bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of dispersive two-photon transitions on femtosecond pulse propagation in semiconductor waveguides
Authors: Yang C. C. , Villeneuve Alain , Stegeman George I. , Lin Cheng-Hui , Lin Hao-Hsiung
Published: July 2002

It is demonstrated that the frequency spectrum of femtosecond pulses becomes highly asymmetric when propagating as transverse magnetic modes in semiconductor multiple quantum well channel waveguides at photon energies near half the band gap. Calculations based on the frequency dispersion in two-photon transitions provide results consistent with the experiment.
Pressure dependence of the electro-optic response function in partially exposed polymer dispersed ferroelectric liquid crystals
Authors: Parmar D. S. , Holmes H. K.
Published: July 2002

Ferroelectric liquid crystals in a new configuration, termed partially exposed polymer dispersed ferroelectric liquid crystal (PEPDFLC), respond to external pressures and demonstrate pressure-induced electro-optic switching response. When the PEPDFLC thin film is sandwiched between two transparent conducting electrodes, one a glass plate and the other a flexible sheet such as polyvenylidene fluoride, the switching characteristics of the thin film are a function of the pressure applied to the flexible transparent electrode and the bias voltage across the electrodes. Response time measurements reveal a linear dependence of the change in electric field with external pressure.
Energy bands in quantum confined silicon light-emitting diodes
Authors: Maruska H. Paul , Namavar Fereydoon , Kalkhoran Nader M.
Published: July 2002

Measurements of the temperature dependence of the current-voltage characteristics of heterojunction light-emitting diodes fabricated by depositing indium tin oxide onto the surface of electrochemically etched p-type silicon (porous silicon) are presented, and the results are compared with those for adjacent devices formed on nonprocessed bulk silicon. The barrier height for the diodes which exhibit quantum confinement effects was determined to be 0.42 eV. Unlike the bulk silicon devices, the diodes prepared on porous silicon did not manifest a photovoltaic effect. These observations allow us to present a potential energy diagram for porous silicon heterojunction diodes which indicates barriers in both the conduction band and the valence band.
Sub-μm wide channels with surface potential compensated by focused Si ion beam implantation
Authors: Fujisawa Toshimasa , Saku Tadashi , Hirayama Yoshiro , Tarucha Seigo
Published: July 2002

We propose and demonstrate a novel technique using focused Si ion beam implantation to produce high-quality mesoscopic channels. Low-energy Si implantation compensates the surface potential of a modulation-doped heterostructure that is designed to have no conductive channels at the heterointerface. The implantation forms a conductive channel separated from the damaged implanted region. The mobility of the channel is improved by decreasing the ion energy from 100 to 35 keV. Sub-μm to 5 μm wide channels fabricated by 35 keV Si+ ions show a mobility of 5.3×105 cm2/V s and a ballistic length of 3.1 μm at 1.5 K.
Evolution of monolayer terrace topography during metalorganic chemical vapor deposition of (100) GaAs
Authors: Epler J. E. , Schweizer H. P.
Published: July 2002

The evolution of surface topography during epitaxial growth of GaAs on (100) GaAs substrate is observed using angle-resolved elastic light scattering within a metalorganic chemical vapor deposition reactor. The temporal and orientation dependence of diffuse (nonspecular) optical scattering is determined at growth initiation, during steady state growth, and at growth conclusion. Phenomena such as persistent monolayer oscillations in surface roughness, nucleation delay, and [01̄1] step development are observed. The influence of substrate miscut, growth temperature, and rate is discussed.
Phase formation and stability in the Pd/GaP system
Authors: Mohney S. E. , Lin C. F. , Chang Y. A.
Published: July 2002

Phase formation in the Pd/GaP system is examined by transmission electron microscopy, Auger depth profiling, and x-ray diffraction of Pd films on (100) GaP, and by x-ray diffraction of bulk phase equilibria samples. The reaction of Pd films with GaP is initiated with the formation of an oriented hexagonal ternary phase, Pd2(GaxP1−x). Another hexagonal ternary phase, Pd12( GaxP1−x)7, forms in the intermediate stages of the reaction, and PdGa and PdP2 are found to be in thermodynamic equilibrium with GaP. The Pd/GaP system is very similar to Pd/GaAs.
Noise reduction in low-frequency SQUID measurements with laser-driven switching
Authors: Cunningham Charles E. , Park George S. , Cabrera Blas , Huber Martin E.
Published: July 2002

We have developed a technique to modulate the input to a superconducting quantum interference device (SQUID) using a very low noise double-pole, double-throw switching network. This network is composed of four niobium microbridges that are driven normal in pairs by pulses of laser light. An input signal is modulated at a frequency above the 1/f noise regime, amplified by the SQUID, and subsequently demodulated to obtain an output in which the excess low-frequency SQUID noise has been removed. With this technique, we have reduced the low-frequency noise by an order of magnitude in energy over measurements made without this technique.
Nonalloyed ohmic contacts to n-Si using a strained Si0.50Ge0.50 buffer layer
Authors: Liou Hsing-Kuen , Yang Edward S. , Tu K. N.
Published: July 2002

We have grown an 80-Å-thick strained Si0.50Ge0.50 layer on n-Si by molecular-beam epitaxy. The strained layer is used to lower the Schottky barrier height for making a nonalloyed shallow ohmic contact to the n-Si. X-ray photoelectron spectroscopy was employed to investigate the Si 2p and Ge 3d core-level binding energies of the strained and the relaxed Si0.50Ge0.50 and to determine their relative Fermi-level positions. Rutherford backscattering and Auger depth profiling were employed to determine the contact reactions using Ti, W, or Pt as contact metals. In the case of Pt, a 500-Å W diffusion barrier can protect the ohmic behavior up to 550 °C for 30 min. The specific contact resistance of the metal/Si0.50Ge0.50/n-Si contact extracted from the D-type cross-bridge Kelvin resistor was 3.5×10−5 Ω cm2.
Assessment of implantation damage by backscatter Kikuchi diffraction in the scanning electron microscope
Authors: Troost K. Z.
Published: July 2002

