bluuebunny/crossref_metadata_2025 huggingface dataset:
High-resolution x-ray diffraction of InAlAs/InP superlattices grown by gas source molecular beam epitaxy
Authors: Chang J. C. P. , Chin T. P. , Kavanagh K. L. , Tu C. W.
Published: July 2002

Structural properties of InAlAs/InP superlattices grown by gas source molecular beam epitaxy on (001)InP were investigated extensively with high-resolution x-ray diffraction. Very high quality material was obtained as indicated by narrow peak widths, numerous satellite peaks, and distinct Pendellosung fringes. Intermixing of group-V elements at each interface was quantified by dynamical simulations of (004), (002), and (115) reflections. The accuracy of the fits to both peak positions and peak intensities for all three reflections provides strong evidence for the proposed four-layer periodic structure.
Optical switching of a new middle trace in an optically controlled parallel resonant tunneling device−Observation and modeling
Authors: Kan S. C. , Sanders S. , Griffel G. , Lang G. H. , Wu S. , Yariv A.
Published: July 2002

Optical switching of a new middle trace observed in an optically controlled parallel resonant tunneling (OPT) device is demonstrated. A circuit model for the OPT is developed. The circuit model satisfactorily explains the existence of the middle trace and its optical switching.
Enhanced dark conductivity during the plastic deformation of red mercuric iodide
Authors: Marschall Jochen , Milstein Frederick
Published: July 2002

An enhanced dark conductivity is shown to exist during the plastic shear deformation of red mercuric iodide single crystals. This enhancement is related to the movement of ‘‘easy glide’’ dislocations during deformation.
High mobility AlInAs/InP high electron mobility transistor structures grown by organometallic vapor phase epitaxy
Authors: Aina L. , Mattingly M. , Burgess M. , Potter R. , O’Connor J. M.
Published: July 2002

We have grown single and double-channel AlInAs/InP modulation doped heterostructures with electron mobilities as high as 5000 and 27 000 cm2/V s at 300 and 77 K, respectively. The sheet electron concentrations for these structures range from 1.5×1012 to 5×1012 cm−2. The layers exhibit strong Shubnikov de Haas oscillations, from which we determined two-dimensional electron gas mobilities at 1.8 K of 40 000 cm2/V s. The electrical properties of the AlInAs/InP heterostructures are the best reported for any device structures with InP as the active layer material.
Single source metalorganic chemical vapor deposition of low microwave surface resistance YBa2Cu3O7
Authors: Hiskes R. , DiCarolis S. A. , Young J. L. , Laderman S. S. , Jacowitz R. D. , Taber R. C.
Published: July 2002

YBa2Cu3O7 films 2000–7500 Å thick were deposited onto [100] LaAlO3 substrates using a novel single source metalorganic chemical vapor deposition technique. We have so far observed critical currents as high as 4×106 A/cm2 at 77 K, transition temperatures (Tc at R=0) as high as 91 K, and the 10 GHz microwave surface resistance Rs as low as 40 μΩ at 4.2 K and 400 μΩ at 77 K.
Over 245 mW 1.3 μm buried ridge stripe laser diodes on n-substrate fabricated by the reactive ion beam etching technique
Authors: Bouadma N. , Kazmierski C. , Semo J.
Published: July 2002

1.3 μm GaInAsP/InP buried ridge stripe lasers have been developed using the reactive ion beam etching process for the realization of the mesa stripe and two-step metalorganic vapor phase epitaxy technique for the layers growth. A cw output power over 245 mW has been achieved in 500-μm-long lasers with front and rear facet reflectivities of 5% and 95%, respectively. Transverse-mode stability at high output power (100 mW) has been demonstrated. In addition, high reliability has been shown in preliminary high-power aging experiments.
Ultrasensitive electroabsorption due to Wannier–Stark localization in extremely shallow superlattices at 77 K
Authors: Goossen K. W. , Cunningham J. E. , Jan W. Y.
Published: July 2002

We have observed Wannier–Stark localization in extremely shallow superlattices (SL) at 77 K, which results in a quasi-blue shift of the absorption edge at very small electric fields. The formation of a Stark ladder is also clearly shown. The blue shift results in a change in absorption coefficient from 1.7 μm−1 (at 0.2 V/μm) to 0.98 μm−1 (at 0.6 V/μm) for a GaAs/Al0.07Ga0.93As SL; for a GaAs/Al0.02Ga0.98As SL we obtain a change from 2.1 μm−1 (at 1.1 V/μm) to 0.9 μm−1 (at 1.5 V/μm).
Initial stage of InAs on GaAs grown by molecular-beam epitaxy studied with low-energy ion scattering
Authors: Kubo Minoru , Narusawa Tadashi
Published: July 2002

We have applied low-energy ion scattering to study the initial stage of InAs epilayer growth on GaAs by molecular-beam epitaxy. We have first observed a characteristic variation of the scattered He intensity with respect to the incident angles of primary He+ ions to the substrate surface. Then we have found a transition stage from the strained structure to the relaxed structure for the 4–15 monolayer thick InAs layer grown on GaAs substrate. Employing the method of surface shadowing for analysis of surface atomic steps, we have been able to observe the surface steps formation due to the island growth. We have discussed the correlation between the transition of growth process and the surface flatness from the standpoint of surface morphology.
Liquid-metal-mediated homoepitaxial film growth of Ge at low temperature
Authors: Xiong Fulin , Ganz Eric , Loeser A. G. , Golovchenko J. A. , Spaepen Frans
Published: July 2002

