bluuebunny/crossref_metadata_2025_split huggingface dataset:
Negative characteristic temperature of InGaN blue multiple‐quantum‐well laser diodes
Authors: Ryu H. Y. , Ha K. H. , Lee S. N. , Jang T. , Kim H. K. , Son J. K. , Chae J. H. , Kim K. S. , Choi K. K. , Paek H. S. , Sung Y. J. , Sakong T. , Nam O. H. , Park Y. J. 
Published: January 2007

AbstractWe report anomalous temperature characteristics of InGaN laser diodes (LDs) emitting around 450 nm. Our blue LD shows negative characteristic temperature in the usual operation temperature range from 20 °C to 80 °C. This peculiar temperature characteristic is attributed to originate from unique carrier transport properties of InGaN quantum wells with high In composition, as deduced from the simulation of carrier density and optical gain. In addition, it is found that wall plug efficiency of the blue LD is even improved as temperature increases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface modifications and optical properties of blue InGaN single quantum well by in‐situ thermal treatments
Authors: Lee Sung‐Nam , Paek H. S. , Son J. K. , Sakong T. , Kwon Y. N. , Nam O. H. , Park Y. 
Published: January 2007

AbstractWe investigated the surface modifications and optical properties of blue InGaN single quantum well (SQW) using the in‐situ annealing process with different two temperatures. The surface of blue InGaN SQW was significantly modified from spiral surface to step‐like surface structure as well as the degradation of InGaN PL emission efficiency after in‐situ annealing process at a 1030 °C for 3 min in the metalorganic chemical vapor deposition (MOCVD) system. However, the surface of InGaN SQW was modified from spiral surface to spinodal pattern surface structure after in‐situ annealing process at the InGaN growth temperature of 750 °C. These results implied that the surface atoms of InGaN could significantly rearranged by the thermal treatments at the high temperatures just after the InGaN growth. This surface reconstruction process can be caused by the desorption, the evaporation, and the surface migration of surface adatoms to reduce the thermodynamical instability. Moreover, it is possible to be happened the spinodal related phase separation of InGaN SQW under the in‐situ annealing process with the InGaN growth temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of internal field effect and blue‐shift in InGaN‐based blue laser diodes by time‐resolved optical technique
Authors: Son J. K. , Sakong T. , Hwang J. S. , Lee S. N. , Paek H. S. , Ryu H. Y. , Ha K. H. , Cho Y. H. , Nam O. , Park Y. 
Published: January 2007

AbstractPower dependent time‐resolved photoluminescence measurements were performed on AlInGaN‐based blue laser diode structures with different well widths. Emission peak shifts were monitored in evolving time at different power of excitation laser. We observed two types of shift. One is power dependent and the other is a constant shift with respect to excitation power density. In particular, the power dependent shift was explained by internal electric field effect but the constant one was not. The reduction of a peak shift was achieved by narrowing the quantum well thickness, mostly attributing to the reduction of the internal field effect. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN property evolution at all stages of MOVPE Si/N treatment growth
Authors: Halidou I. , Benzarti Z. , Fitouri H. , Fathallah W. , Jani B. El 
Published: January 2007

AbstractAn investigation of MOVPE GaN growth on sapphire (0001) using Si/N treatment is reported. The growth was monitored in situ He‐Ne laser reflectometry. By fitting the reflectivity signal, we derived expressions for the refractive index variation of both sapphire substrate and GaN as a function of the temperature. The morphological and optical property evolutions of the layer at all the growth stages were studied by atomic force microscopy (AFM) and transmittance measurements. A good agreement between AFM images and laser reflectometry signal is obtained. During the island growth and coalescence as clearly revealed by AFM images of the GaN layers, the transmittance signal evolves from featureless characteristic to a signal with regular oscillations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the use of the thermal step method as a tool for study of space charge in semiconductor gallium nitride: GaN
Authors: Bergaoui M. S. , Matoussi A. , Chaabane N. , Guermazi S. , Toureille A. , El Jani B. 
Published: January 2007

