bluuebunny/crossref_metadata_2025 huggingface dataset:
High-gain, high-frequency AlGaAs/GaAs graded band-gap base bipolar transistors with a Be diffusion setback layer in the base
Authors: Malik R. J. , Capasso F. , Stall R. A. , Kiehl R. A. , Ryan R. W. , Wunder R. , Bethea C. G.
Published: July 2002

AlGaAs/GaAs heterojunction bipolar transistors (HBT’s) with graded band-gap bases were fabricated from computer-controlled molecular beam epitaxy layers. It was found that the use of an undoped setback layer of 200–500 Å to offset Be diffusion in the emitter resulted in significant current gain increases. Maximum current gains of 1150 for a base width of 0.18 μm were obtained which are the highest yet reported for graded base HBT’s. Zn diffusion was used to contact the base and provides a low base contact resistance. Microwave s-parameter measurements yielded fT=5 GHz and fmax=2.5 GHz. Large signal pulse measurements resulted in rise times of τr∼150 ps and pulsed collector currents of Ic>100 mA which is useful for high current laser drivers.
High efficiency n-Cd(Se,Te)/S=photoelectrochemical cell resulting from solution chemistry control
Authors: Licht Stuart , Tenne Reshef , Dagan Geulah , Hodes Gary , Manassen Joost , Cahen David , Triboulet Robert , Rioux Jacques , Levy-Clement Claude
Published: July 2002

High efficiency (12.7%) CdSe0.68Te0.32/cesium polysulfide photoelectrochemical cells are demonstrated in this work. Crystals of the ternary alloy Cd(Se, Te) of type n type were synthesized by the traveling heater method. The nature of the polysulfide electrolyte, based on Cs polysulfide without excess hydroxide and containing small amounts of copper ions, is shown to be of particular importance in determining the cell efficiency. Reasonable output stability of the cell was obtained under accelerated tests.
A high-sensitivity stressed photoconductor for observing luminescence from germanium
Authors: Perez J. M.
Published: July 2002

We describe a detector for observing luminescence from germanium with a noise equivalent power (NEP)=2×10−14 W/(Hz)1/2 at 0.71 eV. The detector consists of a high-purity Ge photoconductor at 2 K which is stressed 85 kg/mm2 in the 〈111〉 direction to reduce the band gap to 0.68 eV. At this band gap, the detector efficiently absorbs luminescence ≥0.70 eV but is insensitive to room-temperature blackbody radiation which degrades commercial detectors with smaller band gaps. The NEP limit set by shot noise is 1.7×10−15 W/(Hz)1/2 at 0.71 eV. The current at low light level is thought to be space charge limited current.
Combination of open-tube vapor and liquid phase epitaxy of Hg1−xCdxTe
Authors: Sand E. , Levy D. , Nemirovsky Y.
Published: July 2002

A novel growth process of Hg1−xCdxTe epitaxial layers by a combination of open-tube vapor phase epitaxy (VPE) and liquid phase epitaxy (LPE) techniques is described. Device-quality layers with improved morphology, reduced misfit dislocations, and a reflecting boundary with very low surface recombination velocity at the substrate interface are obtained by this method. High performance photodiodes operating at both 77 and 193 K with cut-off wavelengths of 6.2 and 5.3 μm respectively were fabricated. The epitaxial layers obtained on bulk CdTe by the combination of VPE and LPE are in some respects better than layers grown by LPE on alternate substrates such as CdZnTe. off
Analysis of rib waveguides with sloped rib sides
Authors: Dagli Nadir , Fonstad Clifton G.
Published: July 2002

Using a mode matching technique, an approximate microwave equivalent circuit is developed for a dielectric step discontinuity in the transverse direction of a dielectric waveguide. Using this basic building block, rib waveguides with sloped sides are analyzed by approximating the actual rib profile with a staircase function, and cut-off conditions for E12 and E21 modes are calculated. The results of the theoretical analysis are verified with experiments performed on homojunction GaAs rib waveguides. Finally, an effective rib width appropriate for applying the results of analyses of ideal structures to sloped sided guides is identified.
Monolithic integration of a pin photodiode and a field-effect transistor using a new fabrication technique—graded step process
Authors: Miura S. , Machida H. , Wada O. , Nakai K. , Sakurai T.
Published: July 2002

A new fabrication technique of optoelectronic integrated circuit’s (OEIC’s), the graded step process, has been developed and found to improve the photolithographic yield and the overall process reproducibility. By applying this technique, a laterally integrated pin photodiode/field-effect transistor has been fabricated and shown to exhibit a high-speed response and a high sensitivity. This result indicates the potential of this process for applications to larger scale OEIC’s.
Dispersive thermal carrier generation in amorphous SeTe alloys
Authors: Abkowitz M. , Foley G. M. T. , Markovics J. M. , Palumbo A. C.
Published: July 2002

The dark decay of open circuit surface voltage on a series of capacity charged amorphous Se:Te films is analyzed. It is demonstrated that dark decay is controlled by thermal emission from discrete states deep in the mobility gap. The rate of dark decay and the shape of the dark decay function dV/dt vs t vary with alloy composition. This composition induced variation in the thermal emission process is demonstrated to exhibit experimental features analogous to those which characterize dispersive transport.
Metalorganic growth of CdTe and HgCdTe epitaxial films at a reduced substrate temperature using diisopropyltelluride
Authors: Hoke W. E. , Lemonias P. J.
Published: July 2002

