Electron-phonon interaction effects on the direct gap transitions of nanoscale Si films

TL;DR

This paper investigates how electron-phonon interactions affect the optical properties of nanoscale silicon films, revealing significant size and temperature-dependent shifts in their direct gap transitions due to phonon dispersion changes.

Contribution

It demonstrates the impact of electron-phonon interactions on the dielectric function and excitonic transitions in nanoscale silicon quantum wells, highlighting the role of phonon dispersion modifications.

Findings

Energy shifts depend on film thickness and temperature

Phonon dispersion influences dielectric function changes

Dielectric layer modifications alter electron-phonon effects

Abstract

This study shows that the dielectric function of crystalline Si quantum wells (c-Si QW) is influenced by both carrier confinement and electron-phonon interactions. The energy shifts and lifetime broadening of the excitonic E1 direct gap transition of c-Si QWs from 2 to 10 nm are found to have a significant dimensional and temperature dependence that can be traced to changes in the phonon dispersion of nanoscale films. The influence of electron-phonon interactions on the dielectric function was verified by altering the phonon dispersion using different dielectric layers above a 5 nm c-Si QW.