bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical beam epitaxy of InP and GaAs
Authors: Tsang W. T.
Published: February 2003

A new epitaxial growth technique, chemical beam epitaxy (CBE), was demsonstrated and investigated with the growth of InP and GaAs. In this technique, all the sources were gaseous group III and group V alkyls. The In and Ga were derived by the pyrolysis of either trimethylindium or triethylindium and trimethylgallium or triethylgallium at the heated substrate surface, respectively. The As2 and P2 were obtained by thermal decomposition of triethylphosphine and trimethylarsine in contact with heated Ta or Mo at 950–1200 °C, respectively. Unlike conventional vapor phase epitaxy, in which the chemicals reach the substrate surface by diffusing through a stagnant carrier gas boundary layer above the substrate, the chemicals in CBE were admitted into a high vacuum growth chamber and impinged directly light of sight onto the heated substrate surface in the form of molecular beams. The beam nature of CBE resulted in efficient use of the impinging chemicals and allowed the utilization of mechanical shutters. A gas handling system similar to that employed in conventional metalorganic chemical vapor deposition with precision electronic mass flow controllers, was used for controlling the flow rates of the various gases admitted into the growth chamber. Growth rates as high as 3–5 μm/h have been achieved for both InP and GaAs. The InP and GaAs epilayers grown have smooth surfaces and an optical quality comparable to bulk substrates.
Low-temperature vacuum tunneling microscopy
Authors: Elrod S. A. , de Lozanne A. L. , Quate C. F.
Published: February 2003

We report what we believe is the first use of a vacuum tunneling microscope to spatially resolve changes in the electronic structure of a superconducting surface. The exponential dependence of the tunneling resistance on gap spacing is demonstrated at 300, 77, and 15 K. Current-voltage characteristics at low temperature show a structure that can be attributed to the superconducting gap of the Nb3Sn sample studied. We observe reproducible changes in this structure as the tip is laterally scanned between two locations on the surface separated by 220 Å.
Amplification by the phase-locking mechanism in a four-junction SQUID
Authors: McDonald D. G.
Published: February 2003

It is shown that the phase-locking property of an array of Josephson junctions can be used as a basis for amplification. The particular device simulated is a superconducting quantum interference device (SQUID) with four junctions in the loop, rather than the usual one or two. Novel consequences of this design are that it allows direct rather than inductive coupling to the SQUID and, because of its potentially compact form, it probably can have a bandwidth well into the gigahertz range, in agreement with the simulations.
Ion channeling studies of preferentially (111) oriented BaF2 films on amorphous SiO2 substrates
Authors: Ishiwara Hiroshi , Kaifu Noriyuki , Asano Tanemasa
Published: February 2003

The crystalline quality of preferentially (111) oriented BaF2 films grown on amorphous SiO2 has been investigated by ion channeling measurements, as well as x-ray diffraction analyses and transmission electron microscopy (TEM). The films are grown by vacuum deposition onto heated (500–750 °C) Si substrates covered with SiO2 films. It has been found that the channeling effect of MeV ions occurs in BaF2 films on SiO2 and that the minimum yield in the films grown at 700 °C is as low as 9% near the surface. It has also been observed by TEM and x-ray analyses that the average size of the crystallites and the spread of the crystallite orientation in the good films are about 400 nm and 0.4°, respectively.
A fiber-optic laser-Doppler anemometer
Authors: Nguyen Thang T. , Binh Le N.
Published: February 2003

A device to measure water particle velocity in two directions under a breaking water wave was developed using single-mode, polarization-preserving fibers in conjunction with a two-color, three-beam laser-Doppler anemometer. The sensor uses backscatter method with two beams frequency shifted to measure velocity reversal in both directions.
Surface accumulation of tin in tin-doped gallium arsenide grown by low pressure metalorganic vapor phase epitaxy
Authors: Sundaram V. S. , Roth A. P. , Williams D. F. , Yakimova R.
Published: February 2003

The surface accumulation of tin in low pressure metalorganic chemical vapor epitaxy (MOVPE) grown tin-doped GaAs layers has been investigated by secondary ion mass spectroscopy. Our results show that the surface enrichment factor for MOVPE grown layers is negligible for n≲5×1018 cm−3. For layers of higher doping densities this enrichment factor is smaller by more than an order of magnitude than that obtained for molecular beam epitaxy grown layers of comparable doping, in spite of the higher growth temperature used in MOVPE. A qualitative interpretation for the observed low surface enrichment factor is given.
Relationship between the conduction-band discontinuities and band-gap differences of InGaAsP/InP heterojunctions
Authors: Forrest S. R. , Schmidt P. H. , Wilson R. B. , Kaplan M. L.
Published: February 2003

We have measured the magnitude of the conduction-band discontinuities at heterojunctions for several compositions of InGaAsP grown lattice matched on InP. We find that the conduction-band discontinuity (ΔEc) is related to the difference in band gaps (ΔEg) between the InGaAsP and InP layers via ΔEc =0.39(ΔEg). Thus, 40% of the band-gap difference lies in the conduction band of this material system. The measurements were made on a series of composition of InGaAsP spanning the alloy range from In0.53Ga0.47As (with energy gap Eg =0.75 eV) to InP (Eg =1.35 eV) using capacitance-voltage techniques. Depletion deep into the semiconductor layers was facilitated by the formation of organic-on-inorganic semiconductor contact barriers on the InGaAsP surface.
Above threshold characteristics of amorphous silicon alloy thin-film transistors
Authors: Hyun C. , Shur M. S. , Hack M. , Yaniv Z. , Cannella V.
Published: February 2003

