bluuebunny/crossref_metadata_2025 huggingface dataset:
1-to-42 optoelectronic interconnection for intra-multichip-module clock signal distribution
Authors: Tang Suning , Chen Ray T.
Published: July 2002

In this paper, we present a miniaturized compact three-dimensional optical fan-out interconnect suitable for wafer scale very large scale integrated multichip-module optical clock signal distribution. The demonstrated device employs a thin light-guiding substrate in conjunction with a two-dimensional (2D) optical hologram array. The parallel feature among fan-out beams and the planar compact structure convert the unsolvable three spatial and three angular multiple alignment problem into a single-step 2D planar one, which greatly enhances the packaging reliability. A new design scheme for reducing throughput power nonuniformity is presented for the first time. A 25 GHz 1-to-42 highly parallel fan-out interconnect was demonstrated with a signal to noise ratio of 10 dB.
On the dispersion of electromigration failure times of Al alloy contacts to silicon
Authors: Oates A. S.
Published: July 2002

Electromigration failure data for integrated circuit metallizations may only be collected in experimentally convenient intervals by the use of highly accelerated conditions of temperature and current density. Large extrapolations are required to apply these data to circuit operating conditions. A common assumption made with these extrapolations is that the dispersion of the log-normal failure distribution, σ, does not vary with temperature. In this letter we investigate the temperature dependence of the dispersion of failure times due to electromigration of the Al allow layer in contacts to silicon. We show that the dispersion is temperature dependent for these structures and exhibits increasing values with decreasing temperature. The magnitude of the dispersion is consistent with that calculated on the basis of a dominant contribution from fluctuations in the temperature between test structures. It is implied that the intrinsic, temperature- independent contribution to the dispersion is small for contacts to silicon and for contacts between metal levels (vias).
Silicon dioxide thin films prepared by chemical vapor deposition from tetrakis(diethylamino)silane and ozone
Authors: Maruyama Toshiro , Ohtani Satoshi
Published: July 2002

Silicon dioxide thin films were prepared by a low-temperature atmospheric-pressure chemical vapor deposition method. The raw materials were tetrakis(diethylamino)silane and ozone in oxygen gas. The amorphous films were obtained at a substrate temperature above 200 °C. The films were superior in chemical stability and hardness to the films which were prepared from tetraethoxysilane and ozone.
Dependence of dislocation multiplication on time, temperature, and stress distribution in strained InGaAs/InP quantum wells studied by x-ray topography
Authors: Mukai Kohki , Sugawara Mitsuru , Yamazaki Susumu
Published: July 2002

Using x-ray topography, we studied the dependence of the dislocation multiplication in InxGa1−xAs/InP quantum wells on time, temperature, and stress distribution. We compared the dependence of the multiplication on annealing time and temperature with the empirical model for stress relaxation [B. W. Dodson, Appl. Phys. Lett. 51, 1325 (1987)]. We determined a dislocation glide activation energy and a material-specific constant for the model. We explained the dislocation density of as-grown single and multiple quantum wells considering the dislocation multiplication during growth, and show how the dislocation densities in the multiple quantum wells were reduced by introducing opposite strain into barrier layers.
Identification of a moving phase of Al2O3 by Auger electron spectroscopy in the back aluminized surface of Si
Authors: Chakravarty B. C. , Arora N. K. , Singh S. N. , Das B. K. , Chakraborty B. R. , Sen Nirupa
Published: July 2002

Backsurface aluminization of n on p silicon solar cells is preferred because it can provide backsurface field and getter lifetime killing impurities. In this work, depth profiling has been done on aluminized backsurfaces of silicon wafers which were heat treated at 660–820 °C in an ambient of POCl3 and oxygen gas mixture and a new moving phase of Al2O3 has been detected by Auger electron spectroscopy.
Heteroepitaxial growth of InN on AlN-nucleated (00.1) sapphire by ultrahigh vacuum electron cyclotron resonance-assisted reactive magnetron sputtering
Authors: Bryden Wayne A. , Ecelberger Scott A. , Kistenmacher Thomas J.
Published: July 2002

A novel deposition technique, ultrahigh vacuum electron cyclotron resonance (ECR)-assisted reactive magnetron sputtering, has been developed for the preparation of group IIIA nitride thin films. In initial experiments, thin films of the semiconductor InN have been deposited on AlN-seeded (00.1) sapphire substrates, and the properties of these films studied as a function of growth temperature. Comparison to InN thin films grown by conventional reactive magnetron sputtering shows enhanced Hall mobilities (from about 50 to over 80 cm2/V s), a decreased carrier concentration (by about a factor of 2), an increased optical band gap, and an apparent reduction in homogeneous strain that is in part due to film relaxation induced by the ECR beam and in part to enhanced nitrogen content and more nearly stoichiometric films.
Analytical closed form expressions for the effective band edges in shallow quantum wells
Authors: Singh Jasprit
Published: July 2002

Shallow quantum wells are widely used in electronic and optoelectronic heterostructure devices. However, to determine the effective band edges, one needs numerical techniques unless the barrier height is infinite. In this letter the nearly free electron approach used in periodic structures is exploited to provide accurate energy level expressions for the electronic ground state in a number of important quantum wells with different shapes. These include the square quantum well without and with an applied transverse electric field.
High-T
c, multilevel edge junction superconducting quantum interference devices with SrTiO3 barriers operating at 77 K
Authors: Laibowitz R. B. , Sun J. Z. , Foglietti V. , Gallagher W. J. , Koch R. H.
Published: July 2002