We demonstrate liquid-metal-mediated homoepitaxial crystal growth of Ge on Ge(111) at temperatures in the range of 400–450 °C. Crystal growth proceeds by diffusion of Ge through a liquid layer, followed by precipitation onto the substrate by the vapor-liquid-solid mechanism. The liquid-metal phase at the interface is a Au-Ge alloy formed by initial deposition of a thin Au layer above the eutectic temperature. Ge vapor is provided by a molecular-beam evaporator. The resulting films revealed high-crystalline quality by in situ high-energy ion scattering and channeling analysis and ex situ by cross-sectional transmission electron microscopy.
Stability of harmonically driven mode-locked semiconductor lasers
Authors: Onodera N. , Ahmed Z. , Tucker R. S. , Lowery A. J.
Published: July 2002

Previous reports of harmonically driven mode-locked semiconductor lasers have indicated that the intensity correlation between adjacent pulses has a contrast ratio of two, rather than three as expected for mode-locked pulses. We show that this reduced contrast ratio is a result of pulse instabilities in harmonically driven mode-locked lasers. By setting the rf drive frequency to the stable operating condition, stable pulses with a contrast ratio of three have been obtained.
Electron microscopy study of C60
Authors: Li J. Q. , Zhao Z. X. , Zhu D. B. , Gan Z. Z. , Yin D. L.
Published: July 2002

The microstructural features of the powder C60 material have been studied by using scanning microscopy, electron diffraction, and high resolution electron microscopy. Scanning electron microscopy observation reveals that the grains in the samples are packed by extensively disordered crystallites as well as amorphous granules. Electron diffraction measurements have identified that the crystals of C60 have two kinds of structure, one is face-centered-cubic (fcc) with unit cell parameter a=1.41 nm, and the other has the hexagonal closest packed (hcp) structure with cell parameters a=0.958 nm and c=1.63 nm. High resolution electron microscopy as well as electron diffraction observations clearly show the random crystallites packing in the C60 grains.
Cation interdiffusion in GaAs-AlAs superlattices measured with Raman spectroscopy
Authors: Grant J. , Menéndez J. , Pfeiffer L. N. , West K. W. , Molinari E. , Baroni S.
Published: July 2002

A combined Raman and ab initio lattice dynamical study of ultrathin (GaAs)4(AlAs)4 superlattices, focusing mainly on AlAs-like vibrations, clearly shows that a significant amount of interdiffusion occurs in these samples when grown at conventional molecular-beam epitaxy temperatures between 580 and 640 °C. At these temperatures, growth interruption is found to have little impact on the structural quality of the superlattices.
Dopant passivation in AlInAs and InGaP by atomic deuterium
Authors: Pearton S. J. , Kuo J. M. , Hobson W. S. , Lopata J. , Ren F. , Katz A. , Geva M.
Published: July 2002

Shallow dopant passivation in AlInAs and InGaP exposed to low power (0.08 W cm−2) deuterium plasmas was investigated by Hall effect and secondary ion mass spectrometry measurements. The carrier concentration in AlInAs was reduced by factors of 3–4 in both Si- and Zn-doped epitaxial layers upon exposure to a D2 plasma at 200 °C. Substantially greater reductions are observed in Si-doped InGaP (500×reduction) and Be-doped InGaP (15×reduction) under the same conditions. Complete reactivation of all the passivated dopants occurs in the temperature range 350–425 °C for annealing in inert ambients. By contrast, the use of hydrogen containing ambients during post-plasma annealing enhances the apparent stability of the dopant passivation. The diffusivity of deuterium is greater in p-type layers than in n-type layers for each material.
New SiGe dielectrics grown at room temperature by low-energy ion beam oxidation and nitridation
Authors: Vancauwenberghe O. , Hellman O. C. , Herbots N. , Tan W. J.
Published: July 2002

New dielectric materials based on SiGe have been formed at room temperature by direct ion beam oxidation and nitridation. Si0.8Ge0.2 layers were deposited by molecular beam epitaxy on Si(100) and then exposed to a low-energy ion beam of 18O+2 to form oxides and 14N+2 to form nitrides. The ion energies investigated ranged from 100 eV to 1 keV. Thin films of SiGe oxide and SiGe nitride were formed at all energies used as evidenced by in situ x-ray photoelectron spectroscopy analysis. They were found to be insulating by ex situ scanning electron microscopy observations. During the ion beam processing, the Ge content of the alloy layer decreases, due to preferential sputtering of Ge and the Ge compounds. However, as the ion energy is decreased, the concentration of Ge in the alloy remains closer to the original content. The thermal stability of these new SiGe dielectrics was also assessed up to 500 °C.
GaAs/AlGaAs quantum well and modulation-doped heterostructures grown by organometallic vapor phase epitaxy using trimethylamine alane
Authors: Hobson W. S. , Ren F. , Schnoes M. Lamont , Sputz S. K. , Harris T. D. , Pearton S. J. , Abernathy C. R. , Jones K. S.
Published: July 2002

High-quality GaAs/AlGaAs quantum well and modulation-doped heterostructures have been grown by low-pressure organometallic vapor phase epitaxy (OMVPE) using trimethylamine alane (TMAA) as a new aluminum source. TMAA is an alternative to the conventional organometallic precursors and offers the advantage of substantially reduced oxygen and carbon incorporation in AlGaAs. Intense photoluminescence (PL) with narrow linewidths at 2 K was observed from multiple quantum well samples with well widths of 1.5–10 nm. Transmission electron microscopy of a fifty period superlattice (4 nm GaAs/44 nm Al0.18Ga0.82As) revealed abrupt interfaces and excellent well-to-well thickness uniformity. Selectively doped heterostructure transistors (SDHTs) fabricated on the modulation-doped structures exhibited a maximum extrinsic transconductance of 339 mS/mm for a 1-μm-gate length at 300-K, the highest reported for OMVPE grown devices. A unity current gain cutoff frequency, ft, of 16 GHz and a maximum frequency of oscillation, fmax, of 23 GHz were obtained for these SDHTs.
Oscillatory instability in the heterostructure hot-electron diode
Authors: Wacker A. , Schöll E.
Published: July 2002

