Realistic heterointerfaces model for excitonic states in growth-interrupted quantum wells

TL;DR

This paper develops a detailed model for interface disorder in GaAs quantum wells, linking microscopic interface features to excitonic optical properties and matching experimental observations.

Contribution

It introduces a comprehensive heterointerface disorder model including long-range effects and applies it to predict excitonic optical responses in growth-interrupted quantum wells.

Findings

Long-range disorder correlation lengths are about 60-90 nm.

Eigenstate model predicts a distribution of dephasing rates consistent with experiments.

Interface disorder parameters are quantitatively extracted from optical measurements.

Abstract

We present a model for the disorder of the heterointerfaces in GaAs quantum wells including long-range components like monolayer island formation induced by the surface diffusion during the epitaxial growth process. Taking into account both interfaces, a disorder potential for the exciton motion in the quantum well plane is derived. The excitonic optical properties are calculated using either a time-propagation of the excitonic polarization with a phenomenological dephasing, or a full exciton eigenstate model including microscopic radiative decay and phonon scattering rates. While the results of the two methods are generally similar, the eigenstate model does predict a distribution of dephasing rates and a somewhat modified spectral response. Comparing the results with measured absorption and resonant Rayleigh scattering in GaAs/AlAs quantum wells subjected to growth interrupts, their specific disorder parameters like correlation lengths and interface flatness are determined. We find that the long-range disorder in the two heterointerfaces is highly correlated, having rather similar average in-plane correlation lengths of about 60 and 90 nm. The distribution of dephasing rates observed in the experiment is in agreement with the results of the eigenstate model. Finally, we simulate highly spatially resolved optical experiments resolving individual exciton states in the deduced interface structure.