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HL: Fachverband Halbleiterphysik

HL 86: Quantum Dots: Growth and Characterization

HL 86.6: Vortrag

Freitag, 18. März 2011, 11:30–11:45, FOE Anorg

Growth of small-period Si/Ge quantum dot crystals by MBE — •Svetlana Borisova¹, Julian C. Gerharz¹, Yasin Ekinci², Gregor Mussler¹, and Detlev Grützmacher¹ — ¹Institute of Bio- and Nanosystems 1, Forschungszentrum Jülich, D-52425 Jülich, Germany — ²Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen-PSI, Switzerland

We report on growth of arrays of Ge quantum dots (QDs) on Si substrates. The energy structure of small-period QDs arrays is predicted to be significantly modified by the artificial periodicity. High quality self-assembled Ge QDs can be grown by solid source molecular-beam epitaxy (MBE). The main drawbacks of self-assembled Ge QDs are arbitrary positions where the QDs nucleate as well as broad size dispersion. To solve this problem, prepatterned Si substrates were used to define the position and the size of the QDs. Check-patterns with different periods down to 35 nm and depth of 5-20 nm were realized by extreme ultraviolet interference lithography (XIL) and independently by electron beam lithography followed by reactive ion etching (RIE). Influence of both methods on MBE growth was studied from the point of view of final quality of the holes and simplicity of access, usage and precision of positioning on the substrate. The prepatterned Si substrates were overgrown by few single layers of Ge. The influence of substrate temperature and buffer layer thickness on homogeneity of Ge dots in order to optimize growth procedure was investigated by means of atomic force microscopy (AFM) and in-situ scanning tunnelling microscopy (STM).