Epitaxial films of CdTe and HgCdTe have been grown using a new metalorganic compound, diisopropyltelluride. Diisopropyltelluride is found to be less stable than the conventionally used diethyltelluride and consequently makes possible HgCdTe growth at a lower substrate temperature. Specular CdTe and HgCdTe epitaxial films have been obtained with moderate growth rates at substrate temperatures as low as 350 °C. Preliminary infrared and Hall measurements are encouraging for the application of this compound for HgCdTe growth. The reduced stability of diisopropyltelluride compared to diethyltelluride is consistent with a stability model for branched hydrocarbon molecules.
Flash annealing of copper and krypton ion implants in cadmium telluride
Authors: James K. M. , Merz J. L. , Jones C. E.
Published: July 2002

Copper and krypton ions have been implanted into Bridgman-grown CdTe crystals. Radiation from tungsten lamps was used to flash anneal the implant damage. Low-temperature photoluminescence analysis of the annealed samples indicates that the annealing provided almost complete repair of the implant damage. However, Cu implants did not significantly increase the activation of this impurity in the lattice when compared with an unimplanted, annealed standard. A comparison of the luminescence spectral changes following annealing at various temperatures of both implanted and unimplanted samples was made. This comparison indicated that activation of Cd site substitutional impurities in the lattice may be limited by the concentration of Cd vacancies generated by the annealing.
Strongly polarized bound exciton luminescence from GaAs grown by molecular beam epitaxy
Authors: Skolnick M. S. , Harris T. D. , Tu C. W. , Brennan T. M. , Sturge M. D.
Published: July 2002

We report strongly polarized luminescence spectra in the 1.504–1.511-eV spectral region in GaAs layers grown by molecular beam epitaxy. Up to 50 individual features are observed in very well resolved spectra. The sharp lines are attributed to bound exciton recombination at defect pairs preferentially oriented parallel to one of the 〈110〉 directions in the (001) growth plane. The preferential orientation occurs because of the inequivalence during planar growth of the [110] and [1̄10] directions in the zincblende lattice.
Index-guided arrays of Schottky barrier confined lasers
Authors: Temkin H. , Logan R. A. , van der Ziel J. P. , Reynolds C. L. , Tharaldsen S. M.
Published: July 2002

We describe simple, self-aligned, index-guided arrays containing up to 10 ridge waveguide lasers. The Ohmic contact and current confining Schottky barrier are provided by a single broad area metallization. This technique requires only a single growth on a planar (100) substrate and is compatible with all epitaxial growth techniques. Using conventional liquid phase epitaxy of GaAlAs we have obtained astigmatism-free arrays with threshold current as low as 20–30 mA per laser and power output linear to 300 mW/facet at temperatures as high as 100 °C, with the temperature dependence characterized by a large T0 of 240 °C. High optical quality of the output beam is demonstrated by very smooth and narrow far-field patterns, both in the phase-coupled and un-coupled extremes of the waveguide separation.
Cd diffused mesa-substrate buried heterostructure InGaAsP/InP laser
Authors: Yi M. B. , Lu L. T. , Kapon E. , Rav-Noy Z. , Margalit S. , Yariv A.
Published: July 2002

A new type of buried heterostructure InGaAsP/InP lasers grown by a single-step liquid phase epitaxy on Cd diffused mesa substrate is described. These lasers exhibit excellent current and optical confinement. Threshold currents as low as 15 mA are achieved for a laser with a 2-μm-wide active region.
12.5-GHz direct modulation bandwidth of vapor phase regrown 1.3-μm InGaAsP buried heterostructure lasers
Authors: Su C. B. , Lanzisera V. , Powazinik W. , Meland E. , Olshansky R. , Lauer R. B.
Published: July 2002

A small-signal modulation bandwidth of 12.5 GHz is reported for vapor phase regrown 1.3-μm InGaAsP buried heterostructure (BH) lasers operated at a bias optical power of only 6.9 mW/facet. The bandwidth per square root of bias optical power is a factor of 1.6 higher than previous best results. In addition, the optical modulation amplitude remains flat to 12 GHz in sharp contrast to other types of BH lasers which exhibit signal roll-off at frequencies below the resonance frequency. The wide modulation bandwidth is attained by increasing the  p-doping level in the active region and by the choice of short cavity length. The device is grown on a conductive substrate, indicating that it is unnecessary to use a semi-insulating substrate to obtain flat optical response in vapor phase regrown BH lasers.
Dominant intrinsic-exciton related luminescence from ZnSe grown by molecular beam epitaxy
Authors: Park R. M. , Mar H. A. , Salansky N. M.
Published: July 2002

ZnSe layers were grown by molecular beam epitaxy onto (100) oriented GaAs substrates using various incident Zn/Se flux ratios. Substrate temperatures were varied over the range 300–400 °C while the layer growth rate was maintained at about 0.1 μm/h. 4.2-K photoluminescence (PL) spectra were recorded from 0.5-μm-thick ZnSe layers using the 365-nm line from a Hg(Xe) lamp (25-mW/cm2 power density). ZnSe layers which are judged to have been grown under near-stoichiometric growth conditions exhibited dominant intrinsic-exciton related luminescence. A narrow peak at 2.8008 eV dominated the 4.2-K PL spectra obtained from these layers. In addition, we also observed two unreported peaks in the ZnSe excitonic range which we term X at 2.8061 eV and Y at 2.8050 eV. These peaks are as yet unassigned.
Sound speed determination in V2O5 single crystals using laser-generated acoustic waves
Authors: Sigrist Markus W. , Nánai László
Published: July 2002

The application of laser-generated acoustic waves for the determination of sound velocities in solids is reported. As an example the longitudinal sound speed along the crystallographic b axis in vanadium oxide (V2O5) has been measured for the first time yielding a value of 3200 ms−1.
Laser-induced synthesis of thin CuInSe2 films
Authors: Joliet M. C. , Antoniadis C. , Andrew R. , Laude L. D.
Published: July 2002

