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Crystalline Quality (crystalline + quality)
Selected AbstractsGrowth of high-quality 1-inch diameter AlN single crystal by sublimation methodPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007N. Mizuhara Abstract 1-inch diameter AlN single crystals with the thickness of 0.025,2 mm were grown on SiC substrates by the sublimation method. Crystalline qualities were evaluated by X-ray diffraction and EPD measurements. The FWHM of X-ray rocking curve for (0002) reflection was 281 arcsec with 1.2-mm thick crystal and dislocation density measured by EPD was 1.6×106/cm2 with 0.8-mm thick crystal. These results were well consistent with the dependence of those properties on the thickness of the crystal, which was found in our previous work on 10-mm diameter crystals. According to this dependence, growing the thick AlN crystal on SiC substrates by the sublimation method is expected to lead to high-quality free-standing 1-inch AlN substrates. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural and microhardness studies of pure and thiourea doped glycine phosphite single crystalCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2008R. Ezhil Vizhi Abstract Ferroelectric Glycine Phosphite (GPI) crystal have been grown from aqueous solution employing the slow cooling technique. As the crystal solubility in water depends on temperature, single crystals were grown. Transparent, colourless crystals with habit morphology weighing about 8g were obtained with in a month. The same procedure was used to grow single crystals of 10 wt% of Thiourea doped GPI (TUGPI). Formation of a new crystal was confirmed by Powder X-ray diffraction studies as well as FTIR studies. Crystalline quality were found using rocking curve for both the crystals. Due to the presence of Thiourea in TUGPI, it improves the crystalline perfection and also enhances the growth rate. The variation of hardness on (010) faces of monoclinic GPI and TUGPI crystals, with load were studied.Vickers hardness numbers, Hv were found to decrease with the increase in load. The value of Mayer's index, ,n ' was found to be greater than 1.6 for GPI and TUGPI showing soft-material category. The results are discussed in detail. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of annealing temperature on the electrical transport properties of CaRuO3,, thin films directly deposited on the Si substratePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2007Hanjong Paik Abstract We investigate the effect of annealing temperature on the preferentially (110)-oriented CaRuO3,, (CRO) thin films directly prepared on Si(100) substrate by rf magnetron sputtering. Crystalline quality and electrical transport properties of the CRO thin films were modified by post-annealing treatment. It was obvious that 700 °C post-annealing brought about excellent metallic characteristics with the elevation of carrier concentration and mobility. From this result, we suggested that enhanced (110) orientation, and the ratio of chemical composition Ru4+/Ca2+ ion were responsible for the transport properties of CRO thin film. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Selective Angle Electroluminescence of Light-Emitting Diodes based on Nanostructured ZnO/GaN HeterojunctionsADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Hang-Kuei Fu Abstract Selective angle electroluminescence of violet light with a peak wavelength of 405,nm from light-emitting diodes based on nanostructured p-GaN/ZnO heterojunctions is reported. The fabrication of well-aligned nanobottles with excellent crystalline quality is achieved by chemical vapor deposition at temperatures as low as 450,°C with a specially designed upside-down arrangement of substrate configuration. Selective angle light sources are essential in our daily life. With the geometry of the nanobottle waveguides, it is very easy to realize such a practical application. Therefore, the discovery reported here should be very useful for the future development of many unique optoelectronic devices. [source] Electrical Conductivity and Lattice Defects in Nanocrystalline Cerium Oxide Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2001Toshio Suzuki The results of the electrical conductivity and Raman scattering measurements of CeO2 thin films obtained by a polymeric precursor spin-coating technique are presented. The electrical conductivity has been studied as a function of temperature and oxygen activity and correlated with the grain size. When compared with microcrystalline samples, nanocrystalline materials show enhanced electronic conductivity. The transition from extrinsic to intrinsic type of conductivity has been observed as the grain size decreases to <100 nm, which appears to be related to a decrease in the enthalpy of oxygen vacancy formation in CeO2. Raman spectroscopy has been used to analyze the crystalline quality as a function of grain size. A direct comparison has been made between the defect concentration calculated from coherence length and nonstoichiometry determined from electrical measurements. [source] Low-temperature growth of high quality AlN films on carbon face 6H-SiCPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 1 2008Myunghee Kim Abstract AlN films have been grown on atomically flat carbon face 6H-SiC (000) substrates by pulsed laser deposition and their structural properties have been investigated. In-situ reflection high-energy electron diffraction observations have revealed that growth of AlN at 710 °C proceeds in a Stranski,Krastanov mode, while typical layer-by-layer growth occurs at room temperature (RT) with atomically flat surfaces. It has been revealed that the crystalline quality of the AlN film is dramatically improved by the reduction in growth temperature down to RT and the full width at half maximum values in the X-ray rocking curves for 0004 and 102 diffractions of the RT-grown AlN film are 0.05° and 0.07°, respectively. X-ray reciprocal space mapping has revealed that the introduction of misfit dislocations is suppressed in the case of RT growth, which is probably responsible for the improvement in crystalline quality. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical and magnetic properties of c -oriented ZnCoO filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006Huijuan Zhou Abstract We investigated ZnCoO thin films prepared via sol-gel methods and dip-coating techniques. The Co concentrations range from 0.5% to 5%. The films show the wurtzite crystal structure of ZnO and are highly c -axis oriented grown on the quartz substrates. They have a typical grain size of 20 to 50 nm and a thickness between 300 nm and 1 µm. The fine structures of the Co (3d7) internal absorptions are well resolved, all zero-phonon lines (ZPL) and phonon replica related to the 4T1(F) , 4A2 are observed, demonstrating the good crystalline quality of the layers and the incorporation of the Co2+ on Zn2+ lattice sites. The films show paramagnetic behaviour. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis of nickel,zinc ferrite nanoparticles in polyol: morphological, structural and magnetic studiesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2006Z. Beji Abstract Nickel,zinc ferrite monodisperse nanoparticles are synthesized by forced hydrolysis in diethylenglycol. FC and ZFC susceptibility curves suggest that they present superparmagnetic behaviour with a blocking temperature between 63 and 15 K depending on the zinc content. The saturation magnetization of the nanocrystals at 5 K is very close to that of bulk materials, and very high compared to that of similar particles prepared by other chemical routes. High Resolution Transmission Electron Microscopy and In-field Mössbauer studies show clearly that these relatively high values are mainly due to: (i) the high crystalline quality of the particles and (ii) a cation distribution different from the classical distribution encountered in the bulk material. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of growth temperature of AlN interlayers on the properties of GaN epilayers grown on c-plane sapphire by metal organic chemical vapor depositionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010J. S. Xue Abstract The effect of growth temperature of AlN interlayers on the properties of GaN epilayers grown on c-plane sapphire by metal organic chemical vapor deposition has been investigated by high resolution X-ray diffraction (HRXRD) and Raman spectroscopy. It is concluded that the crystalline quality of GaN epilayers is improved significantly by using the high temperature AlN (HT-AlN) interlayer in GaN buffers. The density of threading dislocation is reduced especially for edge type dislocations. Higher compressive stress exists in GaN epilayers with HT-AlN interlayer than with low temperature AlN (LT-AlN) interlayer, which is related to the reduction of strain relaxation caused by the formation of misfit dislocation. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] HVPE GaN substrates: growth and characterizationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010D. Gogova Abstract GaN substrates with low dislocation densities were prepared by halide vapor-phase epitaxy (HVPE) on c-plane sapphire and by means of a post-growth laser-induced lift-off or natural stress-induced (self-) separation process. The HVPE growth on InGaN/GaN buffer layers and subsequent self-separation method was seen as advantageous, in comparison with the laser-induced lift-off one, in terms of lower cost and better crystalline quality of the GaN material obtained. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural analysis of nitride-based LEDs grown on micro- and nano-scale patterned sapphire substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Y. K. Su Abstract The structural properties of nitride-based light-emitting diodes (LEDs) grown on micro- and nano-scale patterned sapphire substrates (PSS) were discussed in detail. The high resolution X-ray diffraction (HRXRD) and etch-pit density (EPD) results reveal that the crystalline quality of the epitaxial GaN film could be effectively improved by using the PSS technique, and depended on the aspect ratio of PSS. The crystalline quality of epitaxial GaN films grown on PSS-2,m and PSS-3,m was better than that of the LED grown on NPSS. The electrical characteristics and junction temperature results of the LED grown on micro-scale PSS were better compared with nano-scale PSS. But the output power of the LED grown on nano-scale PSS was larger than that of the LED grown on micro-scale PSS since the pattern-size of PSS is related to the capability of light extraction. However, when the spacing of PSS is less than 2 ,m, some voids formed at the GaN/sapphire interface may cause the thermal dissipation problem of LEDs. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] GaN layer growth by HVPE on m-plane sapphire substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Alexander Usikov Abstract Semipolar GaN layers were grown on m-plane sapphire substrates by HVPE. Insertion of AlxGa1,xN (x , 0.1-0.6) layer in-between m-plane sapphire substrate and GaN layer promoted to improve crystalline quality and to grow of semipolar (11-22) plane GaN layers. X-ray diffraction (11-22) ,-scan rocking curve FWHM of 298 arcsec was measured for a 30 ,m thick (11-22) GaN layer. Depending on growth conditions, m-plane GaN layer having micro-crystallites of other orientations (mainly of (11-24) plane GaN layer) was also grown. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improvement of crystalline quality of InGaN epilayers on various crystal planes of ZnO substrate by metal-organic vapor phase epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Yohjiro Kawai Abstract We demonstrated InxGa1-xN epitaxial growth with InN mole fractions of x = 0.10 to 0.23 on an m-plane ZnO substrate by metal-organic vapor phase epitaxy. The crystalline quality of the epilayers was found to be much higher than that of epilayers grown on a GaN template on an m-plane SiC substrate. The strain of the epilayers was investigated by X-ray reciprocal space mapping. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mechanism of thermal degradation in GaInN/GaN quantum wellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009H. Bremers Abstract In this contribution we focus on degradation processes of GaInN multiple quantum wells (MQWs) used in laser structures grown by metallorganic vapor pressure epitaxy (MOVPE). The influence of ramp-up time as well as the maximum temperature during growth of the barrier on the quantum well (QW) is investigated. Comparison of X-ray and photoluminescence (PL) measurements implies that a sufficient thickness of a cover layer grown at low temperature is required to prevent degradation of the QW. In a next step samples were grown using an optimal thermal budget during growth of the active region to investigate the influence of capping layers. To improve crystalline quality of these layers high temperatures are required. Our measurements show that these high temperatures lead to a decrease in average indium concentration of the QWs. This decrease is temperature as well as time dependent (, ,t) and can only explained by diffusion processes. The activation energies are in the range 0.7-0.9 eV (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High power AlGaN/GaN HFETs on 4 inch Si substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Nariaki Ikeda Abstract In this paper, we successfully demonstrate an AlGaN/GaN HFET with a high breakdown voltage on 4-inch Si substrates. In order to obtain the high breakdown voltage and to improve the crystalline quality of GaN layers, a thick GaN epitaxial layer including a buffer layer was grown. The breakdown voltage and the maximum drain current were achieved to be over 1.3 kV and 120 A, respectively. Furthermore, the suppression of a current collapse phenomenon was examined. The on-resistance was not significantly increased up to a high drain off-bias-stress of 900 V. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improvement in crystalline quality of thick GaInN on m-plane 6H-SiC substrates using sidewall epitaxial lateral overgrowthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Ryota Senda Abstract We report the fabrication of an epitaxial lateral overgrown (ELO) GaInN layer on a high crystalline-quality-grooved GaN template, which is improved by a sidewall ELO (SELO) technology. The photoluminescence peak intensity of ELO-grown GaInN layer on the SELO GaN underlying layer is twice as high as that of ELO-grown GaInN layer on the m-plane GaN template. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Remarkable improvement in output power for an InAlGaN based ultraviolet LED by improving the crystalline quality of AlN/AlGaN templatesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008T. Takano Abstract The use of quaternary InAlGaN is very attractive for the realization of commercially-available low-cost and high-power ultraviolet light-emitting diodes (UV-LEDs), because highly-efficient UV emission can be obtained from this material due to In-segregation effects. We achieved remarkable improvements in output power from 340 nm-band quaternary InAlGaN-based UV-LEDs and demonstrated high UV-output power by using high-quality AlN buffer templates on sapphire substrates. Threading dislocation densities (TDDs) for screw and edge-type dislocations were 1×108cm,2 and 1×109cm,2, as observed from cross-sectional transmission electron microscope (TEM) images. The output power of a 340 nm-band UV-LED was increased by approximately 7 times by reducing the full-width-at-half-maximum (FWHM) of the (10-12) X-ray ,-scan rocking curve (XRC) from around 800 arcsec to 510 arcsec. As a result, we achieved a maximum output power of 7.1 mW under room-temperature (RT) and continuous-wave (CW) operation. From these results, we confirmed that the crystalline quality of AlN/AlGaN templates strongly affects the output power of UV-LEDs. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Buffer breakdown voltage of AlGaN/GaN HFET on a 4 inch Si(111) substrate grown by MOCVDPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007Masayuki Iwami Abstract The buffer breakdown voltage and the electron mobility in a two dimensional gas (2DEG) of AlGaN/GaN HFETs on 4 inch Si(111) substrates grown by metalorganic chemical vapor deposition was investigated. The relationship between the electrical properties of HFETs and the crystalline quality of the GaN layer are studied by X-ray diffraction and photoluminescence measurements. The buffer breakdown voltage decreases with an increase in the FWHM of the X-ray (0002) diffraction peak. The electron mobility in a 2DEG decreases with an increase in FWHM of the X-ray (102) diffraction peak. These results indicate that a screw component of the threading dislocations in the GaN layer is a primary source for buffer leakage, and that edge dislocations in the GaN layer have a scattering effect on the 2DEG transport. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The effect of Ge doping for lattice-mismatched InGaP/InP (100) with epitaxial lateral overgrowthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2006Kenichi Higuchi Abstract We have proposed the use of 1.3 ,m InGaAs/InGaP laser on an InP (100) substrate to reduce the leakage current. Because of the lattice-mismatch between InP and InGaP, epitaxial lateral overgrowth (ELO) technique is used. Ge doping is an effective way of increasing the amount of lateral growth in InP/InP lattice-matched ELO. In the InGaP/InP lattice-mismatched ELO, the crystal defects of the Ge-doped InGaP layer decrease compared to undoped sample. The Ge doping is effective for growing InGaP/InP with high crystalline quality by ELO. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of annealing temperature on the crystalline quality and phase transformation of Chemically Deposited CdSe filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2005M. Zapata-Torres Abstract Polycrystalline CdSe thin films were grown on glass substrates by chemical bath deposition at 50 ºC. The samples were annealed in air atmosphere at different temperatures and characterized by X-ray diffraction and Raman spectroscopy. It was found that the as-grown films have cubic structure. These samples maintain their cubic structure for annealing temperatures between 60 ºC and 300 ºC. For annealing temperatures higher than 300 ºC we obtain a mixture of cubic and hexagonal phases. The analysis made by X-ray diffraction and Raman dispersion show that the samples annealed at temperatures under the phase-transition temperature increase their crystalline quality. In order to determinate the temperature for the complete transition of the cubic phase, we used the precipitated material obtained during the grown of the CdSe films. This material was annealed on air atmosphere between 300 °C and 500 °C with 50 ° intervals. The samples were measured by X-ray diffraction. The samples maintained the cubic structure if the annealing temperature is under 300 °C. For temperatures between 300 °C and 450 °C we found a mixture of cubic and hexagonal phase. For an annealing temperature of 500°C we obtain only the hexagonal phase. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of MOCVD grown GaN on porous SiC templatesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005F. Yun Abstract We have grown GaN layers by MOCVD on a set of nanoporous SiC templates with different porosity and morphology, produced by etching the anodized porous SiC starting material in a H2 environment at temperatures ,1500 °C, in an effort to attain improved films. The hydrogen etching serves to remove surface damage caused during mechanical polishing prior to anodization, remove the skin layer associated with anodization, tune the pore size, and consolidate pore geometry. Growth conditions favoring lateral overgrowth of GaN were employed on this set of samples to obtian GaN to a thickness of 2 µm. Atomically smooth surfaces were obtained for the epitaxial GaN layers. The GaN quality is highly dependent on the specifics of the porous templates used. An intensity increase of up to a factor of 30 was observed in the GaN excitonic peak compared to GaN grown on standard SiC substrate. The I-V data indicated significant reduction in the leakage current (in reverse bias) compared to GaN grown on standard SiC. The dependence of optical properties, crystalline quality, and surface morphology on the particulars of porous SiC templates is discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of indium incorporation in AlGaN on threading dislocation densityPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005H. Kang Abstract A comparison of dislocation densities in AlGaN and InAlGaN with approximately similar alloy compositions was completed. A systematic series of the AlGaN layers with concentration of 17% Aluminum were grown by metal-organic chemical vapor deposition with trace amounts of indium incorporated into the layers. X-ray diffraction analysis by Williamson Hall plot and reciprocal space mapping was employed to investigate columnar structure in these layers. It was found that lateral coherence length, related to threading dislocation, was systematically varied with Indium content. The lateral coherence length increased with the consequence that the threading dislocation density decreased as Indium content increased, which indicated that even small amounts of indium incorporation could improve crystalline quality. The results are in good agreement with etch pit density study using AFM. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of V/III flux ratio on AlInGaN/AlGaN quantum wells grown by atmospheric pressure MOCVDPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005R. J. Choi Abstract We investigated the structural and optical properties of AlInGaN/AlGaN quantum wells (QWs) and the quaternary AlInGaN epilayers as a function of V/III flux ratio (flow rate of NH3). From the photoluminescence and cathodoluminescence (CL) measurements, the emission wavelengths of the AlInGaN/AlGaN QWs linearly became blueshifted and the intensities decreased with increasing the flow rate of NH3. In the X-ray rocking curve, a pattern of the sample grown at lower NH3 flow rate gives an indication of the good crystalline quality of the films. The monochromated scanning CL image of the AlInGaN epilayers measured at around 80 K showed that more densely and uniformly distributed bright spot densities, indicating In segregation regions, increased at lower NH3 flow rate. Therefore, these results suggest that the relatively decrease of NH3 flow rate results in the increase of In composition fluctuations into the AlInGaN alloys, which generate exciton localized states, and thereby enhances the emission. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improvements in crystalline quality of thick GaN layers on GaAs (111)A by periodic insertion of low-temperature GaN buffer layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003H. Murakami Abstract Thick and high quality GaN layer growth using periodic insertion of low-temperature (LT)-grown GaN buffer layers was investigated by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE). Both morphological and optical properties of GaN epitaxial layers were drastically improved by inserting a second LT-GaN buffer layer. Also, the thickness of the second buffer layer was found to affect the quality of subsequently grown epitaxial layers. The full-width at half maximum (FWHM) value of X-ray diffraction for () plane (, scan) of the GaN layer with double buffer layer structure decreased to 608 arcsec whereas that with single buffer structure was 3600 arcsec. These results indicate that the free-standing GaN substrate with low dislocation density can be possible by reiterating the growth sequence of buffer layer and epitaxial layer. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Metalorganic Chemical Vapor Deposition Growth of a GaN Epilayer on an Annealed GaN Buffer LayerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003F. Degave Abstract We investigated the growth of an epitaxial layer deposited on an annealed buffer layer using transmission electron microscopy. It is shown that crystalline quality of the epitaxial layer depends on the annealing conditions of the buffer layer. Dislocations and formation of V-shaped defects are observed and may originate from the structure and morphology of the buffer layer. [source] III-V concentrator solar cell reliability prediction based on quantitative LED reliability data,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2007Manuel Vázquez Abstract III-V Multi Junction (MJ) solar cells based on Light Emitting Diode (LED) technology have been proposed and developed in recent years as a way of producing cost-competitive photovoltaic electricity. As LEDs are similar to solar cells in terms of material, size and power, it is possible to take advantage of the huge technological experience accumulated in the former and apply it to the latter. This paper analyses the most important parameters that affect the operational lifetime of the device (crystalline quality, temperature, current density, humidity and photodegradation), taking into account experience on the reliability of LEDs. Most of these parameters are less stressed for a III-V MJ solar cell working at 1000 suns than for a high-power LED. From this analysis, some recommendations are extracted for improving the long-term reliability of the solar cells. Compared to high-power LEDs based on compound semiconductors, it is possible to achieve operational lifetimes higher than 105,hours (34 years of real-time operation) for III-V high-concentration solar cells. Copyright © 2007 John Wiley & Sons, Ltd. [source] Growth and characterization of La0.8Sr0.2MnO3/Pb(Zr0.2Ti0.8)O3/La0.8Sr0.2MnO3 heterostructures for three-dimensional circuit studiesANNALEN DER PHYSIK, Issue 1-2 2004X. Hong Abstract The structural and electronic properties of epitaxial colossal magnetoresistive oxide (CMR) / ferroelectric / CMR trilayers have been examined to investigate the feasibility of building all-oxide three-dimensional (3D) circuits. Epitaxial Pb(Zr0.2Ti0.8)O3 (PZT) films sandwiched by ultrathin La0.8Sr0.2MnO3 (LSMO) layers have been fabricated using off-axis magnetron sputtering, with high crystalline quality and smooth surfaces having been obtained. Both the top and bottom layers of LSMO exhibit CMR behavior. [source] | |||||||||||||||||||||||||