Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 86: Quantum Dots: Growth and Characterization

HL 86.10: Vortrag

Freitag, 18. März 2011, 12:45–13:00, FOE Anorg

Cell-internal structure of hexagonal polytypes in III-V semiconductors — •Christian Panse¹, Dominik Kriegner², and Friedhelm Bechstedt¹ — ¹Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Germany — ²Institute for Semiconductor and Solid State Physics, Johannes Kepler University Linz, Austria

Semiconductor nanowires (NW) play a key role in future nanotechnology. Despite of the zinc-blende (3C) bulk structure III-V nanowires exhibit a mixture of wurtzite (2H) and zinc-blende (3C) layers. With better control over the crystal structure it became possible to grow not only pure 3C or 2H layers but also small segments of the hexagonal 4H polytype. This offers a new degree of freedom for NW device design, like polytypic superlattices. Therefore, we investigate the structural properties of the different polytypes (3C, 2H, 4H, 6H). We perform ab-initio calculations within the density functional theory for different III-V compounds (GaAs, InAs, InP, InSb). The structural properties are calculated versus the hexagonality of the polytypes using the LDA exchange-correlation functional. Experiment (XRD) and theory show that hexagonal bilayers tends to increase the layer thickness along the c-axis, while simultaneously reduce the in-plane distances. Thereby, the change of the lattice parameters scales linearly with the hexagonality of the polytype. Overall an increase in the relative aspect ratio of the 2H structure by 0.6% compared to the ideal structure is observed. It turns out that only a careful treatment of the cell-internal parameters could guarantee a correct description of the structural properties.