Thin films of CuInSe2 are synthesized by laser irradiation of Cu-In-Se sandwiches in 1:1:2 atomic proportion. Using transmission electron microscopy (TEM), electron diffraction, and optical spectrometry, the presence of semiconducting ternary compound CuInSe2, with the chalcopyrite structure, is strongly evidenced in all the irradiated samples, supported or not, with no other phases observed. For glass-supported films, the optical absorbance characteristic of a uniformly transformed region indicates a direct optical band gap of (0.95±0.10) eV. Crystallites obtained on free-standing films (i.e., supported on TEM grids) can reach 20 μm in dimension.
Wide band-gap, fairly conductive p-type hydrogenated amorphous silicon carbide films prepared by direct photolysis; solar cell application
Authors: Yamada Akira , Kenne Jean , Konagai Makoto , Takahashi Kiyoshi
Published: July 2002

Wide optical band-gap (2.0–2.3 eV) undoped and boron-doped hydrogenated amorphous silicon carbide (a-SiC:H) films have been prepared by both direct photo and rf glow discharge (GD plasma) decomposition of pure methylsilanes or acetylene and disilane gas mixtures. The photochemically prepared p-type films showed higher dark conductivities and lower activation energies. For an optical band gap of 2.0 eV a high conductivity of 7.0×10−5 (S cm−1) and a low activation energy of 0.33 eV have been measured. The first trial of these wide band-gap, fairly conductive films as a window layer in a p-i-n solar cell showed the high conversion efficiency of 9.46% under AM1 insolation.
Investigation of short time donor annihilation in silicon
Authors: O’Mara W. C. , Parker J. E. , Butler Paul , Gat Arnon
Published: July 2002

We have investigated the annealing of the oxygen donor in silicon in the temperature range 550–700 °C using Heatpulse lamp annealing in the time range of 1–1200 s. As-grown silicon wafers can contain donors due to cooling through 450 °C as a part of the crystal growth process. A 1-s anneal at 650 °C is sufficient to eliminate these donors completely. Intentionally created donors were annealed in order to determine reaction kinetics. A second-order process involving the donor plus another species fits the data, with an Arrhenius behavior as a function of temperature. The activation energy for this process is 1.7 eV.
A p
n
p AlGaAs/GaAs heterojunction bipolar transistor
Authors: Chand Naresh , Henderson Tim , Fischer Russ , Kopp William , Morkoç Hadis , Giacoletto Lawrence J.
Published: July 2002

Preliminary results of the first successful operation of pnp AlGaAs/GaAs heterojunction bipolar transistors grown by molecular beam epitaxy are reported. A common emitter current gain of 50 was obtained for a base width of 0.1 μm. For collector currents larger than a certain value, a negative output differential resistance (NDR) was seen at temperatures between 360 and 83 K. The onset of collector current for NDR was found to increase with decreasing temperature from 40 mA at 360 K to 200 mA at 83 K for emitter-base junction area of 10 μm×50 μm. The NDR was seen for both common base and common emitter characteristics and for both constant input currents and voltages. Increased surface recombination current at the edges of the emitter-base junction at large electric fields, large currents, and high temperatures appears to be the cause for NDR.
Transmission electron microscopy of hydrogenated amorphous semiconductor superlattices
Authors: Deckman H. W. , Dunsmuir J. H. , Abeles B.
Published: July 2002

Transmission electron microscopy (TEM) of amorphous semiconductor superlattices grown by plasma assisted chemical vapor deposition demonstrates that sequential layers can be deposited without cumulative roughening and with atomically abrupt interfaces. Absence of cumulative roughening effects allows layers to be grown flat and smooth to within 5 Å on a∼100-Å lateral scale length, even after deposition of several hundred layers. In highly localized regions unusual defect structures appear as bifurcations of individual layers. The TEM sections used to investigate amorphous superlattice structure were prepared by a novel microfabrication technique.
Structure imaging of commensurate GexSi1−x/Si(100) interfaces and superlattices
Authors: Hull R. , Gibson J. M. , Bean J. C.
Published: July 2002

High resolution electron microscopy is used to study interfacial quality in commensurate GexSi1−x systems grown by molecular beam epitaxy. Structure images of interfaces have been obtained, yielding atomic-scale information about sharpness and smoothness. From careful consideration of image contrast mechanisms at the interface, it is shown that variations in germanium concentration as low as about 5% may be detected under optimum conditions. Single interfaces of GexSi1−x exhibit no detectable diffusion of germanium into the silicon substrate and are locally sharp, but are not constrained to a single atomic plane. Interfacial quality is retained in a commensurate twenty-period 75-Å Ge0.4Si0.6/250-Å Si(100) superlattice. The techniques described here are also applicable to other compositional phase boundaries such as in III-V heterostructures.
Planar GaAs p-i-n photodiode with picosecond time response
Authors: Lenth W. , Chu A. , Mahoney L. J. , McClelland R. W. , Mountain R. W. , Silversmith D. J.
Published: July 2002

A high-speed planar GaAs p-i-n photodiode has been fabricated on a semi-insulating GaAs substrate. The time response and sensitivity have been characterized in the wavelength range typical of GaAlAs diode lasers. An optoelectronic correlation measurement technique was used to determine the time response. The device exhibits an impulse response of 19 ps full width at half-maximum to 4-ps near-infrared dye laser pulses with an external quantum efficiency of 15%. The device is operated at the low bias voltage of −2 V. The planar electrode design and fabrication on a semi-insulating substrate make the diode suitable for incorporation in monolithic optoelectronic circuits.
Polarization characteristics of distributed feedback semiconductor lasers
Authors: Agrawal Govind P. , Dutta Niloy K.
Published: July 2002

