Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 54: Si/Ge
HL 54.1: Vortrag
Freitag, 29. Februar 2008, 10:30–10:45, EW 202
Defect Formation Energies without the Band-Gap Problem: Combining DFT and GW for the Silicon Self-Interstitial — •Patrick Rinke1,2, Anderson Janotti1, Chris G. Van de Walle1, and Matthias Scheffler1,2 — 1University of California at Santa Barbara, CA 93106 — 2Fritz-Haber-Institut der MPG, Berlin
For the self-interstitial in silicon, a defect of high technological relevance, density functional theory (DFT) in the widely applied local-density approximation (LDA) underestimates the formation energies of different configurations in the neutral charge state by about 1.5 eV compared to diffusion Monte Carlo (DMC) calculations [1,2]. We attribute this to artificial self-interaction and the absence of the derivative discontinuity in the exchange-correlation potential in the LDA that give rise to the band-gap problem. Here we present a new formalism that combines LDA with quasiparticle energy calculations in the G0W0 approximation to overcome these deficiencies. The formation of the neutral defect is expressed as successive charging of its 2+ charge state, for which the defect level is unoccupied. This allows us to decompose the formation energy into a lattice (LDA) and an electron addition part (G0W0) [3]. The G0W0 corrections increase the LDA formation energy of the neutral state by ∼1.1 eV. Moreover, the G0W0-corrected charge transition levels, which are also readily available, agree well with recent measurements [4]. [1] E. R. Batista et al. Phys. Rev. B 74, 121102(R) (2006), [2] W.-K. Leung et al. Phys. Rev. Lett. 83, 2351 (1999), [3] M. Hedström et al. Phys. Rev. Lett. 97, 226401 (2006), [4] H. Bracht et al. Phys. Rev. B 75, 035211 (2007)