All high-Tc, multilevel edge junction superconducting quantum interference devices (SQUIDs) which now operate at 77 K have been fabricated using laser-ablated YBaCuO electrodes and in situ laser-ablated SrTiO3 for the barrier material. Devices with a SQUID inductance of about 70 pH have a peak to peak voltage swing, VΦ, up to 8 μV (dV/dΦ≂25 μV) and a flux noise (SΦ) of about 3×10−10 Φ20/Hz in the white noise region. IcRn, products for these devices are about 35 μV at 77 K with Ic in the range of 3–100 μA and operation to temperatures as high as 84 K observed. Scaling of the junction conductance and critical current with junction size has been measured on many devices and we observe an IcRn product that varies approximately as J0.89c.
Sample size effect on the determination of the irreversibility line of high-T
c superconductors
Authors: Li Qiang , Suenaga M. , Li Qi , Freltoft T.
Published: July 2002

The irreversibility lines of a high-Jc superconducting Bi2Sr2Ca2Cu3Ox/Ag tape were systematically measured upon a sequence of subdivisions of the sample. The irreversibility field Hr(T) (parallel to the c axis) was found to change approximately as L0.13, where L is the effective dimension of the superconducting tape. Furthermore, it was found that the irreversibility line for a grain-aligned Bi2Sr2Ca2Cu3Ox specimen can be approximately reproduced by the extrapolation of this relation down to a grain size of a few tens of micrometers. The observed size effect could significantly obscure the real physical meaning of the irreversibility lines. In addition, this finding surprisingly indicated that the Bi2Sr2Ca2Cu2Ox/Ag tape and grain-aligned specimen may have similar flux line pinning strength.
Large magnetoresistance with low saturation fields in magnetic/magnetic superlattices
Authors: Gallego J. M. , Lederman D. , Moran T. J. , Schuller Ivan K.
Published: July 2002

Ni/Co multilayers grown by molecular beam epitaxy are found to exhibit a magnetoresistance ΔR/R at liquid helium temperature as large as 8.2%, with saturation fields ΔH≊22 Oe and a sensitivity (ΔR/R)/(2ΔH)≊0.19% Oe−1. The highest room temperature sensitivity obtained to date in this system is 0.18% Oe−1 and at 4.2 K is 0.29% Oe−1. This demonstrates that high values of the sensitivity can be achieved in multilayers in which both components are ferromagnetic. The magnetoresistance and saturation field can be tuned by the superlattice and growth parameters.
Transparent chemical vapor deposited β-SiC
Authors: Goela J. S. , Burns L. E. , Taylor R. L.
Published: July 2002

Transparent β-SiC has been fabricated by the pyrolysis of methyltrichlorosilane in a hot wall chemical vapor deposition reactor. Characterization of material indicates that transparent SiC is a theoretically dense, highly pure (99.9996%), highly oriented 〈111〉, β-phase (cubic) material possessing high optical transmission in the wavelength region 0.5–6 μm, a high value of hardness, electrical resistivity and thermal conductivity, and a low value of thermal expansion coefficient. These properties make it a good candidate material for use as domes and windows in severe environments such as high speed missiles, laser, combustion and space systems.
Polarization and wavelength dependence of metal-semiconductor-metal photodetector response
Authors: Kuta J. J. , van Driel H. M. , Landheer D. , Adams J. A.
Published: July 2002

Photocurrent and transmission studies for 543<λ<1523 nm of metal-semiconductor-metal (MSM) photodetectors on semi-insulating GaAs substrates demonstrate a polarization and wavelength dependence of the coupling of light into the metal electrodes. Devices with electrode periods of 400 and 800 nm were investigated and differences as large as 85% in efficiency between orthogonal polarizations were measured for the 400 nm devices. Modeling of the energy transmission through lamellar periodic structures using a Greens function formalism and incorporating dispersion of the substrate dielectric constant produces semiquantitative agreement with the measurements. Suggestions for future MSM photodetector design are discussed.
Accelerated aging for AlGaInP visible laser diodes
Authors: Endo Kenji , Kobayashi Kennichi , Fujii Hiroaki , Ueno Yoshiyasu
Published: July 2002

Accelerated aging tests were carried out under constant current conditions at an ambient temperature range of 100–150 °C for 670 nm band AlGaInP visible laser diodes. A degradation rate activation energy of 0.8 eV and an extrapolated lifetime of 106 h at 50 °C has been obtained. It is reported for the first time that lasing wavelength shifts of up to 20 nm to shorter wavelengths accompanied the threshold current increase. This is attributed to disordering of the natural superlattice in the GaInP active layer.
Deflection of ions due to electric field perturbation in electron cyclotron resonance discharges
Authors: Ardehali M.
Published: July 2002

Monte Carlo methods have been used to simulate the transport of ions across the sheath of electron cyclotron resonance discharges. It is found that the local electrical field near the wafer surface is distorted by the geometric shape of the trench, and the nature of this distortion is such that the otherwise normally incident ions are deflected toward the trench sidewalls. The simulation results indicate that the degree of ion deflection due to surface topography scales with the trench depth relative to the sheath thickness and not with the aspect ratio.
High-frequency capacitances in resonant interband tunneling diodes
Authors: Fobelets K. , Vounckx R. , Genoe J. , Borghs G. , Grönqvist H. , Lundgren L.
Published: July 2002

The junction capacitance in resonant interband tunneling diodes is determined using microwave impedance measurements from 40 MHz to 62 GHz and network parameter extraction. The shape of the capacitance in the positive differential resistance region is totally different from the resonant tunneling diode. The difference can be explained by the intrinsic transport process of carriers in a resonant interband tunneling diode, what is manifested in the conductance characteristic of the device.
Quantized conductance and electron focusing spectra of GaAs/AlGaAs point contacts fabricated by optical lithography
Authors: Gao J. R. , van Wees B. J. , Kuipers J. J. , Heida J. P. , Klapwijk T. M.
Published: July 2002