The threshold behavior of an index-guided distributed feedback semiconductor laser is analyzed theoretically with particular attention paid to the effect of internal stress on the polarization of stimulated emission. Using parameters appropriate for a 1.55-μm InGaAsP laser, a distributed feedback laser is found to have a lower threshold margin between the transverse electric (TE) and transverse magnetic (TM) modes than a similar Fabry–Perot laser. This threshold margin is strongly dependent on the internal stress normal to the active layer and depending on its magnitude either TE or TM mode may reach threshold first. The present analysis is in qualitative agreement with the experimental observations and is useful for device optimization.
Monolithic integration of a low threshold current quantum well laser and a driver circuit on a GaAs substrate
Authors: Sanada T. , Yamakoshi S. , Hamaguchi H. , Wada O. , Fujii T. , Horimatsu T. , Sakurai T.
Published: July 2002

An AlGaAs/GaAs graded-index waveguide separate-confinement heterostructure (GRIN SCH) laser and a laser driver circuit composed of four GaAs metal-semiconductor field-effect transistors have been monolithically integrated on a semi-insulating GaAs substrate. By introducing the GRIN SCH single quantum well (6 nm thick) structure, the integrated laser has exhibited room-temperature cw operation characteristics with an extremely low threshold current of 15 mA as well as a high quantum efficiency of 50%. Measurements have also shown the conversion ratio of laser output power to input gate voltage of 4.3 mW/V, and the turn-on and turn-off times of the light output of 400 and 900 ps, respectively, demonstrating high sensitivity and fast response performance of the present monolithic laser/driver.
Precise measurements and computer simulations of mode-hopping phenomena in semiconductor lasers
Authors: Ohtsu M. , Otsuka Y. , Teramachi Y.
Published: July 2002

We precisely measured temporal intensity variations of each longitudinal mode of a two-mode 1.5-μm InGaAsP laser. The intensities of these modes showed clear hopping between each other. It became clear for the first time that their power spectral densities represented typical Lorentzian with a cut-off frequency between 0.7 and 1.9 MHz. This means that mode hopping follows the stochastics of a Poisson process, i.e., it occurs completely at random in time. The results of analog computer simulation, using a detailed theoretical model, supported the experimental results. It is concluded that spontaneous emission acts as a trigger to this hopping.
Surface-emitting GaInAsP/InP laser with low threshold current and high efficiency
Authors: Liau Z. L. , Walpole J. N.
Published: July 2002

A buried-heterostructure laser has been developed whose output is deflected to a direction perpendicular to the substrate surface by a monolithically integrated 45° (parabolic) mirror. The latter is fabricated by smoothing a chemically etched multistep structure using a mass-transport phenomenon. The present devices show threshold current as low as 12 mA, differential quantum efficiency as high as 47% and a surface-emitting far-field pattern with a main lobe as narrow as 12°.
Accelerated aging of 100-mW cw multiple-stripe GaAlAs lasers grown by metalorganic chemical vapor deposition
Authors: Harnagel G. L. , Paoli T. L. , Thornton R. L. , Burnham R. D. , Smith D. L.
Published: July 2002

Lifetime characteristics of multiple-stripe, multi-quantum-well lasers operating in the 810-nm wavelength region at 100 mW cw and heat sink temperatures of 30, 70, and 100 °C are reported. Three failure modes were identified as dark line defect formation during early burn-in, gradual degradation at lower temperatures, and thermal resistance increases for long-term, high-temperature testing. Based upon gradual degradation data, the median operating life at 30 °C is projected to be 22 000 h, with a mean time to failure of 31 000 h. Actual extended life testing at 30 °C supports the validity of this projection.
Optical switching in a CdHgTe étalon at room temperature
Authors: Mathew J. G. H. , Craig D. , Miller A.
Published: July 2002

We report optical switching (dynamic optical bistability) in a 200-μm-thick, uncoated Cd0.23Hg0.77Te étalon at room temperature by two-photon excitation with a short pulse CO2 laser at 10.6 μm.
Operation of individual diode lasers as a coherent ensemble controlled by a spatial filter within an external cavity
Authors: Rediker R. H. , Schloss R. P. , Van Ruyven L. J.
Published: July 2002

Five diode gain elements (diode lasers with one facet antireflection coated) have been controlled to operate coherently with each other by a spatial filter placed between the antireflection coated facet and the mirror of an external cavity which provides the feedback for laser operation. The locking of the lasers is relatively insensitive to phase adjustment in each laser path. Locking has occurred with lasers whose output wavelength when operating individually differed by 60 Å. It is expected that the maximum tolerance to wavelength difference is much larger because lasers used were selected so simple individual temperature control could bring them into wavelength coincidence. These results point to the feasibility of placing well over a thousand diode lasers in an external cavity with coherent output.
New flattening technique of iron garnet films by laser etching
Authors: Ando Koji , Takeda Norio , Koshizuka Naoki
Published: July 2002

A new flattening technique was found through a study of the acceleration of the chemical etching process of iron garnet films by laser irradiation. The films on Gd3Ga5O12 substrates immersed in phosphoric acid were etched by irradiation with a laser beam of 581-nm wavelength. Regardless of the initial film thickness, the etching practically terminated when the thickness reached a certain magnitude. By using this phenomenon, we succeeded in flattening the film and integrating multiple different films on a single substrate.
Temperature dependence of hole mobility in GaAs-Ga1−xAlxAs heterojunctions
Authors: Mendez E. E. , Wang W. I.
Published: July 2002

