Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 73: GaN: Preparation and Characterization IV
HL 73.5: Vortrag
Donnerstag, 29. März 2012, 10:30–10:45, ER 270
Reliable defect energetics in GaN:Mg — •Björn Lange1, Christoph Freysoldt1, Jörg Neugebauer1, Qimin Yan2, John L. Lyons2, Anderson Janotti2, and Chris G. Van de Walle2 — 1Max-Planck Institut für Eisenforschung GmbH, 40237 Düsseldorf, Deutschland — 2University of California Santa Barbara, CA 93106-5050, USA
Density-functional theory (DFT) is a widely used method for electronic structure calculations. The modeling of defects within this method allows us to calculate their formation energies and concentrations in dependence of experimental growth parameters. In the plane-wave DFT description there are several approximations for modeling the electron-ion interaction (pseudo potentials or the PAW approach) and the exchange-correlation functional (LDA, GGA, or hybrid functionals such as HSE). Calculated formation energies of defects with respect to standard reference systems (bulk solids or molecules) may strongly depend on these computational details. In this work we show that the differences arise mainly from the varying quality of description between defects and the reference systems. A new reference system which uses defect states allows for a fair comparison, showing a much better agreement between the different approaches. We discuss the remaining differences for various defects related to Mg doped GaN. The obtained formation energies are then used to calculate defect concentrations in dependence of the Mg concentration. Based on this analysis we identify the mechanism behind the experimental observed drop of the relative hydrogen concentration occurring in highly Mg-doped GaN samples.