A theoretical study of erbium in GaN

Hourahine, B. and Sanna, S. and Aradi, B. and Kohler, C. and Frauenheim, Th. (2006) A theoretical study of erbium in GaN. Physica B: Condensed Matter, 376-377. pp. 512-515. ISSN 0921-4526

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Electroluminescence from rare earth-doped nitride semiconductors shows promise for a variety of applications since strong room temperature luminescence can be observed in these materials for a variety of lanthanide dopants. Modelling of the microscopic structure and properties of the defects involved in the luminescence presents a substantial challenge to current theoretical methods. While it is possible to investigate issues of defect stability using pseudopotential-based approaches, which avoid the problems of modelling strongly correlated f-electron systems, this cannot address luminescence from these centres. Explicitly treating 4f electrons is beyond the reach of the usual mean-field methods normally employed in density-functional theory. In an attempt to improve the theoretical description of these systems while extending the size of models used, we present the results using density-functional -based tight-binding calculations on the properties of erbium in wurtzite GaN. Both substitutional defects and complexes with nitrogen vacancies are considered. We account for strong correlation of the 4f shell using a variant of the LDA+ U method. (c) 2005 Elsevier B.V. All rights reserved.