bluuebunny/crossref_metadata_2025 huggingface dataset:
High-speed metal-semiconductor-metal waveguide photodetector on InP
Authors: Soole J. B. D. , Schumacher H. , Esagui R. , LeBlanc H. P. , Bhat R. , Koza M. A.
Published: July 2002

We demonstrate high-speed performance of InGaAs barrier-enhanced metal-semiconductor-metal (M-S-M) Schottky barrier photodetectors monolithically integrated with double-heterostructure InP/InGaAsP/InP waveguides. Pulse response widths of 77 ps are recorded, with an associated 3 dB power bandwidth of 1.7 GHz. Photodetectors acting as both ‘‘taps’’ of the waveguided signal and as ‘‘terminal’’ devices were fabricated. These detectors have application in receivers which are integrated with semiconductor waveguides for on-chip optical signal processing.
1.54 μm room-temperature electroluminescence of erbium-doped GaAs and GaAlAs grown by molecular beam epitaxy
Authors: Galtier P. , Pocholle J. P. , Charasse M. N. , de Cremoux B. , Hirtz J. P. , Groussin B. , Benyattou T. , Guillot G.
Published: July 2002

GaAs and GaAlAs double-heterostructure light emitting diodes doped with erbium have been grown by molecular beam epitaxy. Both devices exhibit 1.54 μm electroluminescence (EL) at 300 K but the spectra obtained for GaAlAs:Er are much narrower than those of GaAs:Er. 1.54 μm EL has been detected for injection currents as low as 0.8 mA/cm2 and an external quantum efficiency of 10−6 has been found at 300 K. Preliminary data concerning the energy transfer from the injected carriers to the rare earth are provided.
Role of interfaces on the performance and stability of amorphous silicon-germanium alloy p-i-n solar cells
Authors: Arya R. R. , Bennett M. S. , Rajan K. , Catalano A.
Published: July 2002

The performance and stability of a-SiGe:H single junction p-i-n solar cells with interfacial layers at the p/i and the i/n interfaces are reported. It is found that interfacial layers have a strong influence both on the initial performance as well as on the stability of these devices. The device structure, which consists of glass, conductive transparent oxide (SnO2 ), p(a-SiC:H), a-Si:H (buffer layer), graded interface layer (1.7 eV–1.5 eV), i (2500 Å, 1.5 eV), inverse graded interface layer (1.5 eV–1.7 eV), and n (a-Si:H), results in the highest long-term performance. This device structure has resulted in a conversion efficiency of 10.1% with short-circuit current density of 20 mA/cm2 .
Growth and optical characterization of InAs1−xSbx(0≤x≤1) on GaAs and on GaAs-coated Si by molecular beam epitaxy
Authors: Dobbelaere W. , De Boeck J. , Borghs G.
Published: July 2002

Epitaxial layers of InAs1−xSbx(0≤x≤1) have been grown on GaAs and on GaAs-coated Si substrates by molecular beam epitaxy using tetrameric Sb and dimeric As sources. Room-temperature transmission spectroscopy was used to measure the optical band gap of the InAs1−xSbx layers and the composition was determined by x-ray wavelength dispersive spectroscopy. We obtained shiny morphology InAs1−xSbx layers on GaAs-coated Si, comparable to those grown on GaAs. Our results are very encouraging towards the monolithic integration of InAs1−xSbx long-wavelength infrared detectors with Si charge-coupled devices.
Interfacial properties of n-GaAs and polymer deposited by plasma chemical vapor deposition
Authors: Manorama Vardhireddy , Bhoraskar S. V. , Rao V. J. , Kshirsagar S. T.
Published: July 2002

The passivating effects of plasma polymerized thin films of thiophene on the intrinsic properties of the surface of n-GaAs (100) have been studied by means of Raman scattering, photoluminescence, and capacitance-voltage measurements. After passivation, the low-temperature photoluminescence efficiency of n-GaAs is increased three times and the surface barrier at the interface between polymer and GaAs is reduced. The surface electric field and barrier height determined by Raman scattering studies and also from capacitance-voltage measurements are shown to be lowered implying that the band bending is controlled externally.
Scanning tunneling microscopy investigations of the local structure of Tl2Ba2CaCu2O8 single crystals
Authors: Wu X. L. , Lieber C. M. , Ginley D. S. , Baughman R. J.
Published: July 2002

