Spatio-temporal dynamics of localized excitons in semiconductor nanostructures

  • Østergaard, John Erland (Project Manager)
  • Hvam, Jørn Marcher (Project Participant)
  • Leosson, Kristjan (Project Participant)
  • Birkedal, Dan (Project Participant)
  • Langbein, Wolfgang (Project Participant)

Project Details


We have constructed equipment for spatially resolved optical investigation of semiconductor nanostructures, notably a low-temperature microphotoluminescence system and a high resolution imaging spectrometer. The combination of microphotoluminescence and high spectral resolution opens up new possibilities in studying localized carriers in semiconductor nanostructures. The initial focus will be on localized excitonic states in narrow quantum wells and quantum wires. Interface roughness and chemical inhomogeneities in the semiconductor heterostructure introduce fluctuations in the energy landscape, which lead to the localization of low energy excitons. These excitons form quantum-dot-like states with well-defined transition energies and extremely sharp photoluminescence lines. Using the microphotoluminescence technique, such lines may be studied individually and statistical information about the constituents of the luminescent system can be obtained.
To gain more information about carrier dynamics and relaxation in these types of nanostructures the high spatial resolution must be combined with spectroscopic techniques having high temporal resolution. We are therefore establishing high-sensitive differential transmission spectroscopy in our laboratory using femtosecond lasers. With additional pulse shaping, non-degenerate pump-probe studies with picosecond timeresolution will be performed. With this technique in combination with temperature dependent measurements, time-scales and processes for energy relaxation and dephasing of localized excitons can be determined. This fundamental information is important for optimizing their application to optical components such as lasers and amplifiers.
Effective start/end date01/09/199831/08/2001