The mobility and carrier density of two-dimensional hole systems formed at the interface of GaAs-Ga1−xAlxAs heterojunctions have been measured in the temperature range 1.9–100 K. The mobility increased monotonically with decreasing temperature, and in one sample reached 2.35×105 cm2 V−1 s−1, the highest value reported for holes. Optical phonon scattering (for T>40 K) and acoustic phonon scattering (for 15 K≤T≤40 K) are the mechanisms limiting the mobility down to low temperature, where Coulomb scattering dominates (for T<15 K). An observed linear increase of the inverse mobility with temperature cannot be explained quantitatively with a theory that was able to account for a similar behavior found in two-dimensional electrons.
High-speed junction-depleted Ga0.47In0.53As photoconductive detectors
Authors: Chen C. Y. , Dentai A. G. , Kasper B. L. , Garbinski P. A.
Published: July 2002

A high-speed junction-depleted Ga0.47In0.53As photoconductive detector without making use of radiation damage to the sample is reported. The detector has a light absorbing region in the n−layer of an unbiased p-n junction. As a result of the built-in field associated with the p-n junction, the carriers generated far from the surface were removed, leading to a picosecond response time. When tested by 100-ps, 1.55-μm light pulses, the detector showed a fall time of 90 ps with an external gain >1.3 (no antireflection coating). Receiver sensitivity at 1 Gb/s was −25.3 dBm at 1.55 μm and an error rate of 10−9.
Etch rate enhancement of silicon in CF4-O2 plasmas
Authors: White L. K. , Maa Jer-Shen
Published: July 2002

An etch rate enhancement of silicon in CF4-O2 gas mixtures in the presence of alkali metal ion hydroxide contaminants is examined. Sodium ion implanted samples show that the alkali metal ion is responsible for this effect. Other solution contamination experiments show that this effect was absent for hydroxide and chloride contaminants without an alkali metal, chlorine containing etchant gas mixtures, phosphorus-doped silicon, Si3N4, and TaSi2 substrates.
Eutectic melting by pulsed ion beam irradiation
Authors: Fastow R. , Mayer J. W. , Brat T. , Eizenberg M. , Olowolafe J. O.
Published: July 2002

Interfacial melting at near eutectic compositions has been observed for three metal-silicon systems using pulsed ion beam irradiation. In all cases (Ni/Si, Co/Si, and Pt/Si), the reaction occurred below the melting temperature of either the deposited metal layer or the silicon substrate. Compositional steps in the reacted Ni/Si, Co/Si, and Pt/Si films were measured using Rutherford backscattering spectroscopy. These steps had the near eutectic compositions of Ni0.5Si0.5, Co0.73Si0.27, and Pt0.77Si0.23, respectively. The Ni/Si sample was examined using planar and cross-sectional transmission electron microscopy. It was found that the reacted layer, composed of polycrystalline NiSi and Ni2Si, formed a sharp interface with the silicon.
Thermal coupling of particulates to substrates
Authors: Utterback S. , Dacol F. H. , Ermert H. , Melcher R. L.
Published: July 2002

The thermal radiation emitted by small particles heated by a modulated electron beam can be analyzed to give a quantitative measure of the thermal coupling between the particle and the substrate on which it rests.
Effects of substrate temperature on the orientation of ultrahigh vacuum evaporate Si and Ge films
Authors: Chao S. S. , Gonzalez-Hernandez J. , Martin D. , Tsu R.
Published: July 2002

Studies of texture in ultrahigh vacuum deposited Si and Ge films show a (220) preferred orientation for the as-prepared polycrystalline films. On the other hand, amorphous silicon (a-Si) followed by thermal crystallization exhibits a (111) orientation when contamination with oxygen is allowed prior to annealing. Oxygen incorporation is only indirectly involved in promoting the (111) preferred orientation via high annealing temperature. Preferred orientation is absent when contamination is avoided. In contrast, thermally crystallized a-Ge films show no preferred orientation regardless of oxygen contamination.
Niobium nitride Josephson tunnel junctions with magnesium oxide barriers
Authors: Shoji Akira , Aoyagi Masahiro , Kosaka Shin , Shinoki Fujitoshi , Hayakawa Hisao
Published: July 2002

Niobium nitride-niobium nitride Josephson tunnel junctions have been fabricated using amorphous magnesium oxide (a-MgO) films as barriers. These junctions have excellent tunneling characteristics. For example, a large gap voltage (Vg=5.1 mV), a large product of the maximum critical current and the normal tunneling resistance (IcRn=3.25 mV), and a small subgap leakage current (Vm=45 mV, measured at 3 mV) have been obtained for a NbN/a-MgO/NbN junction. The critical current of this junction remains finite up to 14.5 K.
Mechanisms for fluorocarbon reactive ion beam etching of SiO2 by simultaneous Auger electron spectroscopy measurements
Authors: Thomson D. J. , Helms C. R.
Published: July 2002

Auger electron spectroscopy was used to measure the carbon, fluorine, oxygen, and silicon concentrations on an SiO2 surface under bombardment by fluorocarbon ions. The results include the finding that, for CF+3 ions with energies >750 eV, little carbon is observed on the SiO2 surface, indicating a rapid reaction of the carbon with the oxygen. In addition, analysis of the Si LVV line shape showed the presence of flourinated Si on the surface, which has been inferred but never directly measured by other techniques.
AlGaAs/GaAs melt-etched inner stripe laser diode with self-aligned structure
Authors: Watanabe A. , Yamada T. , Imanaka K. , Horikawa H. , Kawai Y. , Sakuta M.
Published: July 2002

