bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical stability of narrow stripe, proton-isolated AlGaAs double heterostructure lasers with gain guiding
Authors: Salemink H. W. M. , Biesterbos J. W. M.
Published: February 2003

Optically stable, proton-isolated, gain-guided (AlGa)As double heterostructure injection lasers are described. A narrow stripe width (3.5 μm) and a very shallow implantation are employed (1.3 μm from the active layer); this results in a cosh−2-like optical mode of ∼9.0-μm full width at half-maximum. The far-field profiles possess strong sidelobes at high optical output power. The optical material loss coefficient and the antiguiding parameter are derived from the measured far-field profiles, using the theory of gain guiding. Key parameters in the description of the optical mode distribution are calculated for several values of output power.
Experimental verification of electron-hole recombination theory for Si-SiO2 interface traps with nonequilibrium, steady-state, admittance measurements
Authors: Agarwal A. K. , Rhodes F. M. , White M. H.
Published: February 2003

An analytical and experimental study of deep level Si-SiO2 interface traps is presented for small-signal, admittance measurements on a gated-diode structure. This technique eliminates the minority-carrier capture process and allows the competing emission process to dominate near the middle of the Si band gap. First-order rate kinetics has been employed to predict the behavior of the nonequilibrium, steady-state, occupancy function and ‘‘trap conductance’’ for states in the midgap region. Theory predicts and experimental measurements verify a sudden decrease or ‘‘pinning’’ of the trap conductance. The ratio of electron to hole capture cross sections, R=σn/σp, has a pronounced influence on the trap energy associated with the onset of ‘‘pinning’’, UTP= 1/2 ln(R).
Characterization of WSix/GaAs Schottky contacts
Authors: Ohnishi T. , Yokoyama N. , Onodera H. , Suzuki S. , Shibatomi A.
Published: February 2003

The Schottky diode characteristics of WSix contacts on n-type GaAs have been investigated and correlated to the film stress in WSix and crystallographic properties of the film. Experimental results show that (1) the high-temperature stability of WSix/GaAs Schottky diode characteristics depends significantly on Si content; (2) WSix/GaAs contacts exhibit very high-temperature-stable Schottky diode characteristics at Si content around 0.60, and at this Si content no metallurgical interactions between WSix and GaAs are observed by 2-MeV 4He+ Rutherford backscattering (RBS) measurements; (3) the optimum Si content for Schottky diode characteristics coincides with that for stress minimum in WSix; (4) the Schottky diode characteristics are not affected by whether WSix is crystallized or not, and a common feature of the regions where the Schottky diode characteristics are very high-temperature stable is that each consists of single-phase (W5Si3 secondary solid solution or amorphous).
Passive mode locking of a long pulse XeCl laser
Authors: Watanabe S. , Watanabe M. , Endoh A.
Published: February 2003

Passive mode locking has been achieved in a XeCl laser with the gain duration over 150 ns. The saturation characteristics of absorber dyes including BBQ, BPBD, and PTP were measured, resulting in the lowest saturation intensity of BBQ. The almost 100% modulated train of 12 pulses was achieved with the rapid pulse sharpening to the duration of ∼2 ns, when BBQ was used as a saturable absorber.
Gain on the green (504 nm) excimer band of I2
Authors: Killeen K. P. , Eden J. G.
Published: February 2003

Gain on the green excimer band (λ∼504 nm) of the iodine dimer has been observed in electron-beam-pumped mixtures of Ar (or Ne), and hydrogen iodide. A peak gain coefficient of γ>1.1% cm−1 is measured at 506 nm with a tunable dye laser and the full width at half-maximum (FWHM) of the gain spectrum in Ar diluent is 13 nm. Temporally resolved gain and fluorescence measurements show that the green emission originates from an I2 ion pair state other than D′. However, strong collisional coupling between the upper states of the UV (λ=342 nm) and green bands and superfluorescence on the UV band (I342∼2 MW cm−2) appear to limit the green gain coefficient to <20% of its small-signal value. Consequently, suppression of superfluorescence on the UV D′→A′ bands of the homonuclear halogens should lead to a new family of excimer lasers with wavelengths extending from the green into the ultraviolet.
Enhanced frequency modulation in cleaved-coupled-cavity semiconductor lasers with reduced spurious intensity modulation
Authors: Tsang W. T. , Olsson N. A.
Published: February 2003

We have observed enhanced analog frequency modulation in a cleaved-coupled-cavity (C3) laser. One diode is dc biased above threshold to produce the desired output power and the other diode, the modulator, is biased below threshold with a dc current and a small modulating current superimposed to achieve analog frequency modulation of the output beam. Comparing with direct analog frequency modulation of a conventional semiconductor laser, the C3 laser has allowed us to obtain significantly larger frequency deviation with negligible spurious intensity modulation. Further, the present frequency modulation response is also much more uniform with respect to modulation frequency. In addition, this scheme is applicable to C3 lasers formed from all laser structures.
Electronic wavelength tuning with semiconductor integrated etalon interference lasers
Authors: Antreasyan Arsam , Wang Shyh
Published: February 2003

A novel method for broadband quasicontinuous wavelength tuning in GaAs-GaAlAs semiconductor lasers is reported. The wavelenth tuning experiment is performed with an interferometric laser consisting of a resonator with curved and straight segments. By separately pumping different segments of the laser the output wavelength can be tuned over a wide range. The outstanding features of the device are (1) very stable single longitudinal mode and stable transverse mode operation, and (2) a wavelength tuning range of as much as 90 Å.
Epitaxial InP/fluoride/InP(001) double heterostructures grown by molecular beam epitaxy
Authors: Tu C. W. , Forrest S. R. , Johnston W. D.
Published: February 2003

