bluuebunny/crossref_metadata_2025 huggingface dataset:
High single-transverse-mode output from external-cavity surface-emitting laser diodes
Authors: Hadley M. A. , Wilson G. C. , Lau K. Y. , Smith J. S.
Published: July 2002

Room-temperature cw electrically pumped external-cavity surface-emitting laser diodes are reported. The external cavity provides a way to control the transverse modes of the surface-emitting laser diodes. Powers greater than 100 mW pulsed and 2.4 mW cw in the lowest order (TEM00) transverse mode are reported. The surface-emitting laser diode was grown on a p-doped substrate, resulting in uniform current injection in devices as large as 100 μm in diameter. To our knowledge, this is also the first report of a working surface-emitting laser diode grown on a p-type substrate.
Unifying explanation for recent temperature sensitivity measurements of Auger recombination effects in strained InGaAs/InGaAsP quantum-well lasers
Authors: Lui Wayne W. , Yamanaka Takayuki , Yoshikuni Yuzo , Seki Shunji , Yokoyama Kiyoyuki
Published: July 2002

Recent temperature sensitivity measurements of Auger recombination effects in compressively strained quantum-well structures, which are seemingly inconsistent, are explained in terms of calculation results from a Monte Carlo analysis. In this analysis, realistic valence subband structures obtained using a 4×4 k⋅p method and Fermi–Dirac statistics are employed, where the conduction-hole-hole-splitoff process is also assumed to be the dominant recombination process. It is found that at low carrier density levels and high temperature—often the conditions under which the Auger recombination coefficient is measured—the temperature sensitivity of the Auger recombination coefficient is expected to be low. A qualitative description of this behavior is also given.
Interface study of Nb/ZrOx-Zr/Nb Josephson junctions
Authors: Morohashi Shin’ichi , Kataoka Yuji , Yagishita Teruo , Hasuo Shinya
Published: July 2002

We studied the interfaces in Nb/ZrOx-Zr/Nb and Nb/AlOx-Al/Nb Josephson junctions using secondary ion mass spectrometry. An adsorbed water vapor layer, which has detached from the chamber wall, exists at the interface of the Nb/AlOx-Al/Nb junctions. This layer does not exist at the interface of the Nb/ZrOx-Zr/Nb junctions. We also find an argon sputtering gas is absorbed in the ZrOx-Zr layer as much as in Nb layers, but not at all in the AlOx-Al layer. The adsorbed water vapor layer acts as a weak barrier for grain boundary diffusion in the Nb/AlOx-Al/Nb structure. In the Nb/ZrOx-Zr/Nb structure, we believe the adsorbed water vapor layer was sputter-etched during the Zr deposition, the high melting point of Zr contributes to the stability of the junction interface.
Disordering and compensation in Si-doped AlGaAs/GaAs superlattices using Ga- and As-rich annealing ambients
Authors: Olmsted B. L. , Houde-Walter S. N.
Published: July 2002

We report on a study of the role of defect diffusion from the crystal surface in the disordering of a multiple quantum well structure that was Si-doped during MBE growth. The distribution of native defects was inferred from correlating the results of photoluminescence spectroscopy, secondary ion mass spectrometry, and electrochemical C-V profiling. No significant change was observed between the Al-Ga interdiffusion coefficients of Si-doped and undoped superlattices when annealed with excess Ga. This is attributed to the lack of a source of group III vacancies. Furthermore, only a small fraction of the enhancement predicted for the Si doping was observed when excess As was used instead. The largest Fermi-level enhancement was observed when no excess Ga or As was included in the evacuated ampoule. The results indicate that the crystal surface was the source and sink of the native defects known to mediate the Al-Ga interdiffusion. Furthermore, significant electrical compensation of the donors was observed after both As- and Ga-rich anneals. This is attributed to ionized group III vacancy generation in the former case, and Si atoms moving from groups III to V sites in the latter.
Integrated high-transition temperature magnetometer with only two superconducting layers
Authors: Kromann R. , Kingston J. J. , Miklich A. H. , Sagdahl L. T. , Clarke John
Published: July 2002

We describe the fabrication and testing of an integrated YBa2Cu3O7−x thin-film magnetometer consisting of a dc superconducting quantum interference device (SQUID), with biepitaxial grain boundary junctions, integrated with a flux transformer on a single substrate. Only two superconducting layers are required, the SQUID body serving as the crossunder that completes the multiturn flux transformer. The highest temperature at which any of the magnetometers functioned was 76 K. At 60 K the magnetic field gain of this device was 63, and the magnetic field noise was 160 fT Hz−1/2 at 2 kHz, increasing to 3.4 pT Hz−1/2 at 1 Hz.
Electron beam-induced absorption modulation imaging of strained In0.2Ga0.8As/GaAs multiple quantum wells
Authors: Rich D. H. , Rammohan K. , Tang Y. , Lin H. T. , Maserjian J. , Grunthaner F. J. , Larsson A. , Borenstain S. I.
Published: July 2002

We have examined the effects of electron-hole plasma generation on excitonic absorption phenomena in nipi-doped In0.2Ga0.8As/GaAs multiple quantum wells (MQWs) using a novel technique called electron beam-induced absorption modulation imaging. The electron-hole plasma is generated by a high-energy electron beam in a scanning electron microscope and is used as a probe to study the MQW absorption modulation. The influence of structural defects on the diffusive transport of carriers is imaged with a μm-scale resolution.
Metastable and nonmetastable deep states of Ge in GaAs
Authors: Skierbiszewski C. , Suski T. , Wisniewski P. , Jantsch W. , Ostermayer G. , Wilamowski Z. , Walker P. G. , Mason N. J. , Singleton J.
Published: July 2002

