bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of AlxGa1−xAs buffer layers on the performance of modulation-doped field-effect transistors
Authors: Drummond T. J. , Kopp W. , Thorne R. E. , Fischer R. , Morkoç H.
Published: February 2003

Normally-off and pseudo-normally-on modulation-doped Al0.3Ga0.7As/GaAs Schottky barrier field-effect transistors were fabricated and characterized. The structures were grown by molecular beam epitaxy and exhibited electron mobilities as high as 8000, 100 000, and 200 000 cm2/Vs at 300, 78, and 10 K, respectively. Inclusion of an Al0.3Ga0.7As buffer layer between the substrate and the modulation-doped layers improved the transconductance and saturation characteristics substantially. This improvement was observed to be strongly dependent on the substrate temperature during the buffer layer growth, with the best results being obtained at 700 °C.
Infrared absorption of the 78-meV acceptor in GaAs
Authors: Elliott K. R. , Holmes D. E. , Chen R. T. , Kirkpatrick C. G.
Published: February 2003

We observe the infrared absorption spectra associated with a residual 78-meV acceptor in undoped liquid encapsulated Czochralski GaAs. The acceptor appears to be associated with an intrinsic defect, most likely the antisite GaAs. This acceptor is the dominant level in material grown from heavily Ga-rich melts. The concentration of the level depends strongly on melt stoichiometry increasing from about 3×1015 cm−3 to 3×1016 cm−3 as the As atom fraction changes from 0.47 to 0.43.
A novel p+n
n+ GaAs/Al0.30Ga0.70As/GaAs double heterojunction diode for high-temperature electronic applications
Authors: Zipperian T. E. , Dawson L. R. , Barnes C. E.
Published: February 2003

Mesa-isolated, p+nn+, GaAs/Al0.30Ga0.70 As/GaAs, double heterojunction diodes are reported which have excellent electrical characteristics over the full temperature range from 23 to 400 °C. These devices have diode law ideality factors of approximately 1.1 at any temperature for forward current densities greater than 10−3 A/cm2 and have reverse leakage current densities of 4×10−10 A/cm2 at 23 °C and 2×10−2 A/cm2 at 400 °C. AlxGa1−x As is used only in critical device regions to ensure that GaAs heterojunction contacts are made to the wider band-gap materials and to allow the chemically reactive AlxGa1−x As to be encapsulated by GaAs. These results demonstrate that the GaAs/AlxGa1−x As chemical system is a good materials candidate in which to base a technology for electronic components operated at high temperatures.
Amplifying continuous wave phase conjugate mirror with strontium barium niobate
Authors: Fischer Baruch , Cronin-Golomb Mark , White Jeffrey O. , Yariv Amnon , Neurgaonkar Ratnakar
Published: February 2003

We report the use of Sr1−x Bax Nb2O6 as an efficient holographic four-wave mixing medium. We have used this material in a continuous wave phase conjugate mirror with reflectivity exceeding unity, and in a phase conjugate resonator.
Optically pumped ring laser oscillation in the 6Li2 molecule
Authors: Rajaei-Rizi A. , Bahns John T. , Verma K. K. , Stwalley W. C.
Published: February 2003

Stable unidirectional ring laser oscillation of optically pumped 6Li2 molecules was obtained for the first time. We observed transitions in the range 5237–5889 Å excited by different argon ion laser lines in the range 4579–4965 Å. Using our laser-induced fluorescence results for this molecule, we have assigned unambiguously 23 of 27 lines to specific rovibronic transitions in the B1Πu→X1Σ+g band system of 6Li2. The optimum pressure for operation of the optically pumped 6Li2 laser was found to be ∼4 Torr.
Properties of the Mo-CuInSe2 interface
Authors: Russell P. E. , Jamjoum O. , Ahrenkiel R. K. , Kazmerski L. L. , Mickelsen R. A. , Chen W. S.
Published: February 2003

Mo has been suggested and used as an ohmic back contact for CdS/p-CuInSe2 solar cells. The Mo- p-CuInSe2 interface has been studied for both polycrystalline and single- crystal CuInSe2, using electron beam induced current and capacitance-voltage techniques. The interface is found to form a Schottky barrier, thereby limiting the attainable voltage of a solar cell with Mo back contact. Au is the only known ohmic contact to p-CuInSe2.
Ultrarapid crystal growth and impurity segregation in amorphous silicon annealed with short Q-switched laser pulses
Authors: Cullis A. G. , Webber H. C. , Chew N. G.
Published: February 2003

Very short Q-switched laser pulses have been used to produce especially high-speed crystal growth in ion implanted, amorphous Si layers. This is shown to occur in an unstable, explosive manner which can give pronounced lateral modulation of layer structure. Novel phenomena relating to impurity segregation and cell formation in amorphous Si are also presented. These provide strong evidence that amorphous Si melts to form an undercooled, normal, low viscosity liquid and that the amorphous phase itself is not a glassy state.
Laser marking of thin organic films
Authors: Wrobel J. J. , Marchant A. B. , Howe D. G.
Published: February 2003

Laser marking of thin organic films on reflective substrates involves three general physical processes—optical absorption, heat flow, and mass motion—all of which can proceed on nanosecond time scales. We report observations of pit morphology and discuss the contributions of these processes to pit formation.
A multiplexible bistable nematic liquid crystal display using thermal erasure
Authors: Boyd G. D. , Cheng Julian , Thurston R. N.
Published: February 2003