We report the first epitaxial semiconductor-dielectric-semiconductor (SDS) double heterostructures using the III-V compound semiconductor InP. The samples, InP/CaF2/InP(001) and InP/BaxSr1−xF2/InP(001), were grown by molecular beam epitaxy and have lattice mismatches of −6.9% and +2.0%, respectively. In situ high-energy electron diffraction showed that the initial stage of epitaxy of the InP/fluoride structure, unlike that of the fluoride/InP structure, exhibits pseudomorphism. Analysis of the electrical properties of SDS devices with an insulator thickness of ∼100 Å indicates both Ohmic and trap-assisted tunneling conduction.
Sputtered Schottky barrier solar cells on p-type GaAs
Authors: Edweeb Mousa E. , Charlson E. J. , Charlson E. M.
Published: February 2003

Schottky barrier solar cells have been produced on single crystal p-type GaAs by sputtering gold to form the barrier. The rectifying action for the gold sputtered p-type device is unique to the method since normal thermal evaporated gold onto p-type produced Ohmic contacts. The opposite behavior was observed for n-type GaAs. Barrier heights have been measured for both p-type (sputtered) and n-type (thermal) diodes using current-voltage and capacitance-voltage methods and are 0.90 and 0.95 eV, respectively. The power conversion efficiencies without AR coatings have values of 6.56% (p) and 5.58% (n). Deep level transient spectroscopy has been used to identify the trap center concentrations and energy levels for both diodes to account for the relatively large dark currents in the p-type (sputtered) diodes.
Deep level impurities and current collection in CdS/CdTe thin-film solar cells
Authors: Isett L. C.
Published: February 2003

Current collection in thin-film CdS/CdTe solar cells prepared by close-spaced sublimation is limited to the depletion region. The width of the depletion region is altered by minority-carrier trapping under light bias. The deep levels responsible for this phenomenon have been identified by deep level transient spectroscopy (DLTS). Heat treatment at 373 K changes the energy distribution of the deep levels. Heat treatment with illumination produces an energy level distribution greatly different from that produced by heat treatment without illumination. The observed photocapacitance changes are understood in terms of the emission rates measured in DLTS.
Wavelength-selective absorption enhancement in thin-film solar cells
Authors: Sheng Ping , Bloch A. N. , Stepleman R. S.
Published: February 2003

We present the general principle of wavelength-selective enhancement of absorption in thin-film solar cells by a periodic grating substrate. By exact numerical calculation we demonstrate that substantial short-circuit current gains are realizable in thin-film amorphous silicon (a-SiHx) solar cells. In particular, for a 0.5-μm-thick a-SiHx solar cell, optimal texturing of an Ag substrate to form a one-dimensional reflective grating can yield a 2-mA/cm2 enhancement over the flat substrate case. For a two-dimensional cross-hatched grating substrate the enhancement is estimated to be 3.5–4 mA/cm2.
Incoherent light-induced diffusion of arsenic into silicon from a spin-on source
Authors: Borisenko V. E. , Larsen A. Nylandsted
Published: February 2003

A new approach to impurity diffusion in semiconductors based on the use of a spin-on source and short-time incoherent light exposure has been developed and experimentally investigated for arsenic diffusion into silicon. Arsenic-doped oxide films, ∼0.19 μm thick, were spin-on deposited onto 〈100〉 oriented silicon crystals and heated with radiation from a xenon lamp to temperatures between 950 and 1200 °C for times of 10 and 25 s. Arsenic diffused layers tested with resistivity measurements and Rutherford backscattering analysis were characterized by a maximum surface concentration ∼1×1020 atom/cm3 and a maximum depth ∼0.40 μm.
Resonant tunneling through quantum wells at frequencies up to 2.5 THz
Authors: Sollner T. C. L. G. , Goodhue W. D. , Tannenwald P. E. , Parker C. D. , Peck D. D.
Published: February 2003

Resonant tunneling through a single quantum well of GaAs has been observed. The current singularity and negative resistance region are dramatically improved over previous results, and detecting and mixing have been carried out at frequencies as high as 2.5 THz. Resonant tunneling features are visible in the conductance-voltage curve at room temperature and become quite pronounced in the I-V curves at low temperature. The high-frequency results, measured with far IR lasers, prove that the charge transport is faster than about 10−13 s. It may now be possible to construct practical nonlinear devices using quantum wells at millimeter and submillimeter wavelengths.
Energy levels and alloy scattering in InP-In (Ga)As heterojunctions
Authors: Bastard G.
Published: February 2003

We present the results of self-consistent variational calculations for the energy levels and wave functions of modulation-doped InP-In(Ga)As heterojunctions. With the variational wave functions we calculate the electron scattering by alloy disorder. Retaining the bulk In(Ga)As value (∼0.6 eV) for the alloy disorder potential the mobility limited by alloy disorder is only ∼2×105 cm2/Vs for ne ∼3×1011 cm−2.
Inequality of semiconductor heterojunction conduction-band-edge discontinuity and electron affinity difference
Authors: Bauer Robert S. , Zurcher Peter , Sang Henry W.
Published: February 2003