Split gate quantum point contacts on a two-dimensional electron gas (2DEG) of GaAs/AlGaAs heterostructures are fabricated using conventional optical lithography. The typical opening of the split gates ranges from 0.25 to 0.5 μm. Applying negative voltages to the gate introduces horn-shaped constrictions. In a double point contact device, the point contact conductances are measured as a function of gate voltage, and transverse electron focusing is studied using one point contact to inject electrons ballistically into the 2DEG and the other to collect the electrons. Clear quantized conductance steps in units of 2e2/h are found at temperatures between 0.1 and 2 K. Also, electron focusing spectra are obtained for various point contact widths and some features are characterized by the geometry of the split gate.
Field effect in weakly compensated Si under condition of impurity conduction
Authors: Vedeneev A. S. , Gaivoronskii A. G. , Zhdan A. G. , Rylkov V. V. , Tkach Yu. Ya. , Modelli A.
Published: July 2002

Peculiarities of electron transport in a thin (0.5 μm) Si:B layer of p-channel depletion-type metal-oxide-semiconductor transistors with a high doping level (NA≂1018 cm−3) and a low compensation degree (K≂10−3) are described. These peculiarities manifest themselves in the helium temperature range as an increase and successive saturation of the impurity-band conductance when the negative charge near the Si surface is increased by applying positive gate voltages. A model is suggested which explains the conduction enhancement as a result of the appearance of an additional channel for hopping in the transition region which divides completely ionized and neutral acceptors. The estimated hopping activation energy is in agreement with the experimental results.
High efficiency indium gallium arsenide photovoltaic devices for thermophotovoltaic power systems
Authors: Wilt David M. , Fatemi Navid S. , Hoffman Richard W. , Jenkins Phillip P. , Brinker David J. , Scheiman David , Lowe Roland , Fauer Maria , Jain Raj K.
Published: July 2002

The development of indium gallium arsenide (Eg=0.75 eV) photovoltaic devices for thermophotovoltaic power generation is described. A device designed for broadband response had an air mass zero efficiency of 11.2 % and an internal quantum yield of over 90% in the range of 800 to 1500 nm. Devices designed for narrow-band response have also been developed. Both structures are based on a n/p junction which also makes them applicable for integration into indium phosphide based, monolithic, tandem solar cells for solar photovoltaic applications.
Magnetic properties of CoxNi1−x/Pt multilayers
Authors: Krishnan R. , Lassri H. , Seddat M. , Porte M. , Tessier M.
Published: July 2002

We have prepared CoxNi1−x/Pt multilayers by evaporation under ultrahigh vacuum conditions and studied their magnetic and magneto-optical properties. The addition of Co to Ni leads to an increase in both the surface anisotropy and TC. It is found that the surface anisotropy Ks of CoxNi1−x/Pt multilayers can be expressed as the sum of Ks of Ni/Pt and of Co/Pt times their respective concentration. In Co0.3Ni0.7/Pt multilayers, for t(Co,Ni)=0.45 nm, one observes a perpendicular M-H loop with a good rectangularity and a coercivity of 1 kOe and TC of 180 °C. These characteristics are very interesting for application in magneto-optic storage.
Measurement of the effective temperature of majority carriers under injection of hot minority carriers in heterostructures
Authors: Belenky G. L. , Kastalsky A. , Luryi S. , Garbinski P. A. , Cho A. Y. , Sivco D. L.
Published: July 2002

We propose and demonstrate a purely electrical method for measuring the effective temperature Te of majority carriers under the injection of hot minority carriers. The Te of holes in a thin p-type InGaAs layer, heated by electron injection from an InAlAs layer in a three-terminal lattice-matched heterostructure, was determined by measuring the thermionic emission current of holes over another specially designed InGaAs/InAlAs barrier. At T=77 K, we observed an overheating Te−T of over 50 K, even at moderate injection power levels.
Limitations of two-dimensional passive waveguide model for λ=980 nm Al-free ridge waveguide lasers
Authors: Näppi J. , Ovtchinnikov A. , Asonen H. , Savolainen P. , Pessa M.
Published: July 2002

The performance characteristics of ridge waveguide InGaAs/InGaAsP/GaAs strained quantum well lasers emitting at 980 nm are reported. Factors limiting the validity of a passive waveguide two-dimensional approximation model are investigated. In particular, is was found that a gain-guiding effect is responsible for the fundamental mode stabilization and lateral far-field broadening. Ridge waveguide laser parameters which influence the stability of lateral single mode operation are discussed. An output power of 180 mW in spatial single mode operation was attained, and it was limited by catastrophic optical damage of the mirror facet.
Surface-emitted green light generated in Langmuir–Blodgett film waveguides
Authors: Bosshard Ch. , Otomo A. , Stegeman G. I. , Küpfer M. , Flörsheimer M. , Günter P.
Published: July 2002

We demonstrate second-harmonic generation due to counterpropagating beams in planar waveguides of 2-docosylamino-5-nitropyridine (DCANP). The DCANP molecules were deposited by Langmuir–Blodgett techniques and have a preferred alignment within the substrate plane. Four-layer waveguide structures were used to optimize the trade-off between propagation loss and efficient surface-emitted green light.
Novel silicon waveguide switch based on total internal reflection
Authors: Liu Yuliang , Liu Enke , Li Guozheng , Zhang Shengliang , Luo Jinsheng , Zhou Fan , Cheng Meiqiao , Li Bingchen , Ge Huang
Published: July 2002