Surface damage caused by ion implantation is assessed by backscatter Kikuchi diffraction in the scanning electron microscope. Backscatter Kikuchi diffraction patterns from Si(100) specimens implanted with different doses of 80-keV Ge ions between 3×1012 and 3×1014 ions cm−2 are obtained. The pattern contrast is quantified in a straightforward procedure employing standard image-processing operations. A comparison between the contrast in backscattering Kikuchi diffraction patterns and the channeling minimum in energy spectra by Rutherford backscattering spectrometry as a measure for surface implantation damage is made. As it turns out, both measures are about equally sensitive to the level of the surface implantation damage. The lateral resolution (<100 nm) and the high surface sensitivity (of the order of 10 nm) of backscatter Kikuchi diffraction may be exploited to study lateral implantation profiles with sub-μm resolution.
Temperature dependence of ion beam mixing in GaAs, AlAs, and GaAs/AlAs/GaAs
Authors: Klatt J. L. , Averback R. S. , Forbes D. V. , Coleman J. J.
Published: July 2002

Ion beam mixing of AlAs markers in GaAs and GaAs markers in AlAs has been measured as a function of irradiation temperature with 1 MeV Kr ions. The mixing parameter in the GaAs matrix was ≊140 Å5/eV at temperatures between 110 and 473 K, but dropped to ≊120 Å5/eV at 573 K. The value was smaller in the AlAs matrix, ≊90 Å5/eV between 110 and 473 K, but it increased to ≊120 Å5/eV between 473 and 625 K. Ion beam mixing in a trilayer sample, GaAs/AlAs/GaAs, was also measured for comparison. At the deeper interface, AlAs on GaAs, and low temperature, the mixing parameter was 440 Å5/eV, but only 250 Å5/eV at the other interface, GaAs on AlAs. Mixing at the lower interface decreased at 573 K to 160 Å5/eV while it decreased at 473 K at the other interface to 110 Å5/eV. These results are interpreted on the basis of the influence of crystal structure on ion beam mixing.
Ultrafast nonequilibrium carrier relaxation in single-crystal Nd1.85Ce0.15CuO4−y
Authors: Liu Yongqian , Whitaker John F. , Uher Ctirad , Peng Jian-Liang , Li Z. Y. , Greene R. L.
Published: July 2002

We present a temperature-dependent investigation of the femtosecond relaxation dynamics of the n-type superconductor Nd1.85Ce0.15CuO4−y using ultrashort pulses from a Ti-sapphire laser in a transient absorption, pump-probe configuration. The energy relaxation time of the single crystals in the normal state was observed to increase by over an order of magnitude as the critical temperature was approached. This behavior has been modeled by the scattering of electrons with two-dimensional phonons. In the superconducting state, an increase and subsequent saturation of the relaxation time has been discerned. A possible reason for this is a complex interplay among the characteristic relaxation times, including scattering and recombination of quasiparticles optically excited by ultrashort laser pulses and order parameter relaxation close to Tc.
All-optical bistable switching and signal regeneration in a semiconductor layered distributed-feedback/Fabry–Perot structure
Authors: He J. , Cada M. , Dupertuis M.-A. , Martin D. , Morier-Genoud F. , Rolland C. , SpringThorpe A. J.
Published: July 2002

We report the experimental observation of optical bistable switching in a combined distributed-feedback/Fabry–Perot structure. The sample had a high switching contrast with almost zero reflectivity in the on-state. A turnoff time as short as 4 ns was measured. The threshold power for bistability was about 2 mW. Bistable switching with the memory effect and a potential application for all-optical signal regeneration were demonstrated.
Iodine doping in mercury cadmium telluride (Hg1−xCdxTe) grown by direct alloy growth using metalorganic chemical vapor deposition
Authors: Murakami S. , Okamoto T. , Maruyama K. , Takigawa H.
Published: July 2002

We investigated iodine doping in mercury cadmium telluride (Hg1−xCdxTe) grown by direct alloy growth using metalorganic chemical vapor deposition, with isopropyl-iodine (IPI) as the dopant source. The memory effect in iodine doping is much smaller than that in indium doping. We confirmed by secondary ion mass spectroscopy (SIMS) measurement that sharp dopant transitions (0.2 μm/decade) were obtained by switching off the IPI during growth. The electron concentration at 77 K was linearly proportional to the dopant partial pressure from 5×1015 to 2×1018 cm−3. We confirmed by SIMS that 20%–100% of the iodine was active as a donor. The Hall coefficient shows classical n-type extrinsic behavior from 20 to 300 K. The electron mobility was as high as that in an indium-doped sample. The layer with a Cd fraction of x=0.23, doped to 5×1016 cm−3, exhibited a mobility of 4.7×104 cm2/V s at 77 K and 6.9×104 cm2/V s at 20 K. The iodine in the HgCdTe layers was thermally stable. We found no variation in the electrical properties and the iodine depth profile after annealing at 400 °C for 2 h.
Improvements of microstructural and superconducting properties of Ag-Bi2Sr2CaCu2Ox screen-printed tape by controlled oxygen partial pressure during cooling procedure
Authors: Noji H. , Zhou W. , Glowacki B. A. , Oota A.
Published: July 2002