The commonly used Anderson electron affinity rule is shown not to provide the band-edge offsets at the interface between different semiconductors. Using synchrotron radiation excited photoelectron spectroscopy, we determine electron affinities χ of 4.14 +0.17−0.09 eV for a Ge(110) surface and of 4.15 +0.17−0.09 eV for a 18-Å GaAs(110) epitaxial overlayer on Ge(110). In the same experiment, for the same layers, a conduction-band discontinuity ΔEc of 0.54±0.08 eV is measured for the heterojunction of GaAs grown by molecular beam epitaxy on Ge(110). Compilation of data on 14 recent photoemission studies confirms that ΔEc≠Δ χ for most heterojunction systems investigated to date.
Estimation of alloy scattering potential in ternaries from the study of two-dimensional electron transport
Authors: Basu P. K. , Nag B. R.
Published: February 2003

A theory of alloy scattering of two-dimensional electron gas in ternary semiconductors is developed by assuming spherically symmetric square scattering potential, randomly distributed between two kinds of alloy sites. The theory predicts a temperature independent mobility, in agreement with the experimental results for In0.53Ga0.47As. The calculated value at 4.2 K comes close to the experimental value, in which the effect of impurity scattering has been reduced by using an undoped spacer layer. It is concluded that the study of two-dimensional transport in the devices may lead to a correct estimation of the alloy scattering potential.
Ferromagnetic multifilamentary Fe and Ni wires with high coercive fields produced by powder metallurgy processing
Authors: Yao Y. D. , Foner S.
Published: February 2003

Powder metallurgy processed multifilamentary Cu-Fe, Cu-Ni, and Nb-Ni ferromagnetic composite wires were fabricated with a relatively high coercive field Hc at room temperature. Compacts of Cu-36 wt. % Fe, Cu-36 wt. % Ni, and Nb-36 wt. % Ni powders were reduced in cross section to produce ferromagnetic multifilamentary materials. Nominal areal reduction ratios of 108 for Cu-36 wt. % Fe and 104 for Nb-36 wt. % Ni and Cu-36 wt. % Ni resulted in values of Hc ∼195 Oe, 94 Oe, and 77 Oe, respectively. A final 300 °C anneal of the Cu-36 wt. % Fe composite gave Hc ∼460 Oe. The average ferromagnetic fiber diameters are estimated to be 100–1000 Å for the Fe fibers and are about 1 μm for the Ni fibers.
Direct determination of a radiation damage profile with atomic resolution in ion-irradiated platinum
Authors: Pramanik Dipankar , Seidman David N.
Published: February 2003

The field-ion microscope technique has been employed to determine directly a radiation damage profile, with atomic resolution, in a platinum specimen which had been irradiated at 60 K with 20-keV Kr+ ions to a fluence of 5×1012 cm−2. It is shown that the microscopic spatial vacancy distribution (radiation damage profile) is directly related to the elastically deposited energy profile. The experimentally constructed radiation damage profile is compared with a theoretical damage profile—calculated employing the transport of ions in matter (TRIM) Monte Carlo code—and excellent agreement is obtained between the two. Thus, it is demonstrated that it is possible to go directly from a microscopic spatial distribution of vacancies to a continuous radiation damage profile.
Low-noise 115-GHz receiver using superconducting tunnel junctions
Authors: Pan S.-K. , Feldman M. J. , Kerr A. R. , Timbie P.
Published: February 2003

A 110–118-GHz receiver based on a superconducting quasiparticle tunnel junction mixer is described. The single-sideband noise temperature is as low as 68±3 K. This is nearly twice the sensitivity of any other receiver at this frequency. The receiver was designed using a low-frequency scale model in conjunction with the quantum mixer theory. A scaled version of the receiver for operation at 46 GHz has a single-sideband noise temperature of 55 K. The factors leading to the success of this design are discussed.
Influence of isochronal annealing on superconducting properties, electrical resistivity, and irradiation behavior of amorphous (Mo0.6Ru0.4) 82B18 films
Authors: Söldner L. , Adrian H. , Saemann-Ischenko G.
Published: February 2003

Thin amorphous films of the superconducting metallic glass (Mo0.6 Ru0.4) 82B18 were annealed for 1 h at various temperatures TA up to 650 °C. The structural relaxation caused by the isochronal annealing well below the crystallization temperature leads to a decrease of the critical temperature Tc and to an increase of the electrical resistivity ρ. Subsequently the films were irradiated with high energetic sulphur ions below 30 K. It is shown that the structural effects induced by the heat treatment are opposite to the irradiation effects and can be reversed by the ion irradiation. After high dose irradiation the saturation values of ρ and Tc indicate that the structural states of the amorphous films are identical for all samples independently of the initial stage of relaxation. The experimental results confirm our former interpretation of the irradiation effects in this compound as a smearing of the structure factor S(k).
Tunneling properties of single crystal Nb/Nb2O5/Pb Josephson junctions
Authors: Celaschi S. , Geballe T. H. , Lowe W. P.
Published: February 2003

Preparation of high quality single crystal Nb tunnel junctions based on Nb/Nb2O5/Pb structures is reported. Vm values of 30±10 mV were obtained. The average specific capacitance of these junctions is 0.020±0.002 pF/μm2. From measurements of the oxidation rate, the conductance at high voltage bias, and observations of the tunneling behavior, we show that some characteristics previously associated with oxidized niobium barriers are not intrinsic and are significantly improved when the underlying niobium film is single crystal.
Giant magnetoelastic effects in amorphous ribbons by exciting standing torsional waves
Authors: Hernando A. , Madurga V.
Published: February 2003

