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SYEC: Symposium Exact-exchange and hybrid functionals meet quasiparticle energy calculations
SYEC 2: Exact-exchange and hybrid functionals meet quasiparticle energy calculations II
SYEC 2.8: Vortrag
Donnerstag, 28. Februar 2008, 15:45–16:00, A 053
Hybrid functional and GW calculations on defects in semiconductors: from quantitative to qualitative changes of defect levels and states compared to standard DFT methods — •Adam Gali1, Peter Deák2, Bálint Aradi2, and Riccardo Rurali3 — 1Department of Atomic Physics, Budapest University of Technology and Economics, Budapest, Budafoki út 8, H-1111, Hungary — 2Bremen Center for Computational Materials Science, University of Bremen, D-28359 Bremen, Germany — 3Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
The state-of-the-art method to calculate defect properties in semiconductors is density-functional theory (DFT) in a supercell geometry. Standard implementations of DFT, like the local density or the generalized gradient approximation, suffer from the underestimation of the band gap, which may lead to erroneous defect level positions. We applied and compared hybrid functional and model GW method to correct the one-electron DFT defect levels in various semiconductors. We show i) the very simple scissor correction may work for vacancy defects but fails for interstitial defects ii) the standard DFT method can predict even qualitatively wrong description of the defect states iii) the correct description of the defect state can lead to different geometry of the defect, therefore, the self-consistent correction of the total energy and forces is also necessary. Finally, we compare hybrid functional and GW method on bare and defective semiconductor nanostructures.