The effect of different cooling procedures, after sintering, on the microstructural and superconducting properties of Bi2Sr2CaCu2Ox (B-2212) screen-printed tapes has been investigated. It was found that the amorphous phase originally present in grain boundaries at the sintering temperature undergoes a conversion to the Bi-2212 phase during slow cooling. However, the excess oxygen absorbed during slow cooling (in 21% oxygen) disturbs the order and ordering process of Bi-2212 crystals, but if the slow cooling process is conducted under monotonically reduced oxygen partial pressure, to ensure that the optimum oxidation state at sintering temperature of the Bi-2212 phase can be retained during the cooling procedure, tapes are then characterized by narrow grain boundaries and the highest Jc value ≳104 A/cm2 at 77 K and 0 T.
Dislocation networks in Bi2Sr2CaCu2Oy single crystals
Authors: Shang P. , Yang G. , Jones I. P. , Gough C. E. , Abell J. S.
Published: July 2002

Highly regular dislocation networks in superconducting Bi2Sr2CaCu2Oy single crystals have been observed by means of transmission electron microscopy. A model describing their geometrical configuration, Burgers vectors, and formation mechanism is presented. The ratio of the stacking fault energy to shear modulus has been estimated. Such networks are suggested as possible planar pinning centers for flux in the superconducting state.
Diamond nucleation on epitaxially grown Y-ZrO2 layers on Si(100)
Authors: Kanetkar S. M. , Kulkarni A. A. , Vaidya Anil , Vispute R. D. , Ogale S. B. , Kshirsagar S. T. , Purandare S. C.
Published: July 2002

Enhanced nucleation of polycrystalline diamond has been achieved on Si(100) with an epitaxial intermediate layer of yttria stabilized zirconia (Y-ZrO2). The epitaxial Y-ZrO2 layer was grown by pulsed excimer laser ablation and the diamond deposition was accomplished using the hot filament chemical vapor deposition method. The morphological, structural, and defect properties of the diamond crystallites are studied using the techniques of scanning electron microscopy, x-ray diffraction, and laser Raman spectroscopy, respectively.
Demonstration of colliding-soliton all-optical switching
Authors: Friberg Stephen R.
Published: July 2002

A colliding-soliton switch that takes advantage of the conservation properties of interacting solitons is demonstrated experimentally. We show that the switch, which can operate as an optical demultiplexer or as a logic gate, responds to incoming signal solitons without altering them. This is a consequence of its quantum nondemolition measurement capabilities, and allows multiple operations to be performed with the same soliton. Operation at rates exceeding 250 Gbit/s should be possible.
Resonant-cavity p-i-n photodetector utilizing an electron-beam evaporated Si/SiO2 microcavity
Authors: Hunt N. E. J. , Schubert E. F. , Zydzik G. J.
Published: July 2002

A new photodetector configuration consisting of an integrated Si/SiO2 microcavity on the light-collecting surface of an InGaAs photodetector is proposed and demonstrated. The resulting resonant cavity p-i-n (RC-PIN) detector exhibits a narrow spectral response of 14 nm width at a wavelength of 1350 nm, while reflecting all other wavelengths from 1100 to 1700 nm. The high degree of tailorability of spectral position, spectral detection width, and numerical aperature of efficient detection, as well as the ease of layer deposition make the RC-PIN attractive for use in wavelength de-multiplexing applications.
Third order nonlinearity of 4-dialkylamino-4′nitro-stilbene waveguides at 1319 nm
Authors: Kim Dug Y. , Sundheimer Michael , Otomo Akira , Stegeman George , Horsthuis Winfried H. G. , Möhlmann Guus R.
Published: July 2002

The intensity dependent optical properties of 4-dialkylamino-4′nitro-stilbene polymer channel waveguides were measured at 1319 nm with a pulse modulated Mach–Zehnder interferometer to be n2=0.8×10−13 cm2/W and β2<0.08 cm/GW. This material is promising for all-optical switching at 1319 nm because it satisfies both the W and T figures of merit.
Parametric dependence of timing jitter in gain-switched semiconductor lasers
Authors: Pepeljugoski Petar K. , Cutrer David M. , Lau Kam Y.
Published: July 2002

In this letter we derive analytic results for the timing jitter in gain-switched semiconductor lasers driven with electrical pulse shapes commonly used in practice. The analytic results allow us to identify laser parameters as well as electrical bias and pulse conditions which affect timing jitter. These results are in good agreement with experimental observations.
Intracavity second-harmonic generation using a deuterated organic ionic crystal
Authors: Minemoto Hisashi , Ozaki Yusuke , Sonoda Nobuo , Sasaki Takatomo
Published: July 2002

A large organic ionic crystal (10×28×15 mm3):4-nitrophenol sodium(:Na) salt dihydrate (NPNa) crystal, which had good optical, mechanical, and thermal properties, was grown for the second-harmonic generation (SHG) device. Its effective nonlinear constant was found to be 5.0 pm/V at 1064 nm. The Vickers hardness and thermal conductivity were about two times larger than those of molecular crystals. The SHG device made of DNPNa, in which the water of crystallization of NPNa was deuterated, was used for the intracavity SHG of a diode-pumped cw Nd:YVO4 laser. High SHG power of 4.4 mW at 532 nm was obtained for the first time with an organic nonlinear material.
High-reliability GaAs/AlGaAs multiquantum well lasers grown at a low temperature (375 °C)
Authors: Miyazawa Sei-ichi , Sekiguchi Yoshinobu , Okuda Masahiro
Published: July 2002

