Regensburg 2013 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 11: Topical Session: TEM-Symposium - STEM

MM 11.6: Vortrag

Montag, 11. März 2013, 17:15–17:30, H4

STEM HAADF characterization of dilute Bi containing GaAs — •Nikolai Knaub, Andreas Beyer, Peter Ludewig, and Kerstin Volz — Structure and Technology Research Laboratory, Materials Science Center and Faculty of Physics Philipps-Universität Marburg, Germany

Incorporating small amounts of Bi in III/V semiconductors has a huge influence on the energetic position of the valence bands, mainly also of the spin-orbit split-off band. Therefore, dilute bismides such as Ga(AsBi) are promising materials for optical and electronical devices. For a sufficent incorporation of Bi in GaAs, the growth temperature of MOVPE (metal organic vapour phase epitaxy)-grown samples has to be low, typically between 375° C and 450° C. Because of such relatively low growth temperatures point defects, such as Bi or As antisites, can arise and influence the crystal structure. We present the results of STEM (scanning transmission electron microscopy) high angle annular dark field (HAADF) measurements on a MOVPE-grown Ga(AsBi) sample. We used a spherical aberration corrected JEOL JEM 2200 FS with an annular dark field detector for the high resolution. For quantitative comparison with the experimental images, an absorptive potential approximation based simulation software was used for simulations of antisite defects in GaAs and Ga(AsBi). The present contribution will show how to gain information of crystal stochiometry and composition out of experimental as well as simulated HAADF images by using the Voronoi map method. It will be shown that it is possible to describe the influence of point defects on an atomic scale quantitativley.