bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vertical PIN ultraviolet photodetectors based on 4H‐SiC homoepilayers
Authors: Liu X. F. , Sun G. S. , Li J. M. , Ning J. , Zhao Y. M. , Luo M. C. , Wang L. , Zhao W. S. , Zeng Y. P. 
Published: April 2007

AbstractVertical PIN ultraviolet photodetectors based on 4H‐SiC homoepilayers are presented. The growth of the 4H‐SiC homoepilayers was carried out in a LPCVD system. The size of the active area of the photodetector was 300 × 300 µm2. The dark and illuminated I‐V characteristics were measured at reverse biases from 0 V to 30 V at room temperature. The illuminated current was at least two orders of magnitude higher than the dark current at a bias of below 12 V. The photoresponse was measured from 200 nm to 400 nm at different reverse biases and the peak values of the photo response were located at 310 nm. The calculated spectral detectivity D* was shown to be higher than 1013 cmHz1/2/W from 260 to 360 nm with a peak value of 5.9 × 1013 cmHz1/2/W at 310 nm. The peak value of the photoresponse was hundreds of times higher than the response at 400 nm, which showed the device had good visible blind performance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Understanding quantum dots: overheating of the LO‐phonon modes
Authors: Král K. 
Published: April 2007

AbstractLongitudinal optical phonons have been used recently to explain the electronic energy relaxation in quantum dots. In this theory they served as a reservoir, on which the electron executes multiple scattering acts. Rather naturally such a phonon subsystem is expected to be passive, namely, in a long‐time limit of development the whole system should be able to achieve such a stationary state in which statistical distributions of both subsystems, electron and phonons, do not change in time. Here we remind briefly that the recent approach to the relaxation theory in quantum dots displays a non‐passivity of such a reservoir. We remind briefly the method of a partial elimination of this phonon overheating effect by using the Lang‐Firsov transformation. We apply the modified relaxation theory to the electronic relaxation at low electronic densities in quantum dot systems and come to conclusions about the role of e‐LO scattering mechanism in these situations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogeneity assessment of large‐diameter III‐V compound semiconductor substrates by near‐infrared transmittance measurement
Authors: Inoue Yusuke , Kitamoto Takuya , Yamada Masayoshi , Kawase Tomohiro 
Published: April 2007

AbstractThe light absorption mechanisms below the fundamental energy gap in undoped and Si‐doped GaAs crystals have been investigated to assess EL2 defects and the carrier concentration distribution in III‐V compound semiconductor substrates. It is demonstrated, that the near‐infrared transmittance mapping equipment consisting of a high‐brigthness LED, a high‐sensitivity CCD camera, and a digital image processing system is capable to reveal surface scratches and local crystal imperfections such as inclusions, voids, and twining inside the substrate, besides EL2 defects and the carrier concentration distribution. Hence, the homogeneity of III‐V compound semiconductor substrates with diameter up to 6 inches can be assessed in less than several seconds with high spatial resolution of 640×480 pixels. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Performance comparison of Cu and Ni gates for deep submicrometer AlGaN/GaN HFETs
Authors: Sun H. F. , DiSanto D. W. , Bolognesi C. R. 
Published: April 2007

AbstractCopper (Cu) was investigated as the gate contact metallization in AlGaN/GaN heterostructure field‐effect transistors (HFETs). For comparison, Nickel/Gold (Ni/Au) gate devices were fabricated on the same sample using electron beam lithography. Both metallization schemes yielded comparable transconductance characteristics: the maximum extrinsic transconductance reached 290 mS/mm. At gate voltage of ‐20 V, the reverse current for the Cu Schottky contact was roughly one to two orders of magnitude lower than that of Ni/Au contact. For Cu/Au gate devices, the product of current gain cut‐off frequency (fT) and gate length LG improved by 15% compared to Ni/Au gate devices. The power gain cut‐off frequency (fmax) also improved by at least 15%. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Blue‐shift of phosphorous‐implanted InGaAs/InGaAsP MQW laser structures by two‐step anneals
Authors: Byun Young Tae , Choi Kyoung Sun , Kim Sun Ho 
Published: April 2007

