bluuebunny/crossref_metadata_2025 huggingface dataset:
Stop-cleaved InGaAsP laser monolithically integrated with a monitoring detector
Authors: Antreasyan A. , Chen C. Y. , Napholtz S. G. , Wilt D. P.
Published: July 2002

We report the monolithic fabrication of a stop-cleaved laser with a monitoring detector. Stop-cleaved, double channel planar buried heterostructure lasers with threshold currents of 57 mA have been obtained emitting at 1.3-μm wavelength. For the monitoring detector on the same substrate we have estimated a quantum efficiency of 31% from the measured responsivity of 14.4 μA/mW and the theoretical diffraction coupling efficiency.
Interfacial forces and the fundamental nature of brittle cracks
Authors: Lawn Brian R.
Published: July 2002

A new conception of brittle fracture processes is presented. It is proposed that the crack-tip structure is immutably sharp at the atomic level, such that the attendant growth laws are uniquely determined by the stress intensity factor K of ‘‘fracture mechanics’’ origin. Threshold features in the measured v(K) function for crack growth in interactive environments, previously put forward as evidence for fundamental changes in the tip structure by blunting, are shown to be more consistent with a negative K contribution from interfacial adhesive forces. These adhesive forces should be determinable from the crack velocity characteristics.
Growth of the 889 cm−1 infrared band in annealed electron-irradiated silicon
Authors: Svensson Bengt G. , Lindström J. Lennart , Corbett James W.
Published: July 2002

Isothermal annealing of electron-irradiated Czochralski silicon has been studied at four different temperatures ranging from 304 to 350 °C using infrared spectroscopy. At annealing temperatures above 300 °C the irradiation-induced band at 830 cm−1, usually attributed to a vacancy-oxygen complex (the A center), disappears and a new band at 889 cm−1 grows up. Within the experimental accuracy , the activation energy for the growth of this band is found to be identical with the value given by Stavola et al. for ‘‘anomalous’’ oxygen diffusion in silicon. Also the frequency factors for the two processes are in reasonable agreement. Our results show that a vacancy-assisted process may provide an explanation for enhanced motion of oxygen in silicon.
Phase-matched second harmonic generation by a surface polariton along a silver layer on a slab-type optical waveguide
Authors: Sasaki K. , Kawagishi H. , Ishijima Y.
Published: July 2002

Phase-matched second harmonic generation by a surface-plasmon polariton was observed along a silver layer on a slab-type optical waveguide with a Q-switched neodymium:yttrium aluminum garnet laser (1.064 μm). A numerical analysis previous to the experiment was carried out by a perturbation method employing the conception of coupled modes between surface polariton waves and guided waves. In this case the slab-type optical waveguide played the role of an energy storage layer to realize a longer macroscopic propagation length.
A high-power channeled-substrate-planar AlGaAs laser
Authors: Goldstein B. , Ettenberg M. , Dinkel N. A. , Butler J. K.
Published: July 2002

A channeled-substrate-planar AlGaAs laser has been operated to 190 mW cw, and 170 mW cw in single fundamental spatial mode. A single fundamental spectral mode is observed up to about 70 mW. Beyond 70 mW there are minor increases in spectral sideband power and the far-field pattern broadened asymmetrically with increased drive. Both these effects are attributed to spatial ‘‘hole burning.’’
Lattice and atomic structure imaging of semiconductors by high resolution transmission electron microscopy
Authors: Ourmazd A. , Ahlborn K. , Ibeh K. , Honda T.
Published: July 2002

We show that the new generation of high resolution transmission electron microscopes allows the lattice imaging of semiconductors in at least four crystallographic orientations and present the first atomic structure images of Si, both in the 〈100〉 and 〈111〉 orientations. We demonstrate the ability to lattice image along different orientations such as 〈111〉 and 〈112〉 by tilting between them. Thus, the potential exists to obtain three-dimensional maps of atom positions around individual features of interest such as defects and interfaces.
Refractory metal silicide formation by ion beam mixing and rapid thermal annealing
Authors: Kwong D. L. , Meyers D. C. , Alvi N. S. , Li L. W. , Norbeck E.
Published: July 2002

We have shown that uniform, stoichiometric, low-resistivity refractory metal silicides (MoSi2 and WSi2) can be formed by implanting As ions through respective metal films (Mo and W) deposited on Si and rapid thermal annealing. Rapid diffusion of the implanted As ions is observed during the formation of the metal silicides.
Mixing gasdynamic laser driven by decomposed gas of liquid N2O
Authors: Kitagawa Katsushi , Komatsu Katsuhiko
Published: July 2002

A high-temperature decomposed gas of liquid nitrous oxide is employed as a donor gas in a downstream mixing gasdynamic laser. A small-signal gain and a laser power have been measured as a function of H2O concentration at the CO2 (001)–(100) transition. The maximum gain and power were obtained at ∼0.1% H2O concentration which is almost an order of magnitude smaller than the values reported for the CO2+N2+H2O gasdynamic lasers.
Long range material relaxation after localized laser damage
Authors: Fauchet P. M. , Campbell I. H. , Adar F.
Published: July 2002

We observe, for the first time, structural modifications that extend many microns beyond the area where laser-induced damage is visible by high resolution optical microscopy. These modifications are recorded by a Raman microprobe, which is sensitive to stress and microcrystallinity.
Magneto-optic determinations of the pressure dependence of band-gap energies and effective masses in strained-layer superlattices
Authors: Jones E. D. , Ackermann H. , Schirber J. E. , Drummond T. J. , Dawson L. R. , Fritz I. J.
Published: July 2002