We have found that transverse field annealed ribbons of Metglas 2605 SC exhibit shear modulus variations, Δμ effect, larger than 50 and transverse coupling coefficient about 0.99. Excited in standing torsional wave the peak resonant frequency has been measured as a function of the applied tensile stress when a constant dc current was flowing through the ribbon. A simplified model has been developed in order to explain the appearance of such giant values, one order of magnitude larger than any other previously reported. It has been found that the symmetrical distribution of shear strain concerning the longitudinal and transverse ribbon axes is the main source of the magnetoelastic effects enhancement.
Longitudinal mode spectrum of GaAs injection lasers under high-frequency microwave modulation
Authors: Lau K. Y. , Harder Ch. , Yariv A.
Published: February 2003

Experimental observations of the lasing spectrum of a single mode semiconductor laser under continuous microwave modulation reveal that the lasing spectrum is apparently locked to a single longitudinal mode for optical modulation depths up to ∼80%, beyond which the lasing spectrum becomes multimoded, whose envelope width increases very rapidly with further increase in modulation depth. These results are satisfactorily explained by a theoretical treatment which enables one to predict the dynamic lasing spectrum of a laser from its cw lasing spectra at various output powers.
Relative efficiency of 2Hg 79Br, Hg 79Br, and HgBr electric discharge lasers
Authors: Hanson F. E. , Rieger H. , Cavanaugh D. B.
Published: February 2003

The spectra and relative efficiency of 200Hg 79Br, Hg 79Br, and HgBr in a small UV preionized electric discharge laser have been measured. There is a similar improvement in laser energy for both isotopic samples compared to the natural abundance mixture which can be attributed to a narrower gain spectrum and consequent higher peak gain. At the highest output measured, the increase in laser energy was about 25%. We estimate this is due to roughly 15% increase in small-signal gain.
Transient stimulated Raman scattering of femtosecond laser pulses
Authors: May P. G. , Sibbett W.
Published: February 2003

Transient stimulated Raman scattering of amplified pulses from a passively mode-locked ring cw dye laser has been demonstrated to be a useful method for the production of coherent near infrared femtosecond light pulses. Hypershort Stokes radiation is generated in capillary waveguides containing high pressure hydrogen (830 nm, 1265 nm) and methane (752 nm, 964 nm, 1340 nm) and pulse shortening factors as large as 2.9 have been observed.
An optical modulator based on electrocapillarity
Authors: Lea Michael C.
Published: February 2003

An optical modulator based on the electrocapillarity effect has been built and demonstrated. Optically, the device consists of a plane, variable radius circular mirror formed by the contact of mercury and a glass sheet. The mercury is also in contact with an aqueous electrolyte, and the diameter of the mirror is switched between two stable values by applying voltage pulses to the mercury/electrolyte interface. Switching times of 3 ms have been observed.
Phonon assisted gain coefficient in AlGaAs quantum well lasers
Authors: Sugimura Akira
Published: February 2003

The phonon assisted gain coefficient is evaluated theoretically for AlGaAs quantum well lasers by means of a renormalization theory. It is clarified that the phonon assisted gain coefficient saturates strongly with respect to the phonon number. Its maximum value is smaller than the corresponding gain coefficient of the direct transition. The wavelength, where the phonon assisted gain coefficient is maximum, approaches the direct transition wavelength as the pump rate increases.
Independently variable band gaps and lattice constants in GaAsP strained-layer superlattices
Authors: Biefeld R. M. , Gourley P. L. , Fritz I. J. , Osbourn G. C.
Published: February 2003

The capability of independently varying band gaps and lattice constants in ternary strained-layer superlattices has been experimentally demonstrated for the first time. High-quality GaAsxP1−x/GaP superlattices (0<x≤0.62, lattice mismatches up to 2.3%) were grown by metalorganic chemical vapor deposition and their band gaps and lattice constants were measured. The band gaps at each composition agree with calculated values, and differ significantly from the band gaps of bulk alloys with the same lattice constant. This newly demonstrated capability could allow high-quality heterojunction devices to be grown in a variety of lattice-mismatched ternary systems.
Silicon doping in InP grown by molecular beam epitaxy
Authors: Kawamura Y. , Asahi H.
Published: February 2003

Silicon-doped InP layers were grown on (100) InP substrates by molecular beam epitaxy (MBE), and compared with MBE grown Sn-doped InP layers. Room-temperature electron concentrations up to ∼1×1019 cm−3 were successfully achieved with good doping controllability. The electrical optical properties of Si-doped InP layers were comparable with those of Sn-doped InP layers. These results show that Si is a useful n-type dopant in MBE growth of InP layers, especially to obtain abrupt doping profiles.
Photoinduced effects in AgNO3-mica intercalation compounds
Authors: Kambe N. , Yamada Tomoaki
Published: February 2003

Photoinduced optical properties observed for newly synthesized AgNO3-intercalated mica are presented. AgNO3 mica is the first intercalation compound to show photochromism triggered by alternate illumination with 0.4- and 0.8-μm light. Moreover, under continuous illumination with monochromatic light, iterative optical switchings occur between two states. The switchings occur at random, which could be associated with a chaotic state. The system shows large nonlinearity in the illumination power dependence of reflectivity.
I
n s
i
t
u laser heating in a scanning transmission electron microscope
Authors: Hodgson R. T. , Boebinger G. S. , Batson P. E.
Published: February 2003

We have introduced a modest power (50 mW) laser beam into a high resolution scanning transmission electron microscope in order to heat samples to high temperatures and cool them rapidly enough to ‘‘freeze in’’ the effects of the high temperature. Sequential micrographs of the sample taken after 0.1-s heating pulses show, for example, material migration, grain growth, and crystallization of amorphous silicon evaporated on to 50-nm Si3N4 substrates.
Planar monolithic integration of a photodiode and a GaAs preamplifier
Authors: Kolbas R. M. , Abrokwah J. , Carney J. K. , Bradshaw D. H. , Elmer B. R. , Biard J. R.
Published: February 2003