AbstractWe describe studies of implantation‐enhanced quantum‐well intermixing in a lattice‐matched InGaAs/InGaAsP multiple quantum well p‐i‐n heterostructure. Samples were implanted with a dose of 5×1014 P+ ions /cm2 at high energy of 1 MeV. The band gap for the samples was determined from photoluminescence at room temperature. The maximum blue‐shift of the band gap was 107 nm after the RTA process at 675 °C for 9 minutes. However, it was improved to 140 nm after two‐step anneals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characteristics of electron beam‐evaporated high k ‐TiOx thin films on n‐GaAs
Authors: Oyama Yutaka , Ohno Takeo , Sato Taiji , Nishizawa Jun‐ichi 
Published: April 2007

AbstractElectrical and structural evaluations have been performed on high‐k TiOx dielectrics which had been de‐posited on {001} oriented n‐GaAs at 100 °C by electron beam evaporation of TiO2 in a mixed atmosphere of O2/Ar. A permittivity, εs, as high as 100 has been achieved, and a breakdown field strength of 0.5 MV/cm has been obtained. Room temperature transistor action was realized utilising a p+n+ tunnel transistor with TiOx gate dielectric, both in enhancement and depletion mode operation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Room temperature Sb‐based mid‐infrared VCSELs
Authors: Genty F. , Cerutti L. , Garnache A. , Ouvrard A. , Pérona A. , Grech P. , Romanini D. , Chevrier F. 
Published: April 2007

AbstractThe fabrication and the characterization of Sb‐based Mid‐Infrared emitting VCSELs are described in this paper. Both external‐cavity and microcavity optically‐pumped devices exhibit very high performances particularly well‐adapted for trace gas detection by laser spectroscopy. Concerning electrically‐pumped Sb‐based VCSELs, the first results obtained with an hybrid dielectric‐semiconductor structure are presented. However, such devices remain less mature than similar optically‐pumped laser and only microcavity‐enhanced electroluminescence could be observed near 2.3 µm at room temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reflectivity of deep‐etched InGaAs‐InP waveguide Bragg reflectors
Authors: Chong H. M. H. , Tan W. K. , Bryce A. C. 
Published: April 2007

AbstractDeep etched Bragg reflector gratings in InGaAs‐InP waveguide structures have been realized. The width of the waveguide was 2 µm and was dry etched to a depth of more than 1.5 μm using CH4/H2‐based chemistry. The Bragg reflectors were designed to be first order and to have a large bandwidth – with one to three slots in the waveguide structure. The single slot reflector has a width of 190 nm and the period of other two‐slots grating is 420 nm and slot width of ∼200 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two‐dimensional simulation of type‐II InP/GaAsSb/InP double heterojunction bipolar transistors
Authors: Tao N. G. M. , Liu H. G. , Bolognesi C. R. 
Published: April 2007

AbstractTwo‐dimensional (2D) numerical simulations of self‐aligned sub‐micron InP/GaAsSb double heterojunction bipolar transistors (DHBTs) were performed to investigate the effects of base band gap narrowing and surface recombination. Base energy band gaps of 0.72 eV and 0.67 eV for GaAs0.51Sb0.49 bases with doping levels of 5×1018 and 5×1019 cm–3 were extracted from the comparison between the measurement data and simulation results. We took into account the surface Fermi level pinning and introduced a surface state model for the emitter side wall and extrinsic base surface. To the best of our knowledge, a good match between measured and simulated InP/GaAsSb DHBTs characteristics, from low to high current densities has not been achieved prior to the present work. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromagnetic properties of epitaxial MnAs films on GaAs surfaces
Authors: Hesjedal Thorsten , Engel‐Herbert Roman , Schaadt Daniel M. , Ploog Klaus H. 
Published: April 2007

AbstractWe present a systematic study of the micromagnetic properties of MnAs deposited by molecular‐beam epitaxy on GaAs(001) and GaAs(111)B surfaces. In epitaxial MnAs films, the strain state in MnAs‐on‐GaAs(001) (anisotropic) and MnAs‐on‐GaAs(111)B (isotropic) has a strong influence on the magnetostructural phase transition and thus the micromagnetic properties. The ferromagnetic α and the β phase coexist over a wide temperature range exhibiting self‐organized, magnetically coupled nanostructures. Independent of the substrate orientation, magnetic flux‐closure domain patterns are formed in the basal plane of MnAs. The spatial distribution of the phases in equilibrium (stripes and quasi‐hexagonal islands, respectively) stabilizes various magnetic states, which were found experimentally and confirmed by micromagnetic simulations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comprehensive modelling of resonant‐cavity light‐emitting diode
Authors: Li Z. Q. , Li Z. M. Simon 
Published: April 2007

