Münster 1999 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 4: Heterostrukturen I
HL 4.2: Vortrag
Montag, 22. März 1999, 10:45–11:00, H3
X-ray structural investigation of strained InAs-films on GaAs (001) — •Kai Zhang1, A. Foede2, J. Falta2, Ch. Heyn1, I. Lohse1, G. Materlik2, and W. Hansen1 — 1Institut f"ur Angewandte Physik, Universit"at Hamburg, Jungiusstr. 11, 20355 Hamburg — 2HASYLAB am DESY, Notkestr. 85, 22607 Hamburg
Ultra thin strained InAs films on GaAs (001) crystals prepared by molecular beam epitaxy (MBE) were structurally characterized by X-ray techniques using synchrotron radiation. The layers were deposited at a substrate temperature of 500 ∘C with coverages ranging from 1 to 2.1 monolayers (ML). For characterization grazing incidence X-ray reflectivity (GIXR), crystal truncation rods (CTR), and X-ray standing waves (XSW) were employed. GIXR and CTR were ulitized to determine the average layer thickness, interface roughness, and the stoichiometry of the layers. XSW experiments allow to determine the In lattice site. For higher coverages the XSW clearly reflect the transition to the Stranski Krastanov growth mode. By means of in-situ reflection high energy electron diffraction (RHEED) patterns monitored during growth, the change from two-dimensional to Stranski-Kranstanow growth mode was found at 1.8 ML InAs deposited as determined from the In-flux measurement. GIXR and CTR crystal results reveal a strong tendency for intermixing of In and Ga at the interface. The interface roughness of the film decreases with increasing InAs coverage up to In deposits of 1.8 ML and increases again after the transition to Stranski Krastanow growth mode. The formation of three-dimensional InAs islands at 1.8 ML is also confirmed by XSW. We presently study the islands formed in the Stranski Krastanow mode in more detail and preliminary results will be presented.