Spatio-temporal dynamics of quantum-well excitons

TL;DR

This study explores the complex lateral transport of excitons in ZnSe quantum wells, revealing deviations from classical diffusion due to hot-exciton effects, supported by high-resolution measurements and Monte Carlo simulations.

Contribution

It demonstrates that classical diffusion assumptions and the equivalence of exciton population and photoluminescence evolution are invalid at low temperatures.

Findings

Deviation from classical diffusion observed up to 400 ps

Hot-exciton effects significantly influence transport dynamics

Monte Carlo simulation effectively models coupled transport-relaxation processes

Abstract

We investigate the lateral transport of excitons in ZnSe quantum wells by using time-resolved micro-photoluminescence enhanced by the introduction of a solid immersion lens. The spatial and temporal resolutions are 200 nm and 5 ps, respectively. Strong deviation from classical diffusion is observed up to 400 ps. This feature is attributed to the hot-exciton effects, consistent with previous experiments under cw excitation. The coupled transport-relaxation process of hot excitons is modelled by Monte Carlo simulation. We prove that two basic assumptions typically accepted in photoluminescence investigations on excitonic transport, namely (i) the classical diffusion model as well as (ii) the equivalence between the temporal and spatial evolution of the exciton population and of the measured photoluminescence, are not valid for low-temperature experiments.