bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal waveguiding in oxide-defined, narrow-stripe, large-optical-cavity lasers
Authors: Chen Y. C. , Reisinger A. R. , Chinn S. R.
Published: February 2003

The characteristics of oxide-defined, narrow-stripe large-optical-cavity (LOC) AlGaAs lasers are described. Compared with regular narrow-stripe double heterostructure (DH) lasers, the LOC version exhibits more narrowing of the near-field and far-field distributions, higher astigmatism, higher differential quantum efficiency, and higher incidence of sustained pulsations. We have found that these phenomena can be explained in terms of the formation of a thermal waveguide. There is often a striking similarity in characteristics of narrow-stripe LOC and degraded narrow- stripe DH lasers. We suggest that a thermal waveguiding effect is an important factor in determining the behavior of degraded semiconductor lasers.
Optimum operational parameters of the ultrashort cavity laser
Authors: Yao J. Q.
Published: February 2003

The influence of input parameters and cavity parameters of the ultrashort cavity laser is discussed in terms of numerical calculation of the rate equations of this laser. The optimum parameters of the ultrashort cavity laser are obtained. The results of this letter will provide some theoretical guides for designing and adjusting picosecond tunable dye lasers with ultrashort cavities.
Tensile stress dependence of magnetically induced ultrasonic shear wave velocity change in polycrystalline A-36 steel
Authors: Kwun H. , Teller C. M.
Published: February 2003

Magnetically induced changes in the velocity of 4.5-MHz ultrasonic shear waves have been measured as a function of tensile stress in polycrystalline A-36 steel. The velocity changes are dependent on the relative orientations of the shear wave polarization, the magnetic field, and the external tensile stress. When the shear wave is polarized and propagated perpendicular to the tensile stress, the velocity changes induced by a magnetic field applied parallel to either stress or polarization were found to decrease with stress. This stress dependence of the magnetically induced velocity change shows potential for the nondestructive evaluation of stress in ferromagnetic materials.
Gases for possible use in diffuse-discharge switches
Authors: Christophorou L. G. , Hunter S. R. , Carter J. G. , Mathis R. A.
Published: February 2003

Desirable electron attachment and electron drift characteristics of gases for possible use in diffuse-discharge switches are indicated. Gas mixtures for possible use in externally sustained (e- beam) diffuse-discharge switches are suggested on the basis of electron attachment rate constants and electron drift velocities measured as a function of the density-normalized electric field E/N. Of particular promise are mixtures of Ar and C3F8.
Rutherford backscattering, nuclear reaction, and channeling studies of nitrogen implanted single-crystal stainless steel
Authors: Whitton J. L. , Ferguson M. M. , Ewan G. T. , Mitchell I. V. , Plattner H. H.
Published: February 2003

The techniques of channeling and backscattering of MeV He+ ions have been used in conjunction with nuclear reactions on nitrogen-implanted single crystals of stainless steel in an attempt to find the mechanism responsible for the well documented improvement in mechanical properties of such implanted steels. The nitrogen, as implanted, is found by the 15N( p,α)12C reaction to sit in the octahedral interstitial site. The present results support the suggestion that CrN forms in the implanted layer and could play a role in the improvement in mechanical properties.
Rotationally relaxed, grating tuned laser oscillations in optically pumped C2D2
Authors: Fischer T. A. , Wittig C.
Published: February 2003

Rotationally relaxed, grating tuned laser oscillations are obtained in the frequency range 500–562 cm−1 via the optical pumping of C2D2/He mixtures with a transverse, electric, atmospheric (TEA) CO2 laser. Strong Q-branch oscillations at 530.8 cm−1 are also reported.
Temperature dependence of the growth rate of silicon prepared through chemical vapor deposition from silane
Authors: Beers A. M. , Bloem J.
Published: February 2003

Below about 650 °C a new region is reported in the temperature dependence of the growth rate of silicon through chemical vapor deposition (CVD) from SiH4 in H2 at atmospheric pressure (Eact = 51 kcal/mole). Emissivity measurements during and after deposition offer experimental evidence for the presence of a hydrogenated layer a-Si:H near the surface of the growing material. At higher surface temperatures the activation energy (32–38 kcal/mole) depends on the silane partial pressure. The solid growth is amorphous on both sides of the transition, which is governed by the incorporation of hydrogen.
Empirical study of the metal-nitride-oxide-semiconductor device characteristics deduced from a microscopic model of memory traps
Authors: Ngai Kia L. , Hsia Yukun
Published: February 2003

A graded-nitride gate dielectric metal-nitride-oxide-semiconductor (MNOS) memory transistor exhibiting superior device characteristics is presented and analyzed based on a qualitative microscopic model of the memory traps. The model is further reviewed to interpret some generic properties of the MNOS memory transistors including memory window, erase-write speed, and the retention-endurance characteristic features.
Pumping mechanism of Javan’s pure rotational OH laser
Authors: Robinson Dean W.
Published: February 2003

Javan and coworkers have reported pure rotational laser oscillation from OH and OD in a pulsed discharge through H2-O2-SF6 mixtures. The pumping mechanism was not established, but it was thought at the time to be chemical. The intensity distribution can be understood as resulting from the electronic to rotational transfer of 13 200 cm−1 from O2(1Σ+g ) to ground vibrational state OH(2Π) leaving the O2 in its ground 3Σ−g state. Unexcited OH would be formed from either the reaction O+H2 = OH+H or H+O2 = OH+O. Nothing can be said about the efficiency of this E-R transfer compared to E-V; however, E-R appears to be a new mechanism for pumping diatomic, pure rotational inversions. The full explanation of this laser also demands the conclusion that SF6, like the rare gases, can serve as a collision partner inducing intramolecular V-R transition in OH.
Electron density and energy output limits of plasma-recombination lasers
Authors: Wood O. R. , Silfvast W. T.
Published: February 2003