AbstractWe extended the theory by Henry (J. Lightwave Technol. LT‐4, 288 (1986) [1]) to accurately treat the coupling of spontaneous emission noise with microcavity modes. The Green's function method is employed to solve the inhomogeneous wave equation including a Langevin force Fω which accounts for spontaneous emission by carriers at angular frequency ω. The optical wave equation is coupled with the self‐consistent calculations of the material spontaneous emission rate of quantum well/dot using envelope wavefunction method. Finally the carrier transport equations are solved within the framework of 2D/3D drift‐diffusion model implemented in the Crosslight Software package APSYS (Crosslight APSYS User's Manuals, Copyright © Crosslight Software Inc. (version 2005. 11) [2]). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN/AlN electro‐optical modulator prototype at telecommunication wavelengths
Authors: Baumann E. , Giorgetta F. R. , Hofstetter D. , Guillot F. , Leconte S. , Bellet‐Amalric E. , Monroy E. 
Published: April 2007

AbstractWe report on a prototype electro‐optical modulator at telecommunication wavelength based on intersubband (ISB) transitions in a short‐period GaN/AlN superlattice (SL). The device has a vertical architecture resembling a nitride‐based high‐electron mobility transistor, whose barrier layer has been replaced by a 5 period SL. By applying an electrical field, we were able to influence the bandstructure and as a consequence to quench the ISB absorption peak originating from the SL. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A study on influence of micropipes in SiC substrate on overgrown AlGaN/GaN HEMT DC characteristics
Authors: Bang Hyungjin , Mitani Takeshi , Sazawa Hiroyuki , Nakashima Shinichi , Hirata Koji , Kosaki Masayoshi , Okumura Hajime 
Published: April 2007

AbstractA deterioration mechanism of DC characteristics of AlGaN/GaN high‐electron mobility transistors (HEMTs) fabricated around hollow cores that extend from micropipes in SiC substrates was studied. Various sizes of hollow cores were investigated to study the influence of size dependence. Prominent deterioration of the DC characteristics of HEMTs fabricated in the vicinity of hollow cores with a diameter of 5 μm was observed, while no major deterioration was observed for HEMTs fabricated around hollow cores whose diameters were 1.5 and 3 μm. Clear correlation between the size of hollow cores and free carrier densities at the peripheries of the cores was observed using micro‐Raman imaging. The high density of free carriers around relatively large hollow cores causes deterioration of the DC characteristics of HEMTs fabricated in the vicinity of hollow cores. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication of porous ZnO nanostructures and morphology control
Authors: Lee Sang Hyun , Lee Hyun Jung , Goto Hiroki , Cho Meong‐whan , Yao Takafumi 
Published: April 2007

AbstractPorous 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)
Study of nuclear quadrupolar interaction using a novel all‐electrical GaAs NMR device
Authors: Ota T. , Kumada N. , Yusa G. , Miyashita S. , Hirayama Y. 
Published: April 2007

AbstractWe study the nuclear quadrupolar interaction using a resistively‐detected NMR device. The nuclear spins are dynamically polarized in a sub‐micron scale region defined by split gates. In pulsed NMR spectra for 69Ga and 75As nuclei, three distinct peaks are observed. The peak splitting depends on the electric quadrupolar coupling constant EQ. By comparing the spectra of both nuclei, we find that the relative peak intensity is opposite, which is independent of the condition for the dynamic nuclear spin polarization. This result indicates that the electric‐field gradient in EQ has opposite sign at 69Ga and 75As nuclear site. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hydrogen‐assisted molecular‐beam epitaxy of ZnO layers on Zn‐polar ZnO
Authors: Suzuki H. , Minegishi T. , Park S. H. , Cho M. W. , Yao T. 
Published: April 2007