A monolithic optical receiver chip consisting of a pin photodiode and a transimpedance preamplifier on a GaAs semi-insulating substrate is reported. The epitaxial layers for the photodiode are grown by hydride vapor phase epitaxy and the circuit elements are fabricated by selective ion implantation in the semi-insulating substrate. The integration scheme results in a planar surface which simplifies the processing of optoelectronic integrated chips.
Ridged substrate internally diffused stripe AlGaAs laser emitting in the visible wavelength region
Authors: van Oirschot T. G. J. , Valster A. , de Poorter J. A.
Published: February 2003

The ridged substrate internally diffused stripe (RIDS) laser, a new gain-guided AlGaAs diode laser structure emitting light in the short wavelength region, is described. The five-layer structure, including an intermediate n-type Ga1−xAlxAs current blocking layer, is grown by one-step liquid phase epitaxy on a p-type substrate with a mesa etched in the stripe direction. Above the mesa a narrow current injection path is created by local conversion of the blocking layer due to outdiffusion of p-type dopants from the neighboring p-type cladding layer and substrate. Lasers emitting at 770 nm have thus been obtained with cw room-temperature threshold currents of 70 mA and operating stably in the fundamental transverse mode up to pulsed output powers of 100 mW.
Current-voltage transients in (Cd,Zn)S/CuInSe2 solar cells
Authors: Potter R. R. , Sites J. R.
Published: February 2003

Transients in the current-voltage characteristics of (Cd,Zn)S/CuInSe2 solar cells after sudden changes in illumination are reported. The transients are found to vary with bias across the cell, intensity, temperature, illumination wavelength, and recent illumination history. Multiple trapping levels, primarily in the CuInSe2 near the interface, are seen as responsible for the observed dc voltage shift and are photoexcited in less than 1 ms. Relaxation in the dark takes tens of seconds and appears dominated by states in the (Cd,Zn)S which gives wavelength dependent effects on fill factor and transient decay.
Electron mobilities in In0.2Ga0.8As/GaAs strained-layer superlattices
Authors: Fritz I. J. , Dawson L. R. , Zipperian T. E.
Published: February 2003

We report the first Hall effect and resistivity measurements on strained-layer superlattices (SLS’s) in the (In,Ga)As system. The samples, grown by molecular beam epitaxy, had 60 periods of alternating, 120-Å-thick In0.2Ga0.8 As and GaAs layers. Both uniform-doped and modulation-doped structures (with Si donors) were studied. Low-temperature mobilities of over 3×104 cm2/Vs were obtained for structures with doping in only the central 30-Å region of each GaAs layer. Our results are comparable to reported results on similar (Al,Ga)As superlattices, confirming that high crystalline quality can be obtained in SLS’s with significant mismatch (∼1.4%) and many interfaces (>100).
X-ray photoelectron spectroscopy study of the surface chemistry of freon-oxygen plasma etched silicon
Authors: Thomas J. H. , Maa J-S.
Published: February 2003

X-ray photoelectron spectroscopy has been used to study residual film formation on silicon exposed to an oxygen-containing CF4 plasma. Experimental results indicate that the plasma reaction produces a surface phase SixOFy, which varies in thickness with the O content of the plasma. Film thickness is shown to correlate with the previously observed etch rate dependence on oxygen content.
Laser-enhanced jet plating: A method of high-speed maskless patterning
Authors: von Gutfeld R. J. , Gelchinski M. H. , Romankiw L. T. , Vigliotti D. R.
Published: February 2003

We describe a metal deposition technique that combines free-standing jet plating with an intense laser beam, directed collinearly along the jet. Experiments were made to deposit gold areas on nick-plated beryllium-copper substrates. The deposits are found to be crack-free and dense, possessing excellent adhesion to the substrate. Deposition rates for 0.05-cm-diam gold spots are on the order of 10 μm/s, faster than any previously reported rate for gold plating.
Submicron x-ray lithography using laser-produced plasma as a source
Authors: Yaakobi B. , Kim H. , Soures J. M. , Deckman H. W. , Dunsmuir J.
Published: February 2003

X-ray lithography was studied, using laser-produced plasma as a source. A single target shot of a frequency-tripled Nd:glass laser (λ=0.35 μm, 35 J in 1 ns) was found to be sufficient for submicron x-ray lithography in poly(butene-1-sulfone) (PBS) or poly(glycidyl-methacrylate-ethyl acrylate) (COP) resists. The incident x-ray flux is about an order of a magnitude smaller than that normally required. This behavior could be the result of the transient character of the exposure and an abrupt rise in the resist temperature.
Field-effect transistor sensitive to dipolar molecules
Authors: Blackburn Gary F. , Levy Max , Janata Jiří
Published: February 2003

A field-effect transistor with metal gate suspended above the gate insulator has been fabricated. Fluid samples can freely penetrate into the gap formed between the metal and the insulator. If the molecules carry an electrical dipole, they will alter the surface potential on these two materials giving rise to a change in the drain current of the transistor. Our preliminary results confirm this mechanism for dipolar molecules such as methanol and methylene chloride.
High-performance, focusing-type, time-of-flight atom probe with a channeltron as a signal detector
Authors: Sakurai Toshio , Hashizume T. , Jimbo A.
Published: February 2003

