Berlin 2005 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 17: Poster Ib

HL 17.39: Poster

Freitag, 4. März 2005, 16:30–19:00, Poster TU F

Laser-induced absorption changes in Cu₂O — •Tibor Fleck, Michael Jörger, and Claus Klingshirn — Institut fürAngewandte Physik, Universität Karlsruhe (TH), D-76128Karlsruhe

It is already known that a high density of 1s-excitons in the yellow series of Cu₂O leads to a density-dependent absorption change, i.e. increasing bleaching of np states with increasing density. To gather more information about e.g. the lifetime of the para-excitons we monitor the differential absorption spectra (DAS) for different excitation conditions (ℏω_exc, P_exc) and delay times after pulsed ns-excitation with excimer- or dye-laser of our naturally grown Cu₂O samples.
Different ℏω_exc between the phonon-assisted 1s-absorption and excitation high above the band gap including resonant excitation of the np-states with P_exc up to the destruction threshold of the samples were chosen. The delay time between pump and probe ranges from time resolved ns-regime to time-integrated µs→ms-regime (the latter with a time resolution of ≈ 4µs). Some of the problems arising with DAS of small absorption changes and their interpretation are discussed.
We compare these results with true 3d numerical simulations of the diffusion equation including the excitonic lifetime as well as surface recombination and exciton creation efficiency.