We present experimental evidence to show that the field-effect mobility in amorphous silicon alloy thin-film transistors in the above threshold regime is dependent on the gate voltage. The current-voltage transistor characteristics exhibit a power law dependence on gate voltage with an exponent close to 2.85.
Impurity and interfacial effects on the formation of amorphous Si from the melt
Authors: Campisano S. U. , Jacobson D. C. , Poate J. M. , Cullis A. G. , Chew N. G.
Published: February 2003

Amorphous Si has been formed from the melt by the UV laser heating of surface layers of single crystal (111) Si. The single crystals were doped with As, Bi, In, or Te to concentrations of approximately one part in 103. For the same quenching rates, the amorphous layers produced on the doped Si were substantially thicker than those on pure Si. Maximum amorphous thicknesses of 1200 Å were obtained. The amorphization phenomena are correlated with melt depths and interfacial segregation effects.
Effects of prelayers on minority-carrier lifetime in GaAs/AlGaAs double heterostructures grown by molecular beam epitaxy
Authors: Dawson P. , Woodbridge K.
Published: February 2003

From room-temperature measurements of the photoluminescence decay time, values for the sum of the interface recombination velocities in a series of GaAs/AlGaAs double heterostructures have been obtained. The effects of various combinations of prelayers of GaAs and AlGaAs have been investigated and we show that it is possible to reduce the sum of the interface recombination velocities to as low as 60 cm/s.
Anomalous decomposition profile of the excited triplet SiH3F: A prediction by a
b i
n
i
t
i
o molecular orbital calculations
Authors: Sato Kota , Hirano Tsuneo , Natsuaki Hiroatsu , Fueki Kazuo , Koinuma Hideomi
Published: February 2003

In search of new starting materials for producing amorphous silicon by plasma chemical vapor deposition, decomposition profiles through triplet states have been studied for fluorosilanes SiHmF4−m (m=0–4) by energy-gradient ab initio molecular orbital calculations with the 6–21G** basis set. Anomalous Si–F bond cleavage at the first stage was concluded for triplet SiH3F, while all the other fluorosilanes decompose through the Si–H bond cleavage. The anomaly observed for triplet SiH3F is due to the positive charge on F and to the negative overlap population of the Si–F bond. Thus, SiH3F is expected to be a unique source for amorphous silicon films.
Temperature behavior of optical absorption in InGaAsP lasers
Authors: Shen T. M. , Dutta N. K.
Published: February 2003

The temperature dependence of the optical absorption in InGaAsP laser emitting at 1.3 μm is studied by measuring the relaxation frequency as a function of output power at various temperatures. Our results show that the optical absorption does not vary significantly with increasing temperature. This suggests that the threshold carrier density in InGaAsP lasers is weakly temperature dependent compared to the threshold current density. Thus, the strong temperature dependence of threshold current in 1.3-μm InGaAsP lasers is primarily due to the temperature dependence of the carrier lifetime at threshold. The shorter carrier lifetime (i.e., increased carrier loss) at high temperature can be due to Auger recombination.
Optical hysteresis in fast transient experiments near the band gap of cadmium sulfide
Authors: Dagenais M.
Published: February 2003

Calculations which include the effects of lattice heating on recent transient nanosecond experiments done near the band gap of cadmium sulfide at low temperatures are presented. For a detuning of 5.7 meV below the A free-exciton resonance and for input intensities of about 1×107 W/cm2 large optical hysteresis in the transmitted power is predicted. Good agreement between our theoretical predictions based on lattice heating and the experimental results of Bohnert, Kalt, and Klingshirn [Appl. Phys. Lett. 43, 1088 (1983)] is obtained.
Photon echo optical pulse compression
Authors: Bai Y. S. , Mossberg T. W.
Published: February 2003

It is predicted that linearly chirped optical excitation pulses give rise to photon echoes whose shortness is limited only by the total material bandwidth that contributes to the echo signal. The photon echo process acts as a frequency-dependent optical delay line whose dispersion is determined by the chirp rate of the excitation pulses rather than by their bandwidth. Consequently, long and short pulses can be compressed with equal facility without complicated alignment procedure. Accumulated echoes have similar properties and can be used with trains of weak excitation pulses.
Applicability of the Meyer–Neldel rule to solar cells
Authors: Goradia Chandra , Weizer Victor G.
Published: February 2003

A comparison of data taken on high quality silicon, GaAs, and GaInAs solar cells with those taken on a variety of homojunction, heterojunction, and metal-insulator-semiconductor devices indicates that while the Meyer–Neldel rule may be applicable to certain types of solar cells it is not applicable to well-behaved, diffusion-controlled homojunction devices. It cannot be used, therefore, as a universal rule to predict maximum achievable solar cell voltages.
Quantum well oscillators
Authors: Sollner T. C. L. G. , Tannenwald P. E. , Peck D. D. , Goodhue W. D.
Published: February 2003

Oscillations have been observed for the first time from double barrier resonant tunneling structures. By eliminating impurities from the wells, we have been able to increase the tunneling current density by a factor of nearly 100. With the attendant increase in gain and improved impedance match to the resonant circuit, the devices oscillated readily in the negative resistance region. Oscillator output power of 5 μW and frequencies up to 18 GHz have been achieved with a dc to rf efficiency of 2.4% at temperatures as high as 200 K. It is shown that higher frequencies and higher powers can be expected.
Fabrication of single mode glass waveguides by electrolytic release of silver ions
Authors: Lagu R. K. , Ramaswamy V.
Published: February 2003

