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Taboada, A. G. et al., We report on the mask-less integration of GaAs crystals several microns in size on patterned Si substrates by metal organic vapor phase epitaxy. The lattice parameter mismatch is bridged by first growing 2-μm-tall intermediate Ge mesas on 8-μm-tall Si pillars by low-energy plasma enhanced chemical vapor deposition. We investigate the morphological evolution of the GaAs crystals towards full pyramids exhibiting energetically stable {111} facets with decreasing Si pillar size. The release of the strain induced by the mismatch of thermal expansion coefficients in the GaAs crystals has been studied by X-ray diffraction and photoluminescence measurements. The strain release mechanism is discussed within the framework of linear elasticity theory by Finite Element Method simulations, based on realistic geometries extracted from scanning electron microscopy images. © 2014 AIP Publishing LLC., Financial support by the Swiss Federal Program Nano-Tera through projects NEXRAY and COSMICMOS and Spanish MINECO and CAM through projects EPIC-NANOTICS and Q&C Light are gratefully acknowledged.

In this work we extend the droplet epitaxy growth technique to the fabrication of low density InAs quantum dots (QDs) on GaAs (001) substrates with control in size, energy emission, and top surface location. In particular, depending on the amount of InAs material deposited, it has been possible to tune the QD energy emission over a range of 1.12–1.40 eV while keeping constant the nanostructures density at 2×108 cm−2. Moreover, the capping growth process of these QD shows mounding features that permit their spatial identification once embedded by a GaAs capping layer., The authors acknowledge the financial support by Spanish MEC and CAM through Project Nos. TEC-2005-05781- C03-01/-03 and NAN2004-09109-C04-01/-03, by Consolider Grant No. QOIT CSD2006-0019 and S-505/ESP/ 000200.

http://link.aip.org/link/?JAPIAU/104/033523/1, Self-assembled InAs/InP (001) quantum wire stacks have been investigated by means of Raman scattering. The characteristics of the observed vibrational modes show clear evidence of confinement and atomic intermixing between As and P atoms from the wire and the spacer. The change in the intermixing with spacer layer thickness and growth temperature is investigated. Likewise, the effect of annealing on the exchange of As and P atoms is also studied. Resonance effects in confined and interface phonons are discussed for excitation in the vicinity of the InAs E1 critical point. Finally, the energy of the interface modes is related to the structural characteristics of the wires by comparing the experimental data with a lattice dynamic calculation based on the dielectric continuum model., The authors are thankful to the Ministry of Education and Science of Spain (Project No. MAT2006-01825,FEDER), the Generalitat Valenciana, and the European Network SANDIE (Grant No. NMP4-CT-2004-500101) for financial support.

Atomic steps at growth surfaces are important heterogeneous sources for nucleation of epitaxial nano-objects. In the presence of misfit strain, we show that the nucleation process takes place referentially at the upper terrace of the step as a result of the local stress relaxation. Evidence for strain-induced nucleation comes from the direct observation by postgrowth, atomic resolution, Z-contrast imaging of an InAs-rich region in a nanowire located on the upper terrace surface of an interfacial diatomic step., This work was supported by the DOE Office of Basic Energy Sciences, Division of Materials Sciences and Engineering (MV and SJP), the SANDiE European Network of Excellence (Contract No. NMP4-CT-2004-500101), the Spanish MEC (TEC2005-05781-C03-01 y 02, NAN2004-09109-C04-01, and Consolider-Ingenio 2010 CSD2006-00019), the CAM (S 0505ESP 0200), and the Junta de Andalucia (PAI research groups TEP-120 and TIC-145; Project No. PAI05-TEP-00383).

Isolated InAs/InP self-assembled quantum wires have been grown using in situ accumulated stress measurements to adjust the optimal InAs thickness. Atomic force microscopy imaging shows highly asymmetric nanostructures with average length exceeding more than ten times their width. High resolution optical investigation of as-grown samples reveals strong photoluminescence from individual quantum wires at 1.5 µm. Additional sharp features are related to monolayer fluctuations of the two-dimensional InAs layer present during the early stages of the quantum wire self-assembling process., The authors gratefully acknowledge financial support by the Spanish MEC and CAM through Project Nos. TEC-2005-05781-C03-01/03, NAN2004-09109-C04-01/03, CSD2006-0019, and S-505/ESP/000200, and by the European Commission through SANDIE Network of Excellence (No. NMP4-CT-2004-500101).

3 páginas, 4 figuras., In this work, the authors present results on the growth by atomic layer molecular beam epitaxy and characterization of lasers with one and three stacked layers of InAs quantum wires (QWRs) as active zone and aluminum-free waveguides on (001) InP substrates. The separated confinement heterostructure consists of n-p InP claddings and a waveguide formed by short period superlattices of (InP)5/(GaInAs)4 lattice matched to the InP substrate. The optimum growth conditions (substrate temperature and As and P pressures) have been determined to obtain waveguides with a flat surface in order to get a uniform QWR distribution. Lasing emission is observed at a wavelength of ~1.66 µm up to 270 K from 15×3000 µm2 devices, with a threshold current density at that temperature of 2 kA/cm2., This work was financed by Spanish project Nos. MEC TEC-2005-05781-C03-01 and CAM S 0505ESP 0200, by the SANDIE Network of excellence (Contract No. NMP4-CT-2004-500101), and by the European Commission Growth program NANOMAT project, Contract No. G5RD-CT-2001-00545.