Berlin 2012 – wissenschaftliches Programm
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KR: Fachgruppe Kristallographie
KR 10: Crystallography in Nanoscience
KR 10.1: Hauptvortrag
Donnerstag, 29. März 2012, 09:30–10:00, E 124
On polytypism in III-V nanowires — •Friedhelm Bechstedt1, Abderrezak Belabbes1, Christian Panse1, Jürgen Furthmüller1, Dominik Kriegner2, and Julian Stangl2 — 1Friedrich-Schiller-Universität, Max-Wien-Platz 1, 07743 Jena, Germany — 2Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austria
Nanowires (NWs) based on III-V semiconductors, whose bulk crystals crystallize in zinc-blende structure, are usually grown in [111]B direction. Therefore, their bond stacking fluctuates, and the formation of different polytypes is a common phenomenon in NWs. The properties of the hexagonal 6H, 4H, and 2H polytypes are however modified with respect to the cubic zinc-blende (3C) structure.
A systematic study of structural and electronic properties of the Ga-V and In-V compounds (V = P, As, Sb) is reported for four polytypes. The lattice-constant and internal-cell parameters are derived within well-converged density-functional calculations within the local density approximation (LDA) and discussed versus the polytype hexagonality. The comparison with recent X-ray diffraction measurements shows excellent agreement and clear trends.
The quasiparticle electronic structures are computed with high accuracy including spin-orbit interaction applying a recent calculation scheme, the LDA-1/2 method. The fundamental gaps increase with the hexagonality. The results are used to derive band offsets between different polytypes. We predict a type-II heterocrystalline character for the junctions between two polytypes in agreement with spectroscopic studies.