We show from transport investigations that Ge doped GaAs can be either semimetallic or semiconducting depending on hydrostatic pressure and previous sample illumination. This property results from a unique crossover of two states of the Ge donor in GaAs in their energetic position under pressure. The experimental results obtained make it possible to identify the nature of these Ge-donor states: The drastic enhancement of the electron mobility after illumination is taken as evidence of the electron transfer from the two-electron DX− state to a neutral, localized, and unrelaxed state of the Ge donor.
Very short intracavity directional coupler for high-speed communication
Authors: Griffel Giora
Published: July 2002

We propose a novel intracavity modulator/switch that consists of a directional-coupler located inside a Fabry–Perot cavity. The back mirror of the cavity has a unit reflectivity so that both input and output signals are at the same side. In this way we obtain a two-port, single side element, with coupling length of 83.5 μm, which is the shortest modulation coupler proposed so far. The upper frequency limit due to photon lifetime is 275 GHz, which is well over the bandwidth constraints of microwave lumped structures. A unified approach for the analysis of this device and other similar structures is presented and discussed.
Spectroscopic ellipsometry of Si1−xGex epilayers of arbitrary composition 0≤x≤0.255
Authors: Carline R. T. , Pickering C. , Robbins D. J. , Leong W. Y. , Pitt A. D. , Cullis A. G.
Published: July 2002

Critical point (CP) transition energies have been calculated for strained Si1−xGex (0≤x≤0.255) between 2.5 and 3.5 eV from Lorentzian fits to the second differential of reference dielectric function spectra. E1 and E′0 transition energies are similar to those of the relaxed alloy. Comparison with deformation potential theory shows E1+Δ1 to be coincident with E′0 due to a strain-induced up shift in the former’s transition energy. The reference spectra and CP transition energies are used in an interpolation procedure to analyze spectroscopic ellipsometry spectra of both uncapped and buried layers of strained Si1−xGex. Compositions and thicknesses are obtained in good agreement with alternative techniques.
New electroabsorptive device with negative resistance based on a low-responsivity GaAs/AlAs multiple quantum well
Authors: Ryvkin B. S. , Goodwill D. J. , Walker A. C. , Stanley C. R. , Pottier F. , Holland M. C.
Published: July 2002

We propose and demonstrate a novel electroabsorptive device which possesses N-type negative resistance. The device consists of a low responsivity GaAs/AlAs multiple quantum well modulator on top of a GaAlAs photodetector. The structure has a larger photocurrent contrast ratio in the negative resistance region (∼3:1 as the voltage changes from 0 to 15 V) than conventional self-electro-optic effect devices (SEEDs). The characteristics of the device change only a little up to high illumination levels (2 mW continuous wave in a 2.8 μm/1e2 diameter spot). We discuss the possible applications of this element as an improved bistable reflection-mode SEED and as an optically controlled microwave oscillator.
Magnetic force microscopy images of magnetic garnet with thin-film magnetic tip
Authors: Wadas A. , Moreland John , Rice Paul , Katti R. R.
Published: July 2002

We present magnetic force microscopy images of YGdTmGa/YSmTmGa magnetic garnet, using a thin magnetic film deposited on Si3N5 atomic force microscopy tips. We have found correlations between the topography and the magnetic domain structure. We show that by using either magnetized Fe-Ni bilayer tips versus unmagnetized single layer Fe tips that the image contrast shows domains versus domain walls, respectively.
Mössbauer effect measurement of the recoil-free fraction for 57Fe implanted in a nanophase diamond film
Authors: Sinor T. W. , Standifird J. D. , Davanloo F. , Taylor K. N. , Hong C. , Carroll J. J. , Collins C. B.
Published: July 2002

The Mössbauer effect was used to investigate films of nanophase diamond (NPD) implanted with isotopically pure 57Fe at a dose of 5×1016 atoms/cm2 and an energy of 20 keV. When defects and voids created by the implantation were repaired with an overcoating layer of NPD, the recoil-free fraction at room temperature for these samples was found to be fdia=0.94±0.06 with a corresponding Debye temperature of 1140 K. This relatively high value for f makes NPD films a promising host matrix for microgram quantities of Mössbauer isotopes.
In situ investigation of silicon surface cleaning and damage by argon electron cyclotron resonance plasmas
Authors: Hu Y. Z. , Buaud P. P. , Wang Y. , Spanos L. , Irene E. A.
Published: July 2002

An argon electron cyclotron resonance (ECR) plasma process has been optimized to successfully remove oxide films from a silicon surface at elevated temperatures leaving smooth Si surfaces devoid of an amorphized silicon damage layer. Etch rates of over 10 nm/min have been achieved at ion energies below 100 eV. The low ion energy (−50 V dc bias) and high ion fluxes (1×1016 ions/cm2 s) represent a significant improvement from conventional Ar ion sputter cleaning processes. In situ spectroscopic ellipsometry and ex situ atomic force microscopy were used to characterize the surface condition during and after cleaning to establish a 700 °C argon plasma cleaning process for silicon. Real-time single wavelength ellipsometry was used to study the cleaning kinetics, determine the optimal end point, and elucidate a controversy about the level of damage in the argon ECR plasma cleaning process.
Strain relaxation in strained buried heterostructure lasers
Authors: Faux D. A. , Howells S. G. , Bangert U. , Harvey A. J.
Published: July 2002

Calculations of the stress/strain distribution in a buried strained heterostructure laser are performed for active regions with aspect ratios ranging from 1:1 to 40:1 and an overall misfit strain of 1%. The strain relaxation is found to be small for the high aspect ratios over the central 75% of the active region. Considerable relaxation of the strain occurs at the edges of the active region, however, and throughout the whole cross section for the smaller aspect ratios. The maximum shear stress is found to occur at the corners of the strained region in agreement with previous calculations.
Bi1−xSbx/Bi superlattice grown by molecular beam epitaxy
Authors: Yi X. J. , Wang H. C. , DiVenere A. , Hou C. L. , Chen J. , Ketterson J. B. , Wong G. K.
Published: July 2002