We report a novel electrolytic process that is used to fabricate reproducible, low loss, single mode waveguides. By precisely controlling the current pumped through high purity Ag and Pt electrodes in molten NaNO3, as well as its duration, a high degree of accuracy over the release and hence the control of Ag+ concentration is achieved. The inherent capability of the process to generate very low level of silver ion concentration with high precision implies much higher time of diffusion, thus removing the time criticality factor faced by the existing processes while fabricating single mode waveguides.
Reduced chirping in coupled-cavity-semiconductor lasers
Authors: Agrawal G. P. , Olsson N. A. , Dutta N. K.
Published: February 2003

Chirping in coupled-cavity lasers is studied experimentally and theoretically. Using a conventional and a cleaved-coupled-cavity (C3) laser obtained from the same wafer, we find that the chirp for a C3 laser is typically reduced by a factor of 2. A simple rate equation model is presented to account for reduced chirping. Mode selectivity arising from the cavity coupling is incorporated through wavelength-dependent cavity-loss variations.
Doubly mode-locked, Q-switched, continuously pumped neodymium:yttrium aluminum garnet laser
Authors: deViry D. , Pelle F. , LeBrumant J. , Duran J.
Published: February 2003

We describe the analysis and operation of an improved actively mode-locked, Q-switched continuously pumped neodymium:yttrium aluminum garnet laser. Basically the picosecond laser has been modified by a substitution of the classical output mirror by a convenient Fabry–Perot resonator which is used as the reflective element in order to provide an efficient reshaping of the picopulses. Instead of providing transform limited pulses with 100-ps duration at 1-MW peak power, our system is able to deliver sharper picopulses (18 ps) without significant loss in the overall efficiency. Besides obvious basic research applications, this low cost, easy to do modification may turn out to be extremely useful whenever laser implants and material cutting are concerned.
Important role of dynamical atomic processes on x-ray line emissions from picosecond laser-produced plasmas in the ionizing phase
Authors: Nakano Noboru , Kuroda Hiroto
Published: February 2003

Transient characteristics of x-ray line radiation from high density plasmas in an ionizing phase are computationally shown in the picosecond region by solving coupled rate equations. Many atomic processes associated with x-ray radiation are found to affect temporal changes of x-ray intensities and, especially, the x-ray intensity ratios. It is pointed out that in the evaluation of electron temperatures in transient plasmas, undesirable errors are apt to be brought about by usual conventional methods based on computations in which steady state equilibrium is assumed.
Oxygen gettering by hafnium implanted in beryllium: A 〈0001〉 Hf-O dumbbell?
Authors: Soares J. C. , Melo A. A. , da Silva M. F. , Freitag K. , Herrmann C. , Herzog P. , Rudolph H. J. , Schloesser K. , Vianden R. , Wrede U. , Boema D. O.
Published: February 2003

The interaction of hafnium implanted into beryllium single crystals with diffusing oxygen was studied using hyperfine interaction and Rutherford backscattering channeling techniques. It was observed that oxygen is trapped at hafnium in a well defined lattice position. The formation of a 〈0001〉 Hf-O mixed dumbbell in the tetrahedral interstitial cage of the beryllium lattice is suggested to explain the experimental results.
Photoluminescent and electroluminescent properties of GaAs1−xPx-GaAs1−yPy isotype heterojunction electrodes
Authors: Hobson William S. , Johnson Phelps B. , Ellis Arthur B. , Biefeld R. M.
Published: February 2003

The photoluminescence (PL) of N-n GaAs0.59P0.41-GaAs0.70P0.30 heterojunction electrodes has been studied in stable, efficient photoelectrochemical cells employing aqueous ditelluride electrolyte. When excited at several ultra-band-gap wavelengths, electrodes whose surface n-GaAs0.70P0.30 layers are ∼0.2 μm thick exhibit PL spectra derived from the emission bands of the heterojunction constituents. Besides being dependent on excitation wavelength, the PL spectral distribution is a function of applied potential. Field-induced quenching of PL from the electrodes is shown to be consistent with a dead-layer model. Electroluminescence (EL) can be observed when the solids are used as cathodes in a formamide solution of Na2S2O8. The EL spectrum indicates that radiative recombination due to hole injection is largely confined to the surface layer.
Effect of chlorine implantation on oxidation enhanced diffusion of phosphorus in silicon
Authors: Solmi Sandro , Negrini Paolo
Published: February 2003

It is shown that chlorine implantation in silicon reduces the phosphorus enhanced diffusivity in oxidizing atmosphere (both dry O2 and steam) at 1000 and 1100 °C. On the contrary, no change has been evidenced on the diffusivity in inert ambient. Cl implantation is shown to be effective also in avoiding the formation of oxidation induced stacking faults. These effects can be explained hypothesizing a direct interaction between chlorine atoms and silicon self-interstitials, which reduces the interstitial excess produced by oxidation. Furthermore, it has been observed that the presence of chlorine in silicon enhances the oxidation rate both in dry O2 and in steam atmospheres.
Graded band-gap p/n AlGaAs solar cells grown by organometallic vapor phase epitaxy
Authors: Wagner D. K. , Shealy J. R.
Published: February 2003

The growth of p/n graded band-gap AlGaAs/GaAs solar cells by organometallic vapor phase epitaxy is reported. The best performance is obtained for a cell with the emitter graded from 0 to 45 at. % aluminum over a distance of 0.3 μm. The corresponding solar cell parameters are Isc=27.3 mA/cm2, Voc=1.01 V, and FF=0.73 at 1 sun AM0, corresponding to a conversion efficiency of 14.7%.
Characteristics of amorphous silicon staggered-electrode thin-film transistors
Authors: Powell M. J. , Orton J. W.
Published: February 2003

