Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 1: III-V semiconductors I
HL 1.6: Vortrag
Montag, 23. März 2009, 11:45–12:00, BEY 81
Analysis of segregation profiles in InGaAs quantum wells via TEM and STEM — •Thorsten Mehrtens1, Marco Schowalter1, Knut Müller1, Andreas Rosenauer1, Dongzhi Hu2, and Daniel M. Schaadt2 — 1Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen — 2Institut für Angewandte Physik/DFG-Center für funktionelle Nanostrukturen, Universität Karlsruhe (TH), Wolfgang-Gaede-Str. 1, 76131 Karlsruhe
Knowledge of the composition distribution in epitaxially grown semiconductor nanostructures is essential to understand the growth process, where segregation plays an important role. We report on InGaAs heterostructures grown by molecular beam epitaxy (MBE). Before the growth of the InGaAs layer the specimen was heated up briefly to remove Ga from a possible Ga floating layer. The temperature has been varied for different wells to study the influence on segregation. Composition profiles were measured by scanning transmission electron microscopy (STEM) with a high-angle annular dark field (HAADF) detector. This setup exploits the Z-dependence of the thermal diffuse high angle scattering. Simulations were performed with the frozen lattice approach in dependence on sample thickness and concentration. Comparing the measurement with the simulations leads to the concentration profile. Segregation coefficients have been calculated and compared to coefficients obtained with the composition evaluation by lattice fringe analysis (CELFA), which uses the chemical sensitive (002) and the undiffracted (000) beam. Both methods do not reveal a significant influence of the specimen heating on the segregation coefficient.