Theoretically estimated limiting electron densities for plasma-recombination lasers are shown to agree with experimentally measured values over a wavelength variation of nearly one decade. Radiation trapping is found not to restrict the electron densities in recombination lasers that operate at wavelengths longer than about 100 nm. For wavelengths shorter than 150 nm predicted specific output energies for plasma-recombination lasers may exceed those of excimer lasers.
Transient behavior of an actively mode-locked semiconductor laser diode
Authors: AuYeung John C. , Bergman Larry A. , Johnston Alan R.
Published: February 2003

Experimental investigation was carried out to study the transient regimes during the buildup and decay of the active mode-locked state in a laser diode. The mode locking was achieved through a sinusoidal modulation of the diode current with the laser in an external cavity. The pulse shape evolution and the time constants for the buildup and decay were determined.
Determination of the density of localized states in fluorinated a-Si using deep level transient spectroscopy
Authors: Hyun C. H. , Shur M. S. , Madan A.
Published: February 2003

The density of localized states distribution in fluorinated a-Si (a-Si:F:H) was investigated using a digital deep level transient spectroscopy (DLTS) system. The DLTS spectra indicate a minimum in the density of states of about 1015 cm−3 eV−1, which is comparable to the value previously reported for a-Si:H using DLTS. Since field-effect measurements show that the density of localized states is much lower in a-Si:F:H than in a-Si:H, we can conclude that the density of surface states in (a-Si:F:H) is much smaller than in a-Si:H. This has important consequences in potential applications of amorphous silicon-based films.
Zone-melting recrystallization of 3-in.-diam Si films on SiO2-coated Si substrates
Authors: Fan John C. C. , Tsaur B-Y. , Chapman R. L. , Geis M. W.
Published: February 2003

We have constructed a scaled-up graphite strip-heater system that permits routine zone-melting recrystallization of 3-in.-diam Si films on SiO2-coated Si wafers. The recrystallized films are similar in crystal quality to those obtained previously in a smaller system, except that they contain higher densities of small protrusions along the subgrain boundaries. Seeded recrystallization has been accomplished by scribing a stripe opening, that extends through the Si and SiO2 films to the Si wafer.
An explanation for anomalous donor activation energies in Al0.35Ga0.65As
Authors: Thorne R. E. , Drummond T. J. , Lyons W. G. , Fischer R. , Morkoç H.
Published: February 2003

Transport properties of Si-doped Al0.35Ga0.65 As epitaxial layers grown by molecular beam epitaxy were studied and the activation energy of the Si donors determined. Previously reported values for the Si-donor activation energy for x = 0.35 have varied considerably and values as high as 100 meV have been suggested. For x values above and below x = 0.35, the activation energies reported are much lower, and show better consistency. Anomalously high activation energies for Se (300 meV) and Te (150 meV) doped AlxGa1−x As near the direct-indirect transition have also been reported. In this letter, a possible explanation for these anomalies in previous results based on the modulation doping effect is described. Results obtained for layers grown so as to avoid modulation doping indicate the activation energy of Si in Al0.35Ga0.65 As is less than 14 meV. When modulation doping effects were not suppressed, apparent activation energies as high as 125 meV were obtained. Finally, electron mobilities in samples not displaying modulation doping effects for an electron concentration of 6.5×1017 cm−3 were approximately 1 100 cm2/Vs.
Thermally induced vortex-to-vortex transitions in a superconducting quantum interference device
Authors: Naor M. , Tesche C. D. , Ketchen M. B.
Published: February 2003

Thermally induced vortex-to-vortex transitions between the zero-quantum vortex state and one- flux-quantum vortex state of a symmetric two-junction dc superconducting quantum interference device (SQUID) have been observed. The characterization of transitions of this type is an essential part of the modeling of Josephson junction logic and memory devices. The transition rates, measured as a function of bias current, applied flux, and temperature, are in excellent agreement with rates predicted by a thermal activation model for two-junction SQUID’s.
Electroplated cobalt film for perpendicular magnetic recording medium
Authors: Chen Tu , Cavallotti P.
Published: February 2003

In this letter, we report that pure cobalt can be prepared with the easy axes of magnetization normal to the film plane. This unusual condition is achieved through an electroplated columnar growth that produces needlelike crystallites with their hexagonal close-packed (hcp) c axes parallel to the growth direction. The magnetic properties of these films make them ideal candidates for vertical magnetic recording.
Breakdown mechanism of buffer layers in vapor phase epitaxial GaAs for metal-semiconductor field-effect transistors
Authors: Kodama Kunihiko , Ozeki Masashi , Shibatomi Akihiro
Published: February 2003

Infrared light emission was observed at an edge of a source contact in gateless GaAs metal- semiconductor field-effect transistors (MESFET’s) when a source-drain voltage was increased to be nearly equal to breakdown voltage. Its wavelength was found to correspond to the band gap of GaAs. This indicates that the emission is from an interface between an active and a buffer layer where a depletion layer is formed. Taking account of this result, a model is presented for breakdown in buffer layers. In this model, an electric-field concentration at the interface plays an important role. This was experimentally verified.
Large area silicon sheet for solar cells
Authors: Maeda Yasuhiro , Yokoyama Takashi
Published: February 2003

