bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hinge Sensitivity in a Micro-Rotating Structure for predicting Induced Thermo Mechanical Stress in Integrated Circuit Metal Interconnects
Authors: dos Santos J. M. M. , Wang K. , Soare S. M. , Bull S. J. , Horsfall A. B. , Wright N. G. , O'Neill A. G. , Terry J. G. , Walton A. J. , Gundlach A. M. , Stevenson J. T. M. 
Published: April 2011

ABSTRACTThe process-induced stress in interconnects within integrated circuits (IC) has a direct influence on the mean time to failure of the devices. Since measurement of stress in individual metallised lines is not possible by existing techniques, another approach has been adopted where a test structure is generated during fabrication based on a micro-rotating cantilever sensor. To support the design, finite element modeling (FEM) has been performed. By comparing the rotation predicted by FEM simulations and that observed experimentally, a clear discrepancy is observed which is critically dependent on the details of the sensor design, the pattern transfer of the lithographic process and on the dry etching processing.
Anti-Weak-Localization Study of Rashba Spin-Splitting Energy as a Function of Well Asymmetry in InAlAs/InGaAs/InAlAs Quantum Wells
Authors: Koga Takaaki , Nitta Junsaku , Akazaki Tatsushi , Takayanagi Hideaki 
Published: April 2011

ABSTRACTWe have investigated the values of the Rashba spin-orbit coupling constant α in In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As quantum wells using an anti-weak-localization (AWL) analysis as a function of quantum well asymmetry. We have found that the deduced α values have strong correlations with the structural inversion asymmetry of the pertinent quantum wells as predicted theoretically. This fact suggests that the AWL analysis provides a reliable way to deduce α values experimentally for designing future spintronics devices.
Imaging Self-Organized Domains at the Micron Scale in Antiferromagnetic Elemental Cr Using Magnetic X-ray Microscopy
Authors: Evans P. G. , Isaacs E. D. , Aeppli G. , Cai Z.-H. , Lai B. 
Published: April 2011

ABSTRACTThe domains of antiferromagnetic order in elemental chromium can be observed with spatial resolution that is improved by orders of magnitude in comparison with previous techniques using magnetic x-ray scattering with an incident x-ray beam focused to a submicron spot. This use of magnetic x-ray microscopy takes advantage of the incommensurate spin density wave order in Cr to isolate magnetic scattering. The spin polarization dependence of the magnetic x-ray scattering cross section allows the first order spin-flip transition near 120 K to be imaged directly.
High Luminescence Efficiency from GaAsN Layers Grown by MBE with RF Nitrogen Plasma Source
Authors: Ustinov Victor M. , Cherkashin Nikolai A. , Bert Nikolai A. , Tsatsul'nikov Andrei F. , Kovsh Alexei R. , Wang Jyh-Shang , Wei Li , Chi Jim Y. 
Published: April 2011

Abstract(In)GaAsN based heterostructures have been found to be promising candidates for the active region of 1.3 micron VCSELs. However, (In)GaAsN bulk layers and quantum wells usually demonstrate lower photoluminescence intensity than their nitrogen-free analogues. Defects associated with lower temperature growth and N-related defects due to plasma cell operation and possible nonuniform distribution of nitrogen enhance the non-radiative recombination in N-contained layers. We studied the photoluminescence intensity of GaAsN layers as a function of N content in MBE grown samples using rf-plasma source. Increasing the growth temperature to as high as 520 °C in combination with the increase in the growth rate allowed us to avoid any N-related defects up to 1.5% of nitrogen. Low-temperature-growth defects can be removed by post-growth annealing. We achieved the same radiative efficiency of GaAsN samples grown at 520°C with that of reference layer of GaAs grown at 600°C. Compositional fluctuations in GaAsN layers lead to characteristic S-shape of temperature dependence of photoluminescence peak position and this feature is the more pronounced the higher the amount of nitrogen in GaAsN. Annealing reduces compositional fluctuations in addition to the increase in the photoluminescence intensity. The results obtained are important for further improving the characteristics of InGaAsN lasers emitting at 1.3 micron.
The Role of Nitrogen-Induced Localization and Defects in InGaAsN (? 2% N): Comparison of InGaAsN Grown by Molecular Beam Epitaxy and Metal-Organic Chemical Vapor Deposition
Authors: Kurtz Steven R , Allermana A. A. , Klem J. F. , Sieg R. M. , Seager C. H. , Jones E. D. 
Published: April 2011

