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PL Intensity (pl + intensity)
Selected AbstractsUp-Conversion Photoluminescence in Polyfluorene Doped with Metal(II),Octaethyl PorphyrinsADVANCED MATERIALS, Issue 24 2003P.E. Keivanidis The up-conversion photoluminescence (PL) in films of polyfluorene (PF) doped with metallated porphyrins is reported for the first time. The dependence of the up-conversion process on the pump laser intensity and wavelength, the central metal moiety of the dopants, and the temperature is presented. Up-conversion emission is observed at pump intensities as low as 2 kW,cm,2. Comparison of the PF integral PL intensities after laser excitation by 532, 543, and 405 nm enables the discussion of the energy-transfer mechanism and the efficiency of the process. [source] Donor,Acceptor Systems: Energy Transfer from CdS Quantum Dots/Rods to Nile Red DyeCHEMPHYSCHEM, Issue 14 2008Suparna Sadhu Abstract We demonstrate strong evidence of shape-dependent efficient resonance energy transfer between CdS quantum dots (QDs) and quantum rods (QRs) (donor) to Nile Red dye (acceptor). We also report a simple solution-based method for the preparation of high quality CdS QDs and CdS QRs at relatively low temperature. The observed quenching of PL intensities are 78.8,% and 63.8,% for CdS QDs and QRs, respectively in the presence of Nile Red dye. The calculated energy-transfer efficiencies are 45,% and 19,% from QDs and QRs to dyes, respectively. The energy transfer varies with changing the shape of the nanoparticles. The estimated Förster distances (R0) are 37.8 and 33.8 Å for CdS QDs and QRs, respectively. In the present study, the estimated distances (r) between one donor and one acceptor are 39.1 and 43.1 Å for QDs and QRs, respectively, using the efficiency of Förster resonance energy transfer (FRET) which depends on the inverse sixth power of the distance of separations between one nanocrystal and one dye molecule. Considering single donor and multiple acceptors interactions, the calculated average distances (rn) between the donor and acceptor are 47.7 and 53.9 Å for QD's and QR's, respectively. The steady-state and time-resolved spectroscopic analysis of nanoassemblies confirm the formation of one donor and multiple acceptors. [source] Simultaneous Optimization of Luminance and Color Chromaticity of Phosphors Using a Nondominated Sorting Genetic AlgorithmADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Asish Kumar Sharma Abstract Acquiring materials that simultaneously meet two or more conflicting requirements is very difficult. For instance, a situation wherein the color chromaticity and photoluminescence (PL) intensity of phosphors conflict with one another is a frequent problem. Therefore, identification of a good phosphor that simultaneously exhibits both desirable PL intensity and color chromaticity is a challenge. A high-throughput synthesis and characterization strategy that was reinforced by a nondominated sorting genetic algorithm (NSGA)-based optimization process was employed to simultaneously optimize both the PL intensity and color chromaticity of a MgO,ZnO,SrO,CaO,BaO,Al2O3,Ga2O3,MnO system. NSGA operations, such as Pareto sorting and niche sharing, and the ensuing high-throughput synthesis and characterization resulted in identification of promising green phosphors, i.e., Mn2+ -doped AB2O4 (A,=,alkali earth, B,=,Al and Ga) spinel solid solutions, for use in either plasma display panels or cold cathode fluorescent lamps. [source] Photoluminescence Detection of Biomolecules by Antibody-Functionalized Diatom BiosilicaADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Debra K. Gale Abstract Diatoms are single-celled algae that make microscale silica shells called "frustules", which possess intricate nanoscale features imbedded within periodic two-dimensional pore arrays. In this study, antibody-functionalized diatom biosilica frustules serve as a microscale biosensor platform for selective and label-free photoluminescence (PL)-based detection of immunocomplex formation. The model antibody rabbit immunoglobulin G (IgG) is covalently attached to the frustule biosilica of the disk-shaped, 10-µm diatom Cyclotella sp. by silanol amination and crosslinking steps to a surface site density of 3948,±,499 IgG molecules µm,2. Functionalization of the diatom biosilica with the nucleophilic IgG antibody amplifies the intrinsic blue PL of diatom biosilica by a factor of six. Furthermore, immunocomplex formation with the complimentary antigen anti-rabbit IgG further increases the peak PL intensity by at least a factor of three, whereas a non-complimentary antigen (goat anti-human IgG) does not. The nucleophilic immunocomplex increases the PL intensity by donating electrons to non-radiative defect sites on the photoluminescent diatom biosilica, thereby decreasing