs/InGaAs/GaAs quantum wells affects their electronic transport and optical properties, revealing significant modifications in carrier behavior and energy transitions.

Contribution

It provides a comprehensive analysis combining experimental measurements and self-consistent calculations to understand the impact of a central AlAs barrier on quantum well properties.

Findings

Transport parameters are strongly affected by the AlAs barrier.

Insertion of the barrier increases transition energies in photoluminescence spectra.

Formation of hybrid states extends over multiple layers.

Abstract

Shallow GaAs/InGaAs/GaAs quantum well structures with and without a three monolayer thick AlAs central barrier have been investigated for different well widths and Si doping levels. The transport parameters are determined by resistivity measurements in the temperature range 4-300 K and magnetotransport in magnetic fields up to 12 T. The (subband) carrier concentrations and mobilities are extracted from the Hall data and Shubnikov-de Haas oscillations. We find that the transport parameters are strongly affected by the insertion of the AlAs central barrier. Photoluminescence spectra, measured at 77 K, show an increase of the transition energies upon insertion of the barrier. The transport and optical data are analyzed with help of self-consistent calculations of the subband structure and envelope wave functions. Insertion of the AlAs central barrier changes the spatial distribution of the electron wave functions and leads to the formation of hybrid states, i.e. states which extend over the InGaAs and the delta-doped layer quantum wells.