A new concept for matrix addressing a bistable nematic liquid crystal display with a potential writing capacity of several hundred lines per second is described. The bistability of two optically differentiable configurations provides permanent memory without refresh. The use of uniform electrodes provides a switching threshold that is very sharply defined and suitable for large scale multiplexing. Erasure is achieved by selectively heating any row to a temperature above the clearing point and allowing preferential relaxation to the lower energy configuration. The pulse switching characteristics of ’’writing’’ and the thermal properties of ’’erasure’’ are described. The physical processes involved and their implications for display applications are discussed.
Graphoepitaxy of electrodeposited tin
Authors: Darken L. S. , Lowndes D. H.
Published: February 2003

The crystallographic orientation of electrodeposited tin islands induced by a square wave relief pattern etched into an SiO2 substrate is reported. The islands 〈100〉 axis is normal to the substrate within 0.2° full width at half-maximum (FWHM) and the 〈001〉 axis is parallel to the long or running direction of the relief pattern within 5.0° FWHM. The islands are regular rectangular prisms bounded by the (100), (010), and (001) crystallographic planes, with dimensions ranging from 0.1 to 100 μm. The relief pattern used to induce orientation had a typical depth of 0.1 μm and a periodicity of 2.7 μm. The deposits were investigated by scanning electron microscopy, x-ray fluorescence, and x-ray diffraction.
High current post-hydrogenated chemical vapor deposited amorphous silicon p-i-n diodes
Authors: Szydlo N. , Chartier E. , Proust N. , Magariño J. , Kaplan D.
Published: February 2003

Amorphous silicon p-i-n diodes have been fabricated for the first time by chemical vapor deposition and post-hydrogenation in a hydrogen plasma. By analyzing the current-voltage characteristics we obtain current densities up to 50 A/cm2 and rectification ratios better than 107 for 3-V applied bias. A characteristic reversible breakdown voltage is observed up to voltages of ∼20 V. These results are compared with those obtained on amorphous silicon p-i-n diodes prepared by glow discharge decomposition of SiH4.
Quantum efficiency of fluorescence from the Na-Hg vapor excited by 253.7-nm radiation
Authors: Maya Jakob
Published: February 2003

We have measured the absolute quantum efficiency (QE) of fluorescence from the Na-Hg vapor excited by Hg (253.7 nm) resonance radiation. The measurements were carried out as a function of Na mole fraction (XNa) in the Na-Hg solid amalgam (XNa = 0–100%) and temperature (T = 200– 550 °C). Highest efficiency obtained was 115±15% for XNa = 0.76 and T = 325–375 °C. We believe these to be the first quantum efficiency measurements in gas phase systems where QE≳100% is observed.
Interface morphology studies of (110) and (111) Ge-GaAs grown by molecular beam epitaxy
Authors: Chang Chin-An
Published: February 2003

Interface morphologies of (110) and (111) Ge-GaAs grown by molecular beam epitaxy (MBE) have been studied using reflection high energy electron diffraction (RHEED). For the (110) Ge- GaAs, planar growths of both GaAs on Ge and Ge on GaAs are observed. The (111) Ge-GaAs, on the other hand, shows a rough growth of GaAs on Ge, and a planar one of Ge on GaAs, similar to those of (100) Ge-GaAs. The (110) and (111) results are discussed in terms of the orientation effect on the MBE growth of compound semiconductors and are consistent with that on (100) Ge-GaAs.
Effect of heat treatment on residual stress and electron Hall mobility of laser annealed silicon-on-sapphire
Authors: Kobayashi Y. , Nakamura M. , Suzuki T.
Published: February 2003

The effect of heat treatment on electron Hall mobility and the residual stress of laser annealed silicon-on-sapphire (SOS) has been investigated using Hall effect measurements and laser Raman spectroscopy. The improvement in electron Hall mobility of SOS brought about by pulsed ruby-laser annealing disappeared with subsequent heat treatment at temperatures higher than about 600°C. Raman spectroscopy measurements revealed that the residual stress in the silicon layer, regrown by the laser annealing, was tensile and that the observed decrease in electron Hall mobility was caused by stress changes from tension to compression which accompanied the heat treatment above about 600°C. These results showed that the SOS/metal-oxide-semiconductor field-effect transistor (MOSFET) with improved channel mobility could be realized when it was fabricated from the silicon layer having tensile stress.
Seeded oscillatory growth of Si over SiO2 by cw laser irradiation
Authors: Celler G. K. , Trimble L. E. , Ng K. K. , Leamy H. J. , Baumgart H.
Published: February 2003

Extensive seeded epitaxial growth of crystalline Si over SiO2 was achieved by an oscillatory regrowth method applied to rectangular Si pads recessed into a thick SiO2 film. Narrow (≃5 μm) via holes linked the pads with the bulk (100) Si substrate. Oriented single crystals propagated as far as 500 μm from the seeding area, following the long term advance of a scanned focused laser beam.
Possibility of effect of electric charge on the stability of current-carrying high-field superconductors
Authors: Sugahara M.
Published: February 2003

The charge-diffusion length λ*Q in the flux-pinned superconducting region near the interface between the pinned region and dissipative region is estimated from published experimental data on the minimum current Ir for SN-boundary propagation in Nb-Ti composite conductors. The estimation gives λ*Q≃3.2–3.9 μm irrespective of the variety of conductor shape and structure, applied magnetic field, and cooling conditions. This result reveals the possibility that the gap depression by the accumulated charge at the interface with a flux-depinning effect is the determining factor in the dynamics of the SN boundary in composite superconductors.
Photoresponse of n-type semiconductor NiTiO3
Authors: Salvador P. , Gutierrez Claudio , Goodenough J. B.
Published: February 2003