The in-plane structure of single-crystal samples of Tl2Ba2CaCu2O8 has been imaged at room temperature using a scanning tunneling microscope. Atomic-resolution surface images exhibit areas in which the structure has tetragonal symmetry (peak spacing 2.5±0.2 Å) and regions in which the structure is distorted from tetragonal symmetry. The lattice spacing indicates that the observed structure corresponds to the in-plane thallium and oxygen positions. The observation of both sites also suggests that the Tl-O band makes a significant contribution to the density of states near the Fermi level. In addition, a weak one-dimensional superlattice (period 10±0.5 Å) which shows short-range order has been observed.
Preparation of superconducting Tl-Ca-Ba-Cu thin films by chemical deposition
Authors: Olson William L. , Eddy Michael M. , James Tim W. , Hammond Robert B. , Gruner George , Drabeck Larry
Published: July 2002

A chemical deposition process for the preparation of superconducting thin films of Tl2CaBa2Cu2O8 (2122) and Tl2Ca2Ba2Cu3O10 (2223) has been developed. Oriented, superconducting 2122 and 2223 thin films have been successfully fabricated on single-crystal yttria-stabilized zirconia and magnesium oxide substrates (〈100〉 orientation). Epitaxial films have been prepared on magnesium oxide. Chemical analysis of the film composition by energy dispersive x-ray analysis is in agreement (2122 vs 2223) with the phases indicated by powder x-ray diffraction. The thin films of these compounds exhibited superconducting transition temperatures above 105 K as determined by variable-temperature resistivity and ac magnetic susceptibility measurements. In addition, microwave surface resistance measurements at 150 GHz show that these films have very low losses at 77 K (1 mΩ).
YbBa2Cu3O7 epitaxial films grown by a Ag-enhanced liquid gas solidification process
Authors: Chen H. S. , Kortan A. R. , Thiel F. A. , Kimerling L. C.
Published: July 2002

Effects of Ag addition on the epitaxially grown YbBa2Cu3O7 superconductor on a SrTiO3 (100) substrate by the liquid gas solidification process have been investigated. Ag acts as flux and does not incorporate in the oxide formation. Its addition, however, enhances the transport properties resulting from a reduction in film-substrate interaction. Values of Tc(R=0)=90 K and Jc(77 K, H=0)=3×104 A/cm2 can be achieved reproducibly.
Preparation of Y-Ba-Cu-O high T
c superconducting thin films by plasma-assisted organometallic chemical vapor deposition
Authors: Bai G. R. , Tao W. , Wang R. , Xie L. M. , Zhang X. K. , Huang J. , Qian C. T. , Zhou W. K. , Ye C. Q. , Ren J. G. , Li Y. Q. , Luo W. M. , Chen J. B.
Published: July 2002

Thin films of the high Tc superconducting Y-Ba-Cu metal oxide have been prepared for the first time by plasma-assisted organometallic chemical vapor deposition using β-diketonate chelates of Y, Ba, and Cu, Y(C11H19O2)3, Ba(C11H19O2)2, and Cu(C11H19O2)2 as starting materials, followed by post-annealing under a reduced pressure of oxygen stream. X-ray diffraction spectra indicate that the films deposited on the yttria-stabilized zirconia (YSZ) substrate have a significant preferential orientation of the crystallite c axis being perpendicular to the substrate surface. Four-probe resistivity measurements reveal the temperature of the onset of superconductivity at 91.6 K and zero resistance by 78.5 K.
Oxygen ion irradiation of Tl2Ca2Ba2Cu3O10 superconductors
Authors: Barbour J. C. , Kwak J. F. , Ginley D. S. , Peercy P. S.
Published: July 2002

The superconducting transport properties of polycrystalline Tl2Ca2Ba2Cu3O10 thin films irradiated with 740 keV oxygen ions were monitored as a function of fluence. Both the transition temperature (Tc ) and the critical current density (Jc ) decreased rapidly with fluence; however, the transition temperature onset remained constant. A fluence of 2×1014 O/cm2 (0.028 dpa) was sufficient to eliminate superconductivity in the films. Jc at 76 K decreased from 25 000 A/cm2 in the unirradiated sample to 2000 A/cm2 after a fluence of 2.1×1013 O/cm2. A room-temperature anneal caused both Tc and the normal-state resistivity to recover slightly after low-fluence irradiations.
Effect of a declination angle of substrate position on magnetron sputter deposition from a YBa2Cu3O7−x target
Authors: Kageyama Yasuyuki , Taga Yasunori
Published: July 2002

