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Albert S.,Technical University of Madrid | Bengoechea-Encabo A.,Technical University of Madrid | Sanchez-Garcia M.A.,Technical University of Madrid | Calleja E.,Technical University of Madrid | Jahn U.,Paul Drude Institute For Festkoperelektronik
Journal of Applied Physics | Year: 2013

This work reports on the morphology and light emission characteristics of ordered InGaN nanocolumns grown by plasma-assisted molecular beam epitaxy. Within the growth temperature range of 750 to 650 °C, the In incorporation can be modified either by the growth temperature, the In/Ga ratio, or the III/V ratio, following different mechanisms. Control of these factors allows the optimization of the InGaN nanocolumns light emission wavelength and line-shape. Furthermore, yellow-white emission is obtained at room temperature from nanostructures with a composition-graded active InGaN region obtained by temperature gradients during growth. © 2013 American Institute of Physics.


Barbagini F.,Technical University of Madrid | Bengoechea-Encabo A.,Technical University of Madrid | Albert S.,Technical University of Madrid | Lefebvre P.,Montpellier University | And 4 more authors.
Microelectronic Engineering | Year: 2012

E-beam lithography was used to pattern a titanium mask on a GaN substrate with ordered arrays of nanoholes. This patterned mask served as a template for the subsequent ordered growth of GaN/InGaN nanorods by plasma-assisted molecular beam epitaxy. The mask patterning process was optimized for several holes configurations. The smallest holes were 30 nm in diameter with a pitch (center-to-center distance) of 100 nm only. High quality masks of several geometries were obtained that could be used to grow ordered GaN/InGaN nanorods with full selectivity (growth localized inside the nanoholes only) over areas of hundreds of microns. Although some parasitic InGaN growth occurred between the nanorods during the In incorporation, transmission electron microscopy and photoluminescence measurements demonstrated that these ordered nanorods exhibit high crystal quality and reproducible optical properties. © 2012 Elsevier B.V. All rights reserved.


Albert S.,Technical University of Madrid | Bengoechea-Encabo A.,Technical University of Madrid | Kong X.,Paul Drude Institute For Festkoperelektronik | Sanchez-Garcia M.A.,Technical University of Madrid | And 2 more authors.
Applied Physics Letters | Year: 2013

This work reports on the selective area growth by plasma-assisted molecular beam epitaxy and characterization of InGaN/GaN nanocolumnar heterostructures. The optimization of the In/Ga and total III/V ratios, as well as the growth temperature, provides control on the emission wavelength, either in the blue, green, or red spectral range. An adequate structure tailoring and monolithic integration in a single nanocolumnar heterostructure of three InGaN portions emitting in the red-green-blue colors lead to white light emission. © 2013 AIP Publishing LLC.


Albert S.,Technical University of Madrid | Bengoechea-Encabo A.,Technical University of Madrid | Lefebvre P.,Technical University of Madrid | Lefebvre P.,French National Center for Scientific Research | And 5 more authors.
Applied Physics Letters | Year: 2012

This work reports on the morphology control of the selective area growth of GaN-based nanostructures on c-plane GaN templates. By decreasing the substrate temperature, the nanostructures morphology changes from pyramidal islands (no vertical m-planes), to GaN nanocolumns with top semipolar r-planes, and further to GaN nanocolumns with top polar c-planes. When growing InGaN nano-disks embedded into the GaN nanocolumns, the different morphologies mentioned lead to different optical properties, due to the semi-polar and polar nature of the r-planes and c-planes involved. These differences are assessed by photoluminescence measurements at low temperature and correlated to the specific nano-disk geometry. © 2012 American Institute of Physics.


Bengoechea-Encabo A.,Polytechnic University of Mozambique | Barbagini F.,Polytechnic University of Mozambique | Fernandez-Garrido S.,Polytechnic University of Mozambique | Grandal J.,Polytechnic University of Mozambique | And 6 more authors.
Journal of Crystal Growth | Year: 2011

The influence of the substrate temperature, III/V flux ratio, and mask geometry on the selective area growth of GaN nanocolumns is investigated. For a given set of growth conditions, the mask design (diameter and pitch of the nanoholes) is found to be crucial to achieve selective growth within the nanoholes. The local III/V flux ratio within these nanoholes is a key factor that can be tuned, either by modifying the growth conditions or the mask geometry. On the other hand, some specific growth conditions may lead to selective growth but not be suitable for subsequent vertical growth. With optimized conditions, ordered GaN nanocolumns can be grown with a wide variety of diameters. In this work, ordered GaN nanocolumns with diameter as small as 50 nm are shown. © 2011 Elsevier B.V.

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