The 60-Hz photocurrent of 103-Ω cm, Nb-doped n-TiO3 has been measured by lock-in amplification as a function of wavelength and applied potential. NiTiO3 is oxidized anodically in the dark producing Ni2+ ions in solution; however, this corrosion is but a fraction of the total charge passed either with visible or UV light, which indicates that photogenerated holes are able to oxidize water. The spectral response is shifted towards the visible region, as compared with TiO2, and the flatband potential is 0.4 V more negative than that of the H+/H2 redox couple, which would make possible the use of NiTiO3 for water photoelectrolysis. However, the quantum efficiency for visible light is much lower than that for UV light, primarily because of a low oscillator strength for the visible light Ni2+-Ti4+ charge-transfer excitation in this structure.
Measurement of fluctuations affecting domain formation in transferred-electron logic devices using picosecond optical pulses
Authors: Carruthers T. F. , Weller J. F. , Taylor H. F. , Mills T. G.
Published: February 2003

Picosecond optical pulses have been used to bias the gate region of a transferred-electron logic device to the vicinity of the threshold for domain formation. Single domains with rise and fall times of less than 50 ps are produced when the device is illuminated between the cathode and Schottky-barrier gate electrodes. The probability of domain generation is found to vary with optical intensity and applied bias voltage. Fitting a model of the effects of thermal carrier density fluctuations to these data yields a value for the rms fluctuating electric field component affecting domain formation of 123±14 V/cm in the devices studied.
Current threshold uniformity of shallow proton stripe GaAlAs double heterostructure lasers grown by metalorganic-chemical vapor deposition
Authors: Burnham R. D. , Scifres D. R. , Streifer W.
Published: February 2003

Stripe geometry lasers grown by metalorganic-chemical vapor deposition lasing at 8260 Å (∼7% Al in the active region) are described. Pulsed current thresholds vary little with stripe width for 4-, 6-, and 8-μm stripe widths. For 51 lasers that are 200±10 μm long with 4-, 6-, or 8-μm stripe widths, the average threshold currents were 40.4, 41.1, and 42 mA, respectively, and 37 of these lasers fall within ±1 mA of these averages. External differential quantum efficiencies for these same lasers are 75, 67, and 63%.
Macroscopic surface roughness in metal-dielectric composite films: Photothermal absorber applications
Authors: Nyberg Glen A. , Buhrman R. A.
Published: February 2003

Previous studies have shown that coevaporated metal-dielectric composite films are quite smooth. But a substantially higher deposition temperature results in the surface roughness of Mo/Al2O3 composite films becoming larger than the mean film thickness. This effect was applied to photothermal solar absorbers where, for the first time, a stable selective absorber was produced which absorbs over 99% of the solar spectrum. These results have implications for other surface roughness dependent effects.
Direct observation of electron leakage in InGaAsP/InP double heterostructure
Authors: Yamakoshi S. , Sanada T. , Wada O. , Umebu I. , Sakurai T.
Published: February 2003

The electron leakage through the heterobarrier consisting of a thin InGaAsP active layer and a p-InP confining layer was directly observed by using a novel InGaAsP/InP light-emitting diode (LED) structure. In the present structure, electrons leaking from the active layer were confined in a subsidiary quaternary layer having a crystal composition different from that of the active layer, and the recombination emission caused by these electrons was optically detected. Experimental results showed that significant electron leakage can occur in the present InGaAsP/InP double heterostructure (DH) system, suggesting a possibility of the electron leakage being one of the dominant mechanisms of sublinearity in the light intensity-current characteristics in InGaAsP/InP DH LED’s operating at wavelengths shorter than 1.3 μm and also of the temperature dependence of threshold current in laser diodes.
Molecular beam epitaxial growth of single-crystal Al films on GaAs (110)
Authors: Prinz G. A. , Ferrari J. M. , Goldenberg M.
Published: February 2003

Molecular beam epitaxy methods have been used to grow good quality single-crystal films of fcc Al on (110) GaAs. These films were characterized by Auger, high energy electron diffraction, and glancing incidence x-ray diffraction using a Read camera. Successful growth was found to be dependent upon increased flux rates and lowered substrate temperatures in order to overcome the high surface mobility of Al on GaAs.
Zone-melting recrystallization of encapsulated silicon films on SiO2—morphology and crystallography
Authors: Geis M. W. , Smith Henry I. , Tsaur B-Y. , Fan John C. C. , Maby E. W. , Antoniadis D. A.
Published: February 2003

Large-area films of recrystallized Si with (100) texture, preferred in-plane orientation, and grain sizes ≳1× 10 mm have been produced by using a strip-heater oven to move a narrow molten zone across Si films on SiO2. A composite encapsulation layer of SiO2 and Si3N4 over the Si leads to smooth surfaces and (100) texture. The 〈100〉 axes of grains tend to lie along the direction of motion of the molten zone. A grid of faceted pits etched anisotropically into the Si permits determination of local orientation. As described elsewhere, the recrystallized films have been used for the fabrication of metal-oxide semiconductor field-effect transistors which exhibit electron surface mobilities comparable to devices fabricated on single-crystal Si.
Picosecond pulse generation from a synchronously pumped mode-locked semiconductor laser diode
Authors: AuYeung John C. , Johnston Alan R.
Published: February 2003

A semiconductor laser diode was mode locked in an external cavity when synchronously pumped with 90-ps current pulses. Transform-limited optical pulses with a 10-ps pulse width and a peak power of 160 mW were produced. Operating characteristics of such a system are described.
Silicon-silicon interfaces
Authors: Redfield David
Published: February 2003