Polycrystalline silicon sheets having a 6-in. or 4-in. diameter with a 0.3–0.4-mm thickness have been obtained directly by spinning the silicon melt dropped on the plate. Production time of the sheet formation from the melt is about one second per sheet. The crystallites of the sheet have columnar structures. Material loss in the production process is little or none because of a clean recovery of the surplus silicon. Using this sheet, p-n junction solar cells with an AM1 efficiency of 4.1–6.0% have been made experimentally.
Defects and impurities in thermal oxides on silicon
Authors: Brower K. L. , Lenahan P. M. , Dressendorfer P. V.
Published: February 2003

Oxides grown at 1100 °C in dry oxygen for 60 min to a thickness of 1350 Å on silicon with and without subsequent forming gas anneals were 60Co γ irradiated at 4 K with doses up to 106 rad (Si). In situ electron paramagnetic resonance measurements at 10 K revealed ≊3×1017 atomic hydrogen/cm3 and ∼1017 oxygen-hole centers/cm3 in the oxide. The paramagnetic dangling bond on the silicon side of the Si/SiO2 interface (Pb center) was also observed. The (relative) concentration of these centers was measured as a function of isochronal annealing between 10 and 300 K.
Laser with dynamic holographic intracavity distortion correction capability
Authors: Cronin-Golomb Mark , Fischer Baruch , Nilsen Joseph , White Jeffrey O. , Yariv Amnon
Published: February 2003

We report here a novel laser resonator with the ability to correct for intracavity phase distortions. The optical cavity employs a passive (self-pumped) phase conjugate reflector to provide this capability.
Synchrotron x-ray topographic observation of defect evolution at the Si- Si3N4 interface
Authors: Jourdan C. , Gastaldi J. , Derrien J. , Bienfait M. , Layet J. M.
Published: February 2003

The creation and evolution of linear 〈100〉 defects at the interface of Si3N4 films condensed on Si (100) surfaces are observed by high-flux x-ray topography during the annealing of the Si wafer in flowing nitrogen. These defects are sources for tangled dislocations that develop upon further annealing in oxygen. A mechanism of the gettering at the Si3N4-Si interface is proposed.
Photoelectronic effects in amorphous silicon based alloys
Authors: Hack M. , Madan A.
Published: February 2003

Results are presented which distinguish between surface and bulk changes in the conductivity of amorphous silicon upon illumination and subsequent annealing. Our data indicates that the large changes in the dark conductivity of gap cell samples are caused mainly by surface and not bulk effects.
Two-dimensional electron gas at a molecular beam epitaxial-grown, selectively doped, In0.53Ga0.47As-In0.48Al0.52As interface
Authors: Kastalsky A. , Dingle R. , Cheng K. Y. , Cho A. Y.
Published: February 2003

We report the observation of a high-mobility, two-dimensional electron gas (2DEG) at the interface between a molecular beam epitaxial (MBE)-grown undoped In0.53Ga0.47As layer and a subsequent layer of MBE-grown, Si-doped In0.48Al0.52As . Peak mobilities of ∼92 000 cm2 V−1 s−1 have been observed at 4.2 K. From Hall and Shubnikov-de Haas studies we have found that the 2DEG can be characterized by nch = 6–8×1011 cm−2. In all cases we found two subbands to be occupied at Nch≳4.5×1011 cm−2.
Extrinsic layer at AlxGa1−xAs-GaAs interfaces
Authors: Miller R. C. , Tsang W. T. , Munteanu O.
Published: February 2003

Photoluminescence studies of GaAs-AlxGa1−xAs heterostructures grown by molecular beam epitaxy (MBE) which contain one and two GaAs quantum wells suggest that in some of the samples the first well grown usually exhibits a ’’rough’’ (6 Å≲δL≲15 Å) first interface and an acceptorlike luminescing impurity in the first few tens of angstroms of GaAs grown. The luminescence may arise from carbon which accumulates on the AlxGa1−xAs -vacuum interface during growth and is then deposited in the first few unit cells of GaAs. The phenomenon discussed may be relevant to the problem of growing high electron mobility field-effect transistor heterostructures by MBE with GaAs on the top.
Interface chemistry and electrical properties of tungsten Schottky-barrier contacts to GaAs
Authors: Waldrop J. R.
Published: February 2003

A correlation between the interface chemistry and the electrical properties of evaporated tungsten Schottky-barrier contacts to GaAs is made by using data obtained by x-ray photoemission spectroscopy (XPS), current-voltage (I-V), and capacitance-voltage (C-V) techniques. A chemical reaction and associated nonabruptness was observed both at ideal (initial clean surface) and at practical (initial native-oxide covered surface) W-GaAs interfaces during Schottky-barrier formation at room temperature. The XPS measured W Schottky-barrier height for both types of interface is 0.9 eV. I-V and C-V measurements were made for a sequence of anneal temperatures up to 650 °C; changes in the contact electrical properties occurred at each temperature. The reactive W contacts are compared to relatively nonreactive Au contacts to GaAs similarly prepared and characterized. The I-V and C-V properties of Schottky-barrier contacts are found to be strongly influenced by the chemistry associated with interface formation.
Fabry–Perot photothermal trace detection
Authors: Campillo A. J. , Petuchowski S. J. , Davis Christopher C. , Lin H-B.
Published: February 2003

A novel trace gas detection scheme based upon the photothermal effect following light absorption is described. The resulting index change, which is proportional to the trace species absorption and concentration, is measured interferometrically in a stabilized Fabry–Perot cavity. An experimental noise limit corresponding to an absorption coefficient of 4×10−8 cm−1/( √Hz) was observed. We discuss possible improvements and estimate the ultimate sensitivities achievable with this technique.
Fault-free silicon at the silicon/sapphire interface
Authors: Ponce Fernando A.
Published: February 2003