AbstractHydrogen‐assisted molecular beam epitxy of ZnO on Zn‐polar ZnO is achieved using atomic hydrogen. Exposure of atomic H helps to grow high‐quality ZnO layers on Zn‐polar ZnO substrates even at a low temperature of 400 °C. The full width at half maximum values of X‐ray rocking curves for ZnO epilayers are as narrow as 64 arcsec and 60 arcsec for (0002) and (10‐11) diffractions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Increased power conversion efficiency through photon recycling in quantum well lasers
Authors: Wang J.‐B. , Zhang Y.‐H. 
Published: April 2007

AbstractThis paper reports a study of the photon recycling effect in semiconductor quantum well (QW) lasers and how to enhance such an effect to reduce threshold current density and to increase power conversion (wall‐plug) efficiency. To maximize the enhancement of the spontaneous emission recycling, it is necessary to use metal contacts with high reflectivity, to remove the substrate, and to optimize the overall doping profile design. The modeling results have also shown that the threshold current density in a multiple quantum well laser has a weak dependence on the number of QWs when the photon recycling effect is strong. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of non‐polar (11$ \bar 2 $0) and semi‐polar (11$ \bar 2 $6) AlN and GaN films on the R‐plane sapphire
Authors: Chandrasekaran R. , Ozcan A. S. , Deniz D. , Ludwig K. F. , Moustakas T. D. 
Published: April 2007

AbstractIn this paper, we present detailed studies of growth of AlN and GaN films on R‐plane sapphire substrates. Contrary to previously reported work that GaN grows with its A‐plane (11$ \bar 2 $0) parallel to the R‐plane (1$ \bar 1 $02) of sapphire, our studies indicate that the crystallographic orientation of the III‐nitride films grown on such substrates depends strongly on the kinetic conditions of growth of the AlN buffer. Specifically, the group III‐rich conditions of growth of AlN buffer lead to nitride films having the (11$ \bar 2 $0) planes parallel to the sapphire surface, while growth of the buffer under N rich conditions leads to nitride films with the (11$ \bar 2 $6) planes parallel to the sapphire surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Process simulation of p ‐doping in GaN and related group III nitrides
Authors: Zhou Y. J. , Li Z. Q. , EL Boukili A. , Li Z. M. Simon 
Published: April 2007

AbstractIn this work we use the PROCOM sofware to model Mg doped GaN film growth by MOCVD. The 2/3D conservation equations of mass, energy, momentum and species are solved by the nonsymmetric conjugate gradient method with block preconditioning (H. C. Elman, Preconditioned conjugate gradient methods for nonsymmetric systems of linear equations (Yale University Research Report, 1981) [5]). A kinetics model with gas/surface adduct formation has been incorporated with detailed Mg dopant reaction mechanism. We reproduced broad doping profiles caused by memory effects and verified that the formation of (NH3)2‐MgCp2 and NH3‐MgCp2 adducts play an important role in p‐doping of GaN and related Group III nitrides. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bismuth incorporation in GaAs1–xBix grown by molecular beam epitaxy with in‐situ light scattering
Authors: Young E. C. , Whitwick M. B. , Tiedje T. , Beaton D. A. 
Published: April 2007

AbstractThe dilute bismide semiconductor GaAs1–xBix is an interesting new semiconductor alloy with novel properties and potential device applications. Like the dilute nitride alloy GaAs1–xNx, the dilute bismide shows a giant bandgap bowing effect. Bi alloying primarily affects the states in the vicinity of the top of the valence band rather than the bottom of the conduction band as in the case of N alloying. MBE growth of dilute bismides requires low growth temperatures (320‐390 °C) and near stochiometric group III/V ratios, due to the strong tendency of Bi to surface segregate under usual GaAs growth conditions. Optimal growth conditions are close to conditions that produce Bi and/or Ga droplets. In‐situ light scattering is found to be a useful tool for defining growth conditions that do not produce droplets on the surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InGaN/GaN nanopillar‐array light emitting diodes
Authors: Neufeld C. J. , Schaake C. , Grundmann M. , Fichtenbaum N. A. , Keller S. , Mishra U. K. 
Published: April 2007