Novel silicon asymmetric optical switches with transverse injection structure have been proposed and fabricated which are based on total internal reflection and free-carrier effect. The switches have a quite short operation length of about 200 μm. The device performance was measured at the wavelength of 1.3 μm. It shows that the crosstalk is less than −11.4 dB at an injection current of 85 mA. Response time is 100 ns. They are very suitable for silicon monolithic optoelectronic integration
Novel process for reliable ultrathin tunnel dielectrics
Authors: Hao Ming-yin , Maiti Bikas , Lee Jack C.
Published: July 2002

A new process technique, referred to as the ‘‘oxidized-nitrided silicon (ONS),’’ was developed for producing ultrathin (≤50 Å) dielectrics. Metal-oxide-semiconductor capacitors were fabricated using this novel process to investigate the dielectric quality. It was found that devices with ONS dielectrics exhibit reduced charge trapping and improved interface-state generation characteristics. The stress-induced leakage current, which is one of the major concerns for ultrathin dielectrics, was also suppressed by employing the ONS dielectrics. In addition, precise thickness control can be easily achieved by the ONS process even down to the ultrathin regime. The results suggest that this novel ONS process can synthesize reliable tunnel dielectrics suitable for memory applications.
Growth mechanism of GaAs by metalorganic vapor phase epitaxy
Authors: Hsu C. C. , Xu J. B. , Wilson I. H.
Published: July 2002

We observed concentric ring patterns on metalorganic vapor phase epitaxy grown GaAs surface by atomic force microscopy. The growth mechanism for the concentric ring pattern is different from that of spiral growth due to screw dislocations. A more plausible growth mechanism for the concentric rings is the stacking fault mechanism. Stacking faults that emerge from the (100) growth surface create steps of 1/3 and 2/3 the elementary height. The 1/3 and 2/3 substeps act as persistent step sources for growth.
Resonant tunneling in AlSb-GaSb-AlSb and AlSb-InGaSb-AlSb double barrier heterostructures
Authors: Jimenez J. L. , Li X. , Wang W. I.
Published: July 2002

We report the resonant tunneling of electrons in AlSb-GaSb-AlSb and AlSb-InGaSb-AlSb double barrier heterostructures grown on different substrate orientations. We have investigated the dependence of the current voltage characteristic on barrier and well thicknesses, as well as on temperature. Resonant tunneling peak to valley (P/V) ratios of 7.6 (GaSb well) and 8.7 (InGaSb well) at 80 K have been obtained. We also report the observation of a second negative differential resistance (NDR) region with an anomalous temperature dependence, and give an experimental estimation of the band alignment in the strained GaSb/InGaSb system based on the variation of the NDR position in the tunneling structures.
Nonlinear far-infrared absorption in InSb due to light impact ionization
Authors: Ganichev S. D. , Diener J. , Prettl W.
Published: July 2002

A highly nonlinear far-infrared free-carrier absorption, rising with the radiation intensity, has been observed in InSb. It is shown that the nonlinearity arises from an increase in the number of free carriers caused by the generation of electron-hole pairs by light impact ionization in the radiation field of a powerful far-infrared laser. The observed nonlinearity permits the investigation of the process of impact ionization by a contactless optical method.
Cobalt disilicide intercell ohmic contacts for multijunction photovoltaic energy converters
Authors: Kalkhoran Nader M. , Maruska H. Paul , Namavar and Fereydoon
Published: July 2002

We have created thin buried films of low resistivity CoSi2 in silicon by ion implantation, and used them to provide intercell ohmic contacts for monolithically stacked multijunction photovoltaic energy converters. We have grown epitaxial silicon pn junction diodes by chemical vapor deposition onto the thin film of crystalline silicon formed over the CoSi2 layer after post-implantation annealing. A single junction photovoltaic device with two CoSi2 contacts displayed an open circuit voltage of 0.60 V and a fill factor of 0.80, while a double junction tandem cell with three CoSi2 interconnects generated 1.2 V, under identical conditions of illumination with a Nd:YAG laser. These results indicate very low defect levels in the deposited silicon epitaxial layers, and excellent functioning of the CoSi2 interconnects.
Photoelectron intensity oscillation during chemical vapor deposition on Si(100) surface with Si2H6
Authors: Takakuwa Yuji , Enta Yoshiharu , Yamaguchi Tetsuji , Hori Toyokazu , Niwano Michio , Miyamoto Nobuo , Ishida Hiroyuki , Sakamoto Hitoshi , Nishimori Toshihiko , Kato Hiroo
Published: July 2002

We have found that the photoelectron intensity of the dimer-dangling-bond-derived surface state on Si(100) shows a periodic oscillation during chemical vapor deposition with Si2H6 gas. The substrate temperature and Si2H6-pressure dependence of the oscillation period was measured. By use of a selective-growth method using SiO2-patterned wafers, one oscillation period was clarified to correspond to the Si growth of one atomic layer of the Si(100) plane with a thickness of 1.36 Å.
Critical current increase of high-T
c superconductor pipe with coaxial configuration
Authors: Nakamura Koichi , Abe Yoshihiro , Inukai Eikichi , Sone Mototaka
Published: July 2002

