Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 38: ZnO and Related Semiconductors

HL 38.8: Talk

Wednesday, March 24, 2010, 11:30–11:45, H17

First-principles DFT study of dopant elements at grain boundaries in ZnO — •Christian Elsässer and Wolfgang Körner — Fraunhofer Institut für Werkstoffmechanik, IWM, Freiburg, Germany

We present a first-principles density-functional-theory study of doped ZnO with focus on its application as a transparent conducting oxide (TCO). TCOs with high optical transparency and high electrical conductivity are for example applied in low emissivity windows, as transparent electrodes in photovoltaic cells or light emitting diodes. We investigated the impact of grain boundaries on the physics of atomic defects, and especially the formation energies of oxygen vacancies, cation dopants Al and Ga and anion dopants N and P are determined. The main goal is to obtain information about the positions of the defect levels generated by the different dopants in the electronic band gap. Because of the known deficiency of the local density approximation (LDA) to yield accurate values for band gap energies for insulators like ZnO a self-interaction correction (SIC) to the LDA is employed,which merely increase the computational costs. The main result of our study is that grain boundaries do affect the formation energies for substitutional dopants significantly. Furthermore the position and shape of dopant-induced electronic energy levels at the grain boundaries are changed considerably with respect to the single crystal. This may help to explain for example why N-doping can lead to p-conductivity at room temperature.