Vertical electrical transport in the heterostructure hot-electron diode is considered theoretically. We present a simple dynamical model which consistently explains the measured S-shaped negative differential conductivity in the current-voltage characteristics. The model predicts a new type of self-sustained 60 GHz voltage oscillations between tunneling and thermionic emission if the sample is driven by a dc voltage source having a resistor in series and a capacitor in parallel.
YBa2Cu3O7−x films on flexible, partially stabilized zirconia substrates with fully stabilized zirconia buffer layers
Authors: Harshavardhan K. S. , Ramesh R. , Ravi T. S. , Sampere S. , Inam A. , Chang C. C. , Hull G. , Rajeswari M. , Sands T. , Venkatesan T. , Reeves Mark , Tkaczyk J. E. , Lay K. W.
Published: July 2002

Textured polycrystalline YBCO films with superconducting transition temperatures of ∼90 K have been prepared on flexible zirconia substrates, partially stabilized by 3 mol % yttria. X-ray data suggest undesirable (013) and [(110) (103)] texture in minor amounts within the predominantly c-axis oriented film. The transmission electron microscope data reveal clean, special crystallographic as well as silicon contaminated grain boundaries containing amorphous phases. By depositing a zirconia buffer layer, fully stabilized by 9 mol % yttria, we have demonstrated that the normal-state metallic and superconducting properties of the YBCO films can be considerably improved. These films exhibit critical-current densities of ∼0.9×104 A/cm2 at 77 K in zero field and 2×105 A/cm2 at 4.2 K in zero field.
Morphology-enhanced metal-alumina adhesion by depositing textured alumina films on textured Teflon substrates
Authors: Chang Chin-An , Chan Chin-Jong , Jones Fletcher
Published: July 2002

An enhanced adhesion between metals and alumina has been achieved by texturing the alumina films. The Al2O3 films are deposited on textured Teflon substrate; the latter was presputtered to provide a textured surface for the alumina deposition. For thin alumina layers of about 500-Å, a textured surface is obtained which is nearly identical to that of the starting Teflon. On such an alumina surface, an increase in peel strength of about 40–50 times is obtained for both Cu and Cu90%-Cr10%, from those deposited on nontextured alumina using nontextured Teflon substrates. With an increasing thickness of alumina, the height of the surface texture is reduced, resulting in less enhancements in peel strength than those on the 500-Å alumina. The results are in agreement with the model for the morphology-enhanced adhesion, which was proposed to explain the previously observed enhancement in adhesion between Cu and textured Teflon. The work also provides a simple way of generating a textured surface for the ceramic materials for an enhanced adhesion with metals needed for a variety of technologies.
Effect of Si movement on the electrical properties of inverted AlInAs–GaInAs modulation doped structures
Authors: Brown A. S. , Metzger R. A. , Henige J. A. , Nguyen L. , Lui M. , Wilson R. G.
Published: July 2002

Inverted modulation doped structures typically exhibit degraded electrical characteristics. For the AlInAs-GaInAs heterojunction system, the reduction in electron mobility for two-dimensional electron gases formed at inverted interfaces can be greater than 50% at 300 K as compared to those formed at normal interfaces. Our data show that the reduction in mobility is due to the movement of Si into the GaInAs channel. The Si movement is found to be dramatically reduced by growing the AlInAs spacer at the inverted interface at a substrate temperature of 300–350 °C. Device structures have been grown using this technique which exhibit the highest conductivity obtained for any 2DEG system.
Backside secondary ion mass spectrometry study of a Ge/Pd ohmic contact to InP
Authors: Schwarz S. A. , Pudensi M. A. A. , Sands T. , Gmitter T. J. , Bhat R. , Koza M. , Wang L. C. , Lau S. S.
Published: July 2002

High-resolution SIMS (secondary ion mass spectrometry) depth profiles of Ge/Pd ohmic contacts on InP are obtained by sputter-etching from the back (semiconductor) side. The samples contain an InGaAs-etch stop layer, to allow chemical thinning, and InGaAsP marker layers, which allow alignment and calibration of the depth profiles on the nm scale. At 200 °C, a Pd-In-P alloy layer is observed to form at the contact interface. The thickness of this layer is dependent on the amount of metallic Pd available for reaction. Subsequent processing at 325 °C results in the partial dissolution of this alloy layer, as PdGe forms at the contact interface, and regrowth of the liberated InP. Ge is detected in the regrown region but is not observed to diffuse into the substrate. Ge epitaxy is not observed at the contact interface at 325 °C, in contrast to the behavior of the Ge/Pd-GaAs contact. The experimental evidence suggests that regrowth is a key step in the formation of the ohmic contact.
Surface-emitting lasers with optical cavity along the [111] direction
Authors: Ou S. S. , Yang J. J. , Jansen M.
Published: July 2002

Monolithic horizontal cavity GaAs/GaAlAs surface-emitting lasers with cavities along the [111] direction have been demonstrated for the first time. The vertical facet of the devices was fabricated by reactive-ion etching and the 45° outcoupler micromirror was fabricated by ion-beam etching. Typical uncoated devices have threshold current densities of 330 A/cm2, which is the lowest ever reported for GaAs/GaAlAs surface-emitting lasers. The coated devices have external differential quantum efficiencies as high as 40% (0.6 W/A), and output powers (pulsed) in excess of 3 W. The output power is the highest ever reported from GaAs/GaAlAs horizontal cavity surface-emitting lasers with dry-etched outcoupler micromirrors.
Physical criteria for the direct-to-indirect gap crossover in AlxGa1−xAs alloys
Authors: Capaz R. B. , von der Weid J. P. , Koiller Belita
Published: July 2002

