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HL: Fachverband Halbleiterphysik

HL 34: Quantum dots and wires: Theory

HL 34.1: Talk

Tuesday, March 12, 2013, 09:30–09:45, H15

Bulk and interface defects and impurities in Au-catalyzed GaAs nanowire growth: First principles study — Sung Sakong, Yaojun Du, and •Peter Kratzer — Fakultät für Physik and Center for Nanointegration (CENIDE), Universität Duisburg-Essen, Duisburg, Germany

For the growth of GaAs nanowires, often an Au nanoparticle is used as catalyst, which allows for generating co-existing zincblende and wurtzite polytypes of GaAs, but may also introduce Au impurities in the nanowire. We use density functional theory to calculate the formation energy of various growth-related defects and impurities in both GaAs polytypes and at the Au(111)/GaAs(111)B interface. Defects whose formation energy in bulk is much larger than at the interface, e.g., an As vacancy or a substitutional Au impurity at the As site will travel with the growth zone and hence are less harmful. However, the energetics of the Ga_As antisite defect and the substitutional Au impurity at the Ga site are comparable in bulk and at the interface. Especially, the formation of the Au impurity at the Ga site costs relatively low energy. Thus, we predict that the most abundant defect in the GaAs nanowire will be the Au impurity at the Ga site, in good agreement with the recent experimental findings by Bar-Sadan et al. [Nano Lett. 12, 2352 (2012)]. In conclusion, we suggest that an As-rich growth regime could reduce the defects and impurities in the nanowire by avoiding the Ga-termination of GaAs at the growth zone which could act as a source of defects at the Ga site.