non-radiative electron decay and increasing radiative emission. This unique enhancement in PL emission is correlated to the antigen (goat anti-rabbit IgG) concentration, where immunocomplex binding follows a Langmuir isotherm with binding constant of 2.8,±,0.7,×,10,7M. [source] Tuning and Enhancing Photoluminescence of Light-Emitting Polymer Nanotubes through Electron-Beam IrradiationADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Young Ki Hong A new method for the tuning and enhancing photoluminescence (PL) characteristics of light emitting poly (3-methylthiopnehe) (P3MT) nanotubes through E-beam irradiation under atmospheric environments is reported. An E-beam generated from a linear electron accelerator (1 MeV, 1.6,×,1013,8.0,×,1016 electrons cm,2) is irradiated onto P3MT nanotubes including an Al2O3 template. From laser confocal microscope (LCM) PL experiments, significant enhancements in the PL intensity,up to about 90 times of an isolated single strand of the E-beam irradiated P3MT nanotubes,are observed. The luminescent color of the P3MT nanotubes changes from green to red color depending on the variation of E-beam dosage. These results might originate from the de-doping effect and the conformational modification through E-beam irradiations. Conformational changes of the E-beam irradiated P3MT nanotubes are confirmed by LCM single Raman and ultraviolet-visible (UV/Vis) absorption spectra. From UV/Vis absorption spectra, it is observed that the ,,,* transition peak and the doping induced bipolaron peaks of the P3MT nanotubes dramatically vary with E-beam irradiating conditions. [source] Efficient and Photostable ZnS-Passivated CdS:Mn Luminescent Nanocrystals,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2004H. Yang Abstract Efficient and photostable ZnS-passivated CdS:Mn (CdS:Mn/ZnS core/shell) nanocrystals were synthesized using reverse micelle chemistry. CdS:Mn/ZnS core/shell nanocrystals exhibited much improved luminescent properties (quantum yield and photostability) over organically (n -dodecanethiol-) capped CdS:Mn nanocrystals. This is the result of effective, robust passivation of CdS surface states by the ZnS shell and consequent suppression of non-radiative recombination transitions. The dependence of photoluminescence (PL) intensity has been observed as a function of UV irradiation time for both organically and inorganically capped CdS:Mn nanocrystals. Whereas organically capped CdS:Mn nanocrystals exhibit a significant reduction of PL intensity, CdS:Mn/ZnS core/shell nanocrystals exhibit an increased PL intensity with UV irradiation. XPS (X-ray photoelectron spectroscopy) studies reveal that UV irradiation of CdS:Mn/ZnS nanocrystals in air atmosphere induces the photo-oxidation of the ZnS shell surface, leading to the formation of ZnSO4. This photo-oxidation product is presumably responsible for the enhanced PL emission, serving as a passivating layer. [source] Synthesis and characterization of copolythiopheneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Jie He Abstract Copolythiophenes (Co-PTs), poly(3-hexylthiophene- co -3-thiophene carboxylic acid) (P3HT-TCa), poly(3-hexyloxylthiophene- co -3-thiophene carboxylic acid) (P3HOT-TCa), and poly(3-phenylthiophene- co -3-thiophene carboxylic acid) (P3PhT-TCa), were synthesized by chemical oxidized polymerization to investigate the effect of copolymerization on the properties of polythiophenes (PTs). Gel permeation chromatography showed that the molecular weight (MW) of Co-PT was lower than that of homopolythiophene. Fourier transform infrared (FTIR) spectra indicated that the copolymerization was successful between the monomers. The ,max of Co-PTs gave a "blue shift" in ultraviolet-visible (UV-VIS) spectra. Photoluminescence (PL) spectra showed that the PL intensity of Co-PT became weaker than that of homopolythiophene and the disappearance of PL had been observed in P3HOT-TCa. The thermal stability of Co-PT was influenced by the carboxyl for its low decomposition temperature. Furthermore, the copolymerization between multi-wall carbon nanotube containing thiophene ring (MWNT-Th) and 3-hexyloxylthiphene could also take place successfully. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Annealing experiments of the GaP based dilute nitride Ga(NAsP)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2008B. Kunert Abstract The post-growth annealing behaviour of Ga(NAsP) multi quantum well heterostructures (MQWHs) grown pseudomorphically strained to GaP substrate has been investigated. The optical properties as well as the structural crystal quality of the novel dilute nitride show an obvious dependence on the applied annealing temperature. Photoluminescence (PL) measurements reveal a step-like blue shift of the PL peak position in line with an increase of PL intensity with rising annealing temperature. The PL line width decreases to a mini- mal value for an optimized heating temperature around 800 °C. This annealing behaviour of the Ga(NAsP)/GaP-MQWHs up to 850 °C is quite typical for a dilute nitride, however, the functional dependence of the integrated intensity above 850 °C is unusual. The increase of the PL line width above 850 °C suggests a deterioration of the crystalline MQW quality, but transmission electron microscopy (TEM) and high resolution X-ray diffraction (XRD) prove the opposite. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Rare earth ions in porous silicon: optical propertiesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007H. Elhouichet Abstract Porous silicon (PS) is doped with rare earth (RE) ions (Er, Eu, Tb) by electrochemical anodisation. The penetration of RE into the PS layer is confirmed by Rutherford Backscattering Spectroscopy (RBS) and by Energy Dispersive X-ray (EDX) measurements. Efficient visible and infrared emissions were observed at room temperature. The activation temperatures of Eu, Tb and Er in PS are determined from the effect of thermal annealing on the photoluminescence (PL) intensity. From the evolution of the PL intensity versus temperature, it was found that a RE related level defect can be involved on the excitation and emission processes. Pump intensity dependent PL studies revealed that for the electrochemical incorporation, most of the RE ions are localized inside the Si nanocrystallites and not in stochiometric SiO2. The optical cross section is close to that of erbium in Si nanocrystallites. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of the annealing temperature on the optical transitions of InGaAsP-based quantum well structures investigated by photoreflectance spectroscopyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2005A. Podhorodecki Abstract Photoreflectance (PR) and photoluminescence (PL) spectroscopies have been used to study the effect of the rapid thermal annealing (RTA) on InGaAsP-based quantum wells (QWs) which are the active part of a laser structure tailored at 1.5 µm. In the case of PL, it has been observed that the RTA enhances PL intensity and tunes the emission wavelength of the laser structure to blue. In case of PR due to its absorption character, we were able to study QW transitions related to excited states, besides the fundamental transition observed in PL. In addition, optical transitions related to other part of the laser structure have been observed in PR. It has been shown that there exists a "critical" annealing temperature (720 °C) where the energy shift appears. We have observed a blueshift for both the ground and excited state transitions, but in the case of the ground state transitions the blueshift has been found to be bigger. The magnitude of this blueshift has been found to change linearly from 0 to ,15 meV with the rise of temperature from 720 to 780 °C. Below 720 °C no significant change in the energy of the QW transitions is observed. In the case of PR transitions related to the other part of the laser structure, i.e., the quaternary InGaAsP barriers, it has been observed that after annealing PR features associated with these layers rather do not shift, they change only their line-shape. Also, it has been shown that RTA does not destroy the optical quality of the samples. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Post-annealing effect upon phosphorus-doped ZnTe homoepitaxial layers grown by MOVPEPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007Katsuhiko Saito Abstract The effect of post-annealing treatment upon the photoluminescence (PL) spectra of phosphorus-doped ZnTe homoepitaxial layers grown by metalorganic vapour phase epitaxy using tris-dimethylaminophosphorus (TDMAP) has been investigated. PL properties at 4 K of the layers are dramatically improved by the post-annealing in nitrogen flow, i.e. donor,acceptor pair emission vanishes and instead free-to-bound transition emission (FB) and broadened acceptor-related excitonic emission (Ia) appear. PL intensity at room temperature is enhanced remarkably by the treatment. While the post-annealing treatment in hydrogen flow also gives an increase in PL intensity at room temperature of the layer, PL spectrum at 4 K is almost unchanged. The intensity ratio of FB to broadened Ia for the layer after post-annealing treatment in nitrogen flow increases and the broadened Ia shifts towards longer wavelength side with increasing TDMAP transport rate. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical characterization of Zn0.97Mn0.03Se/ZnSe0.92Te0.08 type II multiple-quantum-well structuresPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007D. Y. Lin Abstract The optical characterization of type II Zn0.97Mn0.03Se/ZnSe0.92Te0.08 multiple-quantum-well structures have been studied using photoluminescence (PL), temperature-dependent PL, polarized PL, power-dependent PL, and photoreflectance (PR) in this study. The PL data reveal that the band alignment of the ZnMnSe/ZnSeTe system is type II. Comparing with the theoretical calculation based on the Schrodinger equation, the valence band offset is estimated to be 0.6 eV. From the power-dependent PL spectra, it is observed that the peak position of PL spectra shows a blueshift under different excitation power. The blueshift can be interpreted in terms of the band-bending effect due to spatially photoexcited carriers in a type II alignment. The thermal activation energy (EA) for quenching the PL intensity was determined from tem- perature-dependent PL spectra. The thermal activation energy was found to decrease as the thickness of ZnMnSe and ZnSeTe layers decreased. The polarized PL spectra exhibit a large in-plane polarization with the polarization degree up to 50%. The polarization does not depend on the excitation intensity as well as temperature. The large polarization is an inherent orientation of the interface chemical bonds. The higher transition features observed in PR spectra show a blueshift with the similar trend observed in the PL spectra as decreasing the thickness of ZnSeTe layer. This result provides a consistent evidence for the assumption that square-like well shapes were built in the ZnSeTe layers. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Impurity levels in the layered semiconductor p-GaSe doped with group V elements As, Bi and SbPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2005S. Shigetomi Abstract The radiative and non radiative recombination mechanisms in the As, Sb and Bi-doped GaSe have been investigated on the basis of photoluminescence (PL) and Hall effect measurements. The PL features (at 77 K) related to the impurity levels coming from the As, Sb and Bi atoms are dominated by a broad emission band at about 1.7 eV. From the temperature dependences of the peak energy and PL intensity and the dependence of excitation intensity of peak energy, it was found that the 1.7 eV emission band is due to the transition from the shallow donor level at about 0.08 eV below the conduction band to the deep acceptor. In addition it was found, from the temperature dependence of hole concentration, that a deep acceptor level at about 0.6 eV above the valence band is formed by the doping atoms. It is associated with defects or defect complexes. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Aligned microcrystalline silicon nanorods prepared by glancing angle hotwire chemical vapor deposition for photovoltaic applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Yanhong Ma Abstract Aligned Si nanorods (SiNRs) were prepared by hot wire chemical vapor deposition (HWCVD) with the glancing angle incident flux. The morphologies of SiNRs are pressure dependent. Crystallized SiNRs were achieved under a substrate temperature of 140 °C with H dilution. The optical and electrical properties of SiNRs were investigated. In a first step, a radial p-n junction solar cell with core-shell structure was prepared by depositing a-Si layer on the SiNRs. The hybrid solar cells were fabricated by spin coating 3-hexylthiophene (P3HT) into the SiNRs arrays. The P3HT shows well penetration into the SiNRs. The quenching of the PL intensity of P3HT/SiNRs indicates an effective electron transfer from P3HT to SiNRs. The hybrid solar cell with the structure of metal grids/ITO/P3HT/SiNRs/c-Si/Al shows a power conversion efficiency of 0.2% under AM 1.5 illumination. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoluminescence properties of PbSe/PbS core-shell quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009Georgy I. Maikov Abstract The present study describes the investigation of the ground-state exciton emission in the PbSe/PbS core-shell colloidal quantum dots (CQDs) with different core-radius/shell-thickness ratio, by recording temperature dependence of ground-state exciton photoluminescence (PL) properties, including line-width, integrated PL intensity, and the temperature coefficient of energy band-gap, over a temperature range from 1.4 K to 300 K. The obtained data reveal a reduction of the temperature coefficient of the energy band-gap as well as slightly decrease of exciton and optical phonon coupling in the PbSe/PbS core-shell CQDs with respect to that in the corresponding PbSe core. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoluminescence and time-resolved photoluminescence in Cu(In,Ga)Se2 thin films and solar cellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2009Sho Shirakata Abstract Photoluminescence (PL) and time-resolved PL (TR-PL) studies have been carried out on Cu(In,Ga)Se2 (CIGS) thin films and solar cells (ZnO/CdS/CIGS) to study the recombination of the photo-excited carriers. The CIGS solar cells exhibited intense near-band-edge (NBE) PL compared with the CIGS films by two orders of magnitude. PL decay time of the cell is strongly dependent on the repetition frequency of the excitation light. PL decay time of the cell is longer than that of the corresponding CIGS thin film. The chemical bath deposition of the CdS buffer layer on CIGS leads to changes in PL intensity, defect-related PL and the PL decay time. They are discussed with relation to the substitution of Cd atom at the Cu site at the Cu-deficient surface of CIGS thin film. Under the open circuit condition, NBE-PL is stronger and the decay time is longer compared with those under the short circuit condition. PL of the cell under the load was examined, and PL intensity and PL decay time are related to the photovoltage during PL measurements. Low temperature PL suggests that the Cd diffusion during the CBD process is pronounced for low Ga content CIGS. The authors demonstrate the effectiveness of PL as a powerful non-destructive device and photovoltaic characterization methods of CIGS solar cells. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoluminescence properties of annealed InAs quantum dots capped by InGaAs layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2009Shingo Hiratsuka Abstract We have investigated the annealing-temperature dependence on photoluminescence (PL) properties of InAs quantum dots (QDs) fabricated on GaAs substrate. The annealing temperatures were varied from 700 to 1000 °C. The observed PL spectra were drastically changed by changing the annealing temperature. The PL peaking-wavelength of non-annealed sample is around 1200 nm. However, the peaking-wavelength is drastically blue-shifted with increasing annealing temperature. The strongest PL intensity is observed from the sample annealed at 875 °C. This PL intensity is more than seven fold compared with that of the non-annealed sample. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nonradiative processes at low temperature in Er,O-codoped GaAs grown by organometallic vapor phase epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008A. Fujita Abstract Er-related photoluminescence (PL) properties have been investigated in Er,O-codoped GaAs (GaAs:Er,O) grown by organometallic vapor phase epitaxy. The GaAs:Er,O which was slightly doped with Er exhibited both strong Er-related and band-edge luminescence. In the temperature dependence of the Er-related PL intensity, the intensity decreased with increasing temperature from 4.2 K to 30 K. The temperature region was quite coincident with the region where the Carbon-related PL intensity decreased. This behaviour implies the existence of a Carbon-related nonradiative process in GaAs. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Pulsed layer growth of AlInGaN nanostructuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Michael Jetter Abstract A pulsed layer growth mode in the metal-organic vapor phase epitaxy (MOVPE) was used to fabricate excellent quality AlInGaN nanostructures. The amount of material was varied, resulting in AlInGaN layer thicknesses between nominally 1.5 nm and 6 nm, respectively. We have analyzed the material properties by X-ray diffraction (XRD) as well as photoluminescence (PL) spectroscopy. The observed XRD-spectra and the PL intensity show the high quality of the deposited material. By analyzing the PL spectra we have found an energetic shift of the resonance lines from 2.65 eV to 3.33 eV with decreasing well thickness. We attribute this shift mainly to the presence of internal electric fields at the AlIn-GaN/GaN interface. Power-dependent and time resolved PL experiments confirm this observation. Comparing the luminescence at elevated temperatures, the pulsed layer epitaxy structures reveal a much higher intensity as the conventional grown samples. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High quality, high efficiency and ultrahigh In-content InGaN QWs , the problem of thermal stabilityPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008D. Fuhrmann Abstract InxGa1-xN/GaN quantum well (QW) structures with Indium concentrations above 30% suited for light emitters in the green and beyond have been investigated. The structures were optimized for homogeneous Indium distributions and abrupt interfaces. We obtained very high internal quantum efficiencies (IQE) of 80% and 70% for 460 nm and 510 nm emission wavelength, respectively. However, for high In concentrations the heterostructures are thermally less stable. This is evident from systematic studies including varied GaN cap temperatures and different post annealing procedures. For elevated temperatures we observe a reduction of the PL intensity, a broadening and a shift to higher energies of the PL lines without indication of phase separation. The reason is the soft indium-nitrogen bond, the