AlxGa1−xAs alloys undergo a direct-to-indirect gap transition when the Al concentration x is increased, or when hydrostatic pressure P is applied to a direct-gap sample of fixed composition. It is usually assumed that either hydrostatic pressure or alloying produce a Γ–X conduction band crossing responsible for the change in the nature of the gap. A critical discussion regarding this widely adopted criterion for the direct-to-indirect gap transition is presented. Alloying and pressure effects in the electronic properties of AlxGa1−xAs are determined through the small crystal approach with a 64-site basic cluster. Finite-size effects are discussed. The photoluminescence emission intensity is calculated as a function of x and P, and physically reliable criteria for the transition from the direct-to-indirect gap regimes based on these results are proposed. A critical concentration consistent with experimental results associated to this change of regime is obtained from our data.
In situ doping of GedxSi1−x with arsenic by rapid thermal processing chemical vapor deposition
Authors: Jung K. H. , Hsieh T. Y. , Kwong D. L. , Liu H. Y. , Brennan R.
Published: July 2002

We report the growth of GexSi1−x epitaxial layers in situ doped with arsenic by rapid thermal processing chemical vapor deposition at 800 and 900 °C. Films were grown with activated doping levels of up to 2×1019 cm−3 and dopant transition widths (1019–1015 cm−3) of better than 350 Å. Doping was observed to reduce growth rates and significantly improve film quality. Defect densities of the order of 103 cm−2 were achieved with normalized film strains of up to 99%.
Operation of nonlinear GaAs/AlGaAs multiple quantum well microresonators fabricated using alloy-mixing techniques
Authors: Sfez B. G. , Rao E. V. K. , Nissim Y. I. , Oudar J. L.
Published: July 2002

We report for the first time the fabrication and the operation of GaAs/AlGaAs multiple quantum well nonlinear microresonators employing defect-induced alloy-mixing techniques. A uniform array of 5-μm square microresonators shows a hysteresis behavior in the reflection mode and in a quasi-continuous regime. We demonstrate that the pixellation indeed improves the nonlinear properties of the structures.
Theoretical analysis of strained-layer InGaAs/GaAs quantum-well lasers with gain suppression and valence-band mixing
Authors: Ahn D. , Yoo T.-K.
Published: July 2002

Linear gain, gain suppression, and L-I characteristics of strained-layer InGaAs/GaAs quantum-well laser are studied theoretically, taking into account valence-band mixing effects with biaxial compressive strain. It is found that the biaxial compressive strain substantially alters subband structure by pushing the light-hold subband bands into higher-energy states. It also alters the optical gain of a quantum-well laser. In particular, the biaxially compressed strained-layer InGaAs/GaAs quantum well shows a pronounced preference for TE polarization over TM polarization and the higher optical gain than does a typical GaAs/AlGaAs quantum well. The L-I characteristics are obtained self-consistently from the rate equations for the carrier and the photon densities and the calculated L-I curve shows reasonable agreement with the experimental data.
Coexistence of Wannier–Stark localization and negative differential velocity in superlattices
Authors: Sibille A. , Palmier J. F. , Mollot F.
Published: July 2002

We show the coexistence of Wannier–Stark localization as monitored by photoconduction experiments, and of negative differential velocity (NDV) for electrons in a perpendicularly biased GaAs/AlAs superlattice. The critical electric field for the onset of NDV, and that for the appearance of localization as monitored optically are nearly the same, which exemplifies the fundamental link between Wannier–Stark quantization [Phys. Rev. 117, 432 (1960)], and Esaki–Tsu nonlinear transport [IBM J. Res. Dev. 14, 61 (1970)].
Zero-loss quantum well waveguide Mach–Zehnder modulator at 1.55 μm
Authors: Zucker J. E. , Jones K. L. , Miller B. I. , Young M. G. , Koren U. , Evankow J. D. , Burrus C. A.
Published: July 2002

We report the first interferometric waveguide intensity modulator with optical gain. A monolithically integrated compressively strained InGaAs quantum well amplifier provides a net 4.2 dB fiber-to-fiber gain at 120 mA forward bias. Reversed-biased InGaAsP quantum wells provide enhanced electrorefraction for the modulator in which we demonstrate a 3 dB electrical modulation bandwidth of 2.25 GHz. The voltage-length product for 180° phase shift is a record Vπ × L = 1.9 V mm. The total device length is under 2 mm.
Study of interface composition and quality in AlSb/InAs/AlSb quantum wells by Raman scattering from interface modes
Authors: Sela I. , Bolognesi C. R. , Samoska L. A. , Kroemer H.
Published: July 2002

We have studied the interface structure and the quality of molecular-beam-epitaxy grown AlSb/InAs/AlSb quantum wells through Raman scattering from interface vibrational modes from single quantum wells. A series of samples was grown by varying the growth temperature and the interface composition (by forcing either a light AlAs or a heavy InSb interface bond configuration at each InAs/AlSb interface). We have observed the InSb modes for all the samples and related the intensity and shape of the interface modes to the structure and quality of the interfaces. This work demonstrates that a single interface heterostructure can be probed by Raman scattering.
Quantum wires prepared by liquid-phase-epitaxial overgrowth of dry-etched AlGaAs-GaAs heterostructures
Authors: Hornischer W. , Grambow P. , Demel T. , Bauser E. , Heitmann D. , von Klitzing K. , Ploog K.
Published: July 2002

We have developed a technique to overgrow deep-mesa-etched AlGaAs-GaAs quantum wires with AlGaAs by liquid-phase epitaxy and achieve improved interfacial properties. In particular, we find a significant reduction of the surface-state density and related lateral edge depletion in modulation-doped quantum wires. We demonstrate the formation of a quasi-one-dimensional electron system by far infrared spectroscopy.
Stable amorphous silicon double stacked solar cell using low band gap amorphous silicon bottom i layer
Authors: Jang Jin , Kim Tae Gon , Kim Sung Chul , Jun Jung Mok , Park Kyu Chang
Published: July 2002