Amorphous silicon staggered-electrode thin-film transistors (TFT’s) can show current crowding near the origin in the output characteristics. The degree of current crowding is governed by the voltage dependence of the current flowing from the n+ contact to the conducting channel. This current is a space-charge-limited current whose magnitude depends on the bulk density of states in the undoped intrinsic layer. For a 0.5-μm-thick i layer, calculations predict negligible current crowding for N(E)<1016 cm−3 eV−1, but severe current crowding for N(E)>3×1016 cm−3 eV−1. Experimental results are consistent with N(E) in the range 1016 cm−3 eV−1–2×1016 cm−3 eV−1. This is lower than the value derived from the transfer characteristic of the TFT (∼1017 cm−3 eV−1), which is evidence for an inhomogeneous distribution of deep gap states through the 0.5-μm film of α-Si:H.
Charge transfer doping in amorphous semiconductor superlattices
Authors: Tiedje T. , Abeles B.
Published: February 2003

Charge transfer doping of amorphous silicon by amorphous silicon nitride is demonstrated in amorphous semiconductor superlattice structures. The transfer-doped material has lower gap-state density and higher photoconductivity than conventional substitutionally doped material.
Space-charge-induced optoelectronic switching in IIa diamond
Authors: Glinski J. , Gu X.-J. , Code R. F. , van Driel H. M.
Published: February 2003

Experimental results are presented concerning the effect of contacts on the performance of high-voltage optoelectronic switching in insulating diamond. For high bias voltages and low intensity 222-nm, ≊7-ns pulse illumination near the cathode, the switched voltage pulse splits into two peaks. The first peak corresponds to the high-speed photoconductive response of the diamond, while the second peak (which can be delayed up to ≊200 ns later) is attributed to space-charge-induced switching in the vicinity of the cathode.
Experimental determination of the temperature dependence of argon annealed fixed oxide charge at the Si/SiO2 interface
Authors: Akinwande A. I. , Ho C. P. , Plummer J. D.
Published: February 2003

Fixed oxide charge density Nf at the Si/SiO2 interface for (100) and (111) wafers oxidized in dry O2 and annealed in argon has been studied as a function of the Ar anneal temperature. In contrast to previous qualitative results, the annealed Nf value was found to be dependent on the anneal temperature. Wafers thermally cycled in Ar between different temperatures showed reproducible, steady state Nf values which also cycled with temperature. These results may indicate that residual charge densities after annealing represent an equilibrium state of the Si/SiO2 interface.
Epitaxial growth of BaF2 films onto PbSe and electronic properties of the interface
Authors: Zogg H. , Vogt W. , Melchior H.
Published: February 2003

Insulating epitaxial BaF2 layers have been grown by vacuum deposition onto in situ grown (111) PbSe single crystal films. BaF2 was chosen as insulating material because of its ideal match in thermal expansion and lattice constant to PbSe. Analysis of metal-insulator-semiconductor capacitors fabricated from such structures revealed breakdown strengths up to 4 MV/cm at 77 K. Capacitance-voltage curves followed theoretical expectations from accumulation to inversion without hysteresis. Interface state densities are of order 1012 cm−2 eV−1 and lifetimes estimated to be in the picosecond range.
Observed circuit limits to time resolution in correlation measurements with Si-on-sapphire, GaAs, and InP picosecond photoconductors
Authors: Hammond R. B. , Paulter N. G. , Wagner R. S.
Published: February 2003

We report cross-correlation measurements of the response of photoconductor pulsers and sampling gates excited by a femtosecond laser. The photoconductors were fabricated in microstrip transmission line structures on Si-on-sapphire, semi-insulating GaAs, and semi-insulating InP wafers. The photoconductor sampling gates were ion beam damaged to produce short carrier lifetimes (<3 ps in one case). Damage was introduced with 6 MeV 20Ne on the Si-on-sapphire, 2 MeV 2H on the GaAs, and 2 MeV 4He on the InP. Doses in the range 1012–1015 cm−2 were used. Our results show circuit limits to the time resolution in correlation measurements from two sources: (a) RC time constants due to photoconductor gap capacitance and transmission line characteristic impedance and (b) dispersion in microstrip transmission lines.
Electron and hole ionization coefficients in (100) oriented Ga0.33In0.67As0.70P0.30
Authors: Osaka Fukunobu , Mikawa Takashi , Kaneda Takao
Published: February 2003

The impact ionization coefficients for electrons and holes in (100) oriented Ga0.33In0.67As0.70P0.30 whose band gap is 0.92 eV have been obtained from photomultiplication measurements on a Zn diffused p+n abrupt junction having a donor concentration of 2×1016 cm−3. It has been shown that the ionization coefficient for electrons is larger than that for holes by a factor of 1.5 over the electric field range from 3.3×105 to 4.3×105 V/cm.
Electromechanical and metallurgical properties of liquid-infiltration Nb-Ta/Sn multifilamentary superconductor
Authors: Ekin J. W. , Hong M.
Published: February 2003

Data are presented on the strain dependence of the critical current and critical field of Nb-Ta/Sn superconductors fabricated by the liquid Sn infiltration process. The results show that liquid infiltrated Nb-Ta/Sn superconductors have several significant advantages over bronze-process Nb/Sn super conductors: an overall Jc that is 3–10 times higher for magnetic fields in the range 13–20 T, an irreversible (damage) strain limit twice as large, and a Jc elastic-strain sensitivity less than half as large at fields above ∼16 T. These improved properties are attributed to several unique characteristics of the liquid infiltration process: a tough Nb-Ta matrix, fine equiaxial A15 grains, and a uniform stoichiometric Sn concentration.
Reactively sputtered TeNx optical recording media
Authors: Bösch M. A. , Haller H. R. , Schiavone L. M. , Shay J. L.
Published: February 2003