A wide variety of measurements on silicon grain boundaries shows that the electronic properties of such boundaries are much like those of Si surfaces in all essential respects. Moreover, the properties of ’’clean’’ surfaces and lightly contaminated surfaces can be studied on many crystallographic orientations of the interfaces without the need for vacuum measurements. Such grain boundaries may therefore be regarded as Si-Si interfaces in the sense used in surface physics. It is shown that the thermal history and the dissolved oxygen of the silicon play major roles in determining the interface properties.
Crystallization of amorphous silicon on silica by cw laser irradiation
Authors: Bösch M. A. , Lemons R. A.
Published: February 2003

Laser crystallization was performed by scanning the substrate through a stationary cw Ar+ laser beam. Amorphous films show two abrupt changes in the optical transmission spectra as a function of laser power. At the first step no grains are observed with 10-nm resolution. The second optical change is accompanied by clear crystallinity with grains from submicron to several 100-μm size.
Punchthrough in a three-junction SQUID
Authors: Ketchen M. B. , Anderson C. J.
Published: February 2003

Josephson latching logic devices can be powered by a bipolar trapezoidal waveform. Ideally, switched devices will always reset as the power supply reverses polarity. Under certain conditions, however, punchthrough can occur: a switched logic device fails to reset and proceeds into the next cycle in the nonzero voltage state. Original theory and experiment held that the punchthrough probability P should be identically zero provided the power supply transition time τ is greater than some critical value. The present experiment on a three-junction superconducting quantum interference device (SQUID) demonstrates, as more recent theories and simulations predict, that there is an exponential tail of P(τ) rather than an abrupt cutoff. We also find P can be strongly modulated by a small dc in the control line over the SQUID.
Electrophotographic photoreceptor with high sensitivity in the near-infrared region
Authors: Arishima K. , Hiratsuka H. , Tate A. , Okada T.
Published: February 2003

A double-layered xerographic photoreceptor has been investigated to obtain high sensitivity in the near-infrared region. The immersion of sublimed chloroaluminum phthalocyanine chloride (AlClPcCl) in an organic solvent was found to induce an absorption peak shift toward the long wavelength region. The new double-layered photoreceptor, in which AlClPcCl and a pyrazoline derivative were employed in the charge generation layer and charge transport layer, respectively, showed a high sensitivity, equivalent to 1.6 cm2/μJ, in the GaAlAs laser diode emission region.
A partially stabilized photoeletrochemical cell using hydrogenated amorphous silicon photoanodes coated with thin films of polypyrrole
Authors: Skotheim T. , Lundström I. , Delahoy A. E. , Kampas F. J. , Vanier P. E.
Published: February 2003

Electrochemical Schottky barrier devices with polypyrrole coated hydrogenated amorphous silicon, (a-Si:H), as photoanodes and a variety of aqueous redox solutions have been investigated. The open circuit voltage reaches 0.63 V for most anodic redox couples and exhibits a high degree of surface pinning due to the barrier formed between a-Si:H and the highly conductive polypyrrole. We report a substantial improvement in the stability of the polypyrrole coated electrodes compared with the bare a-Si:H. The efficiency of the present devices is limited by low photocurrent and fill factor.
Interference enhanced Kerr spectroscopy for very thin absorbing films
Authors: Connell G. A. N.
Published: February 2003

A new method of obtaining polar Kerr spectra from very thin highly absorbing films (α≳104 cm−1) is described. The technique which is termed interference enhanced Kerr spectroscopy is shown theoretically to produce a gain in the Kerr intensity of 10–103 (depending on the optical constants of the material) over that expected from a thick sample. The potential of the method is demonstrated theoretically using MnBi data and experimentally using an amorphous Tb-Fe alloy. The use of this interference technique for studies of other mode conversion phenomena is also mentioned.
Dependence of local sound vibration on time frequency in a monolithic array transducer
Authors: Saiga Noriaki , Suzuki Tatsuro
Published: February 2003

An approach of increasing spatial resolution in a monolithic array transducer was carried out which utilized the thickness vibration at frequencies slightly lower than the resonance band. At those frequencies, the optical probing manifested that an usual spatial impulse response shifted into a more sharp and monotonously damping one with a peak amplitude comparable to those in resonance. An actual imaging as a receiving array demonstrated the improvement of spatial resolution and the high uniformity of image contrast.
Excimer fluorescence for plasma displays
Authors: Nighan W. L. , Ferrar C. M.
Published: February 2003

Experimental tests confirm analytical predictions that usefully bright excimer fluorescence in the visible region can be produced under discharge conditions achievable in conventional ac plasma panel configurations. Results are presented for the Xe2Cl excimer exhibiting broadband blue emission peaked at 476 nm.
Submicroscopic contact imaging with visible light by energy transfer
Authors: Fischer U. Ch. , Zingsheim H. P.
Published: February 2003

The resolution of contact imaging with light is limited by the distance between object and image and not by the wavelength. Contact imaging with visible light at submicroscopic resolution (100 nm) is demonstrated using the concept of imaging by energy transfer. The bleaching of a dye is inhibited by energy transfer to a metal in close proximity. This mechanism is exploited for imaging a planar metal pattern onto a film of a cyanine dye.
Dynamical switching characteristics of a bistable injection laser
Authors: Lau K. Y. , Harder Ch. , Yariv A.
Published: February 2003