AbstractNitrogen vibrational mode spectra, Hall mobilities, and minority carrier diffusion lengths are examined for InGaAsN (≈ 1.1 eV bandgap) grown by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). Independent of growth technique, annealing promotes the formation of In-N bonding, and lateral carrier transport is limited by large scale (Ęmean free path ) material inhomogeneities. Comparing solar cell quantum efficiencies for devices grown by MBE and MOCVD, we find significant electron diffusion in the MBE material (reversed from the hole diffusion occurring in MOCVD material), and minority carrier diffusion in InGaAsN cannot be explained by a “universal”, nitrogen-related defect.
Thermal Anneal Effects on Carbon-Hydrogen LVMs In AlGaN
Authors: Manasreh M. O. , Weaver B. D. 
Published: April 2011

AbstractThermal annealing effects on carbon-hydrogen (C-H) complexes defects in AlGaN grown on sapphire by metalorganic chemical vapor deposition (MOCVD) technique have been investigated using Fourier transform infrared spectroscopy (FTIR). The CH complexes in AlGaN, formed either during growth or by proton irradiation, exhibit five local vibrational modes (LVMs) due to the symmetric and asymmetric vibrational stretching modes of C-H in CHn (n=1–;3) defect complexes. It was found that the annealing temperature (Ta) of 500°C is sufficient enough to dissociate most of the C-H complexes in AlGaN samples. A turning point annealing temperature is found around 300°C for un-irradiated Mg-doped sample, below which the total integrated area of the C-H LVMs continued to increase with increasing annealing temperature and reach the maximum value around 300°C. At Ta > 300°C, the total integrated area of the C-H LVMs starts to decrease and the C-H complexes seem to be completely depleted at Ta > 600°C. The depleted C-H LVMs were observed to partially recover after thermal annealing at Ta > 500°C and waiting for aging periods of several days. This recovery behavior is explained in terms of the hydrogen being remained inside the crystal after the dissociation of C-H complexes, subsequent diffusion and recombining again with carbon atom to reform C-H complexes.
Irradiation Effects in Space Solar Cells Made of Multiple Absorbers
Authors: Romero M. J. , Walters R. J. , Al-Jassim M. M. , Messenger S. R. , Summers G. P. 
Published: April 2011

AbstractSolar cells made of multiple absorbers are a commonly used approach for improving efficiency due to their extended range of spectral sensitivity. Indeed, efficiencies nearing the theoretical maximum have been achieved with a triple-junction device made of In0.51Ga0.49P (InGaP2), GaAs, and Ge solar cells connected in series. For extraterrestrial applications, there is the added requirement of radiation tolerance. The main challenge for space power-generation is therefore the development of highly efficient and radiation-tolerant devices. We have investigated several aspects of the radiation response of solar cells made of multiple absorbers, such as multijunction devices and quantum-well solar cells. Novel possibilities such as quantumdot solar cells and ordered-disordered heterostructures are proposed.
Comparison of AlGaAs Oxidation in MBE and MOCVD Grown Samples
Authors: Chen Y. , Roshko A. , Bertness K. A. , Readey D. W. , Allerman A. A. , Tan M. , Tandon A. 
Published: April 2011

AbstractSimultaneous wet-thermal oxidation of MBE and MOCVD grown AlxGa1−xAs layers (× = 0.1 to 1.0) showed that the epitaxial growth method does not influence the oxidation rate. Nearly identical oxidation depths were measured for samples grown by both techniques. It was found, however, that the oxidation rate is very sensitive to non-uniformities in the Al concentration in the AlxGa1−xAs layers, and that maintaining consistent and uniform Al concentrations is critical to achieving reproducible oxidation rates. The study also showed that the oxidation rate was not affected by the V/III ratio during growth nor by impurities at concentrations less than or equal to 10 ppm.
Exciton Diamagnetic Shifts and Magnetic Field Dependent Linewidths in Ordered and Disordered InGaP Alloys
Authors: Jones E. D. , Bajaj K. K. , Coli G. , Crooker S. A. , Zhang Yong , Mascarenhas A. , Olsen J. M. 
Published: April 2011