AbstractThermal step method (TSM) is a non destructive technique which measures the distribution of electric field and the space charge density across a solid insulators. In this paper, we report the experimental results obtained by the Thermal step method (TSM) and The capacitive voltage (C‐V) characterisations of the gallium nitride films grown by the Metal Organic Vapour Phase Epitaxy on silicon substrate. The C‐V curves shows a MOS structure behaviours, this was attributed to the existence of an SiO2 insulator between silicon and GaN. Experimental results were in good accordance with TSM measurements. These where performed under different applied bias voltage, remnant saturation current indicate a sign inversion above ‐75 mV. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Blue light emitting diodes on Si(001) grown by MOVPE
Authors: Schulze F. , Dadgar A. , Bertram F. , Bläsing J. , Diez A. , Veit P. , Clos R. , Christen J. , Krost A. 
Published: January 2007

AbstractWe report on the growth of GaN‐based light emission diodes on Si(001) substrates. The optically active region of the samples consists of a fivefold InGaN/GaN multiple quantum well grown on a 2.5 µm thick AlGaN/GaN buffer layer structure. By growing on 4° off‐oriented substrates and inserting four thin low‐temperature AlN interlayers, a flat, smooth, and crack‐free surface was obtained. The presented samples show an electrically stimulated emission of bright blue light at 455 and 490 nm, respectively. The crystallographic properties were analyzed by X‐ray diffraction measurements and transmission electron microscopy, and the optical properties by photo‐, electro‐, and spatially resolved cathodoluminescence. The local peak‐wavelength distribution amounts to 14.8 meV. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fast time behavior of the polarization filtering in anisotropically strained M ‐plane GaN films
Authors: Flissikowski T. , Misra P. , Brandt O. , Grahn H. T. 
Published: January 2007

AbstractThe dynamic behavior of the polarization filtering in M ‐plane GaN films is investigated by time‐resolved pump‐and‐probe spectroscopy. The reduced in‐plane crystal symmetry and the anisotropic in‐plane strain in M ‐plane GaN films lead to different absorption coefficients along the two principle in‐plane axes. The absorption can be selectively bleached by additional pumping with polarized light along one of these two axes. On an ultra‐fast timescale, the resulting pump‐and‐probe transients are governed by two different processes, namely the relaxation dynamics of holes in the two uppermost valence bands and the coherent coupling artifact. The recovery of the absorption is analyzed using the time symmetry of the coherent artifact and a rate‐equation model for carrier relaxation and redistribution in the valence bands. The analysis yields redistribution times below 1 ps and carrier recombination times of about 15 ps. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication and optical characterization of III‐nitride air‐bridge photonic crystal with GaN quantum dots
Authors: Li Ning , Arita M. , Kako S. , Kitamura M. , Iwamoto S. , Arakawa Y. 
Published: January 2007

AbstractWe report the fabrication of III‐nitride air‐bridge photonic crystals with GaN quantum dots for the first time. Photonic crystals with various periodicities and airhole diameters were fabricated. Abrupt vertical profiles and high aspect ratio (∼3) were achieved with excellent reproducibility even to the structure with periodicity as small as 150 nm. The fabrication of air‐bridge structure utilizing photoelectrochemical etching of SiC was demonstrated. Strong photoluminescence enhancement by a factor of 5 was observed from GaN QDs embedded in the air‐bridge PC layer. This is due to the coupling of PL light with photonic bands above the light cone, thus results in the enhanced light extraction efficiency. These results will lead to the realization of high efficiency quantum dots based emitting devices in blue and ultraviolet range. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photonic circuits writing with UV pulsed laser
Authors: Kribich K. R. , Gatti S. , Jabbour J. , Pille G. , Calas S. , Mazingue T. , Etienne P. , Legros R. , Moreau Y. 
Published: January 2007

AbstractPhotonics technology is employed in a growing number of applications. Biological and chemical sensors (E. Udd, Fiber Optic Sensors: An Introduction for Engineers and Scientists, Wiley, New York, 1991 [1]) for health and environment demand an adaptable technology. Network development towards the end‐user requires more interconnecting components. Vision, lighting, data processing in hostile environment (spatial, military) need specific technologies. A flexible and low‐cost process using good quality material is necessary. The sol‐gel process is a chemical method to fabricate glasses at ambient pressure and moderate temperature. Hybrid materials (H.K. Schmidt et al., Proc. SPIE 3136, 220 (1997) [2]), mixing organic and inorganic parts, offer the advantages of polymer‐like materials and glasses. We report on a new hybrid sol‐gel technology to overcome the drawbacks of the formerly presented one (H. Krug, F. Teillantes, P.W. Oliviers, and H. Schmidt, Proc. SPIE 1758, 448 (1992) [3]). We present the material synthesis, an accurate and flexible fabrication process based on a pulsed UV laser lithography system and the characterisation of the optical waveguides and photonic circuits realised. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
M ‐plane GaN‐based dichroic photodetectors
Authors: Rivera C. , Misra P. , Pau J. L. , Muñoz E. , Brandt O. , Grahn H. T. , Ploog K. H. 
Published: January 2007

