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K: Fachverband Kurzzeitphysik
K 1: Optische Methoden und Verfahren
K 1.2: Vortrag
Montag, 25. Februar 2013, 14:30–14:45, HS 4
Observing surface charges in oxide coatings on silicon surfaces with THz emission spectroscopy — •Ulrike Blumröder1, Stefan Nolte1,2, and Andreas Tünnermann1,2 — 1Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-University, Max-Wien-Platz 1, 07743 Jena, Germany — 2Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Straße 7, 07745 Jena, Germany
One mechanism leading to the emission of pulsed THz-radiation at semiconductor surfaces is the acceleration of photogenerated carriers in depletion or accumulation layers usually existing at semiconductor surfaces due to occupied surface states lying within the bandgap. The opposite direction of the depletion field in n- and p-doped semiconductors results in a flipping of the polarity of the emitted THz pulse as it has been observed for differently doped GaAs samples. On the other hand surface charges are also known to be present in oxide layers that are used for the passivation of silicon surfaces in the photovoltaic industry. Therefore they lead to the formation of a space charge layer beneath the silicon surface as well. We investigate the THz emission of thermally oxidized and ALD coated silicon wafers with THz emission spectroscopy and proved the existence of surface charges by investigating the polarity of the emitted THz pulse.