AbstractWe have measured the diamagnetic shifts and photoluminescence linewidths of excitonic transitions in ordered and disordered In0.48 Ga0.52 P alloys, lattice matched to GaAs, in pulsed magnetic fields at 4 and 76K. The pulsed magnetic field ranged between 0 and 50T. The variations diamagnetic shifts with magnetic field in disordered and weakly ordered samples are considerably smaller than those calculated using a free exciton model. For a given magnetic field, the value of the diamagnetic shifts are found to increase with increasing order parameter. Furthermore, for all samples, the diamagnetic shifts at 76K are larger than at 4K suggesting that the excitons are strongly localized.
GaInNAs Material Properties for Long Wavelength Opto-Electronic Devices
Authors: Gambin Vincent , Ha Wonill , Wistey Mark , Kim Seongsin , Harris James S. 
Published: April 2011

AbstractDilute nitrogen GaInNAs is a new promising material as an active region for use in 1.3 and 1.55 μm opto-electronic devices. It has been commonly observed that increasing the nitrogen content generally reduces the optical emission intensity and increases laser threshold. However, some non-radiative recombination defects are removed from the material during a post-growth anneal. One drawback to the anneal is that nitrogen out-diffuses from the quantum wells and blue-shifts optical emission. Using a modified active region structure, we have decreased nitrogen out-diffusion and reduced the luminescence blue-shift while still improving crystal quality. The growth consists of high nitrogen GaNAs barriers grown between lower nitrogen GaInNAs quantum wells. As an added benefit, the nitride barriers strain compensate for the compression in the high In content GaInNAs wells. Furthermore, in order to improve luminescence at long wavelengths, we have added Sb to GaInNAs and have observed high intensity photoluminescence (PL) out to 1.6 μm. We have grown and fabricated in-plane GaInNAs lasers that emit at 1.3 μm with a current threshold density of 1.2 kA/cm2 and GaInNAsSb lasers with emissions at 1.46 μm with a current threshold of 2.8 kA/cm2.
Excitonic Diamagnetic Shifts and Magnetic Field Dependent Linewidths in AlxGa1-xAs Alloys
Authors: Coli G. , Bajaj K. K. , Reno J. L. , Jones E. D. 
Published: April 2011

AbstractWe report measurements of both the diamagnetic shifts and the linewidths of excitonic transitions in AlxGa1-xAs alloys as a function of Al concentration and magnetic field at 1.4 K using photoluminescence spectroscopy. The magnetic field was varied from 0 to 13 tesla and Al composition in our samples ranged from 0 to 30%. The samples were grown on GaAs substrates oriented along [001] direction using molecular beam epitaxy at 590°C. We find that for a given value of alloy composition, both the diamagnetic shift and excitonic linewidth increase as a function of magnetic field. To explain our experimental data we propose that the excitons are localized in a very specific manner. To simulate this localization, we assume that the exciton reduced mass is effectively increased and is obtained by using the alloy dependent heavy-hole mass along (001) direction treated isotropically. The calculated values of the variations of the diamagnetic shift and excitonic linewidth as a function of magnetic field obtained using this model agree very well with those reported here.
Novel AlGaAs/CaF2 SESAM Device for Ultrashort Pulse Generation
Authors: Schön Silke , Gallmann Lukas , Haiml Markus , Keller Ursula 
Published: April 2011

AbstractA novel ultrabroadband AlGaAs/CaF2 semiconductor saturable absorber mirror (SESAM) covering nearly the entire Ti:sapphire gain spectrum is demonstrated. This device supports sub-10-fs pulse operation of a laser. In contrast to previous SESAMs of comparable bandwidth, our device can be monolithically grown by molecular beam epitaxy and requires no post-growth processing. GaAs is used as semiconductor saturable absorber material. The high defect concentration of the material is due to the lattice-mismatched growth on a fluoride surface with (111) orientation. With a time response of 1.2 ps for carrier trapping, a saturation fluence of 36 μJ/cm2 and a modulation depth of up to 2.2% , the GaAs saturable absorber is well-suited for all-optical switching in SESAM devices used for ultrashort pulse generation.
Effect of Marangoni Convection on InSb Single Crystal Growth by Horizontal Bridgman Method
Authors: Kodera K. , Kinoshita A. , Arafune K. , Nakae Y. , Hirata A. 
Published: April 2011