A novel liquid phase epitaxy (LPE) used to fabricate a channeled stripe AlGaAs/GaAs laser diode emitting at 780 nm with a self-aligned structure is reported. In the present method, only two-step LPE and a conventional wet chemical etching are required. The inner stripe, 4 μm wide, is grooved by a newly developed preferential melt-etching technique during crystal growth without exposure of the wafer to air. A maximum cw power output of 28 mW per facet without facet coatings and a threshold current of 50 mA are accomplished. Fundamental transverse mode operation up to 10 mW and single longitudinal mode above 2.5 mW are demonstrated.
Origin of phase conjugate waves in self-pumped photorefractive mirrors
Authors: Lam Juan F.
Published: July 2002

We show that stimulated two-wave mixing is the origin of phase conjugate fields in self-pumped photorefractive mirrors. We predict that the bulk photovoltaic effect gives rise to an intensity-dependent frequency shift in the phase conjugate field and is the physical origin for the occurrence of beam fanning.
Lateral extent of oxidation-enhanced diffusion of phosphorus in 〈100〉 silicon
Authors: Taniguchi K. , Antoniadis D. A.
Published: July 2002

The lateral extent of oxidation-enhanced diffusion (OED) of phosphorus in (100) silicon oxidized in dry oxygen has been investigated. OED was observed near the Si/SiO2 interface under an oxidation mask composed of Si3N4/SiO2. It was found that under the mask OED decays nearly exponentially from the edge of the oxidized region. The characteristic decay length increases with square root of oxidation time and is exponentially dependent on temperature with activation energy of 2 eV. It is proposed that the OED observations can be explained on the basis of excess silicon self-interstitials diffusing away from the oxidized regions. Both diffusion and interface capture of self-interstitials play a role in their distribution in the silicon bulk.
Two-dimensional electron gases in quantum well and superlattices of Ga0.25In0.75As0.50P0.50/InP heterostructures grown by low pressure metalorganic chemical vapor deposition
Authors: Razeghi M. , Duchemin J. P. , Portal J. C.
Published: July 2002

We report the first observation of a two-dimensional electron gas from Shubnikov–de Haas experiments, in a Ga0.25In0.75As0.50P0.50-InP heterojunction, multi-quantum well, and superlattices grown by metalorganic chemical vapor deposition at reduced pressure.
Structure of the InP/SiO2 interface
Authors: Liliental Z. , Krivanek O. L. , Wager J. F. , Goodnick S. M.
Published: July 2002

InP/SiO2 interfaces have been studied by high resolution electron microscopy in cross section, by ellipsometry, and by x-ray photoelectron spectroscopy. The roughness of the interface is shown to vary from 10 to 100 Å peak to peak depending on the InP surface treatment prior to SiO2 desposition, and some evidence is found for a small amount of native oxide and P segregation at the interface. Thermal oxide grown on InP at 350 °C is shown to consist of two separate layers, an inner one of 30–70 Å thickness and probably composition InPO4, and an outer one of 60-Å thickness and probably composition In2O3.
Detection of alignment signals for focused ion beam lithography
Authors: Morimoto H. , Sasaki Y. , Onoda H. , Kato T.
Published: July 2002

A detector and the output signal waveforms to be used for alignment in focused ion beam lithography are discussed. It is shown that a microchannelplate (MCP) is suitable for alignment signal detection. Alignment signals for 200-keV Si, 200-keV Be, and 100-keV Au ion beams are studied using the MCP. No deformation of alignment marks is observed in the case of light ions such as Si or Be. As a result, it is demonstrated that alignment can potentially be performed by detecting secondary electrons from the marks.
Thermoelectric figure of merit of boron phosphide
Authors: Yugo Shigemi , Sato Takashi , Kimura Tadamasa
Published: July 2002

The thermoelectric power, thermal and electrical conductivity of boron phosphide grown by chemical vapor deposition of hydrogenated compounds were measured in the temperature range from room temperature to 1000 °C and the figure of merit of boron phosphide was evaluated. The figure of merit of 8×10−4 deg−1 was obtained at 1000 °C. This is one of the largest figures of merit at 1000 °C that have ever been obtained.
Molecular beam epitaxial growth and transport properties of modulation-doped AlGaAs-GaAs heterostructures
Authors: Weimann G. , Schlapp W.
Published: July 2002

Mobilities and sheet carrier densities of single interface, modulation-doped AlGaAs-GaAs heterostructures depend on the structure and molecular beam epitaxial growth parameters. Variation of the thickness of the undoped spacer between 20 and 360 Å gave electron densities in the range 1012–2×1011 cm−2 in two-dimensional electron gases. Thick spacers resulted in high 4.2-K mobilities of 1.2×106 cm2/Vs in dark and 1.8×106 cm2/Vs under illumination with corresponding channel densities of 2.3×1011 cm−2 and 3.9×1011 cm−2, respectively. Two-dimensional hole gases had mobilities of 83 000 cm2/Vs and hole concentrations of 2.7×1011 cm−2 at 4.2 K.
Small-signal response of a semiconductor laser with inhomogeneous linewidth enhancement factor: Possibilities of a flat carrier-induced FM response
Authors: Nilsson O. , Yamamoto Y.
Published: July 2002

It is shown that inhomogeneities in the linewidth enhancement factor in a semiconductor laser exert great influence on the injection current modulation FM response. Several phenomena, which have not been explained so far, such as redshift frequency chirping, flat carrier induced FM response, and absence of phase reversal at the thermal cut-off frequency, are explained by the present theoretical model. A flat carrier induced FM response with either redshift or blueshift may be obtained in a semiconductor laser with an inhomogeneous linewidth enhancement factor without the accompanying spurious intensity modulation.
AlGaAs/GaAs p-i-n photodiode/preamplifier monolithic photoreceiver integrated on a semi-insulating GaAs substrate
Authors: Wada O. , Hamaguchi H. , Miura S. , Makiuchi M. , Nakai K. , Horimatsu H. , Sakurai T.
Published: July 2002