Superlattices of Bi1−xSbx/Bi have been grown by molecular beam epitaxy on CdTe(111) substrates. The typical multilayer, consisting of Bi1−xSbx (85 Å with x=0.16) and Bi (75-Å) layers repeated 50 times, was grown at a substrate temperature of 150 °C. The samples were characterized by reflection high-energy electron diffraction (RHEED), θ-2θ x-ray diffraction analysis, and high-resolution transmission electron microscopy. The streaked RHEED patterns with clear Kikuchi lines and the x-ray satellite peaks indicate a good epitaxial layer quality. The bright field transmission electron microscopy image of the superlattice film confirms that a composition modulation exists, even though the Bi1−xSbx and Bi layers have only a slight image contrast.
Residues, polycrystalline silicon voids, and active area damage with the polycrystalline silicon buffered local oxidation of silicon isolation process
Authors: Mathews Viju K. , Fazan Pierre C. , Maddox Roy L.
Published: July 2002

The effectiveness of various post-field oxidation mask deprocessing sequences has been investigated for the polycrystalline silicon (polysilicon) buffered local oxidation of silicon isolation process. The generation of residues is a minor issue when the gate oxide formation is preceded by the growth and removal of a sacrificial oxide. For sub-0.5 μm ultralarge scale integration technologies, the development of stress induced voids in the buffer polysilicon film is a more severe problem. Stress concentrations that damage both the polysilicon and pad oxide films at the same location result in pitting of the active areas.
Vertical forward coupler based channel-dropping photodetector
Authors: Sakata Hajime , Kawasaki Hideshi
Published: July 2002

We demonstrated an integrated channel-dropping photodetector in which a desired wavelength channel of the optical power is selectively coupled to a detector element. Based on a codirectionally grating-coupled GaAs/AlGaAs filter structure, a 1.2-nm-wide photocurrent response was obtained in an 800-nm-wavelength region with a device length shorter than 1 mm. Light passing through the device exhibited an alternate notch response, promising not to terminate the unselected channels.
Characterization of thermally annealed In0.2Ga0.8As/GaAs single quantum wells by optical spectroscopy and ion beam techniques
Authors: Kozanecki A. , Gillin W. P. , Sealy B. J.
Published: July 2002

Diffusion from ultrathin (10 nm) strained GaAs/In0.2Ga0.8As/GaAs single quantum wells (SQWs) subjected to rapid thermal annealing up to 1050 °C was followed using luminescence and Rutherford backscattering spectroscopy (RBS) in combination with channeling. The SQW shapes (In profiles) determined with the help of RBS have been compared with those predicted from optical measurements. A satisfactory agreement between diffusion length of In at 1050 °C, evaluated using both experimental methods, has been obtained. Angular scans across the 〈110〉 axial channel in the (100) plane were applied to study the strain relaxation in SQWs. No signs of generation or misfit dislocation were found, confirming that the strain relaxes solely via intermixing.
Hard amorphous carbon coatings on soft epitaxial fullerite films by fullerene beam deposition
Authors: Busmann H.-G. , Gaber H. , Strasser H. , Hertel I. V.
Published: July 2002

The technique of energetic cluster impact is used to coat epitaxial fullerite films with amorphous carbon. The energetic all-carbon beam which forms the amorphous carbon is achieved by evaporating, ionizing, and accelerating fullerene powder. Diffraction patterns obtained with a transmission electron microscope show that the lattice structure of the coated fullerite film and its epitaxial relationship to the substrate are maintained during the coating process. Raman spectra give very strong evidence that diffusion of oxygen into the fullerite film is prohibited by the coating.
Lateral band-gap control of InGaAsP multiple quantum wells by laser-assisted metalorganic molecular beam epitaxy for a multiwavelength laser array
Authors: Iga Ryuzo , Yamada Takeshi , Sugiura Hideo
Published: July 2002

We report a new growth technique for laterally changing the band gap of InGaAsP multiple quantum wells by laser-assisted epitaxy. Laser irradiation during InGaAsP well growth can be used to fabricate asymmetric quantum wells consisting of InGaAsP and InAsP layers. The photoluminescence (PL) wavelength of multiple asymmetric quantum wells (MAQWs) shows a continuous gradual shift as the delay in starting time of laser irradiation during the well growth is changed while keeping the supplying materials constant. Using this laser-assisted growth, four MAQWs with different PL wavelengths were grown on different areas of a substrate. This result was applied in the fabrication of a four-wave laser array operating at the wavelength between 1.3 and 1.51 μm by a single-step growth.
Demonstration of confined optical field effect in a vertical microcavity by examining the low temperature photon-exciton interaction in two kinds of quantum wells
Authors: Zhang Z. L. , Nishioka M. , Weisbuch C. , Arakawa Y.
Published: July 2002

We report new results on a photon-exciton interaction in a λ cavity having two kinds of quantum wells (QWs) with the thickness of 62 and 90 Å which are sited at the antinode and two nodes of the standing wave, respectively. By measuring the reflectivity spectrum of the quantum microcavity, mode splitting (two dips) is observed when the photons in the cavity are resonant with the excitons of 62 Å QWs at 14 K. However, no mode splitting (one dip) is observed when the microcavity is tuned to the quantized energy of the excitons arising from the 90 Å QWs. The reason is the difference of the coupled interaction between photons and excitons due to the standing wave distribution of the optical field in the microcavity. The above results clearly demonstrate the controllability of quantum electrodynamics effects due to the confined optical mode (i.e., the standing wave) in a high-Q microcavity.
GaAs/GaInAsP quantum well lasers grown by gas-source molecular beam epitaxy
Authors: Zhang G. , Nappi J. , Pessa M.
Published: July 2002