High-quality lattice images of silicon films grown epitaxially on sapphire substrates directly demonstrate the absence of misfit dislocations at the silicon/sapphire interface. With a point resolution of about 2.5 Å, these images show the absence of lattice faults and detectable strains in the silicon immediately adjacent to the subtrate over interface areas as large as 200 nm in diameter. The incoherent nature of the interface and the absence of misfit dislocations are explained in terms of the chemical bond structure at the interface.
High quality InP grown by molecular beam epitaxy
Authors: Tsang W. T. , Miller R. C. , Capasso F. , Bonner W. A.
Published: February 2003

We report the first high quality InP grown by molecular beam epitaxy (MBE). The undoped InP layers are n type with residual impurity concentrations ∼5×1014–∼5×1015 cm−3. Fine structure attributed to polariton, neutral donor-exciton (D0–X), neutral donor–hole (D0−h), neutral acceptor–exciton (A0–X) transitions at the exciton edge and neutral donor-neutral accepton (D0–A0) transitions are clearly resolved in the low-temperature (5 K) photoluminescence spectra with a linewidth of <1 meV for D0–X as has been observed with high-purity InP layers grown by other methods. Elemental In and P (red phosphorus) were used as the primary molecular beam sources. The growth temperature has a very significant effect on the quality of the InP layers. The advanced design of the present MBE system employed for growing III-V compound semiconductors containing P from elemental red phosphorus is also described.
Technique for the quantitative measurement of the three-dimensional distribution of hydrogen in solids
Authors: Lanford W. A. , Burman C.
Published: February 2003

A technique for measuring full three-dimensional concentration profiles of hydrogen in solids is proposed and demonstrated. The technique uses the resonant nuclear reaction 15N+1H→12C+4He+gamma ray to probe for hydrogen in thin samples with the 4He particles emitted in forward directions used to form an autoradiograph of the lateral distribution of hydrogen within the sample. Results from a demonstration example of H implanted through a mask into silicon are reported.
Optimization of dc SQUID linear amplifiers and the quantum noise limit
Authors: Tesche C. D.
Published: February 2003

A model for inductively coupled linear amplifier and magnetometer circuits employing superconducting quantum interference devices (dc SQUID’s), which is accurate to all values in the coupling strength, is described. The model explicitly includes the interaction between the input circuit and the dc SQUID. The optimization of the untuned linear amplifier is discussed in detail. The uncertainty principle constraint on the noise temperature of a linear amplifier is shown to place a constraint on the minimum achievable values of the noise figures of an isolated dc SQUID in the quantum noise limit.
High-power Cerenkov maser oscillator
Authors: Von Laven S. , Branscum J. , Golub J. , Layman R. , Walsh J.
Published: February 2003

An electron beam driven dielectric-lined waveguide has produced 30–100 kW of coherent radiation over an octave band on the TM01 mode of the waveguide. Operation of the TM02 mode has been realized as well. Impedance mismatches at the ends of the liner section provide a reflected signal, which undergoes amplification during successive passes.
Nanosecond modulation at 10 μm by coherent Stark switching
Authors: Wessel John
Published: February 2003

Coherent transient Stark switching has been investigated for potential application to low-power gigahertz modulation at 10 μm. We have observed free-induction decay and optical nutation in ammonia on a nanosecond time scale. The results suggest that subnanosecond response should be feasible and that the heterodyne beat signal will provide improved modulation depth.
Emission spectrum and quenching kinetics of Xe2F*
Authors: Walter W. , Sauerbrey R. , Tittel F. K. , Wilson W. L.
Published: February 2003

Experiments demonstrating the existence of the triatomic rare-gas excimer Xe2F* are reported. Three-body quenching of XeF*(B,C) yields Xe2F*, which radiates around 610 nm with a bandwidth full width at half-maximum (FWHM) of 120 nm. The two-body quenching constants of Xe2F* by NF3, Xe, and Ar as well as the radiative lifetime of 152 ns are determined.
Isotopes separation experiments in natural UF6 by CF4 and CO2 lasers, analyzed by gamma-ray spectrometry
Authors: Koren G. , Gertner Y. , Shreter U.
Published: February 2003

Multiphoton dissociation of natural UF6 was obtained by simultaneous irradiation with a CF4 laser at 615.2 cm−1 and a transverse, electric, atmospheric (TEA)-CO2 laser at 1073.3 cm−1 using various gas pressures and laser fluences. The dissociation percentages D235 and D238 of 235UF6 and 238UF6, respectively, were determined by comparing results of an irradiated sample to those of a nonirradiated reference sample prepared under identical conditions. For the analysis we employed a simple, high-precision nuclear technique based on gamma-ray spectrometry. The values of D235,D238 and the resulting enrichment factor F = D235/D238 were found from an analysis of the 186-keV peak, originating in 235U, and the 63-keV peak, originating in 234Th, the daughter nucleus of 238U. A representative result shows a dissociation of 41±1% and 235U enrichment factor of 1.049±0.016 yielded by the excitation of 0.47 Torr gas by 25 laser pulses at 20-mJ cm−2 CF4 fluence and 1-J cm−2 CO2 fluence.
High-speed ultraviolet and x-ray-sensitive InP photoconductive detectors
Authors: Deutsch T. F. , Leonberger F. J. , Foyt A. G. , Mills D.
Published: February 2003