A fully monolithic photoreceiver circuit incorporating an AlGaAs/GaAs p-i-n photodiode and a GaAs field-effect transistor based transimpedance amplifier has been fabricated in the form of a horizontally integrated structure on a semi-insulating GaAs substrate. Parasitic capacitances of the circuit elements have been minimized in the present monolithic circuit, and a short rise and fall time of 1.0 ns, corresponding to an approximate −3 dB frequency of 300 MHz, has been demonstrated at the internal feedback resistance of 1.3 kΩ. Preliminary measurement of the noise characteristics of the present circuit has exhibited an encouraging value of the equivalent input noise current of 13 pA Hz−1/2 at 300 MHz.
Power enhancement for argon II narrow tube lasers by a transverse magnetic field
Authors: Kobayashi Shigeaki , Kamiya Takeshi , Hayashi Toshiharu , Goto Tatsumi
Published: July 2002

Appreciable enhancement in output and power efficiency for compact Ar II lasers (488.0 nm) is obtained by applying a transverse magnetic flux density at approximately 700 G. The enhancement factor amounts to as large as 3 in laser output and the efficiency becomes more than twice as much as without magnetic flux. A sharp rise in output occurs above the critical magnetic flux density, 450 G in the present work, where the cyclotron radius of electrons is nearly equal to one-half of the tube radius.
Magnetic field dependence of hot-electron transport in GaAs
Authors: Hayes J. R. , Levi A. F. J. , Wiegmann W.
Published: July 2002

We have studied the magnetic field dependence of hot-electron spectra using hot-electron spectroscopy. It is shown that application of a magnetic field normal to the injection direction has a dramatic effect on the spectra whereas a magnetic field applied parallel to the injection direction has no effect. The magnetic field is shown to increase the effective transit region width of the spectrometer enabling us to deduce a scattering rate for hot electrons that is at least four times greater than would be expected considering phonon emission alone.
Low-temperature impact ionization rates in (111) oriented InP
Authors: Osaka Fukunobu , Kishi Yutaka , Kobayashi Masahiro , Mikawa Takashi
Published: July 2002

Impact ionization rates in (111) oriented InP have been derived in the temperature range 77–293 K from photomultiplication data measured on a planar-type InP avalanche diode, and have been compared with those in (100) oriented InP. It has been found that there is no marked difference in electron ionization rates between the 〈111〉 and 〈100〉 orientations. This result confirms that no ballistic impact ionization occurs in InP at the measured electric field range of 4.1×105 V cm≤E≤5.6×105 V cm.
Period doubling and chaos in large area Josephson junctions induced by rf signals
Authors: Olsen O. H. , Samuelsen M. R.
Published: July 2002

The influence of an applied rf signal on the emitted radiation from a large area Josephson junction is examined. A model of the system is presented in the framework of the one-dimensional sine-Gordon equation. The model linearizes for small and large values of the amplitude of the applied signal. In the intermediate regime lower and upper threshold values (for the amplitude) for transition to chaos are found. Feigenbaum period doubling (period-doubling bifurcation cascade) appears when chaos is approached for increasing amplitude. The findings are supported experimentally.
Fermi energy dependence of linewidth enhancement factor of GaAlAs buried heterostructure lasers
Authors: Arakawa Y. , Yariv A.
Published: July 2002

The linewidth enhancement factor α is measured in a number of GaAlAs lasers with different internal losses. It is found that α decreases monotonically with the increase of the loss (Fermi energy level) in agreement with the theoretical prediction. On the basis of these results the design of cavity length and mirror reflection in order to reduce the spectral linewidth of the laser output is discussed.
Wave front conjugation with gain and self-oscillation with a nematic liquid-crystal film
Authors: Khoo I. C.
Published: July 2002

We have observed for the first time wave front conjugation with amplified reflection return using the thermal nonlinearity of a thin film of nematic liquid crystal in conjunction with a low power laser (intensity on the order of 25 W/cm2). Self-oscillation is also observed.
Effects of implanted hydrogen on Pd2Si formation
Authors: Paccagnella A. , Majni G. , Ottaviani G. , Della Mea G.
Published: July 2002

The Pd2Si growth kinetics for evaporated Pd films on (111) Si have been investigated by means of 2 MeV 4He+ backscattering spectrometry for as-deposited and high dose H implanted samples in the 200–250 °C temperature range. The implantation energy has been chosen so that most of H atoms stop near the Si/Pd interface. The changes in the H distribution in the annealed samples have been investigated by means of the 1H(15N, αγ)12C resonant nuclear reaction. An increase of the growth rate and a decrease of the activation energy of the silicide formation process have been detected in the implanted samples with respect to the as-deposited ones. The thermal treatment induces a noticeable decrease of H content.
Deposition of indium antimonide films by metalorganic magnetron sputtering
Authors: Webb James B. , Halpin C.
Published: July 2002

A new technique, metalorganic magnetron sputtering (MOMS), has been developed for the deposition of compound semiconductors. In particular, results are reported on the deposition of the III-V semiconductor indium antimonide from a high-purity antimony target and trimethylindium (TMI) vapor using rf magnetron sputtering. The indium/antimony ratio of the films is found to depend linearly on the trimethylindium flow rate and the indium/argon emission peak ratio of the plasma. The stoichiometry of the layers is controlled by changing either the TMI flow or the sputter power. InSb layers can be deposited at temperatures considerably below the thermal decomposition temperature of TMI. Auger analysis shows up to 10% carbon incorporation occurs for films deposited at room temperature, but this is reduced below the level of detection for substrate temperatures >190 °C.
Photoinduced modulation absorption by tuning pumping wavelength
Authors: Chen F. Y.
Published: July 2002