We report on gas-source molecular beam epitaxy growth of GaAs/GaInAsP quantum well lasers emitting at 0.87 μm. The active region of this aluminum-free laser structure consisted of a single 12-nm-thick GaAs quantum well layer sandwiched between GaInAsP confinement layers. The lasers exhibited low threshold current density of about 270 A/cm2 and high characteristic temperature (190 K). The internal quantum efficiency and internal waveguide loss were 83% and 3.3 cm−1, respectively. Ridge waveguide lasers having 6×500 μm2 ridge dimensions produced 78 mW continuous-wave light output power per facet at room temperature, with an external differential quantum efficiency of 72%. A fundamental lateral mode operation was maintained up to 65 mW per facet.
Consistent explanation on Lorentz force-free dissipation in H∥I∥c for various high T
c superconductors
Authors: Yuan Songliu
Published: July 2002

It is shown that the extended Josephson coupling model, which takes into account the effective thermal energy and the unusual vortex dynamics in high Tc superconductors, is able to provide a consistent explanation on the Lorentz force-free resistive dissipation generally observed in H∥I∥c for various high Tc materials.
Synchrotron radiation-excited etching of W, Ta, and their oxide films
Authors: Terakado Shingo , Kaneda Kazuhiro , Suzuki Shigeo , Tanaka Kenichiro
Published: July 2002

Synchrotron radiation-(SR-)excited etching of W, Ta, and their oxide films using a mixture of SF6 and Ar gases was studied. Although irradiated regions of W and Ta were only slightly etched, WO3 and Ta2O5 were clearly etched. The etching of the nonirradiated region was almost negligible in all these materials. Introduction of reactive species generated by microwave discharge greatly promoted the etching of these materials, keeping area selectivity high. We found that SR played an important role in the etching through surface photochemical reaction.
Improved composition homogeneity during selective area epitaxy of GaInAs using a novel In precursor
Authors: Eckel M. , Ottenwälder D. , Scholz F. , Frankowsky G. , Wacker T. , Hangleiter A.
Published: July 2002

GaInAs layers were grown selectively on partially masked InP substrates by metalorganic vapor phase epitaxy using the conventional In precursor trimethyl-indium (TMI) and the intramolecularly saturated compound dimethylaminopropyl-dimethyl-indium (DADI) for comparison. We obtained for both TMI and DADI an excellent morphology of the selectively grown structures. Significant differences between the two In sources were determined for the unwanted nucleation on the masked area and for the homogeneity of the composition of the grown ternary material. We attribute this observation to the higher chemical stability of DADI and a changed decomposition behavior, which leads to longer effective diffusion lengths for DADI and its thermally decomposed fragments in the gas phase.
Deposition of in situ boron-doped polycrystalline silicon films at reduced pressures
Authors: Lin Horng-Chih , Lin Hsiao-Yi , Chang Chun-Yen , Lei Tan-Fu , Wang P. J. , Deng Ray-Chern , Lin Jandel
Published: July 2002

We report on the deposition of in situ boron-doped polycrystalline Si films on the SiO2 surface with reduced growth pressures at 550 °C. The deposition rate of these films decreased as the doping level was greater than 1019 cm−3. Such a result is in sharp contrast to what has been observed previously for similar films grown with conventional low pressure chemical vapor deposition techniques. It was also found that the incubation time prior to the deposition of these films diminished as the doping level was increased to 3×1020 cm−3 or higher. It is attributed to the preferential adsorption of boron atoms on the SiO2 surface at the initial stage of growth, which facilitates the nucleation of Si.
Spatial and temporal characteristics of electrically fixed holograms in photorefractive strontium-barium niobate
Authors: Orlov Sergei , Psaltis Demetri , Neurgaonkar Ratnakar R.
Published: July 2002

We report measurements of the holographic diffraction efficiency (HDE) of single photorefractive gratings fixed by an externally applied voltage pulse in Sr0.75Ba0.25Nb2O6. The polarization grating HDE and decay rate are strongly dependent on the grating spacing and also depend on the intensity of the light beams during the recording and erasing/reconstruction process. Knowledge of the dependence of the fixing process on spatial frequency may be useful for the creation of physical models of local polarization switching in ferroelectrics.
Dynamic precipitation processes of Al2Cu in Al-Cu thin films by in situ transmission electron microscopy
Authors: Park M. , Krause S. J. , Wilson S. R.
Published: July 2002

Dynamic precipitation processes of the Al2Cu (θ) phase in Al-1.5 wt % Cu thin films were studied by in situ heat treatments with transmission electron microscopy for films deposited at high temperatures in both the single-phase and the two-phase regions. The film deposited at 325 °C, in the two-phase Al(α)-Al2Cu region, has large irregular precipitates. Upon heating to 380 °C, the precipitates split and grow, and then, at 450 °C, they dissolve. Upon cooling, θ precipitates form at new locations, namely, at grain boundaries (GBs) and at triple points (TPs). Reheating and cooling does not significantly change their location and morphology. The film deposited at 465 °C, in the single-phase Al(α) region, has fine precipitates at the GBs and TPs. Heating causes growth and then dissolution of precipitates, but upon cooling, precipitates reform at the original locations. The coarse θ precipitates, in the as-deposited film at 325 °C, can increase corrosion susceptibility compared to the finer platelike morphology present after annealing or from deposition in the single-phase region.
Ambipolar diffusion anisotropy induced by defects in nipi-doped In0.2Ga0.8As/GaAs multiple quantum wells
Authors: Rich D. H. , Rammohan K. , Tang Y. , Lin H. T. , Maserjian J. , Grunthaner F. J. , Larsson A. , Borenstain S. I.
Published: July 2002