We report on high-reliability GaAs/AlGaAs multiquantum well (MQW) lasers grown at a low temperature (375 °C) by molecular beam epitaxy (MBE). Typically, a threshold current (Ith) of 26 mA and a differential quantum efficiency of 62% were obtained during a continuous wave (cw) operation at room temperature. During the life test, a stable operation was observed beyond 5000 h under a 20-mW cw operation at 70 °C. We also observed an improvement of laser characteristics in low-temperature-grown MQW lasers during a cw operation at room temperature. The threshold current of our MQW lasers was reduced from 26 to 18 mA, and this suggests that the point defects in the low-temperature-grown MQW laser were decreased.
Microwave surface resistance of spin-cast YBa2Cu3O7−x thin films on LaAlO3 substrates
Authors: Chu Peir-Yung , Buchanan Relva C. , Gao Feng , Kruse Jay W. , Feng Milton
Published: July 2002

Microwave properties of spin-cast YBa2Cu3O7−x thin films on LaAlO3 substrates were investigated. The films, prepared with carboxylate solution precursors and by reactive liquid phase sintering mechanism, showed dense epitaxial structure and good electrical properties. The surface resistance, measured at a frequency of 10 GHz, was 0.47 mΩ at 5.4 K and 3.1 mΩ at 77 K. The results indicate that this technique can be used to fabricate superconducting thin films for microwave applications at low cost and with wide area coverage.
Resonant phenomena involving bound-to-continuum transitions in quantum wells
Authors: Serzhenko F. L. , Johnson N. F.
Published: July 2002

We analyze resonant phenomena in finite quantum wells involving intersubband transitions from the ground state into the continuum spectrum. The momentum matrix element is shown to exhibit oscillatory behavior due to the presence of virtual levels. Estimates of the momentum matrix element based on the infinite quantum-well approximation are found to be inaccurate.
Solid phase epitaxy of relaxed, implantation-amorphized Si1−xGex alloy layers grown on compositionally graded buffers
Authors: Shiryaev S. Y. , Fyhn M. , Larsen A. Nylandsted
Published: July 2002

Solid phase epitaxial regrowth of implantation-amorphized, relaxed Si0.75Ge0.25 alloy layers grown by molecular beam epitaxy on compositionally graded buffer layers was investigated with ion channeling techniques. The amorphization was done by Ge implantation. The regrowth velocity follows an Arrhenius curve in the investigated temperature range, 471≤T≤506 °C, with an activation energy, Ea=2.76±0.15 eV, equal to published values for Si. The regrowth velocity, however, is enhanced by almost a factor of 5 in this temperature range as compared to Si.
Hydrogenating silicon dioxide in an electron cyclotron plasma
Authors: Delfino M. , Tsai W. , Reynolds G. , Day M. E.
Published: July 2002

The hydrogenating effect of a low-temperature, electron cyclotron resonance excited H2 plasma on the surface chemistry of thermal SiO2 films is analyzed in situ by x-ray photoemission spectroscopy and static secondary ion mass spectrometry. Hydrogenation with this nominal 10 eV proton flux results in Si-(O4), H-Si-(O3), (H2)-Si-(O2), (H2)-Si-O, and H-Si-(Si3) bonding states to the complete exclusion of Si—OH bond formation. A simple thermodynamic argument accounts for the exclusivity of Si—H bonds terminating the outermost (O3)-Si-O-Si-(O3) network of a thick SiOx<2 film, thereby transforming what is normally a hydrophilic surface into one that is hydrophobic.
Generation of electrically conducting features in polyimide (KaptonTM) films with continuous wave, ultraviolet laser radiation
Authors: Srinivasan R. , Hall R. R. , Allbee D. C.
Published: July 2002

Continuous wave, ultraviolet laser radiation (350–380 nm) from an argon ion laser can be used to write patterns of conducting lines on a film of polyimide (KaptonTM) by moving the laser spot which is focused to an intensity of 1–100 kW/cm2, over the surface of the film. The conductivity of the patterns formed are the order of 102 S/cm and seem similar to the conducting material that has been made by other groups from this polymer by pyrolysis between 550 and 750 °C. The narrowest line that was formed in this manner had a width of 15±5 μm. Since the movement of the laser spot can be controlled by an X-Y scanner that is computer driven, this approach offers a convenient method for writing high-resolution, conducting patterns on a Kapton base. The relationship between the conducting material that is prepared from Kapton by continuous wave, ultraviolet laser writing and by irradiation with ultraviolet laser pulses is discussed.
Strained GaInAsP single-quantum-well lasers grown with tertiarybutylarsine and tertiarybutylphosphine
Authors: Holmes A. L. , Heimbuch M. E. , DenBaars S. P.
Published: July 2002

We report on low threshold current densities in GaInAsP single-quantum-well (SQW) lasers grown with the metalorganic column-V precursors, tertiarybutylarsine and tertiarybutylphosphine, instead of the conventional compressed gas sources, arsine and phosphine. Threshold current densities of 121 A/cm2 for a 1.6% compressive strained SQW laser and 249 A/cm2 for an unstrained SQW laser have been measured and are among the lowest values seen in this material system.
Enhanced reflectivity of soft x-ray multilayer mirrors by reduction of Si atomic density
Authors: Schlatmann R. , Keppel A. , Xue Y. , Verhoeven J. , van der Wiel M. J.
Published: July 2002

We report a significant increase of the reflectivity of a soft x-ray Mo/Si multilayer mirror after low energy hydrogen ion beam bombardment of each of the Si layers after deposition. Cross section transmission electron microscopy pictures indicate no significant qualitative difference in interface roughness between the two samples. Elastic recoil detection and Rutherford backscattering spectrometry reveal a concentration of 22 at. % of H in the ion beam bombarded Si layers and a 12% reduction of the Si atomic density. Calculations using the measured atomic density and a very simple roughness model agree with the measured reflectivities. This is the first report of the modification of atomic density of Si in order to change the x-ray optical constants of the Si layer.
Narrow current dip for the double quantum dot resonant tunneling structure with three leads: Sensitive nanometer Y-branch switch
Authors: Sumetskii M.
Published: July 2002