AbstractThe in‐plane asymmetry of M ‐plane GaN films was used to fabricate polarization‐sensitive photodetectors. The measured contrasts between the detected light polarized perpendicular and parallel to the c‐axis are as high as 7.25 at 363 nm for a 0.4 μm thick film. For other film thicknesses, the polarization‐sensitive bandwidth can be increased. At the same time, the position of the maximum contrast is also affected by the film thickness through a different strain state. Considerations for the detector design show that the film thickness affects both, the contrast and polarization‐sensitive bandwidth, through the absorption and the effect of the strain on the valence‐band splitting. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatial mapping on surface light extraction from 2D photonic quasicrystals patterned GaN‐based light emitters
Authors: Zhang ZhenSheng , Zhang Bei , Dai Tao , Bao Kui , Liu Dan , Wang Xiao , Kang XiangNing , Xu Jun , Yu DaPeng , Zhu Xing 
Published: January 2007

AbstractWe report the observations of surface light extraction enhancement from two‐dimensional (2D) photonic crystal (PC) and Photonic Quasicrystal (PQC) patterns on electrical current injected GaN‐based light emitters. Spatial mapping of the surface extraction was acquired by a microscopic electrical luminescence setup and a scanning near‐field optical microscope (SNOM). Slight difference of mapping profile between twelve‐fold PQC and regular triangular PC was obtained. It is shown that 12PQC was more efficient for light extraction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sol‐gel based YAG:Ce3+ powders for applications in LED devices
Authors: Potdevin A. , Chadeyron G. , Boyer D. , Mahiou R. 
Published: January 2007

AbstractLuminescent Y3(1‐x)Al5O12:Ce3+3x (YAG: Ce3+) (x = 0.001 to 0.05), Lu2.97Al5O12:Ce3+0.03 (LuAG: Ce3+) and Y3‐0.03‐3yAl5O12:Ce3+0.03, Tb3y (YAG: Ce3+,Tb3+) (y = 0.1 and 0.2 phosphor powders have been successfully prepared by the sol‐gel route from alkoxide precursors. Purity of derived materials was investigated by X‐ray diffraction (XRD): Pure YAG phase was obtained without any intermediate whatever the Ce3+ doping rate between 0.1 and 5 mol% and LuAG phase was also effectively achieved.Luminescent properties of samples have been recorded. Excitation spectra of YAG:Ce3+ crystallized powders have revealed a broad excitation band around 470 nm, which matches very well with GaN‐based blue LED. On the basis of the emission spectra study under blue excitation, the Ce3+ optimal concentration of powders has been determined. Eventually, effects of codoping by Tb3+ and substituting Y3+ by Lu3+ have been analysed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Imprint lithography advances in LED manufacturing
Authors: Hershey Robert , Doyle Gary , Jones Chris , LaBrake Dwayne , Miller Mike 
Published: January 2007

AbstractImprint lithography is a promising cost effect alternative to e‐beam and optical lithography for producing photonic crystals and other nano‐scale light extraction and beam directing elements for LEDs; however, there are several challenges that must be overcome before imprint lithography can be applied to typical LED substrates. This paper reviews progress made at Molecular Imprints Inc. (MII) in imprinting representative 3″ GaN on Sapphire substrates including methods for dealing with substrate non‐flatness, multi‐die imprint, and imprinting on warped and bowed substrates. The results of imprinting over typical GaN on Sapphire topography and common defects such as fall‐on particles and EPI defects is presented along with results on GaN wafers optimized for imprint lithography. Whole wafer thin template replication techniques are also discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication and optical properties of blue LEDs with silica microsphere coating
Authors: Kusakabe K. , Funazaki S. , Okamoto K. , Nishizawa S. , Ohkawa K. 
Published: January 2007

