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Valladolid, Spain

Bilousov O.V.,Rovira i Virgili University | Carvajal J.J.,Rovira i Virgili University | Geaney H.,University College Cork | Geaney H.,Tyndall National Institute | And 9 more authors.
ACS Applied Materials and Interfaces

Porous GaN based LEDs produced by corrosion etching techniques demonstrated enhanced light extraction efficiency in the past. However, these fabrication techniques require further postgrown processing steps, which increases the price of the final system. Also, the penetration depth of these etching techniques is limited, and affects not only the semiconductor but also the other elements constituting the LED when applied to the final device. In this paper, we present the fabrication of fully porous GaN p-n junctions directly during growth, using a sequential chemical vapor deposition (CVD) process to produce the different layers that form the p-n junction. We characterized their diode behavior from room temperature to 673 K and demonstrated their ability as current rectifiers, thus proving the potential of these fully porous p-n junctions for diode and LEDs applications. The electrical and luminescence characterization confirm that high electronic quality porous structures can be obtained by this method, and we believe this investigation can be extended to other III-N materials for the development of white light LEDs, or to reduce reflection losses and narrowing the output light cone for improved LED external quantum efficiencies. © 2014 American Chemical Society. Source

Martin-Martin A.,GdS Optronlab | Jimenez J.,GdS Optronlab
IEEE Photonic Society 24th Annual Meeting, PHO 2011

Improving the reliability of high power laser diodes is a crucial issue for their practical application. The understanding of the mechanisms behind the degradation of high power laser diodes is necessary to increase their power and lifetime. The study of the degradation mechanisms requires the investigation of the main defects generated during the laser degradation; therefore, an exhaustive examination of the defect signatures in the degraded devices must be crucial to establish reliable degradation scenarios. Cathodoluminescence (CL) is a unique tool to identify the main defects generated by the device degradation, which will permit to build up a model providing a comprehensive scenario of the laser degradation. CL images of the degraded devices reveal the presence of regions with low, or fully quenched, radiative activity, associated with the presence of extended defects in the active layers of the laser structure, in both the front facet and the cavity. © 2011 IEEE. Source

Martinez-Tomas M.C.,University of Valencia | Hortelano V.,GdS Optronlab | Jimenez J.,GdS Optronlab | Wang B.,Solid State Scientific Corporation | Munoz-Sanjose V.,University of Valencia

The goal of this work is to show the capability of X-ray multiple diffraction (XRMD) to be used in combination with high resolution X-ray diffraction (HRXRD) and cathodoluminescence (CL) as an easy and simple methodology to determine structural and surface defect-related characteristics of samples that could be used as substrates for epitaxial growth. For this study ZnO {0001}-oriented samples have been used in view of their use as substrates for homoepitaxy. The miscut and bending of the samples have been analyzed by measuring the position of the X-ray diffraction peaks. The presence of multiple crystallographic domains and their characteristics have been studied by HRXRD (from the allowed (0002) reflection) and XRMD (from the forbidden (0001) and (0003) reflections) through Renninger scans and omega-scans. Cathodoluminescence adds to the previous structural characterization the possibility of obtaining significant information on surface and bulk defect-related optical properties by means of probe depth modulation. Thus, the combined methodology using HRXRD, XRMD and CL shows its ability to assess the structural and surface defect-related properties of substrates, allowing an easy detection of subtle structural and surface defects that can affect the ulterior use of these substrates in epitaxial growth. © 2013 The Royal Society of Chemistry. Source

Plaza J.L.,Autonomous University of Madrid | Martinez O.,GdS Optronlab | Rubio S.,Autonomous University of Madrid | Hortelano V.,GdS Optronlab | Dieguez E.,Autonomous University of Madrid

The growth of CdTe/CdS films by a close space sublimation (CSS) technique using SiC electrical heating elements is presented. The structure, composition and optical properties of the films are studied as a function of different growth parameters and compared with previous results reported in the literature from films grown by CSS using halogen lamps. The homogeneity and composition of the films are analyzed by scanning electron microscopy, grazing angle (0.5°) X-Ray diffraction and energy dispersive analysis. Electron beam induced current is also used for the preliminary analysis of the CdTe/CdS junctions. © 2013 The Royal Society of Chemistry. Source

Martinez O.,GdS Optronlab | Hortelano V.,GdS Optronlab | Jimenez J.,GdS Optronlab | Parra V.,Grupo Pevafersa | And 3 more authors.
Journal of Electronic Materials

GaInP, an essential material for multijunction structures of III-V compounds for solar cells, can achieve better photovoltaic responses when grown on (111)GaAs faces, due to the large internal electric fields generated by the off-diagonal strain. In this work, we explored metalorganic chemical vapor deposition growth of GaInP layers on (001)-, (111)Ga-, and (111)As-GaAs substrates, using different phosphine flow rates. The structural and optical properties of the layers have been studied by micro-Raman spectroscopy, microphotoluminescence, and cathodoluminescence. Problems such as composition control, growth rate, and the presence of ordered phases are addressed. © 2010 TMS. Source

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