Valency configuration of transition metal impurities in ZnO |
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Authors: | L. Petit T. C. Schulthess A. Svane W. M. Temmerman Z. Szotek A. Janotti |
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Affiliation: | (1) Computer Science and Mathematics Division, and Center for Computational Sciences, Oak Ridge National Laboratory, 37831 Oak Ridge, TN;(2) Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark;(3) Daresbury Laboratory, Daresbury, WA4 4AD Warrington, United Kingdom;(4) Materials Department, University of California, 93106-5050 Santa Barbara, CA |
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Abstract: | We use the self-interaction corrected local spin-density approximation to investigate the ground state valency configuration of transition metal (TM=Mn, Co) impurities in n- and p-type ZnO. We find that in pure Zn1−xTMxO, the localized TM2+ configuration is energetically favored over the itinerant d-electron configuration of the local spin density (LSD) picture. Our calculations indicate furthermore that the (+/0) donor level is situated in the ZnO gap. Consequently, for n-type conditions, with the Fermi energy εF close to the conduction band minimum, TM remains in the 2+ charge state, while for p-type conditions, with εF close to the valence band maximum, the 3+ charge state is energetically preferred. In the latter scenario, modeled here by co-doping with N, the additional delocalized d-electron charge transfers into the entire states at the top of the valence band, and hole carriers will only exist, if the N concentration exceeds the TM impurity concentration. |
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Keywords: | Correlated electrons diluted magnetic semiconductors self-interaction correction |
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