Pressure-dependent magneto-optic studies on strained-layer superlattices have been performed for magnetic fields up to 65 kG and pressures up to 4 kbar in the temperature range of 1.6–4 K. The experimental pressure coefficients of the band-gap energy and the reduced effective mass in both n-type and p-type strained-layer In0.2Ga0.8As/GaAs superlattice structures were determined.
Measurements of dynamic photon fluctuations in a directly modulated 1.5-μm InGaAsP distributed feedback laser
Authors: Choy M. M. , Liu P. L. , Shumate P. W. , Lee T. P. , Tsuji S.
Published: July 2002

We report new results on dynamic photon statistics of 1.5-μm distributed feedback buried heterostructure lasers when driven from below threshold at 1.5-GHz modulation. In contrast to Fabry–Perot lasers, a transient turn-on delay fluctuation in the total power of about 50 ps is observed with no evidence of modal partition. These fluctuations can be explained by the randomized nature of the spontaneous emission. Typically occurring at low frequencies, these turn-on effects can result in system timing errors. This impairment can be eliminated by modulating entirely above threshold or minimized by modulating at frequencies below a few hundred megahertz.
High-power multiple-emitter AlGaAs superluminescent diodes
Authors: Paoli Thomas L. , Thornton Robert L. , Burnham Robert D. , Smith Donald L.
Published: July 2002

A superluminescent AlGaAs diode emitting 350 mW of cw optical power at room temperature has been demonstrated for the first time. This extraordinarily high power for nonlasing operation was achieved by combining efficient quantum well material with an edge-emitting, multiple-emitter, short (250 μm) Fabry–Perot cavity incorporating one highly reflective mirror. Lasing action is suppressed by applying a ZrO2 coating with an ultralow reflectivity to the laser’s output facet. Suppression of the lasing in this way produces the uniform and incoherent radiation pattern required for many applications.
Picosecond excite-and-probe absorption measurement of the 4T2 state nonradiative lifetime in ruby
Authors: Gayen S. K. , Wang W. B. , Petričević V. , Dorsinville R. , Alfano R. R.
Published: July 2002

In a picosecond excite-and-probe absorption measurement, a 527-nm picosecond pulse excites the 4T2 state of the Cr3+ ion in ruby and a 3.4-μm picosecond probe pulse monitors the growth and decay of population in the 2E state as a function of pump-probe delay. From the growth of population in the metastable 2E state, an upper limit of 7 ps for the nonradiative lifetime of the 4T2 state is determined.
Validation of magnetophonon spectroscopy as a tool for analyzing hot-electron effects in devices
Authors: Barker J. R. , Mudares M. , Snell B. R. , Guimaraes P. S. S. , Taylor D. C. , Eaves L. , Hill G.
Published: July 2002

It is shown that very high precision hot-electron magnetophonon experiments made on n+n−n+-GaAs sandwich device structures which are customized for magnetoresistance measurements can be very accurately modeled by a new Monte Carlo technique. The latter takes account of the Landau quantization and device architecture as well as material parameters. It is proposed that this combination of experiment and modeling yields a quantitative tool for the direct analysis of spatially localized very nonequilibrium electron distributions in small devices and low dimensional structures.
Infrared photoluminescence spectra from HgTe-CdTe superlattices
Authors: Hetzler S. R. , Baukus J. P. , Hunter A. T. , Faurie J. P. , Chow P. P. , McGill T. C.
Published: July 2002

We report the first observation of infrared photoluminescence from HgTe-CdTe superlattices. A superlattice grown to have layers of HgTe 38–40 Å thick and layers of CdTe 18–20 Å thick is found to show a peak in the 140-K spectra at 105 meV (11.8 μm). A second superlattice grown to have HgTe layers 50 Å thick and CdTe layers 50 Å thick is found to show a peak at 205 meV (6.0 μm) at 170 K. In both cases, the energy of the luminescence is significantly lower than that for HgCdTe alloys with the same average composition as each sample.
Narrow band infrared detection in multiquantum well structures
Authors: Coon D. D. , Karunasiri R. P. G. , Liu L. Z.
Published: July 2002

A theoretical analysis is performed for photoexcitation of carriers from a quantum well state into a superlattice subband. The parameters of the device structure are chosen so that (a) the first excited state of the quantum well lies within the lowest subband of the superlattice and (b) the lowest subband is narrow. The degeneracy of the first excited state with the subband provides resonant enhancement of photoexcitation into the subband while the subband extrema provide long-wavelength and short-wavelength cutoffs. The response band and bandwidth can be tailored and there is the possibility of high-temperature operation associated with the narrow band response.
Energy levels and electron wave functions in semiconductor quantum wells having superlattice alloylike material (0.9 nm GaAs/0.9 nm AlGaAs) as barrier layers
Authors: Sakaki H. , Tsuchiya M. , Yoshino J.
Published: July 2002

Energy levels and wave functions of carriers are studied both experimentally and theoretically in 4 nm GaAs quantum wells (QW’s), for the case when barriers are formed with alternating layers of 0.9 nm GaAs/0.9 nm AlxGa1−xAs (x=0.39). The photoluminescence spectra of the QW’s are studied at 77 K and are found nearly equivalent to that of conventional QW’s having alloy barriers with Al content of 0.26, which is much higher than the averaged alloy composition (∼0.2). The modified Kronig–Penney analysis is found effective in predicting the observed energy and has clarified a feature of enhanced penetration of wave function into the novel barrier layer.
Thin-film dc SQUID consisting of quasiparticle-injected superconducting weak links
Authors: Kojima K. , Nara S. , Hamanaka K.
Published: July 2002