The optical recording characteristics of TeNx films are described. Te-nitride formation has been achieved by reactive sputtering. The optical writing properties vary drastically with increasing nitrogen incorporation. Films with moderate nitrogen content maintain good hole and rim forming properties while enhancing the sensitivity of the medium. These layers show a considerable resistance against rapid environmental stress.
Electrical discharge channel in cesium vapor initiated by a XeCl laser
Authors: Hijikawa M. , Tamura H. , Arishima H. , Horioka K. , Kasuya K.
Published: February 2003

Plasma channels for transporting intense ion beams were initiated by a 308-nm XeCl laser. The laser beam caused one-photon ionization of the cesium atoms which were seeded in a buffer Ar gas. Utilizing this mechanism, plasma channels were easily initiated up to 70 cm in length. The electron density and temperature of the plasma produced by the laser beam were also measured.
Plasma-deposited thin-film step coverage calculated by computer simulation
Authors: Ross R. C. , Vossen J. L.
Published: February 2003

Thin-film growth contours from a diffuse source onto two-dimensional steps with varied sidewall angles and interstep aspect ratios have been computer simulated using string moving algorithms. Minimum fractional coverage occurs on the sidewall position nearest the step bottom in all cases. This position defines both the conductance limiting region for conductors and the point of voltage breakdown for dielectrics. The variations in minimum fractional coverage with changes in sidewall angle and step dimensional ratios indicate the importance and limitations of sidewall tapering for ‘‘small’’ geometries.
Effect of stress relaxation on the generation of radiation-induced interface traps in post-metal-annealed Al-SiO2-Si devices
Authors: Zekeriya Viktor , Ma T-P.
Published: February 2003

We have found experimentally that both the interfacial stress distribution and the generation of interface traps in an Al-SiO2-Si structure change systematically with time lapse between post-metal-anneal treatment and x-ray irradiation, and strong correlation between the two is established. The results suggest that the device radiation sensitivity is modulated by the interfacial stress and/or the oxide bond strain gradient. Two possible mechanisms based on the variations of the interfacial strained bonds are proposed to explain the results.
Interfacial reactions of Ni-Ta thin films on GaAs
Authors: Lahav A. , Eizenberg M.
Published: February 2003

The interfacial reactions between Ta-Ni thin films and (100) GaAs substrate have been analyzed by Auger electron spectroscopy, x-ray diffraction, and transmission electron microscopy. A pure Ni film reacts with GaAs at 250 °C forming a ternary Ni2 GaAs epitaxial compound, which at 600 °C dissociates to NiGa and NiAs. Ta interacts with GaAs only at 650 °C. In the case of a Ta/Ni film on GaAs at temperatures up to 450 °C only the Ni layer reacts with the substrate forming Ni2GaAs. At higher temperatures the dissociation of Ni2GaAs combined with As outdiffusion results in the structure TaAs/NiGa/GaAs. For the complementary Ni/Ta bilayer, the Ta/GaAs interface is intact up to 500 °C; at this temperature only Ni-Ta intermixing takes place. At 600 °C, Ni penetrates into the interface with GaAs and forms NiGa. The reaction of the alloy film Ni60Ta40 with GaAs starts at 450 °C by Ni leaching out of the alloy and forming Ni2GaAs at the interface with GaAs. At higher temperatures the reaction results in a structure similar to that obtained for the bilayers with NiGa adjacent to the GaAs substrate. The potential applications of the studied metallization schemes for contacting to GaAs are also discussed.
Vertical field-effect transistors in III-V semiconductors
Authors: Rav-Noy Z. , Lu L-T. , Kapon E. , Mukai S. , Margalit S. , Yariv A.
Published: February 2003

Vertical metal-semiconductor field-effect transistors in GaAs/GaAlAs and vertical metal-oxide-semiconductor field-effect transistors (MOSFET’s) in InP/GaInPAs materials have been fabricated. These structures make possible short channel devices with gate lengths defined by epitaxy rather than by submicron photolithography processes. Devices with transconductances as high as 280 mS/mm in GaAs and 60 mS/mm (with 100-nm gate oxide) for the InP/GaInPAs MOSFET’s were observed.
Dependence of photoconductivity on the dark Fermi level position in amorphous silicon alloys
Authors: Hack M. , Guha S. , Shur M.
Published: February 2003

We present results of a new model to describe the dependence of the room-temperature steady-state photoconductivity in amorphous silicon alloys upon the position of the dark Fermi level. This dependence is a consequence of both a change in the recombination path and dopant-created gap states. We also demonstrate the relationship between the power dependence of photoconductivity and dark Fermi level position and show that as a result of space charge neutrality, this dependence can be related to a characteristic energy slope of the density of states only in the absence of injected charge or dopants. Moreover, in agreement with recent experimental data, we show that our model predicts a power dependence of less than 0.5 for high-intensity illumination on n-type amorphous silicon.
Elimination of hillocks on Al-Si metallization by fast-heat-pulse alloying
Authors: Faith T. J. , Wu C. P.
Published: February 2003

Alloying of Al-1% Si integrated-circuit metallization by 5-s heat pulses at temperatures ranging from 490 to 540 °C was compared to standard 30-min furnace alloying at 425 °C. Hillocks were present on all furnace-alloyed samples, but were absent from all heat-pulse-alloyed samples. (Al-Si)/n+Si contact resistances equivalent to those obtained with furnace alloying were obtained for heat-pulse temperatures ranging from 505 to 525 °C. Diode leakage characteristics equal to those obtained with furnace alloying were obtained for heat-pulse temperatures up to 520 °C. Effective radiation-damage annealing was accomplished by a heat pulse in forming gas at 500 °C.
Molecular beam epitaxy of diluted magnetic semiconductor (Cd1−xMnxTe) superlattices
Authors: Kolodziejski L. A. , Bonsett T. C. , Gunshor R. L. , Datta S. , Bylsma R. B. , Becker W. M. , Otsuka N.
Published: February 2003