The switching characteristics of a bistable injection laser with very large hysteresis is examined. Switch-on delays are shown to exhibit a ’’critical’’ part and a ’’noncritical’’ part, both of which can be reduced by increasing the overdrive current. It is possible to obtain fairly fast switching time (<20 ns) with a strong overdrive. Nominal delays of 100–200 ns result under moderate overdrives. These long time scales are due to long carrier lifetimes in the carrier-depleted absorption section, a property intrinsic to these bistable injection lasers.
Observations of the morphology of laser-induced damage in copper mirrors
Authors: Thomas S. J. , Harrison R. F. , Figueira J. F.
Published: February 2003

The results of multiple-pulse damage tests on copper mirrors using 1.7-ns CO2 lasers are reported. The measured reduction in the brightness reflectivity of the mirrors is shown to be correlated to the dramatic appearance of fine scale microstructure on the mirror surface. Scanning electron micrographs of this surface structure are presented and possible explanations of the effects are discussed.
Far-infrared imaging antenna arrays
Authors: Neikirk Dean P. , Rutledge David B. , Muha Michael S. , Park Hyeon , Yu Chang-Xuan
Published: February 2003

A far-infrared imaging antenna array has been demonstrated for the first time. The array is a line of evaporated silver bow-tie antennas on a fused-quartz substrate with bismuth-microbolometer detectors. The measured optical transfer function shows that the system is diffraction limited. This imaging array should find direct application in fusion plasma diagnostics. If the microbolometers can be replaced by more sensitive diode detectors, the array should also find application in radiometry and radar.
Observation of two modes of current transport through phosphorus-doped amorphous hydrogenated silicon Schottky barriers
Authors: Madan A. , Czubatyj W. , Yang J. , Shur M. S. , Shaw M. P.
Published: February 2003

The influence of phosphorus impurities in the active layer of amorphous hydrogenated silicon Schottky barriers is investigated by experimentally studying the current-voltage characteristics of the structure and the physical and electronic properties of the material. With increasing phosphorus concentration excess diode currents develop. Numerical analysis shows that (1) these currents are due to hopping within an impurity band produced by the impurities and (2) a two-channel conduction mechanism is in quantitative agreement with the data.
Carbon-oxygen complexes as nuclei for the precipitation of oxygen in Czochralski silicon
Authors: Oehrlein G. S. , Lindström J. L. , Corbett J. W.
Published: February 2003

Changes in the infrared absorption bands of different carbon-oxygen complexes which exist in as-grown Czochralski crystals occur concurrently with the precipitation of the interstitial oxygen during high-temperature heat treatment. The rate of change in the interstitial oxygen concentration and in the infrared absorption due to the carbon-oxygen complexes can be affected both in the same way through changes in heat treatment parameters such as the temperature and ambient gas. These results support the view that the different carbon-oxygen complexes act as heterogeneous nuclei for oxygen precipitation in Czochralski silicon.
Donor energy level for Se in Ga1−xAlxAs
Authors: Yang Jane J. , Moudy Lavada A. , Simpson William I
Published: February 2003

Electrical properties and the donor energy level in Se-doped n-Ga1−xAlxAs (0⩽x⩽0.82) prepared by metalorganic chemical vapor deposition have been investigated. The van der Pauw technique was used to measure the electrical properties of n-Ga1−xAlxAs. The resistivity and electron concentration of Se-doped Ga1−xAlxAs were found to be strongly affected by the donor energy level for Se. The donor energy levels ED of Se in Ga1−xAlxAs was found to remain constant at 0.003 eV for x<0.25. For x≳0.25, ED takes the form of an inverted V with a maximum at the direct-indirect band crossover.
Nitrogen as shallow acceptor in ZnSe grown by organometallic chemical vapor deposition
Authors: Stutius W.
Published: February 2003

Thin layers of ZnSe were grown on (100) GaAs substrates by organometallic chemical vapor deposition in the presence of ammonia with the intent to incorporate nitrogen as a group V acceptor. Low-temperature photoluminescence studies confirm that nitrogen is indeed incorporated as a shallow impurity with an activation energy of between ∼110 meV. ZnSe grown in the presence of phosphine gas, on the other hand, exhibits a photoluminescence spectrum characteristic of deep impurity level. A comparison of these results with other published data suggests that both N and P are incorporated as substitutional acceptors replacing Se.
Metal/tunnel-barrier/semiconductor/tunnel-barrier/metal fast photodetector
Authors: Thaniyavarn Suwat , Gustafson T. K.
Published: February 2003

A novel symmetric metal/tunnel-barrier/silicon/tunnel-barrier/metal planar junction fast photodetector is described. The device exhibits an observed pulse width of about 45-ps full width at half-maximum in response to synchronously pumped mode-locked rhodamine 6G dye laser pulses of <10-ps duration at 6000-Å wavelength. Detection sensitivity and dark current level are uniquely controlled by adjusting the tunnel-barrier thicknesses, without affecting the response speed. The particular detector described here has a sensitivity of order 1/2 mA/mW in response to the cw HeNe laser wavelength, and a dark current below 1 nA at <20-V bias.
Phase sensitivity and linewidth narrowing in a Fox–Smith configured semiconductor laser
Authors: Petuchowski S. J. , Miles R. O. , Dandridge A. , Giallorenzi T. G.
Published: February 2003

The behavior and spectral characteristics of a constricted double heterojunction injection laser in a regime in which the lasing characteristics are dominated by a cavity comprised of two external mirrors is reported. The Fox–Smith configuration is shown to limit the laser’s emission (previously multimode) to a single longitudinal mode with a linewidth of less than 200 kHz. It is also shown that this laser interferometer configuration is effective as an extended, external cavity laser diode sensor.
InxGa1−xAsyP1−y alloy stabilization by the InP substrate inside an unstable region in liquid phase epitaxy
Authors: Quillec M. , Daguet C. , Benchimol J. L. , Launois H.
Published: February 2003