We propose a model of a non-one-dimensional nanometer resonant tunneling device consisting of two quantum dots and three leads for which a small applied voltage can switch off the current between leads 1 and 2 and simultaneously switch on the current between leads 1 and 3. The switching device proposed is based on the effect of exponentially narrow current dip discovered in the present letter.
Mechanism for enhancement of electrical activation of silicon in GaAs by aluminum co-implantation
Authors: de Souza J. P. , Sadana D. K.
Published: July 2002

A pronounced enhancement in the electrical activation of implanted Si in GaAs is demonstrated by co-implantation of Al. The maximum enhancement (×2) occurs when the Si distribution is shallow, there is a separation between the Si and Al distributions with the Al being deeper, the Si and Al are implanted at doses of ≤1×1013 cm−2, and subsequent annealing of the co-implanted GaAs is performed under capless or proximity cap conditions. A model considering gettering of the oxygen present in the bulk Czochralski-grown GaAs to the implanted Al is invoked to explain the observed activation enhancement.
SiO2 mask erosion and sidewall composition during CH4/H2 reactive ion etching of InGaAsP/InP
Authors: Lee B.-T. , Hayes T. R. , Thomas P. M. , Pawelek R. , Sciortino P. F.
Published: July 2002

SiO2 mask erosion has been studied during CH4/H2 reactive ion etching of InGaAsP/InP double heterostructures. The amount of mesa mask narrowing at a pressure of 100 mT, normalized for an etch depth of 3.5 μm, is approximately 0.4–0.6 μm and decreases slightly with increasing self-bias voltage. It is not strongly dependent on the sidewall angle of the mask or CH4 concentration. Mask residue deposits on the etched sidewall under conditions of relatively high CH4 concentration and low power density. Auger electron spectroscopic analysis of the sidewall shows that the deposit contains a significant amount of elemental Si, which suggests a mechanism for mask erosion in which SiO2 is reduced to Si in the hydrogen/hydrocarbon-rich environment of the plasma.
Lattice vibration in alternating monolayers of ZnSe and ZnTe
Authors: Takemura Yasushi , Kakuno Keiichi , Yamada Akira , Konagai Makoto
Published: July 2002

Lattice vibration in alternating monolayers of ZnSe and ZnTe is studied. Optical vibrational modes observed from (ZnSe)n-(ZnTe)n (n=2, 3, 4) short-period superlattice are evaluated by a theoretical analysis using the linear-chain model. A method of the calculation which can take into account lattice strain is proposed. It is found that the zeroth- and the first-order folded phonons in the ZnSe layer are observed in Raman scattering. By investing the displacement of the atoms, it is also found that the ZnSe-like LO mode is localized in the ZnSe layer, whereas no mode is localized in the ZnTe layer. This characterization is attributed to an overlap of the dispersion curves for ZnSe- and ZnTe-LO modes in the strained layer.
Flat-phasefront fanout-type power amplifier employing resonant-optical-waveguide structures
Authors: Botez D. , Jansen M. , Zmudzinski C. , Mawst L. J. , Hayashida P. , Tu C. , Nabiev R. F.
Published: July 2002

A novel type of fanout master-oscillator power amplifier (MOPA) device using resonant antiguided structures is proposed, modeled, and demonstrated. Light injected in the central antiguide of an antiguided structure fans out, with increasing device length, due to resonant transmission between adjacent antiguide cores. After 1-mm device length the emitting aperture becomes ≊100 μm wide, and the beam has a flat phasefront. The device has a strong built-in index step (Δn=0.02–0.05), which makes it insensitive to the problems encountered with conventional fanout-type amplifiers: filamentation and drive-dependent beam pattern. Experimental results include flat-phasefront and a diffraction-limited emission from a 130-μm-wide exit aperture when the entry aperture is a 3-μm-wide antiguide core.
Fabrication of a one-dimensional microhole array by anodic oxidation of aluminum
Authors: Masuda Hideki , Nishio Kazuyuki , Baba Nobuyoshi
Published: July 2002

A one-dimensional microhole array with high-aspect ratio was successfully obtained using anodic oxidation of an aluminum oxide/aluminum/glass structure. This process allows the fabrication of an array of microholes less than 1000 Å diameter without any exposure mask or resist, and the size of the array can be controlled on the basis of the relationship between the thickness of the aluminum layer and anodizing voltage.
Formation of high resistivity regions in p-type Al0.5In0.5P by ion implantation
Authors: Zolper J. C. , Schneider R. P. , Lott J. A.
Published: July 2002

Ion implantation has been applied to magnesium-doped Al0.5In0.5P to produce high resistivity regions for the first time. Hydrogen, oxygen, and argon ions were implanted at a base dose ranging from 5×1012 to 5×1014 cm−2 and annealed from 400 to 900 °C. Hydrogen did not appreciably compensate the In0.5Al0.5P layer while oxygen and argon produced sheet resistances up to 1×109 Ω/⧠. After annealing at 800 °C, regions with high dose oxygen implants maintained a sheet resistance above 1×107 Ω/⧠, while regions with high dose argon implants recovered most of the unimplanted conductivity.
Microstructural investigation of granular Ag-Fe and Ag-Co thin films by atomic resolution and nanochemical analysis electron microscopy
Authors: Li Z. G. , Wan H. , Liu J. , Tsoukatos A. , Hadjipanayis G. C. , Liang L.
Published: July 2002