A thin-film dc superconducting quantum interference device (SQUID) consisting of quasiparticle-injected superconducting weak links was fabricated and successfully operated. This SQUID was made on a silicon substrate and it consists of a ∼100-nm-thick lead alloy with two injector junctions. The characteristics of this dc SQUID are controllable by varying the injecting rate of quasiparticles; therefore, it can be operated at arbitrary temperatures below the transition temperature of the superconducting material.
Single-wavelength operation of the hybrid-external Bragg-reflector-waveguide laser under dynamic conditions
Authors: Hammer J. M. , Neil C. C. , Carlson N. W. , Duffy M. T. , Shaw J. M.
Published: July 2002

Dynamic wavelength stabilization of an AlGaAs diode laser has been demonstrated. The diode laser is butt coupled to a stripe-loaded optical waveguide which contains a Bragg reflecting grating. The laser is pulsed with 50-ns-long, 25% duty cycle, 100% modulation depth pulses and the waveguide output is observed to remain at single wavelengths over a peak current range of 120–160 mA and 15 °C temperature variations.
Monolithic integration of a lens inside a diode-laser cavity for beam convergence
Authors: Mukai S. , Yajima H. , Tsunekawa Y. , Takabe Y.
Published: July 2002

A lens is monolithically integrated inside a diode-laser cavity for the first time. The lens is formed on one end of the mesa-type waveguide by making the equivalent refractive index lower toward the edges of the mesa. The lens makes the phase front of the lasing mode concave at the facet. Correspondingly, a (laterally) converging laser beam is realized without using any separate optical components. A numeric analysis of the beam convergence is also given.
Implications of the configuration-dependent reactive incorporation growth process for the group V pressure and substrate temperature dependence of III-V molecular beam epitaxial growth and the dynamics of the reflection high-energy electron diffraction intensity
Authors: Madhukar A. , Ghaisas S. V.
Published: July 2002

The critical role of the group V pressure in controlling the dynamic growth front morphology during molecular beam epitaxial growth of III-V compounds is demonstrated via computer simulations based upon a configuration-dependent reactive incorporation growth process and experimentally confirmed via measurements of the dynamics of reflection high-energy electron diffraction during homoepitaxy of GaAs (100). Implications for growth conditions desirable for realizing high quality interfaces and high luminescence efficiency in systems such as GaAs/AlxGa1−xAs are discussed.
Superficial image emphasis lithography
Authors: Matsuda Tadahito , Ishii Tetsuyoshi , Harada Katsuhiro
Published: July 2002

A new approach to electron beam lithography for device fabrications is described. This technique transfers relief images formed at the superficial layer of a positive resist inversely to the bottom layer of the resist. The technique can drastically improve the resolution and linewidth accuracy of delineated patterns by reducing proximity effects and the influence of incident beam spread. Writing time can also be reduced. 0.2-μm very large scale integration patterns and feature with 250-Å linewidth less than the incident beam size have been successfully produced.
Optical transitions and acceptor binding energies in GaAs/AlxGa1−xAs single quantum well heterostructures grown by molecular beam epitaxy
Authors: Pearah P. J. , Klem J. , Peng C. K. , Henderson T. , Masselink W. T. , Morkoç H. , Reynolds D. C.
Published: July 2002

Single quantum wells of varying well size (150–300 Å) exhibiting sharp photoluminescence lines were grown by molecular beam epitaxy. Photoluminescence structure and intensity were comparable to high quality multiple quantum wells in that linewidths as low as 0.5 meV and transitions associated with free heavy-hole excitons as well as bound excitons and acceptor impurities were observed. Also reported for the first time in optical transmission measurements on single wells are excitonic absorption lines. These are as narrow as 0.38 meV full width at half-maximum. In contrast to earlier findings, the binding energy of the acceptor in single quantum wells displays the same functional dependence on the well thickness as in multiple quantum wells as a consequence of an improved bottom (inverted) interface.
Fabrication of submicron deep ultraviolet masks by ion microprojection
Authors: Stangl G. , Rüdenauer F. G. , Stengl G. , Löschner H. , Maurer W. , Wolf P.
Published: July 2002

Photolithographic masks with submicron resolution have been produced in a one-step process by 1:10 ion microprojection of a stencil mask pattern into polymethyl methacrylate resist material. In the implanted pattern areas, light transmission is reduced for wavelengths extending into deep ultraviolet (DUV); thus, these patterns can be replicated into UV-sensitive photoresists using, e.g., excimer laser radiation. In the present ion projection lithography machine a 2.5-mm-diam mask was produced using a single 2-s exposure with 82 keV He+ ions. Replication in poly(butene-1-sulfone) resist was performed by single or double shot exposure using a KrF excimer laser (wavelength 248 nm). Resolutions exceeding 800 lp/mm were obtained in the replicated structures.
Pressure dependence of arsenic diffusivity in silicon
Authors: Nygren Eric , Aziz Michael J. , Turnbull David , Poate John M. , Jacobson Dale C. , Hull Robert
Published: July 2002

The diffusivity of implanted As in crystalline Si has been measured using Rutherford backscattering and channeling for specimens annealed at temperatures between 850 and 1000 °C under hydrostatic pressures up to 30 kbar. The diffusivity, at a given temperature, was found to increase with pressure with a maximum increase of a factor of 10. This diffusivity enhancement can be described by an average activation volume of −5.7±0.8 cm3/mole. The activation enthalpy ranges from an ambient value of 4.5 to 3.6 eV at 30 kbar.
Focusing surface waves using an axicon
Authors: Köymen Hayrettin , Atalar Abdullah
Published: July 2002

