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HL: Fachverband Halbleiterphysik
HL 62: Poster II: Photovoltaics and Organic Semiconductors
HL 62.30: Poster
Donnerstag, 25. März 2010, 18:00–20:00, Poster D2
Defect characterisation of thin a-Si:H- and µc-Si:H-films with FTPS (“Fourier Transform Photocurrent Spectroscopy”) — •Dominik Schael1, Armin Brechling1, Ulrich Heinzmann1, Thomas Westerwalbesloh2, and Helmut Stiebig2 — 1Molecular and Surface Physics, Bielefeld University, Germany — 2Malibu GmbH & Co. KG, Bielefeld, Germany
An important characteristic of silicon semiconductors is the defect concentration. Acting as recombination centers, defects lead to a reduced carrier lifetime, which strongly influences the performance of a solar cell. One way to get information about the defect concentration is the determination of the optical absorption coefficient α(E) in the sub-band range. Obtaining α(E) of thin a-Si:H- and µc-Si:H-layers is a challenge since α(E) varies over several orders of magnitude. A very sensitive method to determine the absorption coefficient is the Fourier Transform Photocurrent Spectroscopy. Here, the a-Si:H- or µc-Si:H-sample acts as an external detector in a FTIR setup, which enables very fast measurements. By calibrating the FTPS-signal with reflectance and transmittance data, absolute values for α(E) are obtained. Depending on the characteristics of α(E), a defect concentration can be calculated.
We will present the measurement setup and will discuss the sub-band gap distribution of different Si based (a-Si:H, µc-Si:H and c-Si) samples.