The microstructure of as-deposited granular Ag-rich (75%–90%) Ag-Fe and Ag-Co thin films was investigated by atomic resolution and nanochemical analysis electron microscopy. Our results suggested that the thin films are two separate phases. The poorly crystallized transition metal particles, with size of less than 1.5 nm in the thin films, were directly observed and were found to be separated by nanosized Ag crystalline particles
Hydrogen-iron interaction in proton-implanted InP:Fe
Authors: Fischer D. W. , Manasreh M. O. , Matous G.
Published: July 2002

We have observed the local vibrational mode (LVM) infrared absorption spectra at 77 K from 2 MeV proton-implanted InP crystals doped with different concentrations of Fe. It is found that the intensity of the LVM which is created at 2286 cm−1 is dependent on the Fe concentration. We conclude that this LVM is due to a P—H, FeIn complex.
Necessity of hydrogen for activation of implanted fluorine in Si/SiO2 structures
Authors: Afanas’ev V. V. , de Nijs J. M. M. , Balk P.
Published: July 2002

The elimination of trapping centers in Al/SiO2/Si structures by means of fluorine ion implantation was studied in oxides with various contents of hydrogen. It was shown that significant reduction in the density of electron and hole traps in the bulk of oxide may be achieved only in the presence of hydrogen in the system (wet oxide, or post-metallization anneal in a hydrogen containing ambient). Similarly, suppression of the generation of Si/SiO2 interface states by radiation is also observed only in hydrogen containing systems. The results suggest that defect precursors such as weakly bonded hydrogen and strained Si—O bonds are eliminated by the fluorine and that hydrogen is necessary for this elimination. It is proposed that H facilitates the F transport by formation of HF molecules.
Two-dimensional electron and hole states at the staggered band line-up interface of InAlAs/InP
Authors: Böhrer J. , Krost A. , Bimberg D. , Helm M. , Bauer G.
Published: July 2002

Crystallographic and electronic properties of the staggered band line-up InAlAs/InP interface grown by metal-organic chemical-vapor deposition are studied using double crystal x-ray diffraction, Shubnikov-de-Haas (SdH), capacitance-voltage, and calorimetric absorption experiments. Observation of a large number of Pendellösung oscillations in the x-ray rocking curves, which can be perfectly modeled using dynamical diffraction theory, demonstrate the high crystallographic quality of the interfaces. A two-dimensional electron gas (2DEG) with ns∼6×1011 cm−2 is formed at the InP side of the interface by carrier transfer from the unintentionally doped InAlAs. The electronic structure of the interface is derived from self-consistent band structure calculation including many particle corrections and good agreements are found with experimentally observed subband transitions up to n=4.
Interference effects in photoreflectance of epitaxial layers grown on semi-insulating substrates
Authors: Lipsanen H. K. , Airaksinen V. M.
Published: July 2002

Interferences were observed in the photoreflectance spectra of homoepitaxial layers grown on semi-insulating GaAs and InP substrates. The modulation mechanism responsible for the interference effect was studied from the frequency and temperature dependence of the interference amplitude and the effect of continuous wave illumination. The results are in agreement with the model that the modulation is due to electrons drifting to the interface from the surface. A simple model was used to fit the interference spectra to the Lorentzian wave forms from the substrate and the epitaxial layer.
High stability single-mode continuous wave photolytic iodine laser
Authors: Hunt J. H. , Burns R. H. , Roullard P. , Widen K. C. , Stanton J. M.
Published: July 2002

Operation of a high-efficiency single mode atomic iodine laser is reported. Although the operation of many photodissociation driven iodine laser have been reported recently, few of them deal with single axial and transverse mode operation, presumably due to the loss of output intensity caused by insertion of intracavity optical elements. Our laser system produces continuous wave operation at 420 mW in a transverse electromagnetic (TEM)00 mode. This corresponds to 23% conversion of output power compared to operation in a multimode fashion. The output power is stable over long periods of operation (8 h) with no adjustment of optics or cleaning of reactant supply.
Electrical characterization of p-type ZnSe:N and Zn1−xMgxSySe1−y:N thin films
Authors: Mensz P. M. , Herko S. , Haberern K. W. , Gaines J. , Ponzoni C.
Published: July 2002

Differential van der Pauw–Hall effect and resistivity measurements have been performed to determine the concentration and mobility of free holes in nitrogen doped ZnSe and Zn1−xMgxSySe1−y thin films. Hall data taken between 120 and 300 K, with magnetic fields up to 4 kG yielded an activation energy of the nitrogen acceptors in ZnSe:N of 104 meV. Donor compensation in the ZnSe:N samples was negligible. Compared with ZnSe:N, samples of Zn1−xMgxSySe1−y:N, exhibited a significantly lower value of room-temperature mobility of holes, and fast-carrier freeze-out at relatively high temperature, approximately T=200 K.
All-fiber traveling-wave laser with nonreciprocal ring configuration
Authors: Okhotnikov O. G. , Lobo Ribeiro A. B. , Salcedo J. R.
Published: July 2002

An all-fiber ring laser geometry in the form of a nonreciprocal S-ring is presented and demonstrated. Its operation is demonstrated to allow unidirectional laser oscillation. The intensity ratio for laser oscillation in each of the two directions were measured, and found to be larger than 150. This value is the largest such ratio obtained for a ring laser without Faraday isolators.
Planar regrowth of InP and InGaAs around reactive ion etched mesas using atmospheric pressure metalorganic vapor phase epitaxy
Authors: Lee B.-T. , Logan R. A. , Karlicek R. F.
Published: July 2002