Thin-film deposition by magnetron sputtering of a multielement target was carried out with respect to the geometrical factors between a target and the substrates. The thin films were deposited on substrates which were located semicircularly over a YBa2Cu3O7−x target in several declination angles measured from the normal to the target surface. The deposition rate decreased to about one-third with the change in the angle from 0° to 90°. In the angles of 45°, 60°, and 75°, films showed significant instability in the atmosphere, which appeared to be caused by an excessive concentration of Ba atoms in the films. Target composition was almost reproduced in the films deposited in the angle of 90°.
Doping effects on intersubband absorption in InGaAs/InAlAs multiquantum wells
Authors: Asai Hiromitsu , Kawamura Yuichi
Published: July 2002

Doping dependence of intersubband absorption in In0.53 Ga0.47 As/In0.52 Al0.48 As multiquantum wells (MQWs) grown by molecular beam epitaxy is investigated. The MQWs having a constant well width of 130 Å are uniformly doped to a sheet carrier concentration of 4×1011–1×1013 cm−2. Above Ns =1.8×1012 cm−2, the intersubband absorption from the second to the third subband is observed, as well as from the first to the second, which agrees well with theoretical calculations.
45° waveguide isolators with phase mismatch
Authors: Dammann H. , Pross E. , Rabe G. , Tolksdorf W.
Published: July 2002

45° waveguide isolators based on magneto-optic channel waveguides with phase mismatch can be realized simply by choosing a proper orientation of the input polarization. This is demonstrated theoretically by visualizing the magneto-optic mode coupling as ‘‘coupling tracks’’ on the Poincaré sphere, and is verified experimentally for real waveguides with considerable phase mismatch. More than 30 dB isolation is feasible in practical devices.
Well-width dependence of intersubband absorption in InGaAs/InAlAs multiquantum wells
Authors: Asai Hiromitsu , Kawamura Yuichi
Published: July 2002

The well-width dependence of intersubband absorption in InGaAs/InAlAs multiquantum wells grown by molecular beam epitaxy is investigated. The energies of the absorption peaks decrease from 300 to 100 meV with an increasing well width from 35 to 200 Å. This well-width dependence of the peak energy is in good agreement with theoretical calculations. For a wide quantum well, two sharp absorption peaks were observed, including the transitions from the second to the third subbands.
Optical waveguiding and nonlinear optics in high quality 2-docosylamino-5-nitropyridine Langmuir–Blodgett films
Authors: Bosshard Ch. , Küpfer M. , Günter P. , Pasquier C. , Zahir S. , Seifert M.
Published: July 2002

The linear and nonlinear optical properties of well-ordered Y-type Langmuir–Blodgett (LB) multilayers of 2-docosylamino-5-nitropyridine (DCANP) have been investigated. The nonlinear optical susceptibilities have been determined for the wavelengths λ=1064 nm [d33=(7.8±1) pm/V, d31=(2.0±0.5) pm/V] and λ=1318 nm [d33=(5.6±1) pm/V]. In first waveguiding experiments carried out TE0 and TM0 modes propagating over more than 20 mm could be excited. Coupling experiments allowed the determination of the dispersion of the refractive index n3 (n632.8 nm3 =1.598). Guided wave attenuation coefficients as low as 12 dB/cm (at the wavelength λ=632.8 nm) are reported.
Long-wavelength (1.0–1.6 μm)In0.52Al0.48As/ In0.53(GaxAl1−x)0.47As/In0.53Ga0.47As metal-semiconductor-metal photodetector
Authors: Griem H. T. , Ray S. , Freeman J. L. , West D. L.
Published: July 2002

We have fabricated a metal-semiconductor-metal Schottky photodetector on a semi-insulating InP substrate using a nominally lattice-matched In0.52Al0.48As/In0.53(GaxAl1−x)0.47As (graded)/In0.53Ga0.47As structure grown by molecular beam epitaxy. On average the graded quaternary layer enhanced the responsivity by about 35% compared to an identical device without the graded region, reaching a maximum of 0.45 A/W at 10 V applied bias. The associated dark current was 95 nA; the dark capacitance was 90 fF. High-speed measurements with a gain-switched 1.3 μm laser diode demonstrated an instrumentation-limited impulse response of 50 ps.
Synchrotron-radiation-stimulated desorption of O+ ions from an oxidized silicon surface
Authors: Niwano Michio , Katakura Hitoshi , Takakuwa Yuji , Miyamoto Nobuo , Hiraiwa Atsushi , Yagi Kunihiro
Published: July 2002