degradation likely occurs by In interdiffusion or outdiffusion via defects in the structures. The critical temperatures are well below those typical for p-GaN contact layer growth and thus need to be considered in device applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fabrication of porous ZnO nanostructures and morphology controlPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2007Sang Hyun Lee Abstract Porous ZnO nanostructures were easily fabricated by annealing and etching of as-grown ZnO nanorods using an aqueous solution method at low temperature. The density of ZnO nanorods was changed by repetition of coating and drying of zinc acetate hydrate in ethanol. The annealing process is a very critical step to make porous ZnO nanorods because nano-sized pore are formed at this step. Without annealing, pores could not be observed at the surface of ZnO nanorods. Furthermore, pore the size gets larger in etching steps following the annealing. The structural and optical properties for porous ZnO nanostructures were investigated using TEM and PL. Porous ZnO nanostructures were grown along the c-axis and pores were distributed in the whole body. PL intensity was increased by annealing and etching. This is ascribed to the improved crystallinity and large surface area. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low threshold GaInAs quantum well lasers grown under low growth rate by solid-source MBE for 1200 nm wavelength rangePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2006M. Ohta Abstract Optical property dependence on growth rates of highly-strained GaInAs quantum wells (QWs) on GaAs was studied by solid-source molecular beam epitaxy (MBE). Noticeable improvement of the photoluminescence (PL) was observed by lowering the growth rate of highly-strained GaInAs. A sample grown at a growth rate of 0.05 µm/h under a low growth temperature and high As pressure showed a high PL intensity and a flat surface in atomic force microscope (AFM) measurements. The lowest threshold current density of 117 A/cm2/well is achieved for GaInAs/GaAs double QW lasers at 1190 nm wavelength. A low growth rate is found to be effective to grow highly-strained GaInAs QWs. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improvement in the luminescence efficiency of GaAsN alloys by photoexcitationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003H. Yaguchi Abstract We found that photoexcitation with high excitation power density at low temperatures improves the luminescence efficiency of GaAsN alloys. From the temporal change of the PL intensity, the improvement occurs in a few minutes. Micro Raman study shows that structural changes occur in the laser-irradiated region. These indicate that the improvement of luminescence properties is due to photoexcitation-induced local structural changes. Since no distinct PL peak shift was observed after the laser irradiation at low temperatures, photoexcitation is a useful technique to improve the luminescence efficiency only. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Impurity free vacancy disordering of self-assembled InGaAs quantum dots by using PECVD-grown SiO2 and SiNx capping filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2003J. H. Lee Abstract Impurity free vacancy disordering (IFVD) of InGaAs self-assembled quantum dots (SAQDs) grown by metal organic chemical vapor deposition (MOCVD) method has been carried out at 700,°C for the time range from 1 min to 4 min by using SiO2 and SiNx,SiO2 dielectric capping layers. The photoluminescence (PL) peak was blue shifted up to 157 meV and its full width at half maximum (FWHM) was narrowed from 76 meV to 47 meV as the annealing time increased. The integrated PL intensity was increased after the thermal annealing, which may be attributed to a defect quenching. There was an optimum annealing condition to get the largest integrated PL intensity for each dielectric capping. SiNx,SiO2 double capping layers have been found to induce larger integrated PL intensity and better carrier confinement after the thermal annealing of SAQDs compared to SiO2 single capping layer, even though SiNx,SiO2 double capping induced larger blue-shift than SiO2 single capping. [source] InAs quantum dots on GaAs substrates with InGaAs strain reducing layer for long wavelength emissionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2003S. Saravanan Abstract InAs QDs on GaAs substrates were grown by molecular beam epitaxy (MBE). The dot density and properties were studied by atomic force microscopy (AFM). The low temperature photoluminescence (PL) characteristics of InAs QDs with different cap layers are discussed. The results suggest that InAs QDs covered by two InGaAs layers with different indium composition have long wavelength emission without much reduction in the PL intensity. [source] | |||||||||||||