Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 50: ZnO: Tansport
HL 50.7: Vortrag
Donnerstag, 28. Februar 2008, 15:30–15:45, ER 164
Determination of the free charge carrier profile in ZnO films — •Chris Sturm1, Holger von Wenckstern1, Rüdiger Schmidt-Grund1, Matthias Brandt1, Tsvetan Chavdarov1, Bernd Rheinländer1, Carsten Bundesmann2, Holger Hochmuth1, Michael Lorenz1, Mathias Schubert3, and Marius Grundmann1 — 1Universität Leipzig, Institut für Experimentelle Physik II, Linnéstraße 5, 04103 Leipzig — 2Leibniz-Institut für Oberflächenmodifizierung e.V., 04318 Leipzig — 3Department of Electrical Engineering, University of Nebraska-Lincoln, 68588-0511 Lincoln, Nebraska, USA
Non-polar ZnO is a promising material for optoelectronic applications since internal electric fields are avoided. For ZnO based devices such as LEDs, FETS and microcavities ZnO-Al2O3 heterostructures are of interest, e.g. as electrical barrier. However it was found that a thin layer in ZnO near to the ZnO-Al2O3 interface shows a high free charge carrier concentration. We present investigations of the thickness and the free charge carrier concentration of this layer using two complementary methods: infrared spectroscopic ellipsometry and Hall measurements.
The nominally undoped non-polar ZnO films were grown by pulsed laser deposition r-plane sapphire substrates with different film thicknesses (30 nm−600 nm). For all ZnO films we have found a remarkably higher free charge carrier concentration at the ZnO-sapphire interface compared to the remaining layer. We obtain an increasing charge sheet density with increasing film thickness. Attempts will be presented to clear up the origin of the experimentally found high concentration.