We studied the preparation of low-band-gap amorphous silicon(a-Si) and the photovoltaic applications of this material. We obtained a-Si with optical band gap between 1.60 and 1.65 eV with hydrogen content less than 6 at.% and used this material as the bottom i layer of a-Si double-stacked solar cells. The conversion efficiency is about 9% and the degradation is less than 4% after light exposure for 100 h under 350 mW/cm2.
Magnetic circular dichroism of the diamagnetic charge state of EL2 in GaAs
Authors: Pillukat A. , Ehrhart P.
Published: July 2002

Within the magnetic circular dichroism spectrum of the optical absorption of semi-insulating GaAs, a temperature-independent line was observed for the first time. This line is located at 1.19 eV and we ascribe it to the same transition which causes the optical absorption line of diamagnetic EL20. We consider first implications for the electronic structure of EL2 and use this line for the analysis of the charge state of EL2 in e−-irradiated GaAs. It is shown that by annealing of low-temperature e−-irradiated GaAs, the concentration of EL2 defects can be made at least an order of magnitude higher than after thermal treatment.
Optical Bloch waves in a semiconductor photonic lattice
Authors: Gourley P. L. , Warren M. E. , Vawter G. A. , Brennan T. M. , Hammons B. E.
Published: July 2002

We have observed multiple optical Bloch waves in a semiconductor photonic lattice. This photonic lattice comprises epitaxial quarter-wave periodic layers surrounding a periodic quantum-well region. After growth, the layers are structured laterally into periodic square unit cells by reactive-ion-beam etching. When photoexcited, the lattice emits a complex angular distribution of photons that reflects its periodic structure. Scattered light is distributed according to the Laue conditions in analogy with x-ray diffraction from a bulk crystal. Optical Bloch waves photostimulated in the lattice are analogous to electron Bloch waves in an atomic lattice. These optical Bloch waves exhibit long-range translational symmetry and local symmetry due to the shape of the unit cell. Interestingly, the far-field pattern of stimulated emission gives a direct mapping of the allowed Bloch wave vectors in the Brillouin zone. The mapping exhibits a wave-vector gap at the Bragg condition and may be associated with a photonic energy gap. In addition to measuring the intensity distribution of these Bloch waves, we directly measure the phase of the wave by polarization shearing interferometry.
Origin of nonlinear gain saturation in index-guided InGaAsP laser diodes
Authors: Frankenberger Rudolf , Schimpe Robert
Published: July 2002

The spectrum of nonlinear gain saturation of InGaAsP diode lasers with a buried heterostructure is measured by means of modulation spectroscopy. The underlying physical processes are identified through comparison with theoretical spectra. At the laser line, contributions to the coefficient of self-saturation by spectral hole burning (1.6×10−17 cm3) and carrier heating (1.1×10−17 cm3) of comparable magnitude are found.
Piezospectroscopy of GaAs and GaAs/GaAlAs single quantum wells grown on (001) Si substrates
Authors: Qiang H. , Pollak Fred H. , Shum Kai , Takiguchi Y. , Alfano R. R. , Fang S. F. , Morkoç H.
Published: July 2002

The effects of large external stress (S) along [100] on the optical features associated with biaxially strained bulk GaAs and two GaAs/GaAlAs single quantum wells (SQWs) grown on (001) Si have been observed using photoreflectance at 300 K. This stress configuration makes it possible to externally alter the light (LH)- and heavy (HH)-hole splitting in both the bulk material and the SQWs. In a SQW of width 200 Å, the ground state was continuously tuned from LH to HH. In the bulk material, a stress-induced anticrossing of the LH and HH features of the fundamental gap was determined with an interesting polarization effect.
Semiconductor distributed feedback lasers with quantum well or superlattice gratings for index or gain-coupled optical feedback
Authors: Tsang W. T. , Choa F. S. , Wu M. C. , Chen Y. K. , Logan R. A. , Chu S. N. G. , Sergent A. M. , Burrus C. A.
Published: July 2002

We introduce a semiconductor distributed feedback (DFB) in which the grating is fabricated out of quantum well (QW) or superlattice multilayers. This approach provides a very simple and effective scheme for achieving gain (loss)-coupled DFB lasers. The present idea was successfully demonstrated with a 1.55-μm wavelength 6-QW In0.6Ga0.4As (5 nm)/InGaAsP (band-gap wavelength=1.25 μm, 18.6 nm) separate confinement heterostructure DFB laser utilizing only a 2-QW In0.62Ga0.38As (4 nm)/InP (9.3 nm) as the grating.
Electron cyclotron resonance plasma deposition of silicon nitride: Effect of very low rf substrate bias
Authors: Buckle K. A. , Rodgers J. , Pastor K. , Constantine C. , Johnson D.
Published: July 2002

Plasma deposition of SiN on silicon substrates in a microwave (2.45 GHz) electron cyclotron resonance SiH4/N2/He, in the ratio 4/10/10, discharge has been investigated as a function of rf (40 MHz) self-biasing of the sample. Low levels of rf bias (0–10 W) were investigated and are reported in this letter. The effect of bias was measured for the deposited films with respect to refractive index, etch rate in BHF, Si—H bonding, and the intrinsic film stress. All depositions were conducted at or near room temperature to evaluate the effect of the applied rf bias on film density. All parameters examined indicated that low levels of rf bias help prepare a high quality, dense film at very low substrate temperatures.
Tailoring of electron and hole energies in strained GaAsP/AlGaAs quantum wells using fluorine-impurity-induced layer disordering
Authors: Das Utpal , Davis Steve , Ramaswamy Ramu V. , Stevie Fred A.
Published: July 2002

Restoration or removal of the light- and heavy-hole degeneracy of the exciton transitions for light polarized parallel to the layers in strained GaAs0.91P0.09/Al0.3Ga0.7As single quantum wells has been demonstrated by fluorine-impurity-induced layer disordering. Disordering due to As and P interdiffusion has also been observed at the quantum-well interfaces. For only a 15-min anneal at 750 °C, accumulation of P and a depletion of As at a distance of 0.05–0.1 μm beneath the surface is found to be closely associated with the redistribution of the implanted F in this region.
Growth of InGaAs/InP optical modulator structures by chemical beam epitaxy
Authors: Chiu T. H. , Goossen K. W. , Williams M. D. , Storz F. G.
Published: July 2002