AbstractWe report the enhancement of light extraction efficiency of InGaN‐based blue light emitting diodes by using a surface light‐scattering layer. A number of SiO2 microspheres embedded into a ZrO2 thin layer played a role of a light‐scattering medium. Coating the light‐scattering layer on device surface, the inter‐ ference fringes of electroluminescence (EL) spectra were eliminated and the EL intensity around 440–450 nm was increased by a factor of 1.3. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth behavior and optical properties of In‐rich InGaN quantum dots by metal‐organic chemical vapor deposition
Authors: Kim Hee Jin , Kwon Soon‐Yong , Kim Hyun Jin , Na Hyunseok , Shin Yoori , Lee Keon‐Hun , Kwak Ho‐Sang , Cho Yong Hoon , Yoon Jung Won , Cheong Hyeonsik , Yoon Euijoon 
Published: January 2007

AbstractWe successfully grew In‐rich In0.8Ga0.2N/GaN quantum dots (QDs) by metal‐organic chemical vapor deposition. We obtained uniform QDs with density of 1.3 x 1010/cm2 by optimizing growth conditions. Strong photoluminescence (PL) emission from In‐rich InGaN/GaN QDs was observed at room temperature and emission wavelength was varied from 404 nm to 454 nm depending on QD size. It is strongly suggested that QDs leads to higher radiative recombination efficiency from temperature‐dependent PL measurement. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deep ridge GaN cw‐laser diodes
Authors: Dennemarck J. , Tessarek C. , Figge S. , Hommel D. 
Published: January 2007

AbstractThe processing of homoepitaxial grown GaN based laser diodes by means of chemical assisted ion beam etching (CAIBE) is discussed. These laser diodes, emitting in the blue/UV spectral region, have been processed as buried ridge wave guide structures. Both, the influence of process parameters during etching such as the angle of incidence of the ions and gas fluxes as well as the impact of the ridge depth on the device performance will be analysed. Steep and smooth sidewalls of the ridge have been achieved by optimising the process parameters and by etching the ridge through the active region, cw‐lasing has been achieved. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homoepitaxial laser diodes emitting at 390 nm and the influence of substrate quality
Authors: Figge Stephan , Dennemarck Jens , Hommel Detlef 
Published: January 2007

AbstractThis paper deals with the homoepitaxial growth of laser diodes and the dependence on the substrate quality. We will present laser diodes emitting at 390 nm which are capable of cw‐operation. Lifetime measurements have been conducted and the degradation of the diodes will be discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of lattice‐mismatch induced built‐in strain on the valence band properties of wurtzite ZnO/Zn1–xMgxO quantum well heterostructures
Authors: Zitouni K. , Kadri A. 
Published: January 2007

AbstractWe present a theoretical study of the effects of lattice‐mismatch induced built‐in strain on the electronic properties of valence band states in wurtzite ZnO/Zn1–xMgxO Quantum Well (QW) heterostructures. In this purpose, a 6x6 k·p method has been used to incorporate the effects of strain and nonparabolicity. The energies corresponding to the transitions between conduction band (C), heavy hole (HH), light hole (LH) and crystal‐field split‐off hole (CH) bands have been calculated as a function of Mg composition and strain. We have also calculated the energy dispersions and wave functions of strained wurtzite ZnO. It is found that ZnO is always under a biaxial tensile strain, in the whole Mg composition range investigated (x < 40%). As a consequence, the light hole valence subband is shifted upwards with respect to the corresponding heavy hole valence subband, resulting in a reduction of ZnO direct band gap by almost 6% when x = 35%. This is found to result in turn in a significantly reduced in‐plane hole effective mass at the top of the valence band which is always LH‐like. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of thick GaN layers on c‐plane sapphire substrates using stress absorbing layer (SAL)
Authors: Goto H. , Lee S. W. , Kinomoto J. , Kim S. T. , Ko H. C. , Cho M. W. , Yao T. 
Published: January 2007