A series of growths from the liquid phase have shown clearly that a large miscibility gap exists in the InxGa1−xAsyP1−y system at relatively high temperatures. The germinations were performed on (100) GaP. Using (100) InP as a substrate, it is shown that the lattice-matched solids are stabilized. This result is believed to be associated with the strain energy induced by the substrate.
Proton-isolated narrow stripe visible laser grown by metalorganic chemical vapor deposition
Authors: Mori Yoshifumi , Sato Hiromitsu , Ikeda Masao , Matsuda Osamu , Kaneko Kunio , Watanabe Naozo
Published: February 2003

Lasing characteristics were investigated on the narrow stripe visible laser grown by metalorganic chemical vapor deposition. The shortest emission wavelength achieved was 715 nm in pulsed operation. While the pulsed threshold current was essentially independent of the stripe width, the threshold current under cw operation increased with decreasing stripe width. The light-output power linearly increased without kinks up to 17 mW per facet for 760-nm devices with less than a 5-μm stripe. The differential quantum efficiency was as high as 70% and was independent both of the stripe width and of the emission wavelength. The beam pattern parallel to the junction plane was non-Gaussian with the full width at half-maximum power of 33°. Beam aspect ratio was less than 1.2.
Observation of deep levels in Hg1−xCdxTe with optical modulation spectroscopy
Authors: Polla D. L. , Aggarwal R. L. , Mroczkowski J. A. , Shanley J. F. , Reine M. B.
Published: February 2003

We have applied the technique of optical modulation spectroscopy to the narrow-gap semiconductor Hg1−xCdxTe. This technique consists of measuring the change ΔIp in the transmitted intensity Ip of a tunable dc probe beam (with photon energy h/ωP<Eg ) due to a fixed-wavelength chopped pump beam (with photon energy h/ωP≳Eg ). The ΔIp/Ip vs h/ωp spectra were measured for liquid phase epitaxial Hg1−xCdxTe samples at 94 K with x≅0.24–0.37. All spectra show three distinct peaks. The strongest peak occurs near Eg. The other two peaks are relatively sharp and occur below Eg. The energies of these two peaks are close to those of deep levels in Hg1−xCdxTe as recently determined by other techniques. This optical modulation technique, which is relatively simple, contactless, and nondestructive, may have significant potential for high-sensitivity and high-resolution study of deep levels in semiconductors.
Origin of the 0.82-eV electron trap in GaAs and its annihilation by shallow donors
Authors: Lagowski J. , Gatos H. C. , Parsey J. M. , Wada K. , Kaminska M. , Walukiewicz W.
Published: February 2003

The concentration of the major electron trap (0.82 eV below the conduction band) in GaAs (Bridgman grown) was found to increase with increasing As pressure during growth. It was further found that (for a given As pressure) the concentration of this trap decreased with increasing concentration of shallow donor dopants (Si, Se, and Te). Donor concentrations above a threshold of about 1017 cm−3 led to the rapid elimination of the trap. On the basis of these findings, the 0.82-eV trap was attributed to the antisite defect AsGa formed during the postgrowth cooling of the crystals.
Electron irradiation effects in lead-alloy Josephson junctions
Authors: Lee Y. H. , Brosious P. R.
Published: February 2003

Electron irradiation was performed on lead-alloy Josephson junctions with incident electron energies of 15 keV to 3.0 MeV. The quasi-particle tunneling current was observed to increase, proportional to the electron fluence over the range (1015∼1018 electrons/cm2). Radiation effects at low energy (⩽30 keV) clearly indicate that radiation-induced point defects within the tunnel barrier are responsible for changes in both the tunneling current and the annealing characteristics of junctions.
Influence of substrate temperature on the mobility of modulation-doped AlxGa1−xAs/GaAs heterostructures grown by molecular beam epitaxy
Authors: Drummond T. J. , Fischer R. , Morkoç H. , Miller P.
Published: February 2003

Single-period modulation-doped Al0.3 Ga0.7 As/GaAs heterostructures were grown by molecular beam epitaxy in a substrate temperature range of 580–750 °C. Excellent surface morphologies were routinely obtained throughout the entire range of growth temperatures. Highest mobilities (in dark) obtained were 8000, 90 000, and 196 200 at 300, 78, and 10 K, respectively. In room light, these figures improved to 9000, 110 000, and 250 000 cm2/Vs. The sheet carrier concentration yielding the best electron mobility was about 8×1011 cm−2. While the mobilities did not depend on the substrate growth temperature between 600 and 675 °C, some degradation was observed above 675 and below 600 °C.
Closed system fabrication of Josephson tunnel junctions
Authors: Hohenwarter G. K. , Nordman J. E.
Published: February 2003

A technique for the fabrication of Josephson tunnel junctions without breaking vacuum and without the use of masks is presented. No chemical processing is done on either of the junction electrode surfaces. Hence, no chemical or reactive cleaning is required before the formation of the tunneling barrier. Nevertheless, standard photolithography and chemical or plasma etching can be employed for defining patterns. I-V characteristics of Nb-NbOx-Pb junctions fabricated by this method have not exhibited a ’’knee’’ at the onset of the quasiparticle current.
GYROFEL—a hybrid electron synchrotron laser
Authors: Schoen Neil C.
Published: February 2003

