Berlin 2012 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
HL: Fachverband Halbleiterphysik
HL 98: Electronic Structure Theory
HL 98.1: Talk
Friday, March 30, 2012, 09:30–09:45, EW 202
Defect levels hiden by the Kohn-Sham band gap — •Bockstedte Michel — Theoretische Festkörperphysik, FAU Erlangen-Nürnberg, Staudtstr 7B2, 91058 Erlangen
Defects in semiconductors are decisive for the electronic properties. Furthermore they can implement Q-bits for quantum computing. To access the underlying physics, the accurate theoretical description of defect levels and excited states is highly desirable. Yet, the theoretical work horse, density functional theory (DFT) with (semi-)local XC-functionals, suffers from the well-known Kohn-Sham band-gap error. This not only affects defect states within the gap, but may turn otherwise localized ones into resonances outside the gap. Many-body perturbation theory (MBPT) on top of the DFT electronic structure was shown recently to yield excellent results for ionization levels and excited states, however, the latter problem of the DFT may easily hamper such calculations. Here we investigate this problem for a defect in SiC for the polytypes 3C and 4H with different band gaps using MBPT on top of DFT with LDA and HSE06 functionals. While in 4H-SiC G0W0 ionization levels for both functionals agree well, the proper defect states in 3C remain resonances within the LDA. Here simple ad-hoc corrections yield already good results.