AbstractGaN light emitting diodes were fabricated from arrays of nanopillars with embedded InGaN quantum wells. InGaN heterostructures were grown by MOCVD on n‐type GaN templates and pillars were fabricated by laser interference lithography and subsequent reactive ion etching and annealing. The tops of the pillars were coalesced by lateral growth of p‐type GaN by MBE forming a planar contact layer. This structure enables integration with standard planar processing while taking advantage of the nanopillar structure. LEDs were fabricated and characterized by electroluminescence, current‐voltage, and output power vs. current measurements. The devices showed rectifying behavior with a turn‐on voltage of 3 V and electroluminescence peak at 400 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enthalpy of Solvation Correlations for Gaseous Solutes Dissolved in Benzene and in Alkane Solvents Based on the Abraham Model
Authors: Mintz Christina , Clark Michael , Burton Katherine , Acree William E. , Abraham Michael H. 
Published: April 2007

AbstractData have been assembled from the published literature on the enthalpies of solvation for more than 100 compounds in heptane, hexadecane, cyclohexane, and benzene. It is shown that an Abraham solvation equation with five descriptors can be used to correlate the experimental solvation enthalpies to within standard deviations of 1.85 kJ/mol (heptane), 1.84 kJ/mol (hexadecane), 1.66 kJ/mol (cyclohexane), and 2.08 kJ/mol (benzene). The derived correlations provide very accurate mathematical descriptions of the measured enthalpy of solvation data, which in the case of benzene span a range of 111 kJ/mol. Division of the experimental values into a training set and a test set shows that there is no bias in predictions, and that the predictive capability of the correlations is better than 2.63 kJ/mol.
Computed structures and relative stabilities of Be@C74
Authors: Slanina Zdeněk , Uhlík Filip , Lee Shyi‐Long , Adamowicz Ludwik , Nagase Shigeru 
Published: April 2007

AbstractThe paper presents computations for a C74‐based endohedral – Be@C74. A set of four C74 cages is considered, namely one cage with isolated pentagons and three isomers with a pentagon–pentagon junction. The computations are carried out with a newly suggested functional, viz. MPWB1K, which has never been applied to metallofullerenes. Special interest is paid to the Gibbs‐energy supported relative‐stability evaluations. Although the endohedral based on the cage with isolated pentagons is the most important species at lower temperatures, at higher temperatures a cage with pentagon–pentagon junction prevails. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Stable strontium isotopic ratios from archaeological organic remains from the Thorsberg peat bog
Authors: von Carnap‐Bornheim Claus , Nosch Marie‐Louise , Grupe Gisela , Mekota Anna‐Maria , Schweissing Mike M. 
Published: April 2007

AbstractStable strontium isotope ratios in archaeological finds have frequently been used to determine their place of origin, in order to reconstruct migration and trade. Peat bogs offer favourable burial conditions for the preservation of organic remains such as woollen textiles and leather by a natural tanning process. However, these finds are impregnated by peat substances including contaminant strontium which is likely to mask the original 87Sr/86Sr isotopic ratio of the specimens. In this paper, we present a pilot study analysing stable strontium isotopic ratios from Iron Age textile and leather finds from the Thorsberg peat bog, focusing on a sample processing method which permits the quantitative removal of contaminating strontium from the specimens. Copyright © 2007 John Wiley & Sons, Ltd.
Bayesian generalized monotonic functional mixed models for the effects of radiation dose histograms on normal tissue complications
Authors: Schipper Matthew , Taylor Jeremy M. G. , Lin Xihong 
Published: April 2007

AbstractWhen treating cancer patients with radiation therapy, the normal tissue in an organ close to the tumour usually receives some dose of radiation. The dose is not of the same intensity throughout the organ. This radiation can cause normal tissue complications, so for treatment planning purposes, it is important to understand the relationship between the distribution of dose intensities in the organ and the occurrence of complications. One general summary measure of the dose effect is obtained by integrating a weighting function (w(d)) over the dose distribution. The weighting function w(d) should be monotone for biological reasons. Because the true shape of w(d) is not known, we estimate it non‐parametrically subject to the monotonicity constraint. In our approach w(d) is written as a weighted sum of monotone basis functions. The weights in this sum are formulated as a mixture of point mass at zero and a Gamma random variable. A key feature of our method is that it allows for flat regions through the use of this mixture prior. The model is estimated using a Markov Chain Monte Carlo algorithm. We illustrate our method with data from a head and neck cancer study in which the irradiation of the parotid gland results in loss of saliva flow. Copyright © 2007 John Wiley & Sons, Ltd.