Impact of defects on photoexcited carrier relaxation dynamics in GeSn thin films.

We report the results of a study that was conducted to investigate the recombination paths of photoexcited charge carriers in GeSn thin films. The charge carrier lifetime was predicted as a function of temperature from a description of photoconductivity transients, assuming co-influence of Shockley-Read-Hall and radiative carrier recombination paths. We identify that dislocations are the source of a band of electronic states with the highest occupied state at E + (85÷90) meV that acts as Shockley-Read-Hall centers determining the charge carrier lifetime.

Circular scanning fluorescence correlation spectroscopy on membranes.

We discuss circular scanning Fluorescence Correlation Spectroscopy (sFCS) as a simple extension of standard FCS for accurate, robust and fast diffusion measurements on membranes. The implementation is based on a straightforward conversion of a conventional FCS instrument to a sFCS device by mounting a mirror onto a two-axis piezo scanner. The measurement volume is scanned in a circle with sub-micron radius, allowing the determination of diffusion coefficients and concentrations without any a priori knowledge of the size of the detection volume.