Regensburg 2000 – scientific programme
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HL: Halbleiterphysik
HL 38: Poster III: Transporteigenschaften (1-14), Optische Eigenschaften (15-31), Grenz-/Oberfl
ächen (32-44), Heterostrukturen (45-57), Bauelemente (58-67), Gitterdynamik (68-69), Diamant (70), Raster-Tunnel-Mikroskopie (71)
HL 38.46: Poster
Thursday, March 30, 2000, 14:00–19:00, B
Structure of MBE Grown InAs Quantum Dots Studied by X-ray Techniques — •kai Zhang1, J. Falta2, Ch. Heyn1, Th. Schimdt2, G. Materlik3, and W. Hansen1 — 1Institut für Angewandte Physik, Universität Hamburg, Jungiusstr. 11, 20355 Hamburg — 2Institut für Festkörperphysik, Universität Bremen, Postfach 330440, 28334 Bremen — 3HASYLAB am DESY, Notkestr. 85, 22607 Hamburg
Grazing incidence small angle x-ray scattering (GISAXS) and x-ray diffraction (GIXRD) experiments have been performed on self-assembled InAs quantum dots (QD) grown by molecular beam epitaxy (MBE). In GISAXS we find pronounced diffuse scattering peaks with high diffraction orders up to ± 3 along [110], [1-10] and [100] orientation, indicating ordering in QD distribution. The ratio of the mean dot-dot distances in [100] and [110] directions is determined to be 1.13. The correlation lengths of the dot distribution are found to be the same along [110] and [1-10] azimuths and smaller along [100] azimuth. We therefore propose an anisotropic ordering of QD distribution. Additional broad diffraction peaks are observed at larger diffraction angles and associated to crystal truncation rod (CTR) intensity of dot facets. With the incoming beam in [110] and [1-10] direction we observe CTR originating from QD facets of the (111) family and in [100] direction facets of the (101) family. This indicates an octagonal-based dot shape. From GIXRD of the (202) Bragg peak, we reveal different strain components with elastic deformation in lateral and vertical directions of samples when the InAs QDs are formed. We also resolve diffraction intensity from In1−xGaxAs alloy which we believe to be contained in the wetting layer beneath the QDs.