Growth patterns around etched mesas were observed during the atmospheric pressure metalorganic vapor phase epitaxy (MOVPE) of InP layers with and without addition of trichloroethane (TCA) and InGaAs layers. It was observed that the addition of TCA during the MOVPE of InP induced rapid growth along high-index directions such as [113] as well as much more enhanced faceting along (001) and (111)p planes, resulting in a planar regrowth around reactive ion etched mesas parallel to [110] directions. No irregularity or interruption of growth was observed, providing an ideal sequence for the blocking layer regrowth used in laser fabrication. Regrowth of InGaAs layers also resulted in a planar regrowth around the mesas along [110] directions but through a somewhat different mechanism. Growth on (111) planes was completely suppressed in this case and the facets were less clearly defined, so that growth from the base plane proceeded without interacting with the sidewalls.
High magnetic field trapping in monolithic single-grain YBa2Cu3O7−δbulk materials
Authors: Gao L. , Xue Y. Y. , Ramirez D. , Huang Z. J. , Meng R. L. , Chu C. W.
Published: July 2002

Results of our study on high magnetic field trapping in unirradiated, high quality monolithic single-grain YBa2Cu3O7−δ disks are reported. A record high 4 T trapped field at the surface of the unirradiated disks is observed. However, below 11 K, large flux avalanches caused by thermal instability severely limit the remnant trapped field. Therefore, flux avalanche, rather than Jc×d, dictates the maximum trapped field at low temperatures. To overcome this problem, a strong high temperature superconductor trapped field magnet is proposed. A novel application of the avalanche effect is also mentioned.
Liquid phase epitaxy centrifuge for 100 mm diameter Si substrates
Authors: Konuma M. , Czech E. , Silier I. , Bauser E.
Published: July 2002

In a novel centrifuge, we perform silicon liquid-phase epitaxy (LPE) on 100 mm diameter Si wafers. The epitaxial Si layers grow from indium solutions. The thickness uniformity of the layers is better than ±4.9% within the central circular area of 90 mm in diameter. The layers show smooth surfaces. The bulk of the layers is free of extended defects and of solution inclusions. Hall effect measurements and transmission electron microscopic observations confirm the high quality of this epitaxial material.
Quantum size effect on optical absorption edge in thin antimony films
Authors: Xu J. H. , Ting C. S.
Published: July 2002

The quantum size effect in thin antimony films grown along (111) direction on a GaSb substrate is studied based on a simple model. The critical film thickness, at which the semimetal-semiconductor transition takes place, is determined. It is proposed that the optical experiments can be used to measure the critical thickness since the dependence of optical transition on thickness in the semimetal region is very different from that in semiconductor region.
Conformal chemical beam deposition of thin metal film for fabricating high density trench capacitor cells
Authors: Hsu David S. Y. , Gray Henry F.
Published: July 2002

The difficult aspect of conformal metal film deposition in narrow, high aspect ratio trenches such as those used in the fabrication of high density metal-oxide-semiconductor trench capacitor cells for computer memory technology is addressed. This work demonstrates the proof of principle of highly conformal deposition of a 40 nm Pt film on the surfaces of a 0.5-μm-wide, 1.5-μm-deep, and 2-mm-long array of oxidized silicon trenches, using the thermal decomposition of a molecular precursor under chemical beam conditions. In addition, scanning electron, x-ray photoelectron, and scanning Auger electron microscopy analyses reveal highly uniform and complete coverage on all surfaces, small metal grain size, and the absence of detectable impurities.
Nearly isotropic etching of 6H-SiC in NF3 and O2 using a remote plasma
Authors: Luther B. P. , Ruzyllo J. , Miller D. L.
Published: July 2002

Nearly isotropic etching of the 6H-SiC carbon face has been achieved in a remote plasma at 330 °C using a mixture of O2 and NF3 in argon. Using evaporated aluminum as a mask, undercutting has been observed to a distance equal to the etch depth. The etch rate is a function of the ratio of O2 to NF3 flow rates and of temperature, peaking strongly to 220 nm/min at 82% oxygen for 330 °C. Smooth surfaces were obtained for gas ratios leading to the maximum etch rate, and also for a NF3-argon mixture, with significant roughening observed for other O2-NF3-argon mixtures. In the absence of a practical wet etch for SiC, this procedure is promising for isotropic etching in SiC device processing.
Impact of in situ photoexcitation on the defectivity of silicon layer implanted with different dose rates of nitrogen ions
Authors: Danilin A. B. , Nemirovski A. W.
Published: July 2002

It was shown using x-ray diffractometry method that dose rate does not influence the defectivity degree of N+-implanted Si if the implantation is carried out with in situ photoexcitation. It was also shown that photoexcitation does not appreciably reduce the concentration of interstitial-type defects.
Random telegraphic noise in double barrier systems
Authors: Salvino R. E. , Buot F. A.
Published: July 2002

A random telegraphic noise (RTN) in a resonant tunneling device (RTD) has been found through a self-consistent particle Monte Carlo (MC) simulation with model quantum dynamics. The onset of RTN coincides with the onset of tunneling conduction, and with the onset of the low-current valley region of the current-voltage (I-V) characteristic. The simulation demonstrates the presence of the statistical capture and release of tunneling charged particles by the quantum well, which is similar to the capture and release of electrons by electron traps (defects, etc.). It is proposed that this may represent a novel mechanism for explaining the experimentally observed RTN behavior of large-area double-barrier structures since it is not restricted to small-area devices.
Optimization of Ge/C ratio for compensation of misfit strain in solid phase epitaxial growth of SiGe layers
Authors: Im Seongil , Washburn Jack , Gronsky Ronald , Cheung Nathan W. , Yu Kin Man , Ager Joel W.
Published: July 2002