The performance of iron-doped InP photoconductive detectors in the optical and x-ray spectral regions is compared. The detectors show uniform, high cw quantum efficiency from 900 to 200 nm. Pulse response times at 193 nm are laser source limited to ⩽12 ns. The response to ∼9-keV-fast x-ray pulses indicates device rise times <90 ps.
Effects of impurities on the characteristics of high-voltage glow discharges in D2 gas—Application to neutron tubes
Authors: Saubignac C. , Faure C.
Published: February 2003

Effects of impurities on the characteristics of high-voltage glow discharges are theoretically studied. These glow discharges are established during a few microseconds between two plane parallel electrodes separated by a few centimeters under a deuterium pressure of about 0.1 mmHg, at currents of the order of 1–10 A, and voltages of about 100 kV. With tritium-loaded cathodes, high-voltage discharge tubes produce neutron pulses. In a one-dimensional theoretical treatment of the discharge, we take into consideration complex processes: charge exchange, ionization of gas by ions, and ion dissociation. Our model shows that some gaseous impurities increase the neutron emission level. Computed variations of neutron output and discharge characteristics as a function of impurity partial pressure are in good agreement with experimental values.
Properties of a GaxIn1−x As-GaAs isotype heterojunction diode
Authors: Bhattacharya P. K. , Bühlmann H. -J. , Ilegems M. , Schmid P. , Melchior H.
Published: February 2003

The properties of a n-n+ GaAs-Gax In1−x As heterojunction grown by molecular beam epitaxy are described. Current-voltage and capacitance-voltage measurements indicate that the junction behaves as a Schottky diode. Significant photoresponse is observed for incident light of wavelength greater than 0.9 μm. Subnanosecond response speeds with full width at half-maximum (FWHM) of ≃250 ps were measured when the diodes were operated as photodetectors.
Amorphous-silicon/silicon-oxynitride field-effect transistors
Authors: Ishibashi Kouichirou , Matsumura Masakiyo
Published: February 2003

The high performance amorphous-silicon field-effect transistors were fabricated by applying silicon oxynitride as the gate insulator and high quality amorphous-silicon film as the active layer. The on-off current ratio was about 107, and the drain current varied by six orders in magnitude while the gate voltage varied by only 3 V. The field-effect mobility was as high as 1.9 cm2/V s, which is several times higher than the one reported to date.
Characterization of ion implanted and laser annealed polycrystalline Si by a Raman microprobe
Authors: Nakashima S. , Inoue Y. , Miyauchi M. , Mitsuishi A. , Nishimura T. , Fukumoto T. , Akasaka Y.
Published: February 2003

The Raman frequency, intensity, and bandwidth of the ion implanted and cw laser annealed polycrystalline Si films have been measured by the Raman microprobe with a spatial resolution of 1 μm. The crystallinity estimated from these quantities changes drastically at the boundary region between the annealed and amorphous regions which is 6∼8 μm in width. The polarization measurement of the Raman scattering enables the estimation of grain size of the annealed region.
Evidence of intrinsic double acceptor in GaAs
Authors: Yu Phil Won , Mitchel W. C. , Mier M. G. , Li S. S. , Wang W. L.
Published: February 2003

Acceptors present in undoped p-type conducting GaAs have been studied with photoluminescence, temperature-dependent Hall measurements, deep level transient spectroscopy, and spark source mass spectrometry. It is shown that p-type conduction is due to presence of the shallow acceptor CAs and the cation antisite double acceptor GaAs. The first and second ionization energies determined for GaAs are 77 and 230 meV from the valence-band edge.
Integrated multilayer GaAs lasers separated by tunnel junctions
Authors: van der Ziel J. P. , Tsang W. T.
Published: February 2003

An integrated multilayer laser consisting of three double heterostructure GaAs laser diodes connected in series by reversed biased p+n+ tunnel junctions have been grown by molecular beam epitaxy. The lasers operate at currents comparable to single double heterostructure lasers but at approximately three times the single laser voltage.
Ultrasonic-wave generation by harmonic heating in composite structures
Authors: Wetsel Grover C.
Published: February 2003

A one-dimensional theory of the generation of ultrasonic waves by photoacoustic absorption in a composite structure is described. The model consists of a backing material, an absorbing bulk or surface film, and a sample. Variations of ultrasonic amplitude and intensity with structure dimensions, optical absorption coefficient, frequency, and material parameters are discussed and compared with reported experimental data. It was found that the important material group—for both backing and film or sample—is α(D)1/2, where α is effectively a thermal-expansion coefficient and D is the thermal diffusivity. The relevance of the parameters in the heated volume to imaging is discussed.
Forming ohmic contacts in CdSe thin-film transistors by dc sputter etching
Authors: Luo F. C. , Freeman E. C. , Slowik J. H. , Poleshuk M.
Published: February 2003

dc sputter etching is used in the photolithographic fabrication of CdSe thin-film transistors to clean the interfaces between Cr or Cr-Au source-drain contacts and CdSe. To evaluate the effects, the devices are tested by both I-V characteristics and transient-reponse-charge injection measurements. The results indicate that dc sputter etching improves the contacts significantly. The charge injection of cleaned contacts approaches the theoretical maximum (ohmic) value.
Deep levels in cw laser-crystallized silicon thin films
Authors: Johnson N. M. , Moyer M. D. , Fennell L. E.
Published: February 2003