Axicons are generators of waves which focus on a line. They are used in various imaging and nondestructive testing applications as bulk wave focusing devices with a very long depth of focus. In this letter, a new type of conical axicon is introduced and it is shown that this axicon, immersed in a liquid, insonifying a plane solid surface can be used to excite surface waves on the solid surface provided that the cone angle of the axicon coincides with the Rayleigh critical angle of the liquid-solid interface. The generated surface waves focus into a diffraction-limited spot. This new surface wave focusing scheme is easy to use, has a conversion efficiency and sensitivity far better than other existing techniques.
Frequency dispersion of sidegating transconductance of GaAs junction field-effect transistors
Authors: Roach James W. , Wieder H. H. , Zuleeg Rainer
Published: July 2002

The complex low-frequency sidegating transconductance of GaAs enhancement-mode junction field-effect transistors exhibits dc bias-dependent resonance and relaxation characteristics. These are attributed to the dynamic balance between emission and trapping of electrons by deep energy levels with activation energies of 0.5 and 0.7 eV located at the surface or within the semi-insulating GaAs substrate.
Optically activated semiconductors as repetitive opening switches
Authors: Chauchard E. A. , Rhee M. J. , Lee Chi H.
Published: July 2002

We demonstrate for the first time the operation of a semiconductor repetitive opening switch. A semiconductor is maintained in a conductive state by illumination with a cw argon laser light. The opening of the switch is obtained by interrupting the light. A turn-off time of 1 ns has been achieved.
Polymer film cutting and ablative etching using a 1-kHz XeCl laser
Authors: Bishop G. J. , Dyer P. E.
Published: July 2002

A 1-kHz XeCl laser has been used to investigate cutting and ablative etching of thin polymer films. Significant increases in cutting efficiency and etch rate occur at high pulse rates (≳100 Hz) apparently due to cumulative heating effects. Cut rates of 130 cm s−1 are obtained at 900 Hz for a 12-μm-thick polyethylene teraphthalate film.
Rapid thermal nitridation of SiO2 for nitroxide thin dielectrics
Authors: Moslehi Mehrdad M. , Saraswat Krishna C. , Shatas Steven C.
Published: July 2002

Nitroxide thin films have been grown by rapid thermal nitridation of oxidized silicon in ammonia. The kinetics of formation of the surface and interface nitrogen-rich layers has been investigated and correlated to the electrical behavior of these films. It could be concluded that rapid thermal nitridation of ≊100 Å SiO2 results in negative shift of flatband voltage, slightly increases the surface state density, increases the low-field conductivity, reduces the high-field conductivity, improves the dielectric breakdown field, modifies the trapping behavior of the insulator, and slows down the generation rate of new surface states due to high-field electrical stress.
Photoacoustic determination of field enhancement at a silver surface arising from resonant surface plasmon excitation
Authors: Jung C. S. , Park G. , Kim Y. D.
Published: July 2002

The field enhancement due to resonant surface plasmon excitation using the attenuated total reflection method is described. For the 500-Å-thick silver film evaporated on the flat side of a hemisphere prism, the absorptance and photoacoustic (PA) signal are measured as functions of incident angle for three different incident photon energies. The angle dependence of the field enhancement is obtained from the power absorptance achieved from the PA signal.
Mode-locked coupled-stripe quantum well laser operation (λ∼7350 Å) in a tunable (Δℏω∼37 meV>k
T) external grating cavity
Authors: Epler J. E. , Jackson G. S. , Holonyak N. , Weinstein M. , Burnham R. D. , Paoli T. L.
Published: July 2002

The performance of an actively mode-locked coupled-stripe Alx′Ga1−x′As-AlxGa1−xAs quantum well laser in a tunable external cavity is described. Pulses as short as 50 ps are measured and a tuning range of Δℏω∼37 meV>kT, which is not the limit, is demonstrated. The existence of the transverse modes of coupled-stripe lasers increases significantly the spectral density of available lasing modes (for mode locking) compared with a single-stripe laser.
Photorefractive effects in LiNbO3 channel waveguides: Model and experimental verification
Authors: Becker R. A. , Williamson R. C.
Published: July 2002

Photorefractive effects in Ti-indiffused LiNbO3 channel waveguides at λ=0.85 μm are modeled and the theoretical predictions are experimentally verified. This model allows, for the first time, the quantitative prediction of the magnitudes and time evolution of photorefractive effects in LiNbO3 channel waveguide devices and provides a consistent method of characterizing the photorefractive behavior of LiNbO3 channel waveguides.
Control of titanium-silicon and silicon dioxide reactions by low-temperature rapid thermal annealing
Authors: Brillson L. J. , Slade M. L. , Richter H. W. , Vander Plas H. , Fulks R. T.
Published: July 2002

Auger electron spectroscopy/depth profiling measurements demonstrate that titanium silicide forms between titanium and silicon dioxide at conventional annealing temperatures. Low-temperature rapid thermal annealing provides a process window in time and temperature to suppress this parasitic reaction relative to silicide formation at titanium-silicon interfaces within the same thin-film structure.
Magnetic field dependence of Fowler–Nordheim tunneling in Cd1−xMnxTe
Authors: Siegrist T. , von Molnar S. , Holtzberg F.
Published: July 2002