AbstractIt is necessary to clarify the effect of Marangoni convection on single crystal growth from a melt in order to improve the quality of the grown crystal. Particularly, the deviation of crystalmelt (C-M) interface from a planar shape is a major problem because it may deteriorate the quality of the grown crystal. In this paper, we investigated the effect of thermal and solutal Marangoni convection on C-M interface shape in an In-Sb binary system by the horizontal Bridgman (HB) method. The C-M interface concavity strongly depends on the cooling rate and the temperature gradient under uniform concentration distribution conditions in the melt. A large concavity was observed at low cooling rates and high temperature gradient conditions. The concavity was found to be caused by thermal Marangoni convection, by taking Péclet number into account. Then, we varied the composition of the In-Sb binary system to induce solutal Marangoni convection intentionally. The C-M interface was kept planar in case solutal Marangoni convection occurred in the direction opposite to the thermal one. Therefore, we believe that the utilization of solutal Marangoni convection will be a new control technique to make the C-M interface planar for the HB system. From these results, it was clarified that Marangoni convection plays a significant role in the HB crystal growth system.
Luminescence from erbium oxide grown on silicon
Authors: Nogales E. , Méndez B. , Piqueras J. , Plugaru R. , García J. A. , Tate T. J. 
Published: April 2011

AbstractThe luminescence properties of erbium oxide grown on crystalline and amorphous silicon substrates were studied by means of photo- and cathodoluminescence techniques. Differences in the luminescence spectra for samples grown on the two types of substrates used are explained in terms of the different types of erbium centers formed by taking into account the substrate properties and the thermal treatments during growth. For comparison, erbium implanted and oxygen coimplanted crystalline and amorphous silicon have been also investigated by luminescence techniques. In the implanted samples, the sharp transitions from erbium ions in the visible range were quenched and the main emission corresponds to the intraionic transitions in Er3+ ions in the infrared range peaked at 1,54 μm.
Shallow-donor states in spherical quantum dots with parabolic confinement
Authors: Duque C. A. , Porras-Montenegro N. , Dios-Leyva M. de , Oliveira L. E. 
Published: April 2011

AbstractThe evidence of a parabolic potential well in quantum wires and dots was reported in the literature, and a parabolic potential is often considered to be a good representation of the “barrier” potential in semiconductor quantum dots. In the present work, the variational and fractionaldimensional space approaches are used in a thorough study of the binding energy of on-center shallow donors in spherical GaAs-Ga1-xAlxAs quantum dots with potential barriers taken either as rectangular [Vb (eV) ??1.247 x for r >] or parabolic [Vb (r) ??β2?r2] isotropic barriers. We define the parabolic potential with a β?parameter chosen so that it results in the same E0 groundstate energy as for the spherical quantum dot of radius R and rectangular potential in the absence of the impurity. Calculations using either the variational or fractional-dimensional approaches both for rectangular and parabolic potential result in essentially the same on-center binding energies provided the dot radius is not too small. This indicates that both potentials are alike representations of the quantum-dot barrier potential for a radius R quantum dot provided the parabolic potential is defined with?β?chosen as mentioned above.
Effects of Electric Fields on Cathodoluminescence from II-VI Quantum Well Light Emitting Diodes
Authors: Nikiforov A. Y. , Cargill G. S. , Tamargo M. C. , Guo S. P. , Chen Y.-C. 
Published: April 2011

AbstractEffects of electrical bias on the cathodoluminescence (CL) have been investigated for a blue II-VI quantum well (QW) light emitting diode structure of ZnCdMgSe, lattice-matched to InP. In CL wavelength scans, the observed effects include largely reversible changes in QW CL intensity and wavelength and changes in cladding CL intensity. In CL time-based scans, the QW CL intensity showed both immediate and long term changes with bias. Irreversible, degradationrelated decreases in QW CL intensity were also observed. Effects of bias on CL were modeled by calculating the rates of carrier production by electron bombardment and the resulting electron and hole currents with different applied bias fields. These model calculations do not explain many of the experimental observations, because the model does not include effects of bias on carrier escape and redistribution in the QW and effects of bias on generation and transport of atomic scale defects.
Strategies For Direct Monolithic Integration of AlxGa(1−x)As/InxGa(1−x)As LEDS and Lasers On Ge/GeSi/Si Substrates Via Relaxed Graded GexSi(1−x) Buffer Layers
Authors: Groenert Michael E. , Leitz Christopher W. , Pitera Arthur J. , Yang Vicky K. , Lee Harry , Ram Rajeev J. , Fitzgerald Eugene A. 
Published: April 2011