In order to study the strain-compensation effect by C atoms in solid phase epitaxial (SPE) growth of SiGe alloy layers, C sequential implantation was performed in [100] oriented Si substrates with various doses after high dose (5×1016/cm2) Ge implantation. When the nominal peak concentration of implanted C was over 0.55 at. % in the present sample series, misfit dislocation generation in the epitaxial layer was considerably suppressed. A SiGe alloy layer with 0.9 at. % C peak concentration under a 12 at. % Ge peak shows the greatest improved crystallinity compared to layers with smaller C peak concentrations. The experimental results, combined with a simple model calculation, indicate that the optimum Ge/C ratio for strain compensation is between 11 and 22.
Step-flow growth on strained surfaces
Authors: Ratsch C. , Zangwill A.
Published: July 2002

A theoretical study is presented of the effect of misfit strain on the transition from step flow to island nucleation dominated epitaxial layer growth on a vicinal surface. The analysis generalizes a set of reaction-diffusion equations used for homoepitaxy to include the fact that heteroepitaxial strain changes the Arrhenius barrier for diffusion and promotes the detachment of atoms from the edge of strained terraces and islands. The first effect is equivalent to changing the deposition flux; the latter can drive the system into a new layer growth mode characterized by moving steps that engulf very many very small islands. Experiments to test these predictions are suggested.
Coherent-electron intrinsic multistability in a double-barrier tunneling diode
Authors: Wagner Mathias , Mizuta Hiroshi
Published: July 2002

Recently, a new mechanism leading to electrical multistability in coherent-electron tunneling devices was proposed. The reflection of coherent electrons at a barrier leads to the formation of resonant states in a quantum well in front of the barrier, and the resulting strongly modulated local density of states allows for multiple stable solutions of the Poisson equation to exist at fixed bias. These solutions are characterized by different resonant states being pinned close to the conduction-band edge, with each solution having its own unique tunneling characteristics. Here we show how these multiple-branch I(V) characteristics can be engineered. This approach may open up new possibilities for high-speed functional devices.
Detecting trapped vortices using variable-range hopping in a two-dimensional system
Authors: Wang T. , Clark K. P. , Spencer G. F. , Li F. , Kirk W. P.
Published: July 2002

Giant magnetoresistance was observed in a disordered two-dimensional electron system in a variable-range hopping regime. The possibility of utilizing the phenomenon as a magnetic field sensor was demonstrated by the detection of trapped vortices in a superconducting Pb film. The minimum size of such a device is discussed.
Laser interferometric detection of ultrasonic waves propagating inside a transparent solid
Authors: Jia X. , Boumiz A. , Quentin G.
Published: July 2002

Ultrasonic waves propagating inside a transparent solid have been investigated by using a combination of laser interferometry and photoelastic effect. In comparison with the classical photoelastic technique, the present heterodyne method is sensitive not only to the amplitude but also to the phase of acoustic strains. Pulsed strains of longitudinal, shear, and Rayleigh waves have been experimentally achieved. The phase changes of ultrasonic pulses reflected at the different interfaces were investigated. In addition, the polarization states of shear waves have been observed using the heterodyne detection.
Donor doping of (211) CdTe epilayers and CdTe/CdZnTe piezoelectric heterostructures by molecular beam epitaxy
Authors: Bassani F. , Tatarenko S. , Kheng K. , Jouneau P. H. , Saminadayar K. , Magnea N. , Cox R.
Published: July 2002

Shallow indium donors have been incorporated in (211) CdTe and CdZnTe epilayers by molecular beam epitaxy. For this orientation, no Cd overpressure is necessary to incorporate the indium donors. Essentially 100% activation of donors was obtained in the 1016–7×1017 cm−3 concentration range. Electron mobility was 7300 cm2 V−1 s−1 at 40 K for 3×1015 donors cm−3. Transmission electron microscopy shows that the doped (211) CdTe layers have high structural quality. Optical spectra of modulation-doped (211) CdTe/CdZnTe quantum wells show that an electron gas present in a piezoelectric CdTe well produces strong screening of the internal electric field.
High-resistivity regions in n-type InGaAsP produced by 4He+ ion bombardment at 80 and 300 K
Authors: Comedi D. , Zhao J. , Jankowska K. , Thompson D. A. , Simmons J.
Published: July 2002

The formation of high-resistivity regions in Si-doped (n=1×1018 cm−3) lattice-matched In0.75Ga0.25As0.54P0.46 on InP by helium ion bombardment at 300 and 80 K has been investigated as a function of ion dose (1×1012–1×1016 cm−2) and subsequent annealing temperature (70–650 °C) by sheet resistance and Hall effect measurements as a function of temperature. Irradiations at 300 K are found to induce an increase in the resistivity by a factor of up to 3×105 relative to that of the unimplanted material. Materials bombarded at 80 K with doses higher than 7×1014 cm−2 exhibit a further increase in the sheet resistance and higher stability upon subsequent annealing. Rutherford backscattering channeling results suggest that this behavior is related to the creation of a highly polycrystalline or amorphous region in the InGaAsP layer which occurs for irradiations performed at 80 K, but not at 300 K.
Reflection high-energy electron diffraction observation of surface reaction triggered by pulsed laser irradiation during GaP growth in chemical beam epitaxy
Authors: Hashimoto Tadao , Yoshimoto Masahiro , Vaccaro Pablo O. , Matsunami Hiroyuki
Published: July 2002

Surface reaction triggered by pulsed laser irradiation in chemical beam epitaxy (CBE) for GaP growth using triethylgallium (TEGa) and PH3 was studied with reflection high-energy electron diffraction (RHEED). The intensity of RHEED showed an abrupt decrease on the irradiating laser followed by gradual recovery, and this change of intensity was different from that in usual CBE growth. The intensity recovery had considerable dependence on the PH3 flow rate, which indicates that the intensity recovery is related to the surface reaction between Ga atoms generated by laser irradiation and P atoms. This result showed that the decomposition of TEGa by laser irradiation and the formation of GaP occur alternately under continuous supply of source gases.