The Zeeman splitting of the conduction band in the magnetic semiconductor Cd1−xMnxTe with x<0.25 has been inferred from measurements of Fowler–Nordheim tunneling characteristics in a metal-semiconductor-metal structure. The large g value of the band electrons leads to a decrease of the barrier height in a magnetic field and, consequently, to an exponential increase in the tunneling current.
Time-resolved exciton recombination in CdTe/Cd1−xMnxTe multiple quantum wells
Authors: Zhang X.-C. , Chang S.-K. , Nurmikko A. V. , Kolodziejski L. A. , Gunshor R. L. , Datta S.
Published: July 2002

The lifetime of excitons in CdTe/Cd1−xMnxTe multiple quantum wells at low temperature has been measured by time-resolved photoluminescence in samples of different well thickness. The excitons, which have elsewhere been shown to be localized preferentially near the heterointerfaces, possess an average lifetime which becomes shorter with decreasing well thickness and increasing external magnetic field. The results are in qualitative agreement with the expectations for a localized quasi-two-dimensional exciton with a large radiative recombination cross section.
7-GHz acoustic transmission through a Hertzian contact
Authors: Heffner B. L. , Kino G. S. , Khuri-Yakub B. T.
Published: July 2002

Transmission of acoustic waves through a Hertzian contact is demonstrated at 7 GHz. A zinc oxide transducer on a sapphire buffer rod is used to excite acoustic pulses which propagate into a sapphire flat through a direct Hertzian contact. Measurement of the reflected pulses yields a transmission loss through the contact of 1.2 dB.
Morphological phases of tungsten thin films on gallium arsenide
Authors: Derkits Gustav E. , Harbison J. P. , Hwang D. M.
Published: July 2002

Tungsten thin layers deposited on GaAs single crystal substrates in ultrahigh vacuum display a variety of distinct morphologies depending on substrate temperature and metal layer thickness. We present a preliminary study of some of these structures, including boundary layers in the metal, columnar growth, and an unusual phase that shows a strong orientational correlation with the substrate. We also discuss the effects of these structures on applications of W metallization to devices and processes of III-V semiconducting compounds.
Stable and unstable current-voltage measurements of a resonant tunneling heterostructure oscillator
Authors: Shewchuk T. J. , Gering J. M. , Chapin P. C. , Coleman P. D. , Kopp W. , Peng C. K. , Morkoç H.
Published: July 2002

Microwave oscillations in double barrier GaAs-AlxGa1−xAs resonant tunneling heterostructures have been investigated. In this letter an approach is presented to obtain stable, dc current-voltage (I-V) curves by using a damped microwave circuit to prevent device oscillations which distort the measured I-V curve. Numerical calculations confirm that if oscillations are allowed while making an I-V measurement, the measured current is the sum of the stable, bias current plus the rectified component of the oscillating current. In addition, the first room-temperature high Q microwave oscillations in resonant tunneling heterostructures are reported, as opposed to relaxation oscillations previously published. At 77 K, the highest power levels and efficiencies that have been achieved to date are presented.
Infrared to visible image conversion capability of a nematic liquid crystal film
Authors: Khoo I. C. , Normandin R.
Published: July 2002

We present a theoretical evaluation and experimental results of the capability of a nematic liquid crystal film for infrared to visible image conversion using nondegenerate four-wave mixing process.
Surface morphology of oxidized and ion-etched silicon by scanning tunneling microscopy
Authors: Feenstra R. M. , Oehrlein G. S.
Published: July 2002

The surface morphology of silicon (100) wafers has been measured by scanning tunneling microscopy. Samples which were bombarded with low-energy argon ions are found to have an average root-mean-square roughness of 4.0 Å, and the surfaces are covered with characteristic 50-Å-diam hillocks. The roughness of nonbombarded (control) samples is observed to be 1.8 Å, and this roughness arises in part from disorder at the interface between a native oxide and the silicon substrate.
Metal cluster size distributions during nozzle jet expansion
Authors: Yang S.-N. , Lu T.-M.
Published: July 2002

The non-steady-state cluster growth during nozzle jet expansion is solved numerically based on the classical liquid-drop theory. We showed that for the expansion geometry such as the one used in the ionized cluster beam system for depositing thin metal films [Yamada and Takagi, Thin Solid Films 80, 105 (1981)], cluster formation has already started under subsonic condition during the expansion. In our realistic calculation of the silver vapor expansion, cluster size up to more than 100 molecules can be formed.
Charge character of interface traps at the Si-SiO2 interface
Authors: Shiono Noboru , Shimaya Masakazu , Nakajima Osaake
Published: July 2002

Interface traps in the upper half of a silicon band gap are acceptorlike. This is based on analyses of the shift in capacitance-voltage curves due to positive bias-temperature aging of metal-oxide-semiconductor capacitors fabricated on n- and p-type substrates. The experimental results show that the interface traps in the upper half are generated without an increase in fixed oxide charges or interface traps in the lower half. The results also show that the flatband voltage shifts positively for n-type capacitors, while it does not shift for p-type capacitors.
Interdiffusion at the Ge(100)/Sn and Ge(111)/Sn interfaces
Authors: Gossmann H.-J. , Feldman L. C.
Published: July 2002

Interdiffusion between an ultrathin film of Sn and the Ge(100)c2×4 and Ge(111)c2×8 surfaces under atomically clean conditions is investigated using Rutherford backscattering. Indiffusion is found only if the Sn coverage exceeds a certain critical coverage θc≊1.15×1015 cm−2 even at temperatures up to 700 K. This result implies that the diffusion coefficient is at least six orders of magnitude smaller than the literature bulk value for θ<θc. We explain the observation in terms of surface segregation concepts. The temperature necessary to drive the Sn into the sample is strongly dependent on the sample surface orientation.
Comparison of the damage and contamination produced by CF4 and CF4/H2 reactive ion etching: The role of hydrogen
Authors: Mu X. C. , Fonash S. J. , Rohatgi A. , Rieger J.
Published: July 2002