A potential new mode of operation of an electron synchrotron radiation device is described, representing a unification of concepts encompassing gyrotron and free-electron laser devices. The GYROFEL configuration utilizes the predicted axial or longitudinal electron beam bunching to allow enhancement of forward-directed, Doppler-shifted synchrotron radiation, provided that appropriate electron beam/wave velocity synchronism occurs. Computer simulations and preliminary experimental data are presented in support of this microwave laser concept.
Interaction of a bistable injection laser with an external optical cavity
Authors: Lau K. Y. , Harder Ch. , Yariv A.
Published: February 2003

Experimental results on interactions of a bistable laser with an external optical cavity are presented. Switching of a bistable injection laser can be done by varying the amount of optical feedback. The optical switching is accompanied by a switching of the voltage across the absorber section. This can be utilized in digital optical disk readout. A bistable laser with an antireflection coating on one facet is more suitable for this task. No pulsations can be observed in a bistable laser with optical feedback if the absorber section is biased with a constant current source; but when it is biased with a voltage source, pulsation occurs at the external cavity round trip frequency. This indicates that even though the intrinsic absorption of the semiconductor material does not saturate easier than the gain, the presence of such absorptions in GaAs lasers can still produce pulsations when the electrical aspect is taken into account.
Effective deep ultraviolet photoetching of polymethyl methacrylate by an excimer laser
Authors: Kawamura Y. , Toyoda K. , Namba S.
Published: February 2003

Photoetching of polymethyl methacrylate (PMMA) for pulsed high power UV light is demonstrated. As a high power UV light source, a KrF excimer laser was used. Etching depth obtained by deep UV light irradiation has not only energy dependence, but also power dependence. It increased abruptly by increasing the exposed power density for the same exposed energy density.These experimental results show that high power excimer lasers are the effective light source for UV photoetching of PMMA.
Current induced trap generation in SiO2
Authors: Badihi A. , Eitan B. , Cohen I. , Shappir J.
Published: February 2003

Trap generation in the gate oxide of metal-oxide-semiconductor structure is studied in this work. It is shown that the application of a field of several MV/cm across the oxide together with electron injection into the oxide results in trap generation, while application of high electric field without electron injection or injection in low electric field does not generate traps. The density of the generated traps is shown to be linearly dependent on the total charge flowing through the oxide and exponentially dependent on the oxide field. For prolonged injection with high oxide field, the trap generation leads to oxide breakdown.
Prediction of negative diffusivity under transient regime conditions
Authors: Boittiaux B. , Constant E. , Reggiani L. , Brunetti R. , Jacoboni C.
Published: February 2003

We report on the possibility of a negative diffusivity under transient regime conditions. This effect is predicted by Monte Carlo calculations in polar semiconductors undergoing Gunn effect.
Determination of the diffusing species and mechanism of diffusion during CrSi2 formation, using 31Si as a marker
Authors: Botha A. P. , Pretorius R. , Kritzinger S.
Published: February 2003

Both the diffusing atomic species and its mechanism of diffusion have been directly determined during metal-silicon interaction to form CrSi2. By using radioactive 31Si (half-life = 2.62h) as a marker, it has been shown that silicon is the diffusing species during CrSi2 formation and that it diffuses by a substitutional (vacancy) mechanism. Complete intermixing of radioactive 31Si and nonradioactive silicon was found to take place throughout the silicide layer at its formation temperature, due to high substitutional (vacancy) self-diffusion of silicon in CrSi2.
Quenched-in defects in laser annealed silicon
Authors: Fan Z. K. , Ho V. Q. , Sugano T.
Published: February 2003

The generation of defects in Si by pulsed laser irradiation was studied by deep level transient spectroscopy. For irradiation with pulsed ruby laser, three defect levels at Ec −0.25 eV, Ec −0.32 eV, and Ec −0.49 eV were observed. These defects, which generate large leakage current at Schottky diodes, are attributed to quenched-in defects because their energy levels are very close to those generated by quenching-in silicon wafer from a resistance heated furnace. However, they can be annealed out by a thermal annealing in nitrogen ambient at 600 °C.
Ion-induced physical and optical densification in obliquely deposited Se0.75Ge0.25 films
Authors: Chopra K. L. , Harshavardhan K. Solomon , Rajagopalan S. , Malhotra L. K.
Published: February 2003

Irradiation of obliquely deposited films of Se0.75Ge0.25 with 50-keV He+ ions produces enormous physical and optical densification. A thickness and hence volume contraction up to 39% accompanied by large changes (0.20 eV) in the band gap and refractive index (10.2%) have been observed. These changes are primarily due to the physical collapse of the low density columnar structure and associated electron-phonon coupling. Such large changes have great potential applications in high resolution image storage, holography, and lithography.
A lateral, unidirectional, bipolar-type insulated-gate transistor—A novel semiconductor device
Authors: Ōmura Yasuhisa
Published: February 2003

A lateral, unidirectional, bipolar-type insulated-gate transistor (Lubistor) is newly proposed. It has three features: a p+-n (or p)-n+ structure, an insulated gate on the n(or p) region, and the thickness of the n(or p) region is approximately equal to or less than the effective Debye length. It is shown that the Lubistor has triodelike current-voltage characteristics, and that the characteristic curve shifts continuously toward a high anode-to-cathode bias along the anode-to-cathode voltage axis when the gate-to-cathode voltage enhances the majority-carrier concentration in the channel region.
Low noise normally on and normally off two-dimensional electron gas field-effect transistors
Authors: Laviron M. , Delagebeaudeuf D. , Delescluse P. , Etienne P. , Chaplart J. , Linh Nuyen T.
Published: February 2003

