Guided Self Assembly of InAs Quantum Dots on a Cleaved Facet
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0959-M16-02
Guided Self Assembly of InAs Quantum Dots on a Cleaved Facet Emanuele Uccelli1, Dieter Schuh2, Jochen Bauer1, Max Bichler1, Jonathan J. Finley1, Matthew Grayson1, Gerhard Abstreiter1, and Anna Fontcuberta i Morral1 1 Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, Garching, 85748, Germany 2 Institut für Angewandte und Experimentelle Physik II, Universität Regensburg, Regensburg, 93040, Germany
ABSTRACT The long range ordering of epitaxial semiconductor quantum dots (QDs) has been obtained by combing self assembly with the cleaved edge overgrowth technique. The introduction of nanometer thick AlAs stripes on a (110) oriented GaAs surface avoids the misfit dislocation growth mechanism of InAs on GaAs (110) and drives the formation of array of QDs. Atomic Force Microscopy (AFM) investigations highlight that InAs QDs only nucleate in chain like structure on Al-rich regions. Here, we present experimental results that demonstrate the ability to create ordered QDs lattices and discuss the conditions under which preferential growth of QDs on the AlAs stripes occurs. INTRODUCTION Semiconductor quantum dots (QDs) are of significant importance for both fundamental physics and device engineering [1]. In general, the arrangement of QDs according to a predetermined design on a substrate is highly desirable. In this respect, deterministic self-assembly of QDs has gained interest in the last decade and different methods have been developed. One of these has been to exploit modified growth kinetics that occurs on high index vicinal surfaces with regularly ordered atomic steps. Examples of such novel approaches include In(Ga)As quantum dots and wires grown on (311)A GaAs [2], on miscut (100)-oriented GaAs [3], at crystal defects [4] and at the bottom of a single V-groove AlGaAs/GaAs heterostructure [5]. All these methods are based on intrinsic substrate properties and lack therefore a design flexibility. An alternative approach has also been the use of lithographically patterned substrates to force controlled dot nucleation [6, 7]. In this case the resolution is unfortunately limited by that of the lithographic technique used. As it has been recently shown [8], it is possible to obtain long range ordered chains of InAs QDs by combining self-assembly with the Cleaved-Edge Overgrowth technique (CEO) [9]. This technique is depicted in Figure 1 and described in the following. First a series of alternating AlAs and GaAs layers are grown on a GaAs (001) substrate by Molecular Beam Epitaxy (MBE) (Fig. 1(a)). Then, the wafer is thinned and cut into 0.7x0.7cm2 pieces and mounted vertically on the MBE holder. The pieces are then cleaved in situ in the MBE chamber along the [110] direction (Figure 1(b)). The resulting (1-10) cleaved surface, which is composed by AlAs (GaAs) nano-stripes, is then exposed to InAs growth (Figure 1(c)). In general, InAs QDs are observed to selectively nucleate on the AlAs stripes.
In the present work, we present an extended study of the parameter space for the selfassembl
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