In this study, the damage and contamination effects of CF4 and CF4/H2 reactive ion etching of silicon are compared. Included for the first time is an electrical, structural, and compositional examination of etched silicon which establishes the material property modifications resulting from the incorporating of hydrogen into the reactive ion etching environment. The results of this comparison of CF4 and CF4/H2 etching show that, for the same etching parameters, the presence of hydrogen causes more structural damage in the etched Si surface. However, the hydrogen is found to passivate its own damage rendering it electrically inactive. Subsequent exposure to temperatures exceeding ∼450 °C removes the passivation.
Nonlinear optical determination of the energy gap of Hg1−xCdxTe using two-photon absorption techniques
Authors: Seiler D. G. , McClure S. W. , Justice R. J. , Loloee M. R. , Nelson D. A.
Published: July 2002

The energy band gap of Hg1−xCdxTe has been determined for the first time using two-photon absorption techniques with CO2 lasers for samples with x≊0.32.
77 K cw operation of distributed Bragg reflector Pb1−xSnxSe/ Pb1−x−yEuySnxSe diode lasers
Authors: Shani Y. , Katzir A. , Bachem K.-H. , Norton P. , Tacke M. , Preier H. M.
Published: July 2002

Distributed Bragg reflector Pb1−xSnxSe/ Pb1−x−yEuySnxSe double heterostructure stripe geometry diode lasers were fabricated using molecular beam epitaxy. We observed cw single mode operation between the heat-sink temperatures 66 and 81 K at λ≊7.8 μm with an average tuning rate of 0.8 cm−1/K. Single mode continuous tuning over a relatively wide range of 6 cm−1, with an average tuning rate of 0.026 cm−1/mA, was obtained at 77 K.
Phase-locking lasers with phase conjugation
Authors: Feinberg Jack , Bacher G. David
Published: July 2002

Techniques are described for phase locking two or more lasers using phase-conjugating mirrors. Any changes in the optical cavity length or in the spatial mode structure of the optical beams are automatically compensated. Two argon-ion lasers were locked using a photorefractive crystal of BaTiO3 acting as a self-pumped phase-conjugating mirror.
Angular distribution of sputtered particles measured by quartz crystal microbalances and Auger electron spectroscopy
Authors: Taglauer E. , Onsgaard J.
Published: July 2002

A method for measuring angular distributions of sputtered particles in situ under ultrahigh vacuum conditions has been developed. It is based on a simultaneous collection of the ejected atoms on a number of quartz crystal microbalances (QCM’s), arranged in a semicircular pattern. Furthermore, it is possible to monitor the chemical state of the surface of the QCM’s and to register the amount of deposited material by means of Auger electron spectroscopy. By this method the time evolution of the angular distribution can be followed from quartz crystal coverages in the submonolayer regime to depositions corresponding to many monolayers.
Icosahedral quasicrystal produced by gas evaporation of an Al-Mn alloy
Authors: Saito Yahachi , Chen Ho S. , Mihama Kazuhiro
Published: July 2002

Al-Mn alloy particles prepared by evaporation of an Al-10 at. % Mn alloy in He gas have been found to exhibit the same diffraction pattern reported for a melt-spun Al6Mn icosahedral quasicrystal. An x-ray energy dispersive analysis shows a Mn content of about 24 at. %.
Time-resolved capacitive coupling voltage contrast—a new voltage measurement technique for passivated devices
Authors: Cole E. I. , Bagnell C. R. , DiBianca F. A. , Johnson D. , Oxford W. , Smith C. , Propst R. H.
Published: July 2002

A scanning electron microscope is used in the voltage contrast mode to examine dynamic voltages on passivated integrated circuits. At low primary electron beam energies negative voltage transients produce a capacitive coupling voltage contrast flash visible through passivation layers. The flash decay time is related to the amplitude of the voltage transient. This new voltage measuring method is called time-resolved capacitive coupling voltage contrast. Preliminary results yield voltage calibration curves with a standard error of 45 mV or lower.
Surface defect segregation in the perovskite-type ferroelectric KNbO3
Authors: Szot K. , Hillebrecht F. U. , Sarma D. D. , Campagna M. , Arend H.
Published: July 2002

Electron spectroscopic investigations are used to show that defects at various concentrations are inherently present on surfaces of KNbO3 crystals. Their concentration at the surface is determined by the bulk concentration as well as by diffusion. These defects are important for most classical measurements on KNbO3 and similar materials.
Use of infrared fibers for low-temperature radiometric measurements
Authors: Zur A. , Katzir A.
Published: July 2002

Silver halide (AgClxBr1−x) infrared fibers were incorporated in a simple radiometer. Using this system we performed noncontact temperature measurements in the range 25–50 °C. Good correlation was found between the radiometric results and those obtained with a regular thermocouple. The minimum resolvable temperature difference was 0.1 °C and the spatial resolution was 0.9 mm.
Tunable optical filters, modulators, and limiters using Stark-induced birefringence and dichroism
Authors: Pepper David M. , Klein M. B.
Published: July 2002