We have constructed a focusing-type, time-of-flight atom probe which enables us to focus the ion beam to a spot of ∼1 mm diameter. Under this condition, a channeltron can be used as a signal detector replacing the conventional channel plate. Practically 100% detection efficiency was achieved for the first time in the atom-probe history.
New electron trap in p-type Czochralski silicon
Authors: Mao B.-Y. , Lagowski J. , Gatos H. C.
Published: February 2003

A new electron trap (acceptor level) was discovered in p-type Czochralski (CZ) silicon by current transient spectroscopy. The behavior of this trap was found to be similar to that of the oxygen thermal donors; thus, 450 °C annealing increases the trap concentration while high-temperature annealing (1100–1200 °C) leads to the virtual elimination of the trap. The new trap is not observed in either float-zone or n-type CZ silicon. Its energy level depends on the group III doping element in the sample. These findings suggest that the trap is related to oxygen, and probably to the acceptor impurity as well.
Single mode operation of a current pulsed GaAlAs laser with dispersive external feedback
Authors: Andrews John R.
Published: February 2003

We report the generation of a stable single longitudinal mode in the transient spectrum of a GaAlAs laser diode using dispersive external feedback. The characteristics of the spectral evolution subsequent to a step increase in the drive current can be adequately understood from consideration of temperature induced shift of the gain spectrum and longitudinal modes as a function of time. Operation in a single longitudinal mode is observed from the first few nanoseconds out to steady state for lasers with both index guiding and gain guiding. Over 7 mW of single mode power is observed with an index-guided laser.
Procedure for electron and ion lens optimization
Authors: Szilagyi M. , Yakowitz S. J. , Duff M. O.
Published: February 2003

This letter describes a computational technique for optimal control problems arising in the synthesis of electron and ion lenses. The method provides an effective search algorithm for electrostatic and/or magnetic imaging fields with minimum aberrations. An optimized electrostatic field distribution is given as an example of application.
Doping effects in off-stoichiometric glow discharge amorphous silicon nitride
Authors: Alvarez F. , Chambouleyron I. , Constantino C. , Cisneros J. I.
Published: February 2003

The effects of boron and phosphorus doping on the electrical properties of a-SiNx:H films are studied. The material is obtained by the glow discharge of SiH4 and N2 mixtures. It is found that for Si-rich materials boron doping produces large conductivity variations while phosphorus appears to be a much less efficient dopant. A phenomenological explanation is given assuming that phosphorus prefers to form bonds in accordance with its own valence configuration; i.e., it will go substitutionally to threefold coordinated N sites. Experimental evidence of such behavior obtained from published IR transmission measurements confirms this assumption.
Formation of optically induced catastrophic degradation lines in InGaAsP epilayers
Authors: Mahajan S. , Temkin H. , Logan R. A.
Published: February 2003

The formation of optically induced catastrophic degradation lines (CDL’s) in (001) InGaAsP epitaxial layers has been investigated by transmission electron microscopy. It appears that CDL’s evolve as a result of the temperature-gradient-induced migration of liquid droplets. These droplets could form in pre-existing regions where nonradiative recombination during optical pumping is very high. Further, the propagation of droplets involves dissolution followed by rapid deposition. Consequently, the resulting microstructures are highly defective and consist of decorated dislocations, loops, and precipitates. These features could act as nonradiative recombination centers and thus degrade the material. CDL’s propagate only along the 〈110〉 direction which is common to the {111}In,Ga and (001) planes. In addition, the Burgers vector of dislocations constituting a CDL is parallel to the direction of its propagation. Arguments have been developed to rationalize these observations.
Reduction of silicon-aluminum interdiffusion by improved semiconductor surface ordering
Authors: Brillson L. J. , Slade M. L. , Katnani A. D. , Kelly M. , Margaritondo G.
Published: February 2003

Aluminum overlayers on highly ordered single-crystal silicon (100) and (111) surfaces in ultrahigh vacuum exhibit characteristic interface widths less than tens of angstroms at room temperature and hundreds of angstroms at 400 °C—orders of magnitude more abrupt than conventionally prepared Al-Si contacts. We demonstrate that surface disorder plays a critical role in promoting Si diffusion into the Al overlayer.
Longitudinal mode behavior and tunability of separately pumped (GaAl)As lasers
Authors: Fang Zu-Jie , Wang Shyh
Published: February 2003

A three-segment laser, when separately pumped, shows both frequency switching and continuous tuning with a modulation current applied to the middle segment. The wavelength changes are attributed to gain peak shift with the carrier concentration and carrier-induced index change. A total wavelength change of 61 Å, a continuous tuning range of 4.1 Å, and a tuning rate of −0.74 Å/mA are obtained. The laser may be useful in optical FM fiber communication.
Polyimide passivation of In0.53Ga0.47As, InP, and InGaAsP/InP p-n junction structures
Authors: Yeats R. , Von Dessonneck K.
Published: February 2003

Techniques for passivating In0.53Ga0.47As, InGaAsP, InP, and InGaAsP/InP p-n junction structures with polyimide have been developed. Low stable leakage current is maintained for prolonged bias, even after exposure to high temperatures (∼320 °C) during packaging. 150-μm-diam In0.53Ga0.47As photodiodes with a breakdown voltage of ∼50 V were passivated with polyimide and were found to consistently have leakage currents of ∼10 nA at a 20-V bias.Details of the passivation process are given.
High-energy product Nd-Fe-B permanent magnets
Authors: Croat J. J. , Herbst J. F. , Lee R. W. , Pinkerton F. E.
Published: February 2003