The critical current (Ic) of high-Tc pipe-like superconductor was found to increase under external magnetic field, when the superconductor pipe and bar are constructed into coaxial cylinder configuration. The superconductor specimens in the Bi-Sr-Ca-Cu-O system used were fabricated by a glass-ceramic method. When the currents in the inner bar are made to flow in the opposite direction against the outer pipe, the critical current of the pipe is observed to increase by a measurable amount, although the pipe is exposed to the magnetic field produced by the inner conductor current. This phenomenon was observed not only in direct current but also in alternating current.
Gain dynamics in quantum well lasers and optical amplifiers: An experimental comparison
Authors: Tessler N. , Mark J. , Eisenstein G. , Mo/rk J. , Koren U. , Burrus C. A.
Published: July 2002

We describe an experimental comparison of gain dynamics in quantum well lasers and optical amplifiers. We demonstrate an approximately 30% increase in the time constant describing the gain recovery on the ∼1 ps time scale in a laser above threshold. The increase is due to the high rate of stimulated emission which modifies the relative significance of the various mechanisms contributing to the gain recovery. We suggest an explanation based on the coupling of two processes: Carrier capture and carrier cooling. We conclude that laser gain dynamics contain details that cannot be revealed in experiments on optical amplifiers due to the vast differences in operating conditions between a laser and an optical amplifier.
Direct electronic compensation of the amplification nonlinearity in semiconductor laser amplifiers
Authors: Tiemeijer L. F. , Thijs P. J. A. , Dongen T. v. , Jansen E. J. , Binsma J. J. M.
Published: July 2002

Direct electronic compensation of the inherent amplification nonlinearity of semiconductor laser amplifiers is investigated. It is found that operating the active layer junction from a voltage source, which in theory would hold the carrier density at a constant value, does not remove the amplification nonlinearity because of the intraband carrier dynamics. However, compensation of the nonlinearity is shown to be possible by driving the laser amplifier from a negative output impedance source. Using this at 80 mA drive current compensation of the amplification nonlinearity is demonstrated for a 1310 nm polarization insensitive multiple quantum well laser amplifier showing 18 dB gain (13 dB fiber to fiber) and a nonlinearity of 0.36 dB/mW. It is further shown that the intraband carrier dynamics, mainly the carrier heating, cause limitations to both the driving conditions for which the nonlinearity can be compensated, and to the use of laser amplifiers as an amplifying detector.
Picosecond pulse generation with a 1.55 μm tunable twin guide laser using blue-chirp compression
Authors: Schell M. , Huhse D. , Bimberg D.
Published: July 2002

Ultrashort lightpulses at λ=1.55 μm are generated by modulating the emission wavelength of a tunable twin guide laser and subsequent compression of the linearly blue-chirped part of the output down to 3.5 ps. Its simplicity, the low jitter, and the possibility of direct triggering the pulses are the main advantages of this new method.
Epitaxial growth of diamond films on the {221} and {100} surfaces of c-BN with microstructures full of (100) facets
Authors: Chai W. P. , Gu Y. S. , Li M. , Mai Z. H. , Li Q. Z. , Yuan L. , Pang S. J.
Published: July 2002

Diamond films on surfaces of cubic boron nitride substrate grown by microwave plasma chemical vapor deposition are investigated. Deposited films are characterized by scanning electron microscopy, reflection high-energy electron diffraction, and micro-Raman spectroscopy. We found a new stacking growth mode of the epitaxial diamond films which is distinguished from the previous observed modes. The morphologies of diamond (100) facets formed on the {221} and {100} surfaces of cubic boron nitride are steps and/or stages, respectively. This is beneficial to growing a fair perfect single-crystal films of diamond.
Band-structure effects in AlSb-InAs-AlSb double-barrier structures
Authors: Chiang Jih-Chen
Published: July 2002

This letter reports the study of the resonant-tunneling characteristics of the AlSb-InAs-AlSb double-barrier structures within a second-neighbor sp3 bond-orbital model. The model employs one s-like antibonding orbital and 3 p-like bonding orbitals per unit site and is capable of describing the lowest conduction band accurately throughout the entire Brillouin zone. The current-voltage curve thus obtained, compared to those obtained using the nearest-neighbor sp3 bond-orbital model or those obtained from the two-band model, gives a much better agreement with the experiment.
High signal to noise level ion beam induced charge images
Authors: Breese M. B. H. , Laird J. S. , Moloney G. R. , Saint A. , Jamieson D. N.
Published: July 2002

The use of MeV α particles to generate ion beam induced charge images with a signal to noise level approximately ten times larger than previously obtained using protons is described. The effect of α particle induced damage on the resultant image contrast is shown and a method of image formation in which the effects of ion induced damage are compensated for is described which enables the use of a higher ion dose.
Observation of mode selection in a radially anisotropic cylindrical waveguide with liquid-crystal cladding
Authors: Chen Shu-Hsia , Chen Tien-Jung
Published: July 2002

Observation of mode selection in an optical fiber with nematic liquid-crystal cladding is reported. The TE01 mode is guided, while the TM01 mode leaks out. This behavior is achieved by radially oriented liquid-crystal directors in the cladding of an optical fiber with isotropic core. A theory which quantitatively accounts for the results is given.
In situ investigation of amorphous silicon-silicon dioxide interfaces by infrared ellipsometry
Authors: Ossikovski R. , Shirai H. , Drévillon B.
Published: July 2002

An in situ investigation of the a-Si:H-a-SiO2 interfaces by infrared phase modulated ellipsometry is presented. 20–30-Å-thick intermixing layers are clearly revealed at the interface whatever the deposition sequence. In particular, the presence of SiO and (O)SiHn bonds in the first monolayers of the growth of the ‘‘top’’ a-Si:H is identified. Likewise a hydrogen accumulation, revealed by SiH vibrations, is observed during the early stage of the growth of a-SiO2 on top of a-Si:H. The nature of the a-Si:H-a-SiO2 and a-Si:H-a-SiNx interfaces is compared.
Bonding partner change reaction in oxidation of Ge on Si(001): Observation of two step formation of SiO2
Authors: Prabhakaran K. , Ogino T. , Scimeca T. , Watanabe Y. , Oshima M.
Published: July 2002

