Excitonic photoluminescence in symmetric coupled double quantum wells subject to an external electric field

TL;DR

This study combines theoretical modeling and experimental measurements to analyze how an external electric field influences excitonic photoluminescence in symmetric double quantum wells, providing insights into exciton behavior and optical properties.

Contribution

It introduces a variational method for accurately predicting excitonic PL spectra in narrow DQWs under electric fields, validated by experimental data.

Findings

Good agreement between theory and experiment for PL spectra

Identification of direct and indirect excitonic transitions

Evaluation of exciton radius and squeezing under electric fields

Abstract

The effect of an external electric field F on the excitonic photoluminescence (PL) spectra of a symmetric coupled double quantum well (DQW) is investigated both theoretically and experimentally. We show that the variational method in a two-particle electron-hole wave function approximation gives a good agreement with measurements of PL on a narrow DQW in a wide interval of F including flat-band regime. The experimental data are presented for an MBE-grown DQW consisting of two 5 nm wide GaAs wells, separated by a 4 monolayers (MLs) wide pure AlAs central barrier, and sandwiched between Ga_{0.7}Al_{0.3}As layers. The bias voltage is applied along the growth direction. Spatially direct and indirect excitonic transitions are identified, and the radius of the exciton and squeezing of the exciton in the growth direction are evaluated variationally. The excitonic binding energies, recombination energies, oscillator strengths, and relative intensities of the transitions as functions of the applied field are calculated. Our analysis demonstrates that this simple model is applicable in case of narrow DQWs not just for a qualitative description of the PL peak positions but also for the estimation of their individual shapes and intensities.