We have explored the hard magnetic properties of melt-spun Nd-Fe-B alloys. A maximum energy product of 14.1 MG Oe has been observed, the highest value ever reported for a light rare earth-iron material. X-ray analyses indicate that the alloys exhibiting optimum characteristics are comprised of roughly spherical crystallites of an equilibrium Nd-Fe-B intermetallic phase. The observed grain sizes are in or near the estimated single-domain range, suggesting that the coercivity arises principally from the formation of single-domain particles.
High-speed optical modulation with GaAs/GaAlAs quantum wells in a p-i-n diode structure
Authors: Wood T. H. , Burrus C. A. , Miller D. A. B. , Chemla D. S. , Damen T. C. , Gossard A. C. , Wiegmann W.
Published: February 2003

A new type of high-speed optical modulator is proposed and demonstrated. An electric field is applied perpendicular to GaAs/GaAlAs multiple quantum well layers using a ‘‘p-i-n’’ diode doping structure of 4-μm total thickness. The optical absorption edge, which is particularly abrupt because of exciton resonances, shifts to longer wavelengths with increasing field giving almost a factor of 2 reduction in transmission at 857 nm with an 8-V reverse bias. The shifts are ascribed to changes in carrier confinement energies in the wells. The observed switching time of 2.8 ns is attributed to RC time constant and instrumental limitations only, and fundamental limits may be much faster.
Time-resolved acoustic pulses generated by 4-MeV protons stopping in aluminum
Authors: Sieger G. E. , Lefevre H. W.
Published: February 2003

Time-resolved acoustic waves generated by pulsed proton beams stopping in aluminum and other solids have been observed. A wide-band capacitive detector indicates the target surface velocity as a function of acoustic time of flight. The near-field signal observed traveling in the beam direction is a measure of the initial pressure distribution along the path of the stopping beam. The measured amplitudes and shapes of such signals are consistent with a simple thermoelastic model of sound generation. Such signals have been used to probe a hydrogen implanted layer in aluminum, and to follow the blistering process in real time while an implanted target was annealed in place.
Bistability in coupled cavity semiconductor lasers
Authors: Dutta N. K. , Agrawal G. P. , Focht M. W.
Published: February 2003

Experimental results on bistable operation of coupled cavity semiconductor lasers are presented. The light level at the upper and lower states can be controlled by varying the injection current. A model calculation of the coupled cavity laser system shows that the bistability is due to nonlinearities associated with above threshold gain saturation. Our results show that a coupled cavity laser can exhibit bistability at all temperatures and, in addition, the size of the ‘‘hysteresis loop’’ can be easily controlled by varying the injection current. These results are significant for a practical bistable optical device.
Observation of Hg diffusion in CdTe by means of 40-MeV O5+ ion backscattering
Authors: Takita K. , Murakami K. , Otake H. , Masuda K. , Seki S. , Kudo H.
Published: February 2003

The diffusion profile of Hg in CdTe crystals was observed by means of heavy ion (40 MeV O5+) backscattering. The near-surface region of CdTe immersed in Hg was investigated up to 1.4 μm from the surface. The observed Hg profile indicated that the concentration of Hg atom at the surface reached 4×1020 cm−3 and the distribution was interpreted by a simple diffusion model. Temperature dependence of the diffusion coefficient was determined to be D=5×103 exp[(−2.0±0.3) eV/kT] (cm2/s). In the case of CdTe immersed in Hg which contained a small amount of Cd, it was found that Hg diffusion did not occur. These experimental facts suggest that the rate of Hg diffusion is controlled by the diffusion of a Cd vacancy which is introduced by the outdiffusion of Cd atoms from CdTe crystals.
Nonlinear carrier dynamics in GaxIn1−xAsyP1−y compounds
Authors: Wintner E. , Ippen E. P.
Published: February 2003

The nonlinear recovery dynamics of optically excited carriers in thin layer samples of GaInAsP (1.3 μm, 1.55 μm) and GaInAs (1.65 μm) have been studied by picosecond optical pump-probe measurements of absorption bleaching using pulses at 1.06 μm for both pump and probe. An evaluation of the data was performed by a careful computer model which takes into account the temporal development of the carrier density and absorption, the spatial averaging of the bleaching, and a convolution with the probe beam. The effective Auger coefficients, determined as curve fitting parameters, were found to be A(1.3 μm)=1.5×10−29 cm6/s, A(1.55 μm) =7.5×10−29 cm6/s, and A(1.65 μm)=9.8×10−29 cm6/s.
Demonstration of a new electrothermal thruster concept
Authors: Whitehair S. , Asmussen J. , Nakanishi S.
Published: February 2003

The design and test of a microwave electrothermal thruster are described. The device, which employs a coaxial microwave discharge, was tested in nitrogen gas with 200–600 W of 2.45-GHz input power. Experimental measurements of thrust, specific impulse, and energy efficiency are presented for different flow and discharge pressures. Measured energy efficiencies varied between 30%–60% and the performance compared favorably with other electrothermal thrusters operating in nitrogen gas. The experimental performance demonstrated the feasibility of the concept.
Extended growth of subgrain-boundary-free silicon-on-insulator via thermal gradient variation
Authors: Lee El-Hang
Published: February 2003

Morphological variations of graphite strip heater recrystallized silicon-on-insulator formed in the initial stage of seeded growth have been analyzed to examine the thermal gradient effect upon the growth stability. Systematic transition of the stable growth into an orderly breakdown of faceted, cellular, and dendritic configurations has been attributed to the decreasing temperature gradient in this region. There are indications that constitutional supercooling could be responsible for the interface stability breakdown and that increased thermal gradients can suppress the onset of breakdown and maintain the stable growth over an extended distance.
Corrections to enhanced optical nonlinearity of superlattices
Authors: Cooperman G. , Friedman L. , Bloss W. L.
Published: February 2003

