Stokes shift in quantum wells: trapping versus thermalization

TL;DR

This study investigates how disorder and temperature affect the Stokes shift in InGaAs/GaAs quantum wells, revealing a transition between trapping and thermalization regimes through photoluminescence measurements.

Contribution

It establishes the validity conditions for two models linking Stokes shift to linewidth broadening and demonstrates a continuous transition between disorder regimes.

Findings

Stokes shift varies from 0 to 8 meV depending on disorder.

Two models are valid under different disorder and temperature conditions.

A continuous transition between trapping and thermalization regimes is observed.

Abstract

Low temperature photoluminescence and photoluminescence excitation measurements have been performed in a set of InGaAs/GaAs samples with different indium molar fraction, well width, growth conditions and post-growth treatment. This has allowed to change in a controlled way the degree and source of disorder in the samples, thus resulting in an excitonic absorption linewidth varying between 1 and 18 meV, and an ensueing Stokes shift changing between zero and 8 meV. The conditions of validity of two different models relating the Stokes shift to the linewidth broadening have been established in terms of different regimes of disorder and temperature. A continuous transition between those regimes has been demonstrated.