The photon-stimulated desorption of ions from a naturally oxidized Si(100) surface has been studied using synchrotron radiation (SR). For mass analysis of the PSD ions, the time-of-flight method was utilized. Desorption of O+ ions is clearly observed on the surface during exposure to unmonochromatized SR in the vacuum ultraviolet (VUV) region. Si 2p core level photoemission measurements show that the photoemission peak corresponding to silicon oxide is reduced in intensity after exposure to the radiation. The present experimental results indicate the possibility of removing a thin SiO2 layer on a Si(100) surface at low temperatures by exposing the surface to SR in the VUV region.
Photo-oxidation of GaAs for i
n s
i
t
u patterned-mask formation prior to chlorine gas etching
Authors: Taneya M. , Akita K. , Hidaka H. , Sugimoto Y.
Published: July 2002

This is the demonstration of ‘‘in-situ masking’’ concept. In situ patterning of GaAs is carried out by using a photo-oxidized surface layer as a mask for subsequent Cl2 etching. Clean GaAs surface provided by molecular beam epitaxy is exposed to pure oxygen and is simultaneously irradiated with an Ar+ ion laser of the 514.5 nm line for photo-oxidation of the surface. Subsequent Cl2 gas etching of the photo-oxidized sample reveals that the GaAs oxide fills the role of an etching mask. The resistance of the oxide mask against Cl2 etching varies depending on the laser fluence with which the oxide of GaAs is formed.
Microfabrication below 10 nm
Authors: Van der Gaag B. P. , Scherer A.
Published: July 2002

We describe a new method of producing ultrasmall structures on thick substrates with electron beam lithography. Using an innovative exposure technique, we obtain features with lateral sizes smaller than the incident beam diameter. These patterns are transferred into GaAs/AlGaAs quantum well heterostructures using chemically assisted ion beam etching, and uniform arrays of structures with lateral dimensions below 10 nm are produced. We employ reflection electron microscopy measurements to correlate the structure size with the exposure and development conditions for this fabrication scheme.
Photoluminescence from Si/Ge superlattices
Authors: Montie E. A. , van de Walle G. F. A. , Gravesteijn D. J. , van Gorkum A. A. , Bulle-Lieuwma C. W. T.
Published: July 2002

We have studied the luminescence of short-period Si/Ge superlattices of varying composition grown on a Si1−xGex alloy buffer layer. X-ray diffraction and Rutherford backscattering were used to analyze the composition of the samples. Luminescence bands at 1.5 and 1.6 μm originate from the superlattice, as is indicated by etching experiments. A strong change in luminescence intensity is observed as the composition and strain of the superlattice vary.
Temperature dependence of growth of GexSi1−x by ultrahigh vacuum chemical vapor deposition
Authors: Racanelli Marco , Greve D. W.
Published: July 2002

We report the deposition of epitaxial films of GexSi1−x on (100) silicon by the ultrahigh vacuum chemical vapor deposition technique. Epitaxial films grown at temperatures ranging from 577 to 665 °C have been characterized with respect to growth rate and germanium content. The results show features which have not been previously reported including an incubation time and a peak in the growth rate as a function of GeH4/H2 flow.
Study of inversion layer mobility in metal-oxide-semiconductor field-effect transistors with reoxidized nitrided oxides
Authors: Lo G. Q. , Ting W. C. , Kwong D. L. , Lee S.
Published: July 2002

The carrier effective mobility μeff in the inversion layer for both n- and p-channel metal-oxide-semiconductor field-effect transistors with ultrathin gate dielectrics prepared by rapid thermal reoxidation (RTO) of rapid thermal nitrided (RTN) SiO2 has been studied. It is found that although RTN/RTO degraded the low-field μeff, it improved significantly the electron μeff under high normal field compared to control SiO2. The effect of RTN/RTO on the hole effective mobility has also been examined and found to be quite different than on the electron effective mobility. A physical mechanism is discussed to account for the observation.
Real-space transfer in three-terminal InGaAs/InAlAs/InGaAs heterostructure devices
Authors: Mensz Piotr M. , Luryi Serge , Cho Alfred Y. , Sivco Deborah L. , Ren Fan
Published: July 2002

Three-terminal real-space