Electronic defect levels in cw laser-crystallized silicon thin films have been measured with deep level transient spectroscopy. Polycrystalline silicon thin films were deposited on thermal oxides over single-crystal silicon and crystallized with a scanning cw Ar-ion laser. Hole-emission spectra, recorded on inverted metal-oxide-silicon capacitors with p-type conductivity, reveal a continuous distribution of deep levels in the lower-half of the silicon band gap. There is no evidence of discrete energy levels with densities ⩾1×1014 cm−3, and its proposed that defect levels at the Si-SiO2 interface are a major source of emission centers in crystallized silicon thin films, along with grain boundaries which can also contribute a continuous defect distribution.
Low-frequency behavior of coupled Josephson junctions near phase locking
Authors: Jain A. K. , Likharev K. K. , Lukens J. E. , Sauvageau J. E.
Published: February 2003

It is shown that the external behavior of a cell of two interacting Josephson junctions in the vicinity of phase locking is quantitatively the same as that of a single equivalent resistively shunted junction operated at the difference frequency of the two interacting junctions, as predicted by perturbation theory. Steps of constant voltage difference closely obeying the familiar Bessel dependence are observed when an external current with a frequency equal to the difference of the two Josephson frequencies is applied.
Supersonic gas shell for puff pinch experiments
Authors: Smith Richard S. , Doggett Wesley O. , Roth I. , Stallings Charles
Published: February 2003

An easy-to-fabricate, conical, annular supersonic nozzle has been developed for use in high-power, puff gas z-pinch experiments. A fast responding conical pressure probe has also been developed as an accurate supersonic gas flow diagnostic for evaluating the transient gas jet formed by the nozzle. Density profile measurements show that the magnitude and radial position of the gas annulus are fairly constant with distance from the nozzle, but the gas density in the center of the annulus increases with distance from the nozzle.
Theory of resonant scattering in semiconductors due to impurity central-cell potentials
Authors: Sankey Otto F. , Dow John D. , Hess Karl
Published: February 2003

Electron scattering by the central-cell defect potential of a substitutional sp3-bonded impurity or vacancy in a zincblende host is considered. Significant scattering of electrons can occur if a ’’deep resonance’’ lies slightly above the conduction-band edge. The theory is applied to scattering of electrons by defects in GaAs.
Compact integrated dc SQUID gradiometer
Authors: de Waal V. J. , Klapwijk T. M.
Published: February 2003

An all-niobium integrated system of first-order gradiometer and dc suprconducting quantum interference device (SQUID) has been developed. It is relatively simple to fabricate, has an overall size of 17×12 mm and a sensitivity of 3.5×10−12 T m−1 Hz−1/2.
Observation of optical signatures of materials
Authors: Cox I. J. , Hamilton D. K. , Sheppard C. J. R.
Published: February 2003

A new technique for the study of surfaces is described, whereby materials with different optical properties may be identified from characteristic responses, and which may be developed to give measurements of the optical properties. The technique is similar to one already used in acoustic microscopy.
Four-wave mixing via optically generated free carriers in Hg1−xCdxTe
Authors: Yuen S. Y.
Published: February 2003

Four-wave mixing experiments are used to study the variation of the third-order susceptibility χ(3), with frequency difference Δω and laser intensity I in low carrier concentration HgCdTe crystals. At small Δω, χ(3) is caused by nonparabolicity of free electrons generated by two-photon absorption, with χ(3) scaling as Δω−1 and I2/3. The Δω variation of χ(3) indicates that the electron thermalization time is longer than 8 ps. At large Δω, χ(3)≃3×10−8 esu is mainly due to bound electrons.
Lasing properties of InGaAsP buried heterojunction lasers grown on a mesa substrate
Authors: Oron M. , Tamari N. , Shtrikman H. , Burrus C. A.
Published: February 2003

The lasing properties of InGaAsP crescent-shape mesa substrate buried heterojunction (CMSB) lasers emitting at 1.3 μm are described. Threshold currents as low as 20 mA have been observed with a temperature sensitivity T0 = 97 °C. An external differential quantum efficiency (two facets) of up to 54% was observed. This combination of the characteristics is directly attributed to the device structure which is specially designed to decrease lateral leakage current. Single transverse and longitudinal mode operation was realized with output powers of at least 5 mW per facet.
Transducer effects in acoustic scattering measurements
Authors: Johnson Richard K. , Devaney A. J.
Published: February 2003

An expression for the electrical input-output response of a circularly symmetric reciprocal electroacoustic transducer is developed for the case of scattering from a layered elastic half-space aligned perpendicular to the transducer axis. The model represents the acoustical output and input of the transducer as angular spectra of plane waves. The expression is in the form of a one-dimensional integral transform (over angles of incidence) of the reflection coefficient for the half-space and is valid for arbitrary separation distances. Good agreement between calculation and measurement is obtained for the case of reflection from an elastic plate.
Time-resolved measurements of stimulated surface polariton wave scattering and grating formation in pulsed-laser-annealed germanium
Authors: Ehrlich D. J. , Brueck S. R. J. , Tsao J. Y.
Published: February 2003

Nanosecond resolution optical probe measurements of the growth of surface ripples in pulsed-laser-annealed Ge are reported. The ripples are shown to arise from stimulated scattering of the incident laser light into surface polariton waves at the air/liquid/solid interfaces which form during the optical excitation. These surface waves grow exponentially from spontaneous scattering via feedback involving modulation of the velocity of the liquid/solid interface. The final ripple structure results from the density change on melting coupled with transverse diffusional processes during the regrowth.
Low-noise GaAs field-effect transistor made by molecular beam epitaxy
Authors: Feng M. , Eu V. K. , D’Haenens I. J. , Braunstein M.
Published: February 2003