The influence of strain-induced defects on the ambipolar diffusive transport of excess electrons and holes in the δ-doped InGaAs/GaAs multiple quantum well system has been examined with a new technique called electron-beam-induced absorption modulation (EBIA). The excess carrier lifetime and diffusion coefficient are obtained by a one-dimensional diffusion experiment that utilizes EBIA. An anisotropy in the ambipolar diffusion along both high-symmetry 〈110〉 directions is found, and this is seen to correlate with the distribution of dark line defects observed in cathodoluminescence.
Surface resonant tunneling transistor: A new negative transconductance device
Authors: Kurdak Ç. , Tsui D. C. , Parihar S. , Santos M. B. , Manoharan H. C. , Lyon S. A. , Shayegan M.
Published: July 2002

A new three-terminal device, the surface resonant tunneling transistor, is realized by the molecular beam epitaxial cleaved edge overgrowth technique in the GaAs/AlGaAs system. The device exhibits negative transconductance as well as negative differential resistance. Some possibilities for future applications of the device to low-power logic circuits are discussed.
Photoluminescence and Raman studies of porous silicon in polymethyl methacrylate
Authors: Guha S. , Hendershot G. , Peebles D. , Steiner P. , Kozlowski F. , Lang W.
Published: July 2002

We report the observation of strong luminescence from porous Si grains containing Si nanocrystallites embedded in polymethyl methacrylate disks. In concentrated samples, forward and backscattered photoluminescence spectra were just as strong as in porous Si on Si wafers. This new result indicates that porous Si grains could be embedded in nonconducting polymers and would retain all its inherent characteristics as in porous Si layers on Si wafers.
Effect of elongation of the c-cell dimension on intrinsic pinning in Bi2Sr2CaCu2Ox single crystals
Authors: Funahashi Ryoji , Matsubara Ichiro , Yamashita Hiroshi , Kawai Tomoji
Published: July 2002

A change of the intrinsic pinning strength by elongation of the c-cell dimension in Bi2Sr2CaCu2Ox whiskers of single crystals has been studied by magnetic relaxation and irreversibility temperature (Tirr) measurements in the magnetic fields parallel to the a-axis. When the c-cell dimension is elongated by annealing under a reduced pressure, the intrinsic pinning strength is weakened. This result is consistent with an intrinsic pinning model.
Photoconductive properties of the Er-doped InP
Authors: Wang X. Z. , Neuhalfen A. J. , Wessels B. W.
Published: July 2002

The photoconductive properties of Er-doped InP layers prepared by atmospheric pressure metalorganic vapor phase epitaxy were investigated. Two Er3+-related photoconductive transitions were observed at 0.807 and 1.27 eV. The 0.807 eV transition involves a 4f-shell intracenter transition. The 1.27 eV transition is attributed to a free to bound transition involving the Er3+-related trapping center. Presumably this trapping level is important in the energy transfer process determining the Er3+-related emission efficiency in InP. A model is developed to explain the photoconductive response of the Er-doped materials.
Raman spectroscopic study on the wirelike incorporation of Si dopant atoms on GaAs(001) vicinal surfaces
Authors: Ramsteiner M. , Wagner J. , Behr D. , Jungk G. , Däweritz L. , Hey R.
Published: July 2002

Raman scattering by collective electronic excitations from a δ-doping layer has been used to investigate the ordered incorporation of Si dopant atoms on vicinal GaAs(001) surfaces. In a series of δ-doped samples grown by molecular beam epitaxy (MBE) under specific conditions the Si dopant atoms were found to be incorporated predominantly on Ga sites, even at a doping concentration as high as 1.8×1013 cm−2. A pronounced polarization asymmetry in the Raman scattering intensity of collective intersubband plasmon-phonon modes was observed in a sample grown under conditions established by real-time high-energy electron diffraction to be favorable for wirelike Si incorporation.
Block-by-block deposition: A new growth method for complex oxide thin films
Authors: Locquet Jean-Pierre , Catana André , Mächler Erich , Gerber Christoph , Bednorz J. Georg
Published: July 2002

An alternative growth method for high-Tc oxide thin films employing molecular beam deposition is proposed. Instead of an uncontrolled local nucleation followed by lateral growth and island coalescence, the new method provides substrate coverage by nonreacting constituents before nucleation is initiated, a controlled reaction path, and reduced lateral growth. DyBa2Cu3O6+δ films without precipitates, with a surface roughness of ±1 unit cell and showing finite size oscillations in the x-ray diffraction spectrum, have been prepared. This method reveals that diffusion dominates the growth process at high substrate temperatures (≂700 °C).
Quantum well lasers with carbon doped cladding layers grown by solid source molecular beam epitaxy
Authors: Micovic M. , Evaldsson P. , Geva M. , Taylor G. W. , Vang T. , Malik R. J.
Published: July 2002

Data are presented which demonstrate that very high quality carbon (C) doped epilayers for the fabrication of AlGaAs-GaAs and AlGaAs-GaAs-InGaAs quantum well (QW) lasers can be grown by solid source molecular beam epitaxy (MBE) using a resistively heated graphite filament as a p-type dopant source. Broad area lasers fabricated from this material exhibit very low threshold current densities (66 A/cm2 for a 2-mm-long single QW AlGaAs-GaAs-InGaAs laser emitting at 980-nm wavelength). It is also shown that lasers with carbon doped cladding layers grown on either n+ or p+ substrates exhibit similar low threshold current densities. These C-doped lasers are expected to have improved long term reliability compared to conventional Be-doped laser structures.
Thermal budget consideration in rapid isothermal processing
Authors: Thakur R. P. S. , Singh R.
Published: July 2002

