Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 43: Ultra-fast phenomena

HL 43.4: Talk

Wednesday, March 18, 2015, 10:15–10:30, EW 202

Asynochronous Optical Sampling of Rolled-up GaAs/InGaAs Superlattices — •Delia Brick¹, Martin Schubert¹, Chuan He¹, Martin Grossmann¹, Vivienne Meier², Guodong Li², Daniel Grimm², Oliver G. Schmidt², and Thomas Dekorsy¹ — ¹Universität Konstanz, Deutschland — ²IFW Dresden, Deutschland

Strained bilayers of different materials can be rolled up to form radial superlattices by controlled release of the bilayers which were deposited on a sacrificial layer [1]. This new kind of rolled-up superlattices has not only a broad field of applications but is also interesting by itself [1,2]. It is important for these tubes to be uniform and defect free, therefore it is of great interest to characterize the superlattice tubes through a fast, non-invasive method like femtosecond pump-probe spectroscopy using asynchronous optical sampling (ASOPS) [3].

Rolled-up GaAs/InGaAs superlattices are optically excited and detected by ASOPS. The acoustic phonon modes are analyzed. The folding of the dispersion relation of the superlattice can be measured and it is possible to determine the quality of the layers by seeing large changes in the spectra. Scans over the length of the tubes can provide information on the homogeneity. Furthermore measurements at different temperatures are performed to measure phonon lifetimes.

References: [1] Deneke et al; Journal of Physics D: Applied Physics; 103, 233114 (2009) [2] Angelova et al; Applied Physics Letters; 100, 201904 (2012) [3] Ristow et al, Applied Physics Letters; 103, 233114 (2013)