Low-noise GaAs metal-semiconductor field-effect transistors (MESFET’s) have been made using molecular beam epitaxy. A noise figure of 1.47 dB with 9.9-dB associated gain has been achieved at 12 GHz, with a 0.6-μm gate length by 300-μm gate width FET device. These are the best results yet reported for low-noise molecular beam epitaxial (MBE) GaAs FET’s, and comparable to the best performance devices made with vapor phase epitaxy and ion implantation. Equivalent circuit elements have been evaluated in an effort to understand the critical parameters necessary to achieve these results.
Impurity redistribution in GaAs metalorganic vapor phase epilayers
Authors: Huber A. M. , Morillot G. , Bonnet M. , Merenda P. , Bessonneau G.
Published: February 2003

This letter reports new experimental results using the secondary ion mass spectrometry technique for quantitative determination of Mg, Cr, Mn, Fe in gallium arsenide layers grown on semi-insulating substrates by means of metalorganic vapor phase epitaxy. Mg amd Fe accumulation at the interface and variable residual impurity levels were found in these layers.
Hydrogen annealing of silicon gate-nitride-oxide-silicon nonvolatile memory devices
Authors: Topich James A. , Turi Raymond A.
Published: February 2003

A hydrogen annealing study of silicon gate-nitride-oxide-silicon (SNOS) nonvolatile memory devices showed that the important parameter in determining the optimum hydrogen annealing temperature for maximum charge retention is the previous thermal history of the memory devices. If a memory device’s charge retention is not degraded by high-temperature processing, then the hydrogen anneal should be at the silicon nitride deposition temperature. If a device is degraded by high-temperature processing, then the hydrogen anneal should be at the degradation temperature.
Electrical rectification caused by lamellar microstructures in platinum-doped TiO2−x ceramics
Authors: Meitzler A. H. , Shinozaki S. S. , Donlon W. T.
Published: February 2003

A heat treatment combining cyclic oxidation/reduction with an applied electric field is described that enhances the diffusion of Pt into TiO2−x ceramics and causes a reaction product of PtTi3 to be formed. The PtTi3 forms as lamellar microstructures within the TiO2−x rutile grains. The ceramics produced by this heat treatment have markedly altered electrical properties showing room-temperature conductivities increased several orders of magnitude and asymmetrical conductivity (rectification) characteristics.
Raman scattering with nanosecond resolution during pulsed laser annealing of silicon
Authors: von der Linde D. , Wartmann G.
Published: February 2003

The development of the anti-Stokes to Stokes ratio of spontaneous Raman scattering in silicon is measured during annealing with a 10-ns laser pulse. Raman measurements with weak UV probe pulses avoid averaging over the penetration depth of the annealing pulses. The data suggest that the surface temperature rises above the melting point for exposure energies greater than 0.35 J/cm2. The absolute temperature inferred from the Raman experiments are subject to some uncertainty because of a lack of information on the temperature dependence of the Raman scattering cross sections.
Large conductivity changes in ion beam irradiated organic thin films
Authors: Forrest S. R. , Kaplan M. L. , Schmidt P. H. , Venkatesan T. , Lovinger A. J.
Published: February 2003

Using 2-MeV Ar+ ion beam irradiation, we have generated conducting patterns in otherwise high resistivity, organic thin films of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 1,4,5,8-napthalenetetracarboxylic dianhydride (NTCDA), and Ni phthalocyanine (NiPc). The room-temperature resistivity of the films changes by 14 orders of magnitude from its as-deposited value of ρ≳1010 Ω cm to ρ≅5×10−4 Ω cm at ion doses of 1017 cm−2. The temperature (T) dependence of the resistivity follows ρ(T)∝exp[+(T0/T)1/2] over a wide range of dose and temperature. The characteristic temperature T0 is found to be a function of dose. The exp(T0/T)1/2 behavior of ρ(T) is consistent with charge transport due to hopping between isolated, conducting islands.
CdTe-HgTe multilayers grown by molecular beam epitaxy
Authors: Faurie J. P. , Million A. , Piaguet J.
Published: February 2003

Monocrystalline multilayers CdTe-HgTe have been grown for the first time using the molecular beam epitaxy (MBE) technique. A multilayer consisting alternately of CdTe (44 Å thick) and HgTe (180 Å thick), repeated 100 times, has been grown at 200 °C with a good crystal quality. As for epilayers grown by MBE the crystallinity of the multilayers is improved by a raise in substrate temperature; moreover, the crystal quality is higher for HgTe than for CdTe up to 200 °C. An upper limit of 40 Å for the interdiffusion depth between HgTe and CdTe layers has been determined from Auger electron spectroscopy and ion microprobe profiling measurements carried out on a 13 1/2 -period multilayer, each period consisting of 150 Å for the CdTe layer and 400 Å for HgTe layer. We have also observed that no decrease occurs in the peak-to-valley ratio Auger signals if the focus of the electron gun is maintained at the center of the ion crater, during all the analysis, using the secondary electron image.
Magneto-optical studies on cobalt substituted MnSb films
Authors: Vijayaraghavan M. S. , Sivaramakrishnan V.
Published: February 2003

Optical and magneto-optical studies MnSb films substituted with 20 at. % of cobalt have been carried out. The results suggest the possibility of these being considered as potential candidates for magneto-optic storage.
Passive (self-pumped) phase conjugate mirror: Theoretical and experimental investigation
Authors: Cronin-Golomb Mark , Fischer Baruch , White Jeffrey O. , Yariv Amnon
Published: February 2003

