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NANOMAT Report Summary

Project ID: G5RD-CT-2001-00545
Funded under: FP5-GROWTH
Country: Belgium

Development of experimental and theoretical tools for the determination of the role of phonons in single layers of quantum dots

Nature of the result
The result involves the development of a methodology for the calculation of phonon modes and the exciton-phonon interaction in single layers of self-assembled quantum dots (SAQDs). Calculations are based on the multimode dielectric continuum model for phonons in confined systems with given geometric and material parameters.

Optical absorption spectra of single SAQDs are calculated using the non-adiabatic theory of phonon-assisted optical transitions in quantum dots. The proposed approach is applied to analyse the optical-absorption and photoluminescence (PL) spectra of single InAs/GaAs SAQDs and quantum-dot quantum wells. It provides a basis also for the calculation of the PL excitation (PLE) and Raman spectra of SAQDs.

The developed methodology of calculations of optical spectra of SAQDs has been used to analyse some experimental data obtained at RSU and TUB. Approximate values of an effective value of the electron-phonon interaction can be obtained directly from PL spectra whenever multiphonon structures clearly appear in the spectra, provided artifacts due to the simultaneous contributions of ground state phonon replica and excited states are taken into account.

In the case of broad PL spectra, low temperature PLE and resonant PL (RPL) gives rise to a fluorescence narrowing and to a partial recovery of phonon structures. Acoustic phonons in self-organized InAs/GaAs quantum dots were investigated through spectral hole burning experiments.

Potential applications of the result:
The result can be used for the characterization of single layers of SAQDs and other semiconductor nanostructures using experimental data on optical-absorption, luminescence and Raman spectra.

End-users of the result:
The end users of this result are all those involved in the research and development of semiconductor nanostructures, including members of the project consortium and the wider scientific community.

Main innovative features/benefits:
As distinct from the models of bulk phonons and the dielectric continuum model, within the developed approach the phonon modes in a quantum dot are hybrids of bulk-like and interface vibrations. The result offers the possibility for an advanced understanding of the vibrational spectra and optical properties of self-assembled semiconductor nanostructures.

Analysis of market or application sectors:
The result is a principally scientific one, so such an analysis is not applicable.

Potential barriers:
There are no barriers to the use of this result, which has been widely disseminated.


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