Rapid isothermal processing (RIP) based on incoherent radiation as the source of thermal and optical energy is emerging as a key low-thermal budget processing technique. Because of high heating and cooling rates, the RIP cycle generally refers to processing time and temperature. In this letter, we have shown that the properties of materials and devices fabricated by RIP depends on the heating and cooling rates. Optimized heating and cooling rates can minimize unwanted phenomena (e.g., higher thermal stress, warpage, etc.) leading to the improved performance of the devices fabricated by RIP. To demonstrate this significance of heating and cooling rates, we report the wafer dimensional analysis results for ramp rates of 15, 75, 100, 150, and 200 °C per second at a maximum steady-state temperature of 1050 °C. Plasma and low-pressure chemical vapor deposition silicon nitride films on 6-in. wafers were studied for warpage. The BF2 and As implanted wafers at a fixed dose of 8×1015/cm2 were studied for slow (15 °C per second) and fast (200 °C per second) ramp rates. We also present stress, secondary ion mass spectroscopy, and diode leakage current results for different RIP cycles of interest.
Reduction of the defect density in hydrogenated amorphous silicon by thermally energized growth precursors
Authors: Ganguly Gautam , Nishio Hitoshi , Matsuda Akihisa
Published: July 2002

The defect density in plasma deposited hydrogenated amorphous silicon (a-Si:H) is known to be dependent on the thermal energy of growth precursors. The precursor temperature can be controlled independent of the substrate temperature by a mesh-type electrode placed close to the substrate. Energized precursors have a higher surface diffusion coefficient which results in a reduction of the steady-state defect density on the growth surface and hence in the film bulk. The optical band gap and hydrogen content depend only on the substrate temperature while the defect density is reduced drastically with increasing mesh temperature. Thereby, we have prepared a-Si:H having low defect density and wide optical band gap.
Modulated reflectance and resonant Raman scattering of GaAs quantum wires grown on nonplanar substrates
Authors: Rinaldi R. , Cingolani R. , Ferrara M. , Maciel A. C. , Ryan J. , Marti U. , Martin D. , Morier-Gemoud F. , Reinhart F. K.
Published: July 2002

Modulated reflectance spectroscopy and resonant Raman scattering have been used to study the quantized states of crescent-shaped GaAs quantum wires. Distinct one-dimensional excitonic transitions originating from the quantum wires together with the expected resonances from the bent quantum wells are observed. The quantum wire transition energies compare very well with those calculated using a V-shaped potential derived from transmission electron microscopy measurements of the lateral variation of the GaAs well width. The spectroscopic techniques employed here provide alternative methods of probing the confined states in quantum wires of low luminescence efficiency.
Structural study of a Si(001) grating surface by white beam x-ray Laue photography
Authors: Shen Qun , Weselak B. , Blakely J. M.
Published: July 2002

We demonstrate in this letter that an x-ray diffraction pattern from a two-dimensional surface grating of periods 0.3 μm can be obtained by means of white beam Laue photography using synchrotron radiation. Such photographs or images can provide direct and useful information on the shape of the grating pillars as well as the crystalline quality of the grating material.
High concentration phosphorus doping of polycrystalline silicon by low temperature direct vapor phase diffusion of phosphine followed by rapid thermal annealing
Authors: Lourdudoss S. , Zhang S.-L.
Published: July 2002

Phosphorus doping of polycrystalline silicon by direct diffusion of PH3 at 685 and 785 °C followed by rapid thermal annealing (RTA) has been investigated. Unlike at 785 °C, the dopant profile is not uniform at 685 °C but becomes so after RTA at 1050 °C for 10 s, as revealed by secondary ion mass spectroscopy (SIMS). In the absence of any protection layer, RTA in N2 causes an out-diffusion of ∼50% of P from the sample diffused at 785 °C, although it activates ∼100% of the remaining P atoms as indicated by Hall and SIMS measurements. In contrast, RTA in O2 results in 95% activation of the incorporated P from the same sample, accompanying an oxidation of ∼7 nm polycrystalline Si. As regards the sample diffused at 685 °C, RTA in N2 does not cause any out-diffusion but activates less than 80% of the incorporated P atoms. This difference in behavior is attributed to the tendency to attain equilibrium concentrations of P in the crystallites and at the grain boundaries at the RTA temperature. The highest active P concentration achieved is 2.0×1020 cm−3 at 785 °C followed by RTA in O2 yielding a resistivity as low as 9×10−4 Ω cm. The simplicity of this relatively low temperature process is attractive for a single-wafer multisequence fabrication scheme.
Theory of YBa2Cu3O7−x/PrBa2Cu3O7−x superlattices as superconductor-insulator multilayers
Authors: Li Jun , Luo Ke qi , de Gong Chang
Published: July 2002

The YBa2Cu3O7−xCu3O7−x superlattices are treated as superconductor-insulator multilayers, where CuO2 planes in the YBa2Cu3O7−x layers are taken as two-dimensional (2D) superconductors and CuO2 planes in the PrBa2Cu3O7−x layer are described by the 2D Mott–Hubbard insulator with large Coulomb repulsion. We obtain good Tc vs number of PrBa2Cu3O7−x unit cells in a single layer by using only one adjustable parameter and without assuming charge-carrier-transfer effect.
Restoration of dual-frequency signals with nonlinear propagation in fibers with positive group velocity dispersion
Authors: Mamyshev P. V. , Wigley P. G. , Wilson J. , Bosshard C. , Stegeman G. I.
Published: July 2002