We show that the alloy composition and the period length of InGaAs/InP multiple quantum wells grown by chemical beam epitaxy is sensitive to the growth temperature and the As overpressure. Around 530 °C, the inhomogeneous broadening of absorption edge due to growth temperature instability is more of a consequence of changing period length than the ternary composition. The arsenic overpressure dependence of the ternary composition is investigated by secondary ion mass spectroscopy for the first time. The Ga/In ratio becomes smaller at high arsine flow rate. Superlattices containing 50–100 periods of InGaAs/InP exhibit x-ray diffraction peak widths comparable to the InP substrate can be prepared under continuous growth mode. Clear quantum confined Stark effect is observed in the electroabsorption characteristics of a 74-period modulator.
In situ fabrication of superconducting Lu-Ba-Sr-Cu-O films by pulsed-laser deposition
Authors: Schwab P. , Wang X. Z. , Bauerle D.
Published: July 2002

Thin superconducting films of single phase LuBa2Cu3O7 and LuBaSrCu3O7 have been synthesized by means of laser sputtering. The films show zero resistance at 90 and 54 K, respectively. The critical current density found with LuBa2Cu3O7 films at 83 K is in excess of 106 A/cm2. The synthesis of these materials by standard solid-state reactions has not yet been achieved successfully.
Measurements of the barrier-well injection bottleneck in a multiple quantum well optical amplifier
Authors: Nagar R. , Tessler N. , Abraham D. , Eisenstein G. , Koren U. , Raybon G.
Published: July 2002

We describe broadband static pump probe measurements of the barrier-well injection bottleneck caused by a complicated interaction between three- and two-dimensional carriers in a 1.5-μm multiple quantum well optical amplifier.
Measurement of ζ potential of YBa2Cu3O7−δ from the adsorption of hydronium ions (H+, OH−)
Authors: Wang Annie Q. , Hart Timothy R.
Published: July 2002

The adsorption of hydronium ions, H+ and OH−, on YBa2Cu3O7 in electrolytic solution is measured. The curve of the ζ potential (zeta potential) of YBa2Cu3O7 gives the point-of-zero ζ potential (pzzp). The electronegativity of YBa2Cu3O7 can be found from the pzzp. The experimental value of the electronegativity is compared with the calculated result.
Temperature-tunable, single frequency microcavity lasers fabricated from flux-grown YCeAG:Nd
Authors: Gavrilovic P. , O’Neill M. S. , Meehan K. , Zarrabi J. H. , Singh S. , Grodkiewicz W. H.
Published: July 2002

Data are presented on a single-frequency, diode-pumped, microcavity YCeAG:Nd laser. The maximum output power was 45 mW in continuous operation, limited by the available pump power of 250 mW. The output was single-frequency, TEM00 at all powers. The lasing frequency was continuously temperature-tunable over a range greater than 180 GHz, with a stability of better than 10 MHz.
Effects of local facet and lattice damage on nucleation of diamond grown by microwave plasma chemical vapor deposition
Authors: Lin S. J. , Lee S. L. , Hwang J. , Chang C. S. , Wen H. Y.
Published: July 2002

Diamond deposition on an anisotropic etched Si and ion implanted Si surfaces have been examined here for the first time. Local facets on an anisotropic etched surface shows no nucleation of diamond. Synthetic diamond, in contrast, has been able to nucleate on an As+ or Si+ ion implanted Si substrate without diamond abrasive pretreatment. Selective deposition of diamond occurs only for low dose ion implantation, 100 keV 1014 cm−2, but not for high dose ion implantation, 100 KeV 1016 cm−2. Strain is proposed as the main reason for nucleation of diamond on the ion implanted Si substrates.
Planar native-oxide AlxGa1−xAs-GaAs quantum well heterostructure ring laser diodes
Authors: Kish F. A. , Caracci S. J. , Maranowski S. A. , Holonyak N. , Smith S. C. , Burnham R. D.
Published: July 2002

Native-oxide planar AlxGa1−xAs-GaAs quantum well heterostructure ring laser diodes (25-μm- wide annulus, 250-μm inside diameter, 300-μm outside diameter) are demonstrated. The curved cavities (full-ring, half-ring, and quarter-ring) are defined by native oxidation (H2O vapor+N2 carrier gas, 450 °C) of the entire upper confining layer inside and outside of the annulus. The native oxide provides current confinement and a sufficiently large lateral index step, and thus photon confinement, to support laser oscillation along the ring. Half-ring laser diodes fabricated in a self-aligned geometry exhibit continuous wave (cw) 300-K thresholds as low as ∼105 mA (∼500-μm circular cavity length), high total external differential quantum efficiencies (∼49%), and cw output powers of ≳40 mW.
Atomic layer epitaxy of GaAs and role of As-source materials on self-limiting mechanism
Authors: Fujii Kazuyuki , Suemune Ikuo , Koui Tomoaki , Yamanishi Masamichi
Published: July 2002

Atomic layer epitaxy (ALE) of GaAs using triethylgallium (TEG) with the combination of arsine has been limited to an extremely narrow temperature range. It is demonstrated that the temperature range for ALE using TEG is substantially expanded when arsine is replaced with an alkyl-As, tris-dimethylamino-arsenic {As[N(CH3)2]3}. The role of the As source materials on the self-limiting mechanism is discussed with the measurement of the surface reaction species employing a transient quadrupole mass spectrometry.
Low-temperature formation of YBa2Cu3O7−x superconducting films from molecular Cu-Ba-Y precursors
Authors: Rupich M. W. , Liu Y. P. , Ibechem J.
Published: July 2002