Normally on and normally off two-dimensional electron gas field-effect transistors (TEGFET’s) have been fabricated. Source, drain, and gate are directly deposited on the Si-doped AlGaAs top layer without any recess. At 10 GHz noise figure is 2.3 dB for both types with an associated gain of 10.3 and 7.7 dB for normally on and normally off device respectively. High performance normally off TEGFET opens a large field of application.
Critical volume fraction of crystallinity for conductivity percolation in phosphorus-doped Si:F:H alloys
Authors: Tsu R. , Gonzalez-Hernandez J. , Chao S. S. , Lee S. C. , Tanaka K.
Published: February 2003

We have used Raman scattering to deduce the volume fraction of crystallinity for the highly phosphorus-doped glow-discharge Si:F:H alloys. The measured critical volume fraction at the onset of rapidly increased conduction in this two-phase system of microcrystallites embedded in an amorphous matrix is 0.18. This value coincides with the theoretical percolation limit and serves to explain the conduction process in these two-phase materials which are useful as contacts in amorphous solar cells.
Preparation and properties of TiO2 varistors
Authors: Yan M. F. , Rhodes W. W.
Published: February 2003

TiO2 varistors with low resistivity were developed to operate at low voltages and have a reasonably high nonlinearity index. The varistor properties of TiO2 ceramics are due to two different groups of dopants. Pentavalent cation dopants are used to decrease the TiO2 lattice resistivity to ≃10–100 Ω cm at 25°C. Divalent cation dopants with large ionic radii are introduced to the grain boundary region by segregation process during cooling to provide a localized transport barrier. Thus, the conductive grain lattice and the resistive grain boundaries result in a low voltage varistor.
Observation of photoinduced changes in the bulk density of gap states in hydrogenated amorphous silicon
Authors: Lang D. V. , Cohen J. D. , Harbison J. P. , Sergent A. M.
Published: February 2003

We have observed a reversible photoinduced modification of the bulk density of gap states in a-Si:H associated with the Staebler–Wronski effect. A detailed numerical analysis of diode admittance and deep level transient spectroscopy measurements shows that the changes in these properties after illumination can be explained by a lowering of the bulk Fermi level and an increase in the density of states below midgap.
Interfacial electronic structure and density of states of intrinsic a-Si:H deposited on clean and oxidized stainless steel
Authors: Nielsen Paul , Gredin Robert
Published: February 2003

Photoemission and Auger measurements on thin a-Si:H films prepared in situ have revealed the presence of an interfacial potential step of 0.3 eV between clean stainless steel and a-Si:H, and 0.5 eV between oxidized stainless steel and a-Si:H. A small shift in the valence-band maximum (VBM) as the thickness of the a-Si:H is increased, if interpreted as band bending, gives an upper limit for the bulk density of states of about 7×1018 states cm−3 eV−1. Direct measurement of the optical density of states reveals less than 1019 states cm−3 eV−1 at energies more than 0.30 eV above the VBM.
Mechanism of ion dechanneling in compound semiconductor superlattices
Authors: Barrett John H.
Published: February 2003

Computer simulations of channeling have been used to evaluate a model proposed by Saris et al. to explain some of their ion dechanneling measurements in InAs-GaSb superlattices. Their model, which involves slight offsets of atomic rows at each interface, produces much less dechanneling than observed experimentally. However, the simulations show that the observed dechanneling can be produced by much larger offsets which would probably be spread over several atomic layers near each interface.
Difference-frequency variation of the free-carrier-induced, third-order nonlinear susceptibility in n-InSb
Authors: Yuen S. Y. , Wolff P. A.
Published: February 2003

Free-carrier-induced optical nonlinearities were studied, via four-wave mixing, in n-InSb as a function of the frequency difference Δω, between two CO2 laser beams. The third-order nonlinear susceptibility increases by more than an order of magnitude as Δω→0. This effect is ascribed to electron temperature fluctuations produced by the nonlinear optical interactions. An energy relaxation time of 3–4 ps is inferred for the highly excited electron gas. Studies of the frequency dependence of the nonlinear susceptibility may provide a new technique for measuring fast relaxation times in semiconductors.
Calculation of capacitance-voltage characteristics of hydrogenated amorphous silicon Schottky diodes
Authors: Chen Inan , Lee Sanboh
Published: February 2003

By adopting a new boundary condition appropriate to hydrogenated amorphous silicon diodes, and using the nonequilibrium Fermi–Dirac statistics, we predict a low-frequency capacitance-voltage relation which is quite different from that obtained by previous calculations in the literature, while in good agreement with more recent experimental results. The physical reasons for the differences are discussed.
Voltage and frequency dependence of simulated rf plasma annealing in metal-SiO2-Si structures
Authors: Chin M. R. , Ma T. P.
Published: February 2003

In a simulation experiment the rf plasma annealing rate of the positive oxide charge in metal-SiO2-Si structures has been found to be a function of the amplitude and frequency of the ac voltage. In the range studied (0.4–8 V, 10 Hz–10 MHz), the rate increases with both the amplitude and the frequency until saturation is reached near the upper figures. For frequencies above 100 kHz, an enhanced annealing rate (compared with the pure thermal annealing) is observed even at an rf voltage as low as 0.4 V. Similarly, for voltages above 4 V, an enhanced annealing rate is observed at a frequency as low as 100 Hz. A simple theory based on the first-order trapping-recombination kinetics in the context of the recombination enhanced defect reactions model has been developed to explain the experimental results.