It is shown experimentally and theoretically that a sinusoidally modulated pulse evolves with time into a train of dark soliton-like pulses and then returns to its initial sinusoidal shape on propagation through a nonlinear single-mode fiber with positive group velocity dispersion. The experimental results are in agreement with predictions from the nonlinear Schrödinger equation.
Milliwatt output levels and superquadratic bias dependence in a low-temperature-grown GaAs photomixer
Authors: Brown E. R. , McIntosh K. A. , Smith F. W. , Nichols K. B. , Manfra M. J. , Dennis C. L. , Mattia J. P.
Published: July 2002

A cw output power up to 0.8 mW is obtained from a low-temperature-grown (LTG) GaAs, 0.3 μm gap, interdigitated-electrode photomixer operating at room temperature and pumped by two modes of a Ti:Al2O3 laser separated in frequency by 0.2 GHz. The output power and associated optical-to-electrical conversion efficiency of 1% represent more than a sixfold increase over previous LTG-GaAs photomixer results obtained at room temperature. A separate LTG-GaAs photomixer having 0.6 μm gaps generated up to 0.1 mW at room temperature and up to 4 mW at 77 K. Low-temperature operation is beneficial because it reduces the possibility of thermal burnout and it accentuates a nearly quartic dependence of output power on bias voltage at high bias. The quartic dependence is explained by space-charge effects which result from the application of a very high electric field in the presence of recombination-limited transport. These conditions yield a photocurrent-voltage characteristic that is very similar in form to the well-known Mott–Gurney square-law current in trap-free solids.
Heterogeneous ceramic system prepared from semiconducting compound InSb
Authors: Jergel M. , Červenák J. , Štrbík V. , Hanic F.
Published: July 2002

A cermet compact consisting of unreacted semiconducting InSb, semiconducting In2O3, and metallic Sb has been prepared by partial oxidation of polycrystalline bulk InSb at elevated temperatures in flowing oxygen. Unusually constant electric resistivity of this heterogeneous system has been observed in the temperature range from 4.2 to 300 K. Stability of the electric resistance depends on the degree of conversion β in the oxidation reaction: 2 InSb+3/2 O2=In2O3+2 Sb. Our thermogravimetric and x-ray studies revealed an escape of Sb from the system at higher temperatures and longer reaction times. The initial polycrystalline InSb was prepared by the method of rapid quenching.
Indium and gallium p-type doping of hydrogenated amorphous germanium thin films
Authors: Fajardo F. , Comedi D. , Chambouleyron I.
Published: July 2002

Hydrogenated amorphous germanium films have been p-type doped with indium and gallium. The room-temperature dark dc conductivity of the films has been found to change by several orders of magnitude within the studied dopant atomic concentration range (∼3×10−5 to ∼1×10−2). The conductivity change from n to p type for the more heavily doped materials indicates effective p-type doping. The hydrogen content and the optical gap of the doped films, on the other hand, remain essentially unchanged with respect to the undoped material. For the most doped samples, signs of metallic segregation have been detected in the case of gallium doping. Metallic segregation is not apparent for indium-doped samples.
Highly efficient blue light generation in KTiOPO4 waveguides
Authors: Eger D. , Oron M. , Katz M. , Zussman A.
Published: July 2002

Very high normalized efficiency, up to 800% W−1 cm−2 for infrared to blue light conversion (425 nm), has been obtained in quasi-phase-matched waveguides in KTiOPO4. It is shown by a detailed calculation that this value is higher by a factor of 4 than that predicted by theory.
Facet degradation of aged strained quantum-well lasers studied by high-voltage electron-beam-induced current
Authors: Wang M. C. , Hwang D. M. , Lin P. S. D. , Dechiaro L. , Zah C. E. , Ovadia S. , Lee T. P. , Darby D.
Published: July 2002

High-voltage electron-beam-induced-current imaging is used to study the aging of two sets of commercial 0.98 μm lasers with identical strained quantum wells (In0.2Ga0.8As) but different cladding layers (Al0.55Ga0.45As versus In0.49Ga0.51P) on GaAs substrates. We observed the development of facet defects only in the InGaAs/AlGaAs lasers which also exhibited larger threshold-current increases. It therefore suggests that this facet degradation mode is related to the cladding layer composition, not to the strains in the active layer.
Spectral noncritically phase-matched near-infrared generation by difference frequency mixing in lithium triborate
Authors: Bhar G. C. , Datta P. K. , Rudra A. M. , Chatterjee U.
Published: July 2002

Retracing behavior of phase matching has been observed in the generation of infrared radiation (1.25–1.85 μm) by both type-I angle-tuned and temperature-tuned difference frequency mixing of a Nd:YAG laser (1064 nm) with its second-harmonic pumped dye laser (570–675 nm) in lithium triborate crystal. Large spectral acceptance of 49 nm at spectral noncritical phase-matching point and angular acceptance of 4.0° at angular noncritical phase-matching point has been obtained.
100 W average power at 0.53 μm by external frequency conversion of an electro-optically Q-switched diode-pumped power oscillator
Authors: Velsko S. P. , Ebbers C. A. , Comaskey B. , Albrecht G. F. , Mitchell S. C.
Published: July 2002

We have generated approximately 100 W of frequency doubled light from the output of an electro-optically Q-switched diode-pumped Nd:YAG slab laser oscillator operating at an average power of 200 W (2.5 kHz repetition rate, 80 mJ/pulse, 30 ns pulsewidth). The Q-switch was a compensated z-axis propagation LiNbO3 electro-optic modulator, and the frequency conversion crystal was a thin slab of KTP. In addition, Q-switched operation at an average power of approximately 250 W with 26 ns pulsewidths has been demonstrated.
Novel in situ method to detect subnanometer-sized particles in plasmas and its application to particles in helium-diluted silane radio frequency plasmas
Authors: Fukuzawa T. , Shiratani M. , Watanabe Y.
Published: July 2002