Novel electro-optic devices using the polarization-, intensity-, and frequency-dependent susceptibility of Stark-active gases have been analyzed and demonstrated, including all-optical limiter/cut-off devices, amplitude modulators, and tunable narrowband filters. The application of the system to other media (e.g., multiple quantum wells) and to the study of coherent optical transients is discussed.
Stabilization of InP substrate under annealing in the presence of GaAs
Authors: Sacilotti M. , Masut R. A. , Roth A. P.
Published: July 2002

We report on the annealing of InP and GaAs substrates, placed side by side, in a hydrogen atmosphere. This annealing is done with and without arsine, and also in the presence of elemental arsenic replacing GaAs. This simple technique shows the stabilization of InP by the presence of GaAs in a temperature range between 550 and 750 °C. It gives information about active species present during substrate annealing. The results obtained show that the protecting species of column V elements, dimers or tetramers, behave differently than the ones resulting from the decomposition of the V hydride.
Phase selection during pulsed laser annealing of manganese
Authors: Follstaedt D. M. , Peercy P. S. , Perepezko J. H.
Published: July 2002

Pulsed (25 ns) laser-induced heating of the α phase of Mn is found to be sufficiently rapid to bypass solid-state transformation to the high-temperature β, γ, and δ allotropes and thus produce melts that are calculated to be undercooled by ∼120 K with respect to the equilibrium melting temperature of the δ phase. Nucleation of the γ phase in this highly undercooled melt is observed for sufficiently long melt durations. The experiments thus demonstrate that pulsed laser-induced melting of metals with allotropes permits the study of nucleation and growth in highly undercooled melts with calculable temperatures.
Capacitance-voltage and current-voltage characteristics of molecular beam epitaxially grown p+-GaAs/AlAs/n-GaAs heterostructures
Authors: Cooper J. A. , Qian Q-D. , Melloch M. R.
Published: July 2002

We have studied the capacitance-voltage (CV) and current-voltage (IV) characteristics of molecular beam epitaxially (MBE) grown p+-GaAs/AlAs/n-GaAs heterostructures as a function of illumination level and temperature. Under illumination we find clear evidence of a hole inversion layer at the AlAs/n-GaAs interface at 77 K, with a maximum inversion layer carrier concentration of about 4.1×1011 cm−2. The samples are essentially free of trapping in the AlAs, as indicated by the almost complete lack of hysteresis in the CV curves. At room temperature under steady-state illumination we see both a voltage shift and a peak in the CV curves. The shift is attributed to the formation of an inversion layer, while the peak is believed due to the ac response of space charge flowing through the AlAs. In contrast to recent reports on similar samples grown by metalorganic chemical vapor deposition, the MBE grown samples appear to be suitable for fabricating field-effect devices.
Organometallic vapor phase epitaxial growth of GaInP/GaAs (AlGaAs) heterostructures
Authors: Shealy J. R. , Schaus C. F. , Eastman L. F.
Published: July 2002

The growth of GaInP/AlGaAs heterostructures by organometallic vapor phase epitaxy is reported. It was observed that different GaInP alloy compositions are required to lattice match films to AlGaAs and GaAs buffer layers for optimum results. Quantum well heterostructures with GaInP regions as narrow as 30 Å have been produced with abrupt transitions of the group III and group V species across each interface. The results suggest that this material system is suitable for the fabrication of high efficiency visible light sources.
Determination of the microscopic quality of InGaAs-InAlAs interfaces by photoluminescence—Role of interrupted molecular beam epitaxial growth
Authors: Juang F-Y. , Bhattacharya P. K. , Singh J.
Published: July 2002

Photoluminescence (PL) studies have been carried out on 120 Å InGaAs/InAlAs single quantum well structures grown by molecular beam epitaxy. Three types of samples were grown with the growth being interrupted before interface formation. The interruption times were 0, 2, and 3 min. The corresponding linewidth of the main excitonic transition associated with the quantum well was found to be 20, 16, and 10 meV, respectively, while the PL intensity changed by the ratio 1:0.4:0.1. We believe this behavior is due to a steady improvement in the interface quality due to interruption accompanied by impurity accumulation during the interruption. Analysis of the 10 meV linewidth, which is among the smallest ever reported, suggests that the InAlAs/InGaAs interface can be described by two-dimensional InAlAs and InGaAs islands which have a height of two monolayers and a lateral extent of about 100 Å.
Pulse diffusion of Ge into GaAs
Authors: Lester S. D. , Farley C. W. , Kim T. S. , Streetman B. G. , Anthony J. M.
Published: July 2002

The diffusion of Ge into GaAs from a thin elemental source using rapid thermal processing has been investigated. Several types of encapsulants and substrates have been examined. The diffusion and activation of Ge have been found to depend on both the encapsulant and substrate growth conditions. Photoluminescence spectroscopy indicates that Ga vacancies may control dopant diffusion and activation. Very shallow n+ junctions and nonalloyed ohmic contacts to semi-insulating GaAs have been formed.
Kinetics of arsenic activation and clustering in high dose implanted silicon
Authors: Kamgar Avid , Baiocchi F. A. , Sheng T. T.
Published: July 2002

We have observed a metastable state in activation of high dose arsenic implants into silicon. This state is marked by a local minimum in the sheet resistance which increases to a local maximum as the anneal time increases. Detailed sheet resistance data as well as Rutherford backscattering and transmission electron microscopy indicate that the initial minimum in sheet resistance is due to activation of arsenic atoms by occupying substitutional sites as the amorphous silicon recrystallizes. The subsequent clustering of arsenic atoms is the cause for the increase in the sheet resistance while the final drop is associated with the lateral diffusion of arsenic. We have studied this effect in the 850–1100 °C temperature range, and have obtained an activation energy of 1.1 eV for the clustering of arsenic atoms.
High-speed GaAs/AlGaAs photoconductive detector using a p-modulation-doped multiquantum well structure
Authors: Kaede K. , Arakawa Y. , Derry P. , Paslaski J. , Yariv A.
Published: July 2002