AbstractAlxGa(1−x)As/GaAs quantum well lasers have been demonstrated via organometallic chemical vapor deposition (OMCVD) on relaxed graded GexSi(1−x) virtual substrates on Si. Despite unoptimized laser structures with high series resistance and large threshold current densities, surface threading dislocation densities as low as 2×106 cm−2 enabled cw room-temperature lasing at a wavelength of 858nm. The laser structures are oxide-stripe gain-guided devices with differential quantum efficiencies of 0.16 and threshold current densities of 1550A/cm2. Identical devices grown on commercial GaAs substrates showed differential quantum efficiencies of 0.14 and threshold current densities of 1700A/cm2. This comparative data agrees with our previous measurements of near-bulk minority carrier lifetimes in GaAs grown on Ge/GeSi/Si substrates. A number of GaAs/Ge/Si integration issues including thermal expansion mismatch and Ge autodoping behavior in GaAs were overcome.
Optical Constants of Annealed a-Si:H from Transmittance at Normal Incidence
Authors: Doi Atsutoshi , Matsumoto Yoshiyuki 
Published: April 2011

AbstractWe study changes in the optical constants of a-Si:H films caused by the thermal annealing involved in solid phase crystallization. The aim is to examine the growth mechanism, since changes in refractive index are most probably caused by a change in the network structure. The refractive index change was studied from interference fringes in transmitted light at normal incidence, and shows differing dependence on temperature in different thermal ranges. DSC measurement was also performed to examine changes in the network structure with temperature. Changes in optical and thermal properties induced by an increase of temperature reveal frequent network changes of a-Si:H below 470°C and of a-Si in the range 470 to 570°C. We also found crystallization at about 570°C, and grain growth above the crystallization temperature. Knowledge of network changes in a-Si film allows orientation control by an external seed.
Simulations of Realizable Photonic Bandgap Structures with High Refractive Contrast
Authors: Gersten Bonnie , Synowczynski Jennifer 
Published: April 2011

AbstractThe transfer matrix method (TMM) software (Translight, A. Reynolds [1]) was used to evaluate the photonic band gap (PBG) properties of the periodic arrangement of high permittivity ferroelectric composite (40 wt% Ba0.45Sr0.55TiO3/60 wt% MgO composite, εR = 80, tanδ?= 0.0041 at 10 GHz) in air (or Styrofoam, εR ∼ 1) matrix compared to a lower permittivity material (Al2O3, εR = 11.54, tanδ?= 0.00003 at 10 GHz) in air. The periodic structures investigated included a one-dimensional (1D) stack and a three-dimensional (3D) face centered cubic (FCC) opal structure. The transmission spectrum was calculated for the normalized frequency for all incident angles for each structure. The results show that the bandgaps frequency increased and the bandgap width increased with increased permittivity. The effects of orientation of defects in the opal crystal were investigated. It was found by introducing defects propagation bands were introduced. It was concluded that a full PBG is possible with the high permittivity material.
Optical study of 2D photonic crystals in an InP/GaInAsP slab waveguide structure
Authors: Ferrini Rolando , Leuenberger David , Mulot Mikaël , Qiu Min , Moosburger Jürgen , Kamp Martin , Forchel Alfred , Anand Srinivasan , Houdré Romuald 
Published: April 2011

AbstractWe report on the optical properties of two dimensional (2D) photonic crystals (PCs) deeply etched in an InP/GaInAsP step-index waveguide. Transmission (T) measurements through simple PC slabs and through one-dimensional (1D) Fabry-Pérot (FP) cavities between PC mirrors are reported and compared to theory. A 2D finite difference time-domain (FDTD) method combined to a phenomenological out-of-plane loss model is used to assess different loss contributions. The PC optical properties are deduced from the FP peak analysis. The origin of the high T level observed inside the stopgap is investigated.
Impact of In content on the structural and optical properties of (In,Ga)N/GaN multiple quantum wells grown by plasma-assisted molecular beam epitaxy
Authors: Waltereit Patrick , Speck James S. 
Published: April 2011

AbstractWe have studied the structural and optical properties of a series of (In,Ga)/GaN multiple quantum wells with identical thicknesses but varied In content grown by plasma-assisted molecular beam epitaxy. Careful choice of the growth parameters returns samples with smooth and abrupt interfaces. The shift of the photoluminescence transition energy with externally applied biaxial tension was investigated. We observed a red-shift for small In contents while a blue-shift was detected for higher In contents. This result is in qualitative agreement with band profile calculations taking into account both the band gap deformation potentials and the piezoelectric polarization in these structures. However, the magnitude of the shift is well in excess of the calculated one. We attribute this finding to a substantial deviation of the piezoelectric constants from those calculated for unstrained material. Finally, we estimate the piezoelectric polarization of InGaN/GaN for linear and non-linear terms in strain.