A new Langmuir probe method is proposed to reveal processes of particulate nucleation and its subsequent early growth in silane radio frequency (rf) plasmas. In the method, subnanometer-sized particles grown during the rf-discharge-on phase are detected as negative ions in the subsequent afterglow phase in which temperature and density of electrons have decayed. Preliminary experiments applying the method to helium-diluted silane rf plasmas have the following features of particle growth: subnanometer-sized particles are mainly generated around the plasma/sheath boundary near the rf electrode; they grow with increase in the rf-discharge-on period, Ton, for Ton≲a gas residence time of the discharge.
Photoelectric properties of self-supporting porous silicon
Authors: Hlinomaz P. , Klíma O. , Hospodková A. , Hulicius E. , Oswald J. , Šípek E. , Kočka J.
Published: July 2002

We present transient and steady-state photocurrent data, measured in a special sample holder on a self-supporting porous silicon (PS) sandwich structure. Although the value of the drift mobility is difficult to find, we have estimated on the basis of the time of flight (TOF) technique the trap controlled value of mobility-lifetime product (μDτD) and from the steady-state photocurrent we have deduced recombination controlled (μτ)ss value. Surprisingly (μτ)ss<μDτD. Charge collection is very low (about 1%) even for electric field F≊105 V/cm. However, the ‘‘schubweg’’=μτF is (for η≊10% and F=108 V/cm) about 1 μm, much more than the quantum size dimensions (2–5 nm).
Effect of carbonization on the growth of 3C-SiC on Si (111) by silacyclobutane
Authors: Yuan C. , Steckl A. J. , Loboda M. J.
Published: July 2002

Chemical vapor deposition of SiC on Si (111) from silacyclobutane (c-C3H6SiH2, SCB) has been carried out on propane carbonized and on virgin Si substrates. The carbonization was performed at 760 Torr and the SiC growth at 5 Torr. Transmission electron diffraction (TED) and x-ray diffraction were used to determine the crystallinity of the resulting films. The minimum temperature for obtaining crystalline films, as indicated by a TED pattern consisting of sharp spots with (111) SiC crystal hexagonal symmetry, was lower with carbonization (∼800–900 °C) than without (∼1000 °C). However, the carbonization process creates voids in the Si just below the SiC/Si interface, while SCB growth without carbonization produces a very smooth and void-free interface. Fourier-transform infrared measurements of SiC films grown at 1200 °C without carbonization exhibit a sharp (full width at half-maximum=30 cm−1) Si-C absorption peak at 794 cm−1.
New selective doping technique for boron using a HBO2 source and a thin oxide mask
Authors: Murakami Eiichi , Kawamura Yoshio , Kimura Shin’ichiro
Published: July 2002

Selective adsorption of HBO2 on Si(100) partially covered with thin (≲1 nm) oxide is observed using a Si molecular-beam epitaxy system. The thin oxide is formed by local oxidation by a ArF excimer laser or wet chemical treatment. A selective adsorption rate of more than 20 is observed at 700 °C. After the adsorption, the oxide can be sublimated at 800 °C annealing in ultrahigh vacuum without boron desorption. These phenomena can be applied to selective shallow doping without photoresist.
Large transconductances observed in an independently contacted coupled double quantum well
Authors: Patel N. K. , Linfield E. H. , Brown K. M. , Grimshaw M. P. , Ritchie D. A. , Jones G. A. C. , Pepper M.
Published: July 2002

Lateral transport in a coupled double quantum well has been studied in a system where each layer can be measured independently. Front and back gates were used to vary the carrier densities in the two wells and hence control the degree of electron coupling. When the carrier densities in the two 2DEGs were matched, the coupling was found to be strongest and resulted in a decrease in the resistance of the measured 2DEG. By using a structure with a low mobility 2DEG in parallel with a high mobility one, we demonstrate a device that displays large resistance changes and a correspondingly high transconductance.
Growth of InSb using tris(dimethylamino)antimony and trimethylindium
Authors: Baucom K. C. , Biefeld R. M.
Published: July 2002

We have grown epitaxial layers of InSb on p−-InSb substrates by metalorganic chemical vapor deposition using tris(dimethylamino)antimony (TDMASb) and trimethylindium (TMIn). Growth temperatures from 285 to 500 °C and pressures from 76 to 660 Torr have been investigated. The V/III ratio was varied from 0.63 to 8.6 using growth rates from 0.06 to 0.67 μm/h. For temperatures ≤425 °C, the growth rate was proportional to the temperature. The growth rate was proportional to the TMIn flow at all temperatures. Temperatures ≳400 °C produced p-type layers while growth temperatures ≤400 °C produce n-type layers. The pyrolysis temperature of TDMASb appears to be lower than that of TMIn.
New Josephson-like effect in a superconducting transformer
Authors: Gilabert A. , Schuller Ivan K. , Moshchalkov V. V. , Bruynseraede Y.
Published: July 2002

The coupled motion of the vortex lattices of two electrically insulated, superimposed, superconducting thin films (primary and secondary) in a perpendicular magnetic field, is predicted to exhibit a Josephson-like behavior. For a dc applied current flowing in the primary film, the voltage difference between the time-averaged primary and secondary flux flow voltages obeys the equations of a resistively shunted junction model. If an ac current is superimposed on the dc current, Shapiro-type steps are predicted in the current-voltage characteristic. In contrast to the conventional Josephson effect; the voltage positions of these steps can be tuned by the applied magnetic field.