Oxidation of 5 Å Ge deposited at room temperature on Si(001) and the dependence of temperature on the oxidation behavior are investigated by employing synchrotron radiation photoelectron spectroscopy. The sample on exposure to air forms a mixture of Ge oxides and a small amount of Si oxides. Upon annealing, oxygen changes its bonding partner from Ge to Si forming SiO2 as the predominant final product. Two distinct steps have been observed in such a reaction. First step is the cleavage of all the Ge—O bonds and formation of Si—O bonds to form mainly Si suboxide. The second step is the rearrangement of Si—O bonds to form SiO2. The former one takes place in the temperature range 200–300 °C whereas the latter one in the range 300–600 °C.
Low temperature growth of silicon-boron layer by ultrahigh vacuum chemical vapor deposition
Authors: Chen T. P. , Lei T. F. , Lin H. C. , Chang C. Y. , Hsieh W. Y. , Chen L. J.
Published: July 2002

A polycrystalline silicon-boron (Si-B) layer with a thickness of 180 nm was grown on recrystallized amorphous silicon in an ultrahigh vacuum chemical vapor deposition (UHV/CVD) system using pure SiH4 and B2H6 (1% in H2). The growth temperature was as low as 550 °C. Auger electron spectroscopy and secondary ion mass spectroscopy showed that the boron concentration is extraordinarily high (2×1022 cm−3). From the analysis of transmission electron diffraction patterns, the phase of silicon hexaboride (SiB6) was found to be present in the as-deposited Si-B layer. After thermal annealing, most of the boron atoms in the Si-B layer were found to be immobile. The presence of SiB6 in the Si-B layer may lead to the reduction of boron diffusivity in the Si-B layer during thermal annealing.
Direct observation of Josephson self-radiation in Bi2Sr2Ca2Cu3Oy break junctions above 77 K
Authors: Lee Kiejin , Iguchi Ienari , Hikata Takeshi , Sato Ken-ichi
Published: July 2002

We have directly observed the Josephson self-radiation emitted from a Bi2Sr2Ca2Cu3Oy break junction at receiver frequencies fREC=11 and 47 GHz above liquid-nitrogen temperature. The results on the current-voltage characteristics, the dV/dI vs I curves, the harmonic Josephson self-radiation, and the dependence of critical current on microwave self-radiation power are well interpreted in terms of the current biased resistively shunted junction model. The maximum first-harmonic self-radiation powers at receiver frequencies fREC=11 and 47 GHz were P(I) =3×10−13 and P(I)=1×10−13 W at 77 K, respectively.
Compact InP-based ring lasers employing multimode interference couplers and combiners
Authors: Roijen R. van , Pennings E. C. M. , van Stalen M. J. N. , van Dongen T. , Verbeek B. H. , van der Heijden J. M. M.
Published: July 2002

Multimode interference (MMI) 3 dB couplers and MMI power combiners have been integrated with compact InP/InGaAsP ring lasers (R=150 μm). Radiative loss from the curves is small, and MMI 3 dB couplers are shown to be more efficient than conventional Y junctions. In addition, we demonstrate improved efficiency by combining counterpropagating beams in a single output by means of a MMI combiner. Single mode spectral behavior, with 35 dB side mode suppression, has been measured and is explained as resulting from coupled cavities.
Phase transition of Cu/Si system obtained by ion beam assisted deposition
Authors: Yang Jie , Zhang H. B. , Tao Kun , Fan Yudian
Published: July 2002

Cu films were formed on Si(100) substrates using three different methods: physical vapor deposition (PVD), ion beam assisted deposition (IBAD), and a combined IBAD-PVD technique. ε-phase (Cu15Si4) was formed directly at the interface of the 14 keV Ar+ IBAD Cu film (350 nm) and the Si substrates during the deposition processes. In the combined film [IBAD Cu (20 nm)+PVD Cu (350 nm)] no new phase was observed until the sample had undergone an annealing treatment (300 °C 30 min), in which the ε phase was formed. The phase sequence of the Cu-Si system in combined films of our experiments is quite different from those observed in a typical annealing process. From discussion the nucleation of ε phase is the key factor to obtain a thermodynamically stable phase at the Cu-Si interface during the annealing process.
New microfabrication technique by synchrotron radiation-excited etching: Use of noncontact mask on a submicrometer scale
Authors: Terakado Shingo , Goto Takashi , Ogura Masayoshi , Kaneda Kazuhiro , Kitamura Osamu , Suzuki Shigeo , Tanaka Kenichiro
Published: July 2002

Synchrotron radiation (SR)-excited etching of Si using a noncontact mask on a submicrometer scale has been investigated. The blank pattern of the noncontact mask was replicated on the etched surface and highly area-selective etching was realized at the size of ∼0.4 μm. The spatial photointensity distribution of SR on the sample determined the depth profile of the etched part of the sample.
Fabrication of three-terminal resonant tunneling devices in silicon-based material
Authors: Zaslavsky A. , Milkove K. R. , Lee Y. H. , Chan K. K. , Stern F. , Grützmacher D. A. , Rishton S. A. , Stanis C. , Sedgwick T. O.
Published: July 2002