A new type of high-speed GaAs/AlGaAs photoconductive detector utilizing the high drift velocity of minority electrons in a p-modulation doped multiquantum well structure is demonstrated. In this modulation-doped structure, the electron scattering is reduced, which leads to the enhancement of the electron (minority carrier) drift velocity which determines the response speed of the detector. A deconvolved pulse response as narrow as 33 ps full width at half-maximum was obtained with an electric field of 3.1 kV/cm at room temperature.
Frequency and power limit of quantum well oscillators
Authors: Jogai B. , Wang K. L. , Brown K. W.
Published: July 2002

The maximum frequency at which amplification can be obtained from quantum well oscillators is discussed. Intrinsically, the frequency limit for having negative differential resistance (NDR) can be very high, of the order of the inverse of the electron transit time. Owing to the large capacitance of the well and barrier regions, the actual frequency limit at which amplification occurs may be lower than the intrinsic limit because of the capacitance charging time. We have estimated the frequency limit of NDR by considering the electron transit time and have calculated the maximum oscillation frequency from an equivalent circuit model. We have also obtained an expression for the high-frequency power output as a function of frequency, based on a transmission line model.
Proton isolated In0.2Ga0.8As/GaAs strained-layer superlattice avalanche photodiode
Authors: Bulman G. E. , Myers D. R. , Zipperian T. E. , Dawson L. R.
Published: July 2002

We have fabricated the first proton isolated strained-layer superlattice (SLS) avalanche photodiode. The grown In0.2Ga0.8As/GaAs p+n SLS structure was bombarded outside the active region with 220 keV protons to a total dose of 1×1015cm−2. These first nonoptimized devices exhibit a breakdown voltage of 23.5 V with a dark current density of 1.3×10−3A/cm2 at 90% of the breakdown voltage. The isolation is stable under annealing for 10 min at 350 °C. Uniform photoresponse is observed across the active region with two order of magnitude reduction in response occurring in the isolation region. A peak uncoated external quantum efficiency of 25% at 910 nm is observed with 10 V reverse bias and photocurrent multiplication is observed at higher bias values. These results demonstrate that proton isolation can be successfully applied to strained-layer systems and can be incorporated in useful device structures.
Direct frequency modulation of vapor phase transported, distributed feedback semiconductor lasers
Authors: Vodhanel R. S. , Cheung N. K. , Koch T. L.
Published: July 2002

The frequency modulation (FM) due to injection current modulation of vapor phase transported distributed feedback (VPT DFB) semiconductor lasers is measured as a function of modulation frequency from 10 kHz to 1 GHz. A large frequency modulation response of 350 MHz/mA is obtained for the modulation frequency range of 10 to 1000 MHz. Demodulation of optical frequency shift keying (FSK) at 560 Mb/s is demonstrated, indicating that frequency modulation due to thermal modulation does not pose a significant limitation at this bit rate or higher. The large FM response together with modulation bandwidths up to 8 GHz makes the VPT DFB laser an attractive source for high bit rate optical FSK transmission.
1100× optical fiber pulse compression using grating pair and soliton effect at 1.319 μm
Authors: Tai K. , Tomita A.
Published: July 2002

We report the first demonstration of two-stage optical fiber pulse compression using the grating pair technique and, successively, the soliton effect. Firstly, 100 ps pulses from a 1.319-μm mode-locked neodymium:yttrium aluminum garnet laser are chirped by a 2-km positive dispersion fiber (zero-dispersion wavelength λ0=1.59 μm) and compressed into 2 ps pulses by a grating pair. Subsequently, the resultant 2 ps pulses are coupled into a 40-m negative dispersion fiber (λ0=1.275 μm) and compressed further into 90 fs pulses via the pulse narrowing effect of high-order soliton propagation. The combined compression factor of 1100 is the largest reported to date using optical fibers.
Kr2F* fluorescence measurements of electron beam pumped KrF laser mixtures
Authors: Kimura W. D. , Salesky E. T.
Published: July 2002

The time-dependent Kr2F* fluorescence and KrF* laser emission of an electron beam pumped KrF laser are measured for two gas mixtures, 89.7% Ar/10% Kr/0.27% F2 and 99.6% Kr/0.4% F2, at initial gas temperatures from 294 to 417 K and for pulse lengths >600 ns. The measurements indicate an inverse square root temperature dependence for the Kr2F* formation, which is weaker than earlier predictions. Analysis of the Kr2F* and KrF* data also indicates that electron quenching and the effects of gas heating during the pump pulse significantly affect the laser performance of the Kr/F2 mixture. Results of a model agree well with the data.
Roles of shallow and deep electron traps causing backgating in GaAs metal-semiconductor field-effect transistors
Authors: Khanna Ravi , Das Mukunda B.
Published: July 2002

In GaAs metal-semiconductor field-effect transistors under backgating conditions, electrons can be trapped in ‘‘shallow’’ and deep trap levels. It is shown that the characteristics of these traps can be determined and those responsible for backgating can be identified by examining the thermally excited emission currents under zero-bias short-circuit conditions. It is established, for the first time, that there are ‘‘shallow’’ traps located under the field-effect transistor active channel, and possibly related to the ion-implantation damage, that are directly related to the backgating, although the process is initiated due to filling of deep levels by electrons near the surface of the semi-insulating GaAs.