We report the results of a theoretical and experimental investigation of a passive (self-pumped) phase conjugate mirror. This device is based on real time holography in materials which allow a spatial phase shift between the refractive index grating and the light interference pattern. An imaging experiment is reported showing the phase conjugating nature of the device. The holographic medium used was a single crystal of barium titanate.
Characterization of phase noise in semiconductor lasers
Authors: Piazzolla S. , Spano P. , Tamburrini M.
Published: February 2003

Phase noise in semiconductor lasers has been investigated by many authors in the range of low frequencies (<1 MHz). In this letter we present for the first time phase noise measurements extended up to frequencies greater than 1 GHz. Experimental results showing the power spectral density Sφ̇(ω) of the instantaneous frequency φ̇(t) and the variance σ2[Δτφ(t)] of the phase shift Δτφ(t) are presented. The peculiar behavior of Sφ̇(ω), which presents a sharp peak at the same frequency of the amplitude noise peak, can account for the excessive broadening of the linewidth of single-mode injection lasers.
NiSi2-Si infrared Schottky photodetectors grown by molecular beam epitaxy
Authors: Harrison T. R. , Johnson A. M. , Tien P. K. , Dayem A. H.
Published: February 2003

We report the first infrared sensitive (λ≳1 μm) Schottky photodetector using nickel disilicide (NiSi2) grown expitaxially on a silicon substrate by molecular beam expitaxy. Measurements utilizing the 1.32-μm line of a neodymium yttrium aluminum garnet (Nd:YAG) laser indicate a barrier height of 0.64 eV and a quantum efficiency of 0.22%. The use of silicon technology has the potential of integrating the detector with electronics on a monolithic chip of silicon. Such systems are attractive for optical communication applications in the 1.3-μm wavelength region.
Fabrication of surface-channel charge-coupled devices with ultralow density of interface states
Authors: Saks Nelson S.
Published: February 2003

Surface-channel charge-coupled devices (CCD’s) have been fabricated with ultralow density of (fast) interface states in the range 1–3×108/cm2 eV. This low interface state density is achieved by hydrogen implantation into the metal-nitride-oxide-silicon (MNOS) insulator structure of the CCD as the final fabrication step after aluminum interconnect metallization. The CCD’s are shown to have excellent operating characteristics including high transfer efficiency (∼0.99995 without bias charge), low dark current (0.25–0.50 nA/cm2 at 20°C), and high signal charge capacity (1.55×1012 e/cm2 for 10-V clock swing).
Diffusion of deuterium and hydrogen in crystalline LiNbO3
Authors: Gonzalez R. , Chen Y. , Tsang K. L. , Summers G. P.
Published: February 2003

The diffusion coefficient of D+ in LiNbO3 single crystals at elevated temperatures has been measured by monitoring the growth of the OD− optical absorbance in samples heated in D2O vapor. The diffusion coefficient at 873 K is ∼5×10−8 cm2/s for diffusion either parallel or perpendicular to the z axis, and the activation energy parallel to the z axis is 1.4 eV.
Effect of p-n junction position on the performance of InGaAsP light emitting diodes
Authors: Temkin H. , Joyce W. B. , Chin A. K. , DiGiuseppe M. A. , Ermanis F.
Published: February 2003

The power-speed relationship of 1.3-μm InGaAsP light emitting diodes is examined as a function of the p-n junction position within the active layer. It is shown that a gradual displacement of the p-n junction into the InGaAsP layer results in devices with increased speed and lower output power. To account for the experimental findings junction displacement is modeled in terms of both electron and hole injection.
Orientation selection by zone-melting silicon films through planar constrictions
Authors: Atwater H. A. , Smith Henry I. , Geis M. W.
Published: February 2003

Recrystallization of encapsulated Si films on SiO2 by zone-melting produces films composed of several grains approximately 1 mm wide and extending the length of the scan. Within grains there are sub-boundaries. We report a technique for producing recrystallized Si films of a single orientation. The technique consists of patterning polysilicon with a narrow, planar constriction and passing a molten zone through it so that only one orientation propagates beyond the constriction. We also show that sub-boundaries can be eliminated in the constriction.
Patterned silicon molecular beam epitaxy with submicron lateral resolution
Authors: Bean J. C. , Rozgonyi G. A.
Published: February 2003

Patterned epitaxial silicon films are grown on silicon substrates by molecular beam deposition (MBE) through an oxide masking layer. Epitaxial patterns faithfully reproduce the oxide mask, which is fabricated by conventional photolithographic processes. Resolution is determined solely by the mask, and linewidths below 1 μ are demonstrated. Sample morphology and crystallinity are examined by scanning and transmission electron microscopy, and Nomarski interference contrast microscopy in conjunction with chemical defect etching. These techniques confirm that patterned films are epitaxial and free of observable defects. A chemical liftoff step dissolves the oxide mask and leaves an elevated silicon pattern. Patterned film growth requires no modification to the MBE apparatus.
New method for generation of Josephson pulses
Authors: Iguchi I. , Nishiura A.
Published: February 2003

A new circuit which generates ultrashort Josephson pulses is presented. The experiments verify the operational principle. Pulse duration, pulse repetition rate, and pulse delay with respect to the trigger output are adjustable from outside the cryostat system. Some application to nonequilibrium superconductivity is given.
Observation of fluxon propagation on Josephson transmission line
Authors: Matsuda A. , Uehara S.
Published: February 2003

This letter reports on the observation of a single fluxon propagating on a Josephson transmission line (JTL). The JTL used has a Nb/Nb-oxide/Pb tunnel structure with a 50-μm width and a 1-cm length. Output signals from the JTL are directly measured by using minicomputer signal processing. The obtained waveform and the threshold property agree with the theoretical results.