Laterally gated three-terminal resonant tunneling devices have been fabricated from Si/Si1−xGex double-barrier structures grown by atmospheric pressure chemical vapor deposition. The gate is insulated from the submicrometer vertical channel by a low-temperature oxide and the entire fabrication scheme is compatible with current silicon technology. At T=77 K the resonant peak current can be modulated by 25% by applying a moderate gate voltage; at T=4.2 K, current modulation reaches 50%. We present calculations demonstrating that devices fabricated from optimized Si/Si1−xGex structures will pinch off fully at moderate gate voltages and operate at liquid nitrogen temperatures.
Picosecond carrier escape by resonant tunneling in pseudomorphic InGaAs/GaAsP quantum well modulators
Authors: Froberg N. M. , Johnson A. M. , Goossen K. W. , Cunningham J. E. , Santos M. B. , Jan W. Y. , Wood T. H. , Burrus C. A.
Published: July 2002

We have used time-resolved transmission and photocurrent measurements at 1.06 μm to study carrier sweepout in strain-relaxed InGaAs/GaAs and strain-balanced InGaAs/GaAsP quantum well modulators. Our results show carrier sweepout on a picosecond time scale from both structures, in agreement with the high saturation intensities measured for these devices. Carrier escape from the InGaAs/GaAs structure is facilitated by a low band offset and occurs in tens of picoseconds even without external bias. In the InGaAs/GaAsP structure, which has a much larger band offset, resonant tunneling reduces the sweepout time from 1.8 ns at zero bias to 10 ps at −6 V.
Experimental study of a waveguide free-electron laser using the coherent synchrotron radiation emitted from electron bunches
Authors: Asakawa Makoto , Sakamoto Naoki , Inoue Naoki , Yamamoto Tatsuya , Mima Kunioki , Nakai Sadao , Chen Jizhong , Fujita Masayuki , Imasaki Kazuo , Yamanaka Chiyoe , Agari Tatsuo , Asakuma Takashi , Ohigashi Nobuhisa , Tsunawaki Yoshiaki
Published: July 2002

We have observed the oscillation of a waveguide mode free-electron laser using the coherent synchrotron radiation emitted from electron bunches. The oscillation was observed at 2.73 mm with a linewidth of 0.4%. This spectral selection was attributed to the dispersion of the radiation in the waveguide. We found that the oscillating radiation had to have the same group velocity as the velocity of the electrons passing through the wiggler field.
Acoustic phase conjugation in highly nonlinear PZT piezoelectric ceramics
Authors: Ohno M. , Takagi K.
Published: July 2002

Acoustic phase conjugate waves at 10 MHz were generated with PZT piezoelectric ceramics as highly nonlinear media. Phase conjugate power reflectivity was 10−3, which was 102 times higher than the conventional values with LiNbO3.
Crystal growth and electronic properties of ultrahigh vacuum ion-beam sputter deposited Sb-doped Si(001)2×1
Authors: Lee N.-E. , Tomasch G. A. , Xue G. , Markert L. C. , Greene J. E.
Published: July 2002

High-quality homoepitaxial Sb-doped Si(001)2×1 films have been grown on p-type Si(001) substrates by ultrahigh vacuum ion-beam sputter deposition (IBSD) at temperatures Ts between 450 and 750 °C. The load-locked multichamber system is equipped with in situ reflection high-energy electron diffraction. Sputter deposition was carried out using a 1 keV Kr+ ion beam generated by a modified Kaufman-type ion source with post-extraction electrostatic ion optics. All films were 1 μm thick and deposited at a rate of 0.35 μm h−1. Results of plan-view, cross-sectional, and convergent-beam transmission electron microscopy analyses showed that as-deposited films are highly perfect with no visible defects. Sb incorporation probabilities σSb ranged from ≂0.1 at Ts=750 °C to ≂1 for Ts≤550 °C with no indication by secondary-ion mass spectrometry (SIMS) of Sb surface segregation. These σSb values are one to three orders of magnitude larger than for coevaporative Sb doping during molecular beam epitaxy where extensive Sb surface segregation is observed. A comparison of calibrated SIMS and Hall-effect measurements established that the incorporated Sb exhibited complete electrical activity. SIMS analyses also showed no detectable Kr (detection limit ≂5×1017 cm−3). Temperature-dependent (15–300 K) electron mobilities were equal to the best reported bulk Si values.
YBa2Cu3O7−δ films grown on ferroelectric Bi4Ti3O12 crystals by radio-frequency sputtering
Authors: Mendoza-Alvarez M. E. , Tabares-Muñoz C. , Alvarez-Fregoso O. , Mendoza-Alvarez J. G.
Published: July 2002

We describe the growth and structural characterization of YBa2Cu3O7−δ (YBCO) thin films on Bi4Ti3O12 (BTO) layered crystals using a radio frequency sputtering technique. A nonhomogeneous laminar morphology probably related with ferroelectric domain walls was obtained. An electron diffraction pattern of a selected area shows evidence of epitaxial growth even when there exists a large mismatch between BTO and YBCO; we explain such a matching in terms of a 45° rotation between lattices.
Correlation of surface morphology with luminescence of porous Si films by scanning tunneling microscopy
Authors: Enachescu M. , Hartmann E. , Koch F.
Published: July 2002

The evolution of visible photoluminescence is demonstrated by measuring the surface morphology of thin (∼20 nm) electrochemically etched porous silicon (PS) films with scanning tunneling microscopy (STM). Using low current densities, three sorts of samples were prepared under different conditions: In the dark (A), under illumination with ultraviolet (UV) light (B), and in the dark followed by a postphotochemical treatment (C). Upon UV light excitation, type A samples do not emit visible light, while samples of type B and C show weak and efficient photoluminescence in the visible range, respectively. STM imaging of these PS layers reveals a considerable decrease in the lateral dimensions of the surface features from approximately 10 nm (type A) to roughly 2 nm (type C), in accordance with the quantum confinement approach in describing the luminescence properties.
Study of thermal oxidation and nitrogen annealing of luminescent porous silicon
Authors: Yan J. , Shih S. , Jung K. H. , Kwong D. L. , Kovar M. , White J. M. , Gnade B. E. , Magel L.
Published: July 2002