Highly oriented superconducting YBa2Cu3O7−x films were prepared on (100) LaAlO3 and (100) yttria-stabilized ZrO2 (YSZ) substrates by sequential thermolysis and oxidation of Cu-Ba-Y μ-oxo alkoxide precursor films at 730 °C. The precursor films were deposited by standard spin-coating techniques. The electrical properties and surface morphology of the YBa2Cu3O7−x films are determined primarily by the thermolysis conditions. YBa2Cu3O7−x films processed at 730 °C show metallic behavior in the normal state and sharp resistive superconducting transitions with Tc (R=0) at 89.5 K. Critical current densities of 2×105 A/cm2 at 77 K were obtained with YBa2Cu3O7−x films on YSZ substrates. X-ray diffraction analysis shows a preferential c-axis alignment normal to the substrate plane.
Electrical anisotropy in Bi-Sr-Ca-Cu-O thin films prepared on (110) SrTiO3 by metalorganic chemical vapor deposition
Authors: Sugimoto Tsunemi , Kubota Nobuhiko , Shiohara Yuh , Tanaka Shoji
Published: July 2002

Highly (119) oriented Bi-Sr-Ca-Cu-O thin films with the transition temperature as high as 70 K on (110) and 5° off (110) SrTiO3 substrates were prepared by metalorganic chemical vapor deposition. The normal state resistivity along the [11̄0] direction (tilted about 45° to the a-b plane of the film) was 200 times larger than that measured along the [001] direction (parallel to the a-b plane of the film) for the film prepared on a 5° off oriented (110) SrTiO3 substrate. The anomalous drop of the resistivity near the Tc,0 was observed in the film prepared on a (110) SrTiO3 substrate.
Photoelectrochemical depth profiling of molecular beam epitaxy grown group III-V heterostructures
Authors: Wei C. , Rajeshwar K. , Alavi K. , Pathak R. N. , Wang L. T.
Published: July 2002

A depth profiling technique is described for molecular beam epitaxy grown (Al,Ga)Al/GaAs heterostructures which combines photoelectrochemical layer-by-layer removal with analyses by photocurrent spectroscopy. The technique is illustrated for two types of samples having a graded and ‘‘flat’’ Al profile in the epilayer.
Van der Waals epitaxy of thick Sb, Ge, and Ge/Sb films on mica
Authors: Osten H. J. , Klatt J. , Lippert G.
Published: July 2002

We attempt to grow 20-nm-thick layers of Sb and Ge as well as periods of (20 nm Sb/20 nm Ge) layers on muscovite (a special form of mica) by van der Waals epitaxy under different growth conditions. The growth process was in situ investigated by reflection high-energy electron diffraction and Auger electron spectroscopy. Epitaxial Sb layers could be obtained even at cold substrates (mica or polycrystalline Ge layers). It was not possible to grow monocrystalline Ge layers by van der Waals epitaxy. Only a formation of oriented Ge grains could be observed at higher temperatures.
Epoxy-amine polymer waveguide containing nonlinear optical molecules fabricated by chemical vapor deposition
Authors: Tatsuura Satoshi , Sotoyama Wataru , Yoshimura Tetsuzo
Published: July 2002

Epoxy-amine polymer thin films are fabricated by chemical vapor deposition using an aliphatic amine, which is very reactive to epoxy groups and has nonlinear optical properties. A transparent thin film is obtained by controlling the temperature and surface condition of the substrate, and the epoxy-amine ratio during deposition. The refractive index of the film is 1.648. A slab waveguide is constructed by depositing the polymer film on SiO2 which is formed by thermal oxidation of a Si wafer. End coupling of a He-Ne laser (632.8 nm) launches a well-propagating beam. This is the first case in which a polymer waveguide is fabricated by dry processing.
Infrared response of Pt/Si/ErSi1.7 heterostructure: Tunable internal photoemission sensor
Authors: Pahun L. , Campidelli Y. , d’Avitaya F. Arnaud , Badoz P. A.
Published: July 2002

We present the first internal photoemission response of a metal-Si-metal heterostructure. Using the Pt/Si/ErSi1.7 system, we show that the photoresponse of this new device can be strongly modified when a bias of a few hundred mV is applied between the two metallic electrodes: the cutoff wavelength is shifted from 1.4 μm to above 5 μm, and the quantum efficiency is increased up to 5% at 1.2 μm wavelength when a positive bias is applied to the front Pt electrode. These dramatic changes are attributed to a modulation of the effective potential barrier experienced by the photoexcited carriers when crossing the Si film.
Direct modulation of blue radiation from frequency-doubled AlGaAs laser diode using the electro-optic effect in a KNbO3 nonlinear crystal
Authors: Senoh T. , Fujino Y. , Tanabe Y. , Hirano M. , Ohtsu M. , Nakagawa K.
Published: July 2002

A novel method for modulating frequency-doubled blue radiation from an AlGaAs laser diode was developed utilizing the electro-optic effect in a KNbO3 nonlinear crystal. Stable blue radiation was obtained from an external ring resonant cavity containing a KNbO3 crystal. The weakly excited counterpropagating mode in the resonant cavity was re-injected into the laser diode to establish self-locking. Nearly 100% intensity modulation was observed when a 3 kV/cm ac electric field was applied parallel to the c axis of the KNbO3 crystal.
Mechanical strength of silicon crystals with oxygen and/or germanium impurities
Authors: Fukuda Tetsuo , Ohsawa Akira
Published: July 2002

