Dresden 2014 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 114: Oxides: Bulk, films and interfaces
HL 114.10: Vortrag
Freitag, 4. April 2014, 12:00–12:15, POT 251
Recharging behaviour of nitrogen-centers in ZnO — •Jan M. Philipps1, Bruno K. Meyer1, Detlev M. Hofmann1, and Matt McCluskey2 — 1Institute of Physics I, Heinrich-Buff-Ring 16, Justus-Liebig-University Giessen, D-35392 Giessen, Germany — 2Department of Physics and Astronomy, Washington State University, Pullman, WA 99164-2814, USA
Nitrogen was quoted to be a candidate to obtain p-type conductive ZnO. One assumes in a simple model that nitrogen substitutes an oxygen atom in the crystal lattice and thus causes an acceptor. The hope was that the recharging level of the nitrogen acceptors is shallow enough to accept electrons from the valence band and thus to promote hole conductivity. Unfortunately, it turned out that this model was too simple, electron paramagnetic resonance experiments (EPR) revealed that substitutional nitrogen centers (NO) are deep defects with a recharging level 1.3 eV above the valence band.
In the following it was speculated that nitrogen-pair centers or complexes consisting of nitrogen and vacancies could act as shallow acceptors. Again EPR was successful to identify N2-centers in ZnO by the observation of a 5-line spectrum caused by the hyperfine interaction of two nitrogen nuclei. The recharging of this center exhibits two steps, a weak onset at about 1.4 eV and a strongly increasing signal for photon energies above 2.1 eV. The later energy coincides with the recharging energy of the NO-centers. These results indicate that also the N2-centers are deep level defects and not suitable to cause significant hole-conductivity at room temperature.