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A B S T R A C T S THURSDAY, JULY 1 N A N O S E A 2 0 1 0 Room Calendal 9H00-9H40 Directed-Self-Ordering of Semiconductor Quantum Nanostructures Grown on Nonplanar. Eli Kapon (EPFL SB IPEQ LPN, PH D3 425 (Bâtiment PH), Station 3CH-1015 Lausanne, Switzerland). Spontaneous nucleation and self-ordering of semiconductor quantum nanostructures such as quantum wires (QWRs) and quantum dots (QDs) has been extensively studied and employed in investigations of the properties and applications of these systems in electronics and photonics. Since the size, composition and environment of these nanostructures fundamentally determine their physical properties, the absence of structural control renders them of little use in deterministic quantum nanostructure systems. An alternative approach is that of directed-self-ordering, in which the nucleation and formation of the nanostructures can be tailored for specific designs. An example of such approach is epitaxial growth on patterned, nonplanar substrates. Here, a non-planar surface template serves to define the location where QWRs and QDs form. Such technique is particularly useful when the surface templates evolves in a selflimiting fashion. This is the case of metal-organic vapor phase epitaxy (MOVPE) on pre-patterned substrates, in which growth rate anisotropy and nano-capillarity play a fundamental role [1]. This approach yields high quality, site-controlled (In)GaAs/(Al)GaAs V-groove QWR and pyramidal QD systems. High-uniformity, regular arrays of these structures (e.g., pyramidal QDs with ~1meV inhomogeneous broadening) have been demonstrated [1,2]. The confining potential of these wires/dots can be controlled by thickness and /or composition adjustment, like in conventional quantum well structures. Capillarity-driven alloy segregation in the pyramidal structures provides the possibility of constructing novel QWR-QD assemblies (e.g., QD molecules) showing novel optical properties [3]. The high symmetry of the pyramidal QDs, grown on the (111)B substrates, yields unique excitonic features such as vanishing fine structure splitting, resulting in efficient emission of entangled photons [4]. The excellent site- and emission wavelength control facilitates integration with optical microcavities for applications in quantum information processing and ultra-low-threshold nano-lasers [5]. References: 1. G. Biasil and E. Kapon, Phys. Rev. Lett. 81, (1998). 2. M. Felici et al., Small 5, 938 (2009); A. Mohan et al., Small, 2010 (in print). 3. Q. Zhou et al., Small 5, 329 (2009). 4. A. Mohan et al., Nature Photonics, March 2010. 5. P. Gallo et al., Appl. Phys. Lett. 92, 63101 (2008); K. Atlasov et al., Opt. Express 17,18178 (2009). 89
A B S T R A C T S THURSDAY, JULY 1 N A N O S E A 2 0 1 0 9H40-10H00 In(Ga)As quantum dots grown by Molecular Beam Epitaxy on Si substrates. A. EL AKRA1, H. DUMONT1, P. REGRENY1, D. PELLOUX-GERVAIS2, B. CANUT2, G. PATRIARCHE3, M. GENDRY1, J.M. JANCU4, J. EVEN4, C. BRU- CHEVALLIER2 (1 INL Université de Lyon, CNRS UMR-5270, Ecole Centrale de Lyon, 69134, Ecully, France. 2 INL Université de Lyon, CNRS UMR-5270, INSA de Lyon –Bât Blaise Pascal, 69621 Villeurbanne Cedex France. 3 LPN, CNRS UPR 20, route de Nozay, 91460 Marcoussis, France. 4 FOTON, CNRS 6082, INSA, 20 avenue des buttes de Coesmes, 35708 Rennes Cedex 7). Catherine.Bru-Chevallier@insa-lyon.fr 1 – Introduction The aim of this study is to achieve homogeneous, high density and dislocation free In(Ga)As quantum dots (QDs) grown by molecular beam epitaxy (MBE) on silicon substrates. This work is part of a project which aims at overcoming the severe limitation suffered by silicon regarding its optoelectronic applications, especially efficient light emission device. For this study, one of the key points is to overcome the expected type II InAs/Si interface by inserting the In(Ga)As QDs inside a thin silicon layer deposited on a SOI substrate. Confinement effects of the Si/SiO2 quantum well are expected to heighten the indirect silicon bandgap and then give rise to a type I interface with the In(Ga)As QDs. In order to get light emission from such QDs, a key point is to avoid any dislocations or defects in the In(Ga)As QDs. 2 – Abstract The main factors responsible for the In(Ga)As QDs size, shape and structural quality are: the lattice mismatch between In(Ga)As and Si substrate, the surface energy of both In(Ga)As and Si, the interface energy between In(Ga)As and Si and the adatom mobility during the growth process. We investigated the dot size distribution and density at different V/III beam equivalent pressure (BEP) ratios and different growth temperatures. TEM images are used to study the structural quality of the QDs. Dislocation free In(Ga)As QD were successfully obtained. RBS-channeling analysis of such QDs on Si will also be presented. Optical properties and band alignment are modeled within the tight binding approximation and state of the art DFT calculations. 3 – Conclusion Further works are going on concerning the capping of these In(Ga)As QD by a silicon epilayer in order to get efficient PL emission from these In(Ga)As QD elaborated on Si substrates. This work is supported by the ANR-pnano program (project “BIQUINIS”). 90
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