In recent publications, a large enhancement of the third order nonlinear optical susceptibility was predicted for GaAs–GaAlAs superlattices, as a result of the band nonparabolicities introduced by the additional periodicity of the superlattice. These predictions, based on the tight binding model, are here extended to the more realistic Kronig–Penney model. Results show that corrections to tight binding are non-negligible; however, enhancements of χ(3) are still large, but reduced by approximately 30%–50% over previous estimates.
Brillouin scattering in thin-film waveguides
Authors: Janaky T. P. , Prasada Rao T. A. , Narasimha Rao D. V. G. L. , Narayanaswamy C. K.
Published: February 2003

Brillouin component is observed for the first time along the backscattered m lines in the anisotropic film waveguides. Each order of the forward as well as the backscattered m lines is found to be split into two components and are attributed to the presence of TE and TM modes. Temperature conditions under which the films are made and the thickness of the films are found to be critical. Polystyrene films are used in the investigations as waveguide materials due to their compatibility.
Temperature dependence of threshold current in III-V semiconductor lasers: Experimental prediction and explanation
Authors: Su C. B. , Olshansky R. , Manning J. , Powazinik W.
Published: February 2003

The newly developed differential carrier lifetime and threshold carrier density measurement techniques are applied to temperature-dependent measurements of the recombination rates and threshold carrier density of III-V semiconductor lasers. Quantities obtained from these measurements are used to predict the temperature dependence T0 of the threshold current, which is in excellent agreement with T0 observed at 20 °C for both InGaAsP and AlGaAs lasers. The main causes for the stronger temperature sensitivity of InGaAsP material are due to Auger recombination and a smaller radiative coefficient.
Infrared birefringence of liquid crystals
Authors: Wu Shin-Tson , Efron Uzi , Hess LaVerne D.
Published: February 2003

The first measurements of infrared birefringence of liquid crystals are reported. Continuous birefringence spectral data were calculated from measurements of phase differences which occur when monochromatic polarized light propagates through a medium with an anisotropic refractive index. It was found that molecular absorption bands can provide significant resonant enhancement of the refractive indices of liquid crystals, and this effect causes the birefringence of these materials to be relatively large throughout the spectral region from 2 to 16 μm. The birefringence and absorption spectra of two particular liquid crystal mixtures indicate that liquid crystals will be useful for electro-optic applications in the infrared region.
Pulsed soft x-ray response of InP:Fe photoconductors
Authors: Kania D. R. , Bartlett R. J. , Wagner R. S. , Hammond R. B. , Pianetta P.
Published: February 2003

We report measurements of the energy-dependent pulse response of InP:Fe photoconductors to soft x rays in the energy range 200 eV–3 keV. The experiments were performed with x-ray pulses from the Stanford Positron Electron Asymmetric Ring storage ring at the Stanford Synchrotron Radiation Laboratory. The detector had an optical impulse response of 180 ps (full width at half-maximum) and an active area of 1×1 mm. An array of filters (carbon, magnesium, and beryllium) was used to unfold the energy response of the detector to the soft x rays. Direct measurements of the time structure of the ring bunches were limited by the bandwidth of the real time recording system (400 MHz), but inidividual ring pulses were easily recorded with a detector pulse amplitude of 65 mV for the unfiltered beam. The detector response was constant over the energy range examined at 2.7×10−3 A/W.
Multistability and soliton modes in nonlinear microwave resonators
Authors: Gasch A. , Wedding B. , Jäger D.
Published: February 2003

Nonlinear optical cavities are known to exhibit bistability and multistability. In this letter the properties of microwave Fabry–Perot and ring resonators with second-order dispersive nonlinearity are analyzed. Experimental results such as multiple-valued output versus input characteristics, resonance curves, and waveforms are described. On the basis of harmonic and subharmonic generation a new mechanism is found leading to multistability, which is quantitatively attributed to well-defined soliton modes propagating in the resonator.
High-sensitivity Ga0.47In0.53As photoconductive detectors prepared by vapor phase epitaxy
Authors: Chen C. Y. , Kasper B. L. , Cox H. M.
Published: February 2003

We report a Ga0.47In0.53As photoconductive detector with a receiver sensitivity better than that of a Ga0.47In0.53As pin photodiode. This is the first time that a 1.3-μm, 1-Gbit/s receiver sensitivity for a photoconductive detector as high as −34.4 dBm was achieved at a bit error rate of 10−9. This result represents a 2.9-dB improvement over the Ga0.47In0.53As pin photodiode used in our measurements. Furthermore, this detector can operate with bias voltage less than 2 V, representing a circuit simplicity over certain detectors. Our study concludes that photoconductive detectors are attractive devices for high data-rate lightwave communication applications.
Molecular beam epitaxial growth and material properties of GaAs and AlGaAs on Si (100)
Authors: Wang W. I.
Published: February 2003

We have grown GaAs and AlGaAs on (100) oriented Si substrates by molecular beam epitaxy. The epitaxial growth was studied in situ by reflection high-energy electron diffraction. Low-temperature photoluminescence, Raman scattering, and scanning electron microscopy were used to characterize the epitaxial layers. It is shown for the first time that antiphase disorder could be suppressed. The doped AlGaAs grown directly on Si substrates exhibited PL efficiency similar to that of AlGaAs grown on GaAs substrates.