Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 3: III-V semiconductors I
HL 3.1: Vortrag
Montag, 27. März 2006, 10:15–10:30, POT 51
Surface concentration mapping of InAs/GaAs quantum dots — •S. Heun1, G. Biasiol1, G. B. Golinelli2, A. Locatelli3, T. O. Mentes3, F. Z. Guo4, C. Hofer5, C. Teichert5, and L. Sorba1,2 — 1Laboratorio TASC INFM-CNR, 34012 Trieste, Italy — 2Universita degli Studi di Modena e Reggio Emilia, 41100 Modena, Italy — 3Sincrotrone Trieste, 34012 Trieste, Italy — 4JASRI/SPring-8, 1-1-1, Kouto, Mikazuki, Sayo, Hyogo 679-5198, Japan — 5Institute of Physics, University of Leoben, 8700 Leoben, Austria
With x-ray photoemission electron microscopy we obtained two-dimensional maps of the in-plane surface composition of InAs/GaAs self-assembled quantum dots [1]. This provides complementary information to cross-sectional studies of InAs dots, which could open the way to a full 3D mapping of the dot composition and to a better knowledge of their formation mechanisms. Besides, the extreme surface sensitivity of our technique (photoelectron escape depth 0.5 nm) yields information essentially on the composition of the growth front. Our data clearly demonstrate that the surface composition of the dots is neither pure InAs nor homogeneous InxGa1−xAs, but we observe an In concentration gradient from the center (high concentration) to the borders (lower concentration) of the dots. In addition, we observe a strong In segregation (x ≈ 0.9) to the surface of the dots and of the surrounding wetting layer. Such segregation, well known for two-dimensional InAs/GaAs growth, had not been directly observed so far on top of the dots, and should be considered to model size and composition of GaAs-overgrown structures.
[1] G. Biasiol et al., Appl. Phys. Lett. 87 (21), in press (2005).