Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 29: Poster Session: Spintronics; Spin-controled transport; Topological insulators; Interfaces / Surfaces; Magnetic semiconductors

HL 29.18: Poster

Montag, 11. März 2013, 16:00–20:00, Poster A

MBE - growth of capped, strained HgTe, a 3D topological insulator — •Christopher Ames, Philipp Leubner, Christoph Brüne, Hartmut Buhmann, and Laurens Molenkamp — Universität Würzburg, D-97074 Würzburg, Germany

The discovery of two (2D) [1] and three dimensional (3D) [2] topological insulator (TI) behavior in HgTe - systems opens a large field for studying magneto transport properties of both.

We grow HgTe as a 3D topological insulator by molecular beam epitaxy. Unstrained bulk HgTe is a semimetal but opens a gap of roughly 22 meV when grown fully strained on <001> CdTe substrate due to 0.3 % lattice mismatch and shows magnetotransport properties of a 3D TI. Hall measurements show electron mobilities of around 50.000 cm^2(V s)^-1. To increase electron mobilities, various growth optimizations have been carried out. Firstly we grew an HgCdTe buffer layer between the substrate and bulk HgTe. Different buffer thicknesses were analyzed ex-situ by HRXRD, AFM and standard Hall measurements. Secondly, we added a cap-layer of HgCdTe on top of the bulk HgTe. Doing so, we were able to raise the electron mobility of the bulk HgTe up to one order of magnitude. Time-dependent XPS measurements allowed us to hold the suppressed oxidization of the surface responsible for this effect.

Through the advanced material quality we have now more prospects for better understanding of the transport properties in strained HgTe.

[1] König et. al., Science 318 766 (2007)

[2] C. Brüne et. al., Phys. Rev. Lett. 106 126803 (2011)