By tuning the pumping wavelength, the technique of photoinduced modulation absorption is shown to be able to measure the lifetime, the diffusion constant, and the effective surface recombination velocity of the carriers in semiconductors. An example of such pumping wavelength tuned modulation absorption for GaP is given as a demonstration.
Anomalous transport in PbTe doping superlattices
Authors: Jantsch W. , Bauer G. , Pichler P. , Clemens H.
Published: July 2002

The Hall coefficient of p-PbTe doping superlattices changes sign twice between 100 and 300 K. This effect is reported here for the first time and explained in terms of the temperature dependences of the static dielectric constant and the electron and hole mobilities. Below 140 K, persistent photoconductivity occurs, which is explained by electron trapping by deep states.
Analysis of ion induced surface damage on silicon etched in a CF4 plasma
Authors: Thomas John H. , McGinn J. T. , Hammer L. H.
Published: July 2002

Etchant residue and backscattered material have been observed on silicon surfaces etched in a CF4 plasma. In addition to chemical contamination, the surface is damaged by ion bombardment with dissociated CF4 ions. X-ray photoelectron spectroscopy and reflection high-energy electron diffraction were used to study the extent of the damage and how it correlates with surface contamination. At low ion energies, a well ordered crystal surface is observed in the presence of fluorine contamination. At higher ion energies (>400 V), the silicon surface is contaminated by backscattered nickel from an unshielded contact lead and the silicon surface becomes polycrystalline.
Strain effects in HgTe-CdTe superlattices grown on CdTe substrates
Authors: Wu G. Y. , McGill T. C.
Published: July 2002

The effects of strain on the band structure, the band gap, and optical properties of the superlattice grown on CdTe substrates are discussed. The presence of strain modifies the band gap and optical properties of the HgTe-CdTe superlattice in a minor way. However, strain does change the band structure as compared to that in the unstrained superlattice. For wave vectors perpendicular to the layers, the top of the valence band is more light-hole-like in constrast to the unstrained case where the top of the valence band is more heavy-hole-like. For wave vectors parallel to the layers, the bands remain unchanged.
High magnetic field transport properties of liquid quenched Nb3Al and Nb3Al(Si,Ge) superconducting compounds
Authors: Clemente G. , Habbal F. , Turnbull D. , Bevk J.
Published: July 2002

Critical current behavior and intrinsic superconducting properties of liquid quenched Nb3Al and its pseudobinaries Nb3 (Al,Si) and Nb3(Al,Ge) have been studied in fields up to 29 T. Our results show that flux pinning in these materials is dominated by strong precipitate pinning at low temperatures and by grain boundary pinning at high (>10 K) temperatures. The best results were obtained in Nb75Al19Ge6 samples with Tc of 20.0 K, estimated Hc2(0) of 43 T and Jc (4.2 K) in excess of 104 A/cm2 at 30 T.
Novel method of producing ultrasmall platinum silicide gate electrodes
Authors: Woerlee P. H. , Hurkx G. A. M. , Josquin W. J. M. J. , Verhoeven J. F. C. M.
Published: July 2002

A novel method has been developed for producing platinum silicide gate electrodes with submicron width. A lateral chemical reaction of platinum with polycrystalline silicon at a step edge was used. The width of the wire is determined by the thickness of a sputtered metal layer. Wires with width between 35 and 300 nm have been produced. The method has been used for making long-channel field-effect transistors with good device properties. Some preliminary results of the study of the low-temperature electrical transport properties of inversion layers with width of 0.12 μm are reported.
Determination of low levels of carbon in Czochralski silicon
Authors: Oates A. S. , Newman R. C. , Woolley R. , Davies G. , Lightowlers E. C. , Binns M. J. , Wilkes J. G.
Published: July 2002

The C(3) vibrational lines at 865 and 1115 cm−1 are shown to correlate in intensity with the 790-meV vibronic band in irradiated Czochralski silicon. The C(3)/790 meV lines may be used as a sensitive measure of the concentration of carbon in silicon.
Lamb wave reflection at plate edges
Authors: Diodati P. , Tassi G. , Alippi A.
Published: July 2002

The changing of modes taking place in Lamb wave reflected from the limiting edge of a plate is taken into consideration by evaluating the coupling of the single shear and longitudinal components, through Snell’s law. Acousto-optical probing of the acoustic field is used for studying the effect in isotropic plates, in the range of a few megahertz.
GaAs field-effect transistor properties, as influenced by the local concentrations of midgap native donors and dislocations
Authors: Dobrilla P. , Blakemore J. S. , McCamant A. J. , Gleason K. R. , Koyama R. Y.
Published: July 2002

Results are presented of electrical parameter mapping for arrays of field-effect transistors (FET’s) fabricated in semi-insulating GaAs wafers, compared with mapping data of the dislocation density and the neutral concentration of the main midgap donor defect (known as EL2) in the same wafers. The work seeks to clarify whether a ‘‘shift’’ of FET parameters such as threshold voltage Vth results directly from dislocation proximity, or whether such a shift results from FET sensitivity to the local EL2 concentration. For a wafer having quite different spatial distributions of EL2 and dislocations, the FET parameters were found to correlate strongly with the local neutral EL2 density, a high density promoting a larger channel current and a more negative Vth. Such results suggest that a reported sensitivity of Vth to dislocation proximity may arise from the role a dislocation can play as a source or sink for point defects.