Using an indentation test at 900 °C, we studied the mechanical strength of epitaxial and Czochralski (CZ) silicon single crystals with germanium concentrations between 1018 and 1021 cm−3. The strength of CZ crystals is found to increase for germanium concentrations above 6×1019 cm−3 and that of epitaxial crystals independent of germanium concentrations below 3×1020 cm−3. Yamada-Kaneta, Kaneta, and Ogawa [16th International Conference on Defects in Semiconductors (Lehigh University, Bethlehem, Pennsylvania, 1991), p. 286] report that in CZ crystals alloyed with germanium in excess of 6×1019 cm−3, oxygen atoms occupy the interstitial sites next to the germanium atoms. A model compatible with the observations is that the increased strength is due to dislocation immobilization by oxygen atoms adjacent to germanium atoms.
100 fs pulse generation from an all-solid-state Nd:glass fiber laser oscillator
Authors: Ober M. H. , Haberl F. , Fermann M. E.
Published: July 2002

An all-solid-state passively mode-locked Nd:glass fiber laser delivering 100 pJ pulses with a minimal pulse width of 100 fs is demonstrated. The oscillator has room-mean-square amplitude fluctuations of 0.2% in a frequency band from 15 Hz to 100 kHz.
Variable width and electron density quantum wires in GaAs/AlGaAs with ion-implanted gates and a surface Schottky gate
Authors: Blaikie R. J. , Cleaver J. R. A. , Ahmed H. , Nakazato K.
Published: July 2002

Beryllium implants have been used to form p-n junctions which confine electrons laterally in a GaAs/AlGaAs heterostructure to make high-mobility quasi-one-dimensional wires whose electrical width can be varied by biasing the implanted regions. Incorporation of an additional surface Schottky gate enables the electron density within the wires to be controlled independently. Magnetoresistance measurements have been performed at 1.7 K and the weak-field boundary-scattering maxima used to determine the width as a function of both the bias applied to the implanted regions and to the surface gate. The mobility is also calculated and is comparable to that reported for wires of similar dimensions fabricated using high energy ion damage.
Single-electron Coulomb blockade in a nanometer field-effect transistor with a single barrier
Authors: Chou Stephen Y. , Wang Yun
Published: July 2002

The first experimental study of a new nanometer field-effect transistor with a single barrier in its one-dimensional channel is presented. At low temperatures and as charge density in the channel was varied, nine reproducible periodic oscillations of conductance, in addition to 2e2/h conductance plateaus, were observed before the onset of the first 2e2/h conductance plateau. It was found experimentally that each conductance oscillation corresponds to the Coulomb blockade of a single electron in the one-dimensional channel. A model that describes the operation of the new single electron transistor is suggested.
Rectifying current-voltage characteristics in YBa2Cu3O7−x/NdGaO3/ n-SrTiO3 diodes
Authors: Takauchi H. , Yoshida A. , Tamura H. , Imamura T. , Hasuo S.
Published: July 2002

Rectifying current-voltage characteristics were analyzed for YBa2Cu3O7−x/NdGaO3/n-SrTiO3 diodes made by depositing NdGaO3 barriers and YBa2Cu3O7−x films on Nb-doped SrTiO3 substrates using KrF excimer laser ablation. The diode capacitance measured at 10 kHz indicated that the relative permittivity of the NdGaO3 barrier was 13 at 10 K. Diodes exhibited rectifying current-voltage characteristics where they conducted better for positive voltages on the n-SrTiO3 than for negative voltages. The current density of the diode having a 5-nm-thick NdGaO3 barrier biased around 1 V on the n-type SrTiO3 was 0.2 A/cm2 at 30 K. This current density is at least six orders of magnitude higher than that obtained for diodes with YBa2Cu3O7−x electrodes directly placed on n-SrTiO3 substrates.
High quantum efficiency monolithic arrays of surface-emitting AlGaAs diode lasers with dry-etched vertical facets and parabolic deflecting mirrors
Authors: Donnelly J. P. , Goodhue W. D. , Bailey R. J. , Lincoln G. A. , Wang C. A. , Johnson G. D.
Published: July 2002

Monolithic arrays of surface-emitting AlGaAs diode lasers with dry-etched vertical facets and external parabolic deflecting mirrors have been operated with both short and quasi-cw current pulses. The arrays emit at 804 nm with threshold current densities as low as 220 A/cm2 and differential quantum efficiencies as high as 66%. The vertical facets and parabolic deflecting mirrors were formed by using chlorine ion-beam-assisted etching with standard photolithography.
Molecular beam epitaxy growth of vertical cavity optical devices with in situ corrections
Authors: Bacher K. , Pezeshki B. , Lord S. M. , Harris J. S.
Published: July 2002

We demonstrate a novel approach to the molecular beam epitaxial (MBE) growth of vertical Fabry–Perot cavities with quarter-wave mirrors. At two selected points, the growth is interrupted and the reflectivity spectrum is measured without removing the wafer from the vacuum system. Corrections are then made in the growth of subsequent layers. By making measurements on the incomplete structure, separate corrections can be made to center both the mirror reflectivity and the cavity resonance at the desired wavelength. We present theoretical and experimental data demonstrating the effectiveness of the approach, and estimate the effects on device performance.
(001) faceting and Bi2Sr2CuO6+x(T
c=7–22 K) phase formation at the Ag/Bi-Sr-Ca-Cu-O interface in Ag-clad Bi2Sr2CaCu2O8+x(T
c=75–95 K) superconducting tapes
Authors: Feng Y. , Larbalestier D. C. , Babcock S. E. , Vander Sande J. B.
Published: July 2002

The Ag/Bi-Sr-Ca-Cu-O (BSCCO) interface in Ag-clad Bi-2212 tapes was investigated by high-resolution transmission electron microscopy. The interface was found to be well bonded and free of nonsuperconducting second phases. However, a one-half-unit-cell-thick layer of the Bi-2201 phase was observed between the Bi-2212 phase and the Ag-cladding. A very strong texturing of the (001) planes of the BSCCO parallel to the Ag was seen. When the interface was nearly parallel to the Bi-2212 (001) planes, it tended to facet onto (001), leaving steps of height equal to one-half the Bi-2201 lattice spacing. Thus, strong (001) texturing extends to the atomic scale.