Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 51: Poster IV
HL 51.52: Poster
Donnerstag, 28. Februar 2008, 16:30–19:00, Poster D
Characterisation of deep defects in ZnO thin films by means of optical deep level transient spectroscopy — •Martin Ellguth1, Robin Weirauch1, Matthias Schmidt2, Holger von Wenckstern1, Rainer Pickenhain1, and Marius Grundmann1 — 1Universität Leipzig, Leipzig, Germany — 2Forschungszentrum Dresden–Rossendorf e.V., Dresden, Germany
We investigated Schottky diodes on ZnO thin films grown by pulsed laser deposition using thermal admittance spectroscopy (TAS), deep level transient spectroscopy (DLTS), optical DLTS (ODLTS), and photocurrent spectroscopy (PC). The typically occuring impurities E1, L2, E3, E4, and E5 were found in DLTS and/or TAS measurements.
ODLTS measurements in the spectral range from 0.4 to 3.5 eV indicated that E1, L2, and E3 are optically inactive. For some samples we detected an optically active impurity by ODLTS which was not accessible to thermal capacitance spectroscopical methods due to its high binding energy. The experimentally determined optical capture cross section reveals that this impurity causes a high lattice distortion. Furthermore, there are at least three states generated by this defect which are situated 50 meV below the conduction band edge, in the mid–gap, and several meV above the valence band edge. ODLTS spectra showed a broad absorption band around 2.4 eV which coincides with the green luminescence in ZnO known from photo luminescence measurements. A configuration coordinate diagram for these defect states is presented.