Berlin 2008 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 32: Quantum dots and wires: preparation and characterization I
HL 32.1: Talk
Wednesday, February 27, 2008, 14:15–14:30, ER 270
Towards quantification of the In-distribution in embedded InGaAs quantum dots — •Holger Blank1, Dimitri Litvinov1, Reinhard Schneider1, Dagmar Gerthsen1, Thorsten Passow2, and Kurt Scheerschmidt3 — 1Laboratory for Electron Microscopy (LEM), University Karlsruhe (TH), 76128 Karlsruhe, Germany — 2Institute for Applied Physics and Center for Functional Nanostructures (CFN), 76128 Karlsruhe, Germany — 3Max Planck Institute for Microstructure Physics, 06120 Halle, Germany
The composition of InAs quantum dots (QDs) grown by molecular-beam epitaxy was studied by high-resolution transmission electron microscopy (TEM) using the composition evaluation by lattice fringe analysis (CELFA) technique [1]. Significant deviations between real and nominal QD composition occur frequently due to In-segregation during GaAs cap layer growth. To understand the opto-electronic properties of the QDs, the real composition needs to be determined. The application of TEM to three-dimensional structures is hampered by the averaging effects over the TEM specimen thickness. This lowers artificially the measured In-concentration in QDs which are embedded in a GaAs matrix. We solve the averaging problem by determining the QD shape and size as well as the TEM sample thickness. We show that QDs deposited at a very low InAs growth rate of 0.0056 ML/s contain a core of almost pure InAs.
[1] A. Rosenauer, D. Gerthsen, Ultramicroscopy 76 (1999), 49-60