The properties of thermally oxidized porous Si were studied by Fourier-transform infrared spectroscopy and secondary ion mass spectroscopy. The results show that residual hydrogen exists in the 1000 °C/10 min thermally oxidized porous Si film in the form of SiOH bonds. The removal of these hydrogen atoms by annealing at 1000 °C in N2 reduces the photoluminescence.
On plastic flow and work hardening in strained layer heterostructures
Authors: Fischer A. , Richter H.
Published: July 2002

We present an alternate model for metastable strain relaxation in heteroepitaxial semiconductor structures which includes the elastic interaction between misfit dislocations. The concept of the self-stress of straight misfit dislocations lying in the interface in two orthogonal arrays is introduced and applied to standard expressions for the residual in-plane epitaxial film stress of noninteracting dislocations. Our model of plastic flow and work hardening in strained layer heterostructures agrees well with the experimental work. The theoretical analysis can be applied to most of the pseudomorphic and heteroepitaxial material systems of current interest.
Characterization of deep traps in semi-insulators by current transients
Authors: Maimon S. , Schacham S. E.
Published: July 2002

Deep traps in semi-insulators (SI) are characterized using a junction composed of an epitaxial p-type layer grown on SI n-type layer. At a reverse bias electrons are released from the traps resulting in a current transient through the substrate. Simultaneously the depletion region in the epilayer expands until the entire layer is depleted leading to a decaying epitaxial current. The analysis of these transients renders the electron emission and capture coefficients and lifetime, and the energy location of the traps. The long current decay are accelerated by illuminating the sample with photons of energy below the band gap, as long as their energy is larger than the difference between trap energy and the bottom of the conduction band. Thus we determined directly this energy difference.
Analytical method for calculation of temperature distribution in laser-irradiated media with an external cooled surface
Authors: Gurevich Y. , Filonenko N. , Salansky N.
Published: July 2002

A method of spatial temperature field calculation based on an approximate analytical solution is presented for laser-induced heating in a light-absorbing medium combined with surface cooling. Example calculations show how this approach can provide temperature field control and heating area localization within the irradiated medium. The concept can be useful for various applications, particularly in medicine.
Large-amplitude Shapiro steps and self-field effects in high-T
c Josephson weak links
Authors: Kautz R. L. , Benz S. P. , Reintsema C. D.
Published: July 2002

We demonstrate contiguous Shapiro steps of orders 0 and 1 having amplitudes of 1 mA in a YBa2Cu3O7−δ step-edge junction operated at 38 K. A wide-junction model that includes self-field effects explains why the observed step amplitudes are smaller than expected from the resistively shunted point-junction model. In spite of their reduced amplitudes, the observed steps are suitable for use in a proposed rapidly programmable Josephson voltage standard.
Scanning tunneling microscopy of diamond-like nanocomposite films
Authors: Rong Zhao Y. , Abraizov Mikhail , Dorfman Benjamin , Strongin Myron , Yang Xiao-Qing , Yan Dong , Pollak Fred H.
Published: July 2002

Scanning tunneling microscopy is used in the present investigation to study metal containing diamond-like nanocomposites, viz. (a-C:H)/(a-Si:O)/Me films. By comparing images taken before and after samples were annealed at 450 °C for two hours, a formation of sp2-rich regions is found in Pt containing samples, in contrast to the high thermal stability shown for transition-metal containing samples. It indicates that the Pt engenders the ‘‘loosening’’ of the diamond-like matrix with a decrease in the energy barrier. These results are further confirmed by Fourier transformation infrared spectroscopy and Raman spectroscopy. The obtained micro- and nanoscale surface images and observed transformation from sp3 to sp2 bonding provides new understanding of the fundamental structure of diamond-like films.
Sharp variation in the magnetoresistance of a Si Schottky diode
Authors: Miller D. J. , Lobb J.
Published: July 2002

The variation of the resistance of a Si Schottky diode with magnetic field in the range 0 to 1 T was monitored at room temperature by measuring the voltage across the diode at constant current using lock-in detection at the modulation frequency of the magnetic field. A sharp feature in the resistance was found to depend on the angle between the field and the plane of the Schottky junction. The result is explained in terms of a level-crossing involving the magnetic sub-levels of a triplet state recombination center in the space-charge region of the diode.
Current gain increase in AlGaAs/GaAs heterojunction bipolar transistors using AlGaAs layer overgrowth
Authors: Kalingamudali S. R. D. , Wismayer A. C. , Woods R. C. , Roberts J. S.
Published: July 2002

Reduction of the surface recombination current components in Npn AlGaAs/GaAs heterojunction bipolar transistors has been achieved by overgrowing the emitter-mesas with an AlGaAs layer approximately 0.5 μm thick. It was observed that the n=2 recombination current was reduced by ∼90%, to about 10% of the original value, with a corresponding 13-fold increase in current gain for 270×20 μm2 devices. In addition, devices with the same emitter-base area, but significantly different perimeters, were observed to have similar current gains and n=2 recombination current values. This was in contrast to devices fabricated without an overgrowth layer. These results suggest that the overgrowth layer causes a very significant reduction in the perimeter recombination current.