AbstractWe investigate the effects of inserting defective stress absorbing layer (SAL) in between sapphire substrate and thick GaN layer. A two‐step growth technique, in which GaN layers grow at different growth rates in each step, is adopted for growing high‐quality GaN layer (NL) at low growth rate and SAL at high growth rate by hydride vapor phase epitaxy (HVPE). SALs grown directly on c‐sapphire show hexagonal columnar shaped rough morphology with low crystalline quality. Nevertheless, strain in SAL is more relaxed compared with high quality NL. SAL contains majority of high‐quality layers and minority of highly defective regions. The highly defective regions are strongly in‐plane compressed by thermal stress and absorbs thermal stress. Overgrown NLs on SALs show lower residual strain compared to NL on NL sample. These results show that bending and microcracks can be suppressed in free‐standing GaN substrates by adopting SALs in GaN growth. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The quantum efficiency of green GaInN/GaN light emitting diodes
Authors: Zhao W. , Li Y. , Detchprohm T. , Wetzel C. 
Published: January 2007

AbstractEnergy efficient lighting can be achieved by help of high efficiency light emitting diodes (LEDs). Substantial performance gains are feasible in the green – 500–555 nm – spectral region by implementing proper design of the active region. Here we analyze external quantum efficiency of high performing LED dies as a function of current and temperature in order to formulate relevant optimization rules. Among a large sample set we identify traits that clearly correlate with respective device performance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phonons in strained AlGaN/GaN superlattices
Authors: Darakchieva V. , Monemar B. , Paskova T. , Einfeldt S. , Hommel D. , Lourdudoss S. 
Published: January 2007

AbstractPhonons in strained AlGaN/GaN superlattices (SLs) with constant periods but different Al composition have been studied using a combination of infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The following SL modes were identified: i) AlGaN localized E 1(TO) modes identified for the first time and AlGaN localized A 1(LO) phonons; ii) GaN localized E 2, E 1(TO) and A 1(LO) phonons; iii) delocalized E 1(LO) phonons; iv) A 1(TO) phonon; v) two modes around 660 cm–1 and 594‐625 cm–1, respectively, not predicted by theory. The effects of strain and composition on the phonon frequencies were established and discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication of GaN‐based electroluminescent devices on Al substrates and their application to red, green and blue pixels for flat‐panel displays
Authors: Sugimoto Koichi , Egawa Shinichi , Arai Masatoshi , Honda Tohru 
Published: January 2007

AbstractGaN‐based thin‐film electroluminescent devices (TF‐ELDs) operating in the UV spectral region were fabricated on Al substrates. GaN films were deposited by compound‐source molecular beam epitaxy (CS‐MBE) technique. During the deposition, the cell temperature of the GaN compound source is one of the key factors for reducing the excess Ga in the films. The UV light emission (peak wavelength 375 nm) corresponding to the near‐band‐edge emission of hexagonal GaN was observed from GaN‐based TF‐ELDs. Furthermore, red, green and blue (RGB) lighting pixels were fabricated using UV GaN‐based TF‐ELDs in combination with RGB phosphors. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An electrospray membrane probe for the analysis of volatile and semi‐volatile organic compounds in water
Authors: VanHassel Emily , Bier Mark E. 
Published: January 2007

AbstractA new membrane probe incorporating electrospray ionization (ESI) was designed, built and coupled to an ion trap mass spectrometer to detect low levels of semi‐volatile organic compounds (SVOCs) in water. Similar to other membrane introduction mass spectrometry (MIMS) systems, the probe contains a capillary polydimethylsiloxane (PDMS) membrane to allow for the preferential permeation of small molecules but, in contrast, the interface uses a liquid/membrane/liquid interface rather than liquid/membrane/gas. The ESI source allows the probe to be operated at atmospheric pressure in positive or negative ionization mode and the lack of fragmentation in ESI allows for the simultaneous screening of many analytes with high sensitivity. The interface allows for the addition of additives to both the external and the internal liquid mobile phases to selectively improve permeation and/or the ionization efficiency of various classes of compounds. Characterization of the probe with methanol as the internal mobile phase showed that the signal for aniline optimized at 60°C and an internal flow rate between 2–5 µL/min. The transfer of analyte through the membrane from water to methanol ensures a strong signal and robust electrospray for both positive and negative ion mode which is not typical when spraying pure water. Detection limits for aniline, pyridine and pentachlorophenol, and for the herbicides alachlor, atrazine, butachlor, metolachlor and simazine, were in the ppb to pptr range. Copyright © 2007 John Wiley & Sons, Ltd.