In this letter we report the first growth of diluted magnetic semiconductor superlattices. Bright and dark field transmission electron microscopy images confirm that the superlattices consist of distinct periodic layers of uniform composition and thickness. The photoluminescence spectra of the superlattices are found to be over three orders of magnitude more intense when compared to uniform thin films (and bulk samples) grown under similar conditions. The reason for this large increase is not clearly understood but this effect may have important consequences for future applications of these novel materials in optoelectronic devices.
Molecular and ion beam epitaxy of 3C-SiC
Authors: Miyazawa T. , Yoshida S. , Misawa S. , Gonda S. , Ohdomari I.
Published: February 2003

SiC films were grown on (100) silicon substrates using a Si molecular beam and a C+ ion beam with the same impingement rates of Si atoms and C+ ions. Reflection high-energy electron diffraction analysis showed that 3C-SiC grows epitaxially on the Si substrate at temperatures ranging from 820 to 1000 °C and at the ion energies of 50 and 100 eV with the ion current density of about 3 μA/cm2. Auger electron spectroscopy measurements showed that the films obtained were stoichiometric and do not contain impurities such as oxygen. The influence of surface treatments of Si substrates was also studied.
Direct imaging of dopant distributions in silicon by scanning transmission electron microscopy
Authors: Pennycook S. J. , Narayan J.
Published: February 2003

The first direct images of dopant distributions in Si have been observed using scanning transmission electron microscopy, by detecting Rutherford-scattered transmitted electrons. Strong atomic number (Z) contrast is obtained allowing images to be formed of Bi at concentrations of the order of 0.2 to 1 at. % and of Sb at concentrations of 0.5 to 6 at. %. The image contrast from cross-section specimens correlated closely with the dopant concentration profiles determined by x-ray microanalysis and with Rutherford ion backscattering analysis of the bulk materials. This technique should prove extremely valuable for studying dopant segregation phenomena in semiconductors.
Spectroscopic ellipsometry and Raman scattering study of the annealing behavior of Be-implanted GaAs
Authors: Chambon P. , Erman M. , Theeten J. B. , Prévot B. , Schwab C.
Published: February 2003

The annealing of the lattice damage induced by Be-ion implantation in GaAs has been studied by spectroscopic ellipsometry and Raman scattering after each step of an isochronal thermal treatment. These two optical (i.e., nondestructive) techniques are shown to be very sensitive both to the lattice recovery and to the electrical activation of the implants. It has been observed that the latter process occurs after the lattice perfection recovery at T=550 °C, while for the ultimate annealing temperatures (T>750 °C) a significant Be redistribution takes place resulting in a decrease of the electrical activity which is confirmed by differential Hall effect measurements.
Effect of oxygen contamination on the properties of cosputtered tantalum silicide
Authors: Murarka S. P.
Published: February 2003

The role of oxygen contamination in determining the properties, particularly the resistance, of the cosputtered tantalum disilicide has been investigated. As-deposited films with silicon/tantalum atomic ratios in the range of 1.9 to 2.5 were monitored. There is no noticeable effect of the small amounts of oxygen (≲0.5 at. %) on the stress and the reactive ion etching characteristics of these films. The resistance, however, changed significantly due to the presence of oxygen even in a concentration as small as 0.02 at. %. The results are discussed in view of the changing Si/Ta ratio and oxygen concentration and the possible hopping electron conduction mechanism.
Integrated picosecond photoconductors produced on bulk Si substrates
Authors: Hammond R. B. , Paulter N. G. , Wagner R. S. , Eisenstadt W. R.
Published: February 2003

We report optoelectronic cross-correlation measurements of the response of photoconductor pulsers and sampling gates formed on Si wafers. These photoconductors were fabricated with standard integrated circuit fabrication techniques followed by shadow-masked ion beam irradiation. Successful ion beam irradiations were performed with 2 MeV 2H, 6 MeV He, and 30 MeV O with doses of 1015 ion/cm2. Deep damage was necessary to eliminate long-lived background currents in the cross correlations. Carrier lifetimes of 96, 47, and 29 ps were observed in photoconductors with carrier mobilities of ∼250 cm2/Vs.
Far-field supermode patterns of a multiple-stripe quantum well heterostructure laser operated (∼7330 Å, 300 K) in an external grating cavity
Authors: Epler J. E. , Holonyak N. , Burnham R. D. , Paoli T. L. , Streifer W.
Published: February 2003

A multiple-stripe quantum well heterostructure laser diode operated in an external grating cavity is shown to exhibit the far-field radiation patterns of the ‘‘supermode’’ eigenstates predicted by coupled mode analysis. Data (∼7330 Å) are presented on a gain-guided laser array at various continuous (cw, 300 K) operating currents to illustrate the progression of the supermodes from double-lobed patterns (phase shift between emitters) to a single-lobed pattern (no phase shift between emitters). As the cavity wavelength is scanned a cyclical progression (2.8-Å period) of far-field patterns (supermodes) is observed.
Longitudinal mode behavior in a separately pumped, multiple twisted double-heterostructure laser
Authors: Sugino Takashi , Chen Kuo-Liang , Wang Shyh
Published: February 2003

Behavior of longitudinal modes in a separately pumped, multiple twisted double-heterostructure laser is investigated. A single longitudinal mode operation is observed in the current range up to 1.3Ith under uniform pumping. The lasing wavelength is locked to a single longitudinal mode over a temperature range of 12 °C under uniform pumping. A continuous tuning range of 3.3 Å is obtained in one longitudinal mode. The wavelength shifts at a rate of 0.07 Å/mA in the continuous tuning range.
Direct W–Ti contacts to silicon
Authors: Cohen S. S. , Kim M. J. , Gorowitz B. , Saia R. , McNelly T. F. , Todd G.
Published: February 2003

We have studied the contact resistance in a metallization system that employs a direct contact between a tungsten–titanium alloy and shallow junctions in silicon. The values obtained in the present study are all within acceptable limits (<100 Ω μm2) for very large scale integration applications. The metal–silicon system has been subjected to moderate heat treatments, similar to those required in processing two-level metallization schemes. No detrimental effects on the electrical properties of these contacts have been observed.
Polarization-dependent gain in GaAs/AlGaAs multi-quantum-well lasers: Theory and experiment
Authors: Yamada M. , Ogita S. , Yamagishi M. , Tabata K. , Nakaya N. , Asada M. , Suematsu Y.
Published: February 2003

Polarization-dependent lasing gain in GaAs/AlGaAs multi-quantum-well lasers is theoretically calculated and experimentally determined. The dipole moment representing the electron transition is calculated based on the k⋅P perturbation method. Gain broadening due to the intraband relaxation of electron wave is also taken into account. Experimentally measured gain profiles of TE and TM modes agree well with the theoretical results.
λ≊1.5 μm InGaAsP ridge lasers grown by gas source molecular beam epitaxy
Authors: Temkin H. , Panish M. B. , Logan R. A. , van der Ziel J. P.
Published: February 2003

Separate confinement heterostructure wafers grown by gas source molecular beam epitaxy have been used to prepare ridge waveguide lasers operating up to 50 °C. Laser threshold currents varied from 45 to 65 mA at room temperature and output powers up to 9 mW have been obtained with the external quantum efficiency of ∼36%. Gain profile measurements indicate excellent material uniformity. Frequency response flat to at least 2 GHz is consistent with the material free of interfacial traps or any capacitive shunt paths.
Experimental study of an SF6 Brillouin amplifier pumped by KrF laser radiation
Authors: Fedosejevs R. , Tomov I. V. , McKen D. C. D. , Offenberger A. A.
Published: February 2003

Experimental measurements are presented of the gain for a backward Brillouin amplifier using SF6 gas, in the pressure range of 3–10 atm, pumped by KrF laser radiation. A small signal gain of 6×10−4 cm MW−1, pump depletion of 20%, and an intensity gain of 2.5 have been demonstrated.
Room-temperature pulsed oscillation of GaAlAs/GaAs surface emitting injection laser
Authors: Iga K. , Ishikawa S. , Ohkouchi S. , Nishimura T.
Published: February 2003

We report the first room-temperature pulsed oscillation of a GaAlAs/GaAs surface emitting injection laser. A ring electrode of which the outer/inner diameter is 20 μm/10 μm has been introduced to distinguish a mirror and Ohmic contact in order to increase the reflectivity. The threshold current was as low as 510 mA at room temperature under pulsed conditions. The cavity length was 7 μm and single longitudinal mode operation was achieved at λ=8740 Å against the temperature variation of 80 K.
11-GHz direct modulation bandwidth GaAlAs window laser on semi-insulating substrate operating at room temperature
Authors: Lau K. Y. , Bar-Chaim N. , Ury I. , Yariv A.
Published: February 2003

We have demonstrated a direct modulation bandwidth of up to 11 GHz in a window GaAlAs buried heterostructure laser fabricated on a semi-insulating substrate, operating at room temperature.
Failure of reciprocity in light-induced changes in hydrogenated amorphous silicon alloys
Authors: Guha S.
Published: February 2003

From a study of the effect of light exposure on photoconductivity and solar cell performance of hydrogenated amorphous silicon alloys for different exposure time and intensity, we show that the light-induced changes do not obey reciprocity. Degradation is larger at high intensity light exposure for a shorter time than at low intensity exposure for a longer time even though the product of the exposure time and light intensity is kept a constant. A model that can explain the failure of reciprocity is discussed.
SF6 enhanced nitridation of silicon in active nitrogen
Authors: Giridhar R. V. , Rose K.
Published: February 2003

A new procedure for thermal nitridation of silicon is reported. Active nitrogen generated using a microwave discharge is passed over silicon wafers in an externally heated quartz tube at low pressure (0.3 Torr). Nitridation is shown to be significantly enhanced by the addition of small amounts (20–200 ppm) of SF6 to the nitrogen before it enters the discharge. In this way films about 100 Å thick with a refractive index of 2.0±0.06 can be grown at 1050 °C in 4 h. The films have etch rates of 10–15 Å/min in buffered HF (NH4F:HF=7:1). Auger analysis shows [N]/[O] atomic ratios of about 2. A 60-Å film grown at 1000 °C inhibited substrate oxidation for over 16 h in dry oxygen at 1000 °C.
Phonon-limited mobility in GaAlAs/GaAs heterostructures
Authors: Vinter B.
Published: February 2003

A calculation of the phonon-limited mobility of electrons confined to the channel of a GaAlAs/GaAs heterostructure has been performed with full account of the quasi-two-dimensionality of the channel. At 77 K the results show a reduction of mobility of about 25% as electron density increases from threshold to 7×1011cm−2; at room temperature the mobility of pure bulk GaAs is found almost independent of confinement.
Anode heating in an intense ion beam diode with a CO2 laser
Authors: Camarcat N. , Devin A. , Peugnet C. , Patou C.
Published: February 2003

In order to accelerate intense ion beams, we heat the anode of a pinch-reflex diode with a CO2 laser. At laser power densities of 1010 W/cm2 over a 2-mm focal spot, we demonstrate that gap closure is avoided and that ion efficiency is increased by at least a factor 3 over diode operation without the laser.
Photothermal spectroscopy of weakly absorbing samples using a thermal wave phase shifter
Authors: Coufal H.
Published: February 2003

The concept of a thermal wave phase shifter for photothermal studies of weakly absorbing samples is described. Both sample and reference are excited simultaneously, but their respective photothermal signals reach the detector subsequently. Depending on the phase shift photothermal absorption or transmission spectra can be recorded readily with the same sample. The versatility of this technique is demonstrated by spectroscopic studies of neodymium oxide doped poly(methyl methacrylate) film. At energy fluences in the order of 10 mJ/cm2 sensitivities of 1014 molecules/cm2 are achieved with conventional, unstabilized light sources. The quantum yield for nonradiative decay is determined to be 90% throughout the entire visible spectrum.
Epitaxial growth of CrSi2 on (111)Si
Authors: Shiau F. Y. , Cheng H. C. , Chen L. J.
Published: February 2003

Epitaxial CrSi2 has been successfully grown on (111)Si. Substrate heating at 300 or 400 °C during Cr deposition was found to be more effective than two-step annealing in promoting the growth and improving the quality of epitaxial CrSi2. The best epitaxy was obtained when sample substrates were heated at 300 or 400 °C followed by 1000–1100 °C annealing for 1 h. The orientation relationships were found to be (0001) CrSi2//(111)Si, (224̄0)CrSi2//(224̄)Si, (202̄0)CrSi2//(202̄)Si, and [12̄13]CrSi2//[101]Si. Dislocations present in the regular interfacial dislocation network were found to be of edge or 60° type with (1)/(6) <112> Burgers vectors. The average dislocation spacings were measured to be 270–320 Å. The discrepancy of the measured and theoretically expected value of dislocation spacing was attributed to the difference in the thermal expansion coefficients of CrSi2 and Si.
Capless annealing of InP for metal-insulator-semiconductor field-effect transistor applications
Authors: Pande K. P. , Nair V. R. K. , Aina O.
Published: February 2003

A simple capless annealing process for post-implantation annealing of InP material is described. The technique incorporates a simple boat design and uses InP+Sn as the source of phosphorus overpressure. Using this process, Si-implanted (4×1012 cm−2 dose) InP layers show mobilities at room temperature and 77 K in the range of 3200 and ∼10 000 cm2/Vs, respectively. Dopant depth profiles with peak donor densities of 2×1017 cm−3 and minimal redistribution of impurities were obtained. Depletion-mode InP metal-insulator-semiconductor field-effect transistors fabricated with 4-μm gate lengths using ion-implanted channel and source-drain regions, show channel mobilities of 2500 cm2/Vs.
Molecular beam epitaxy of GaAs and AlGaAs on Si
Authors: Tsaur B-Y. , Metze G. M.
Published: February 2003

Epitaxial layers of GaAs and AlxGa1−x As (0.2≤x≤0.5) have been grown directly on single-crystal Si (100) substrates, without an intermediate Ge layer, by molecular beam epitaxy (MBE). To improve nucleation, after being chemically cleaned the Si substrates were preheated in the MBE system to reduce surface contamination and achieve ordered surface reconstruction prior to growth. Reflection electron diffraction, Rutherford backscattering channeling, and photoluminescence measurement were used to characterize the epitaxial layers. The AlGaAs layers were found to be superior to the GaAs layers.
Electroluminescence from a heterojunction bipolar transistor
Authors: Hayes J. R. , Leheny R. F. , Temkin H. , Gossard A. C. , Wiegmann W.
Published: February 2003

Electroluminescence has been observed from a GaAlAs/GaAs heterojunction bipolar transistor. The absence of luminescence from the GaAlAs emitter confirms that compositional grading significantly enhances hole confinement. In addition, it is suggested that electroluminescence occurring from the radiative recombination of excess electrons in the base may cause significant cross talk between devices of an integrated circuit.
Disorder of an AlxGa1−xAs-GaAs superlattice by donor diffusion
Authors: Meehan K. , Holonyak N. , Brown J. M. , Nixon M. A. , Gavrilovic P. , Burnham R. D.
Published: February 2003

The Si impurity is diffused (850 °C, 10 h, xj ∼2.4 μm) into 2.4 μm of AlxGa1−xAs-GaAs (x≳0.6) superlattice (barrier LB ≊320 Å, quantum well Lz ≊280 Å) and disorders it into bulk-crystal Alx′Ga1-x′As (x′≳0.32). The as-grown infrared gap superlattice is converted selectively to red gap bulk crystal and, where undiffused and not disordered, is still capable of continuous 300-K photopumped laser operation at a threshold of 4×103 W/cm2 (or Jeq ∼1.7×103 A/cm2, 5145 Å pump photon).
Liquid phase epitaxial growth of (AlzGa1−z)xIn1−xAsyP1−y pentanary on (100)GaAs substrate using a two-phase solution technique
Authors: Kawanishi Hideo , Suzuki Takeshi
Published: February 2003

Liquid phase epitaxy of (AlzGa1−z)xIn1−xAsyP1−y pentanary is reported for the first time. The pentanary of (Al0.05Ga0.95)0.55In0.45As0.07P0.93 is grown successfully on a (100) oriented GaAs substrate by liquid phase epitaxy using a two-phase solution growth technique at Tg=845 °C. Existence of Al in the epitaxial layer is determined by x-ray microanalyzer, x-ray diffractometer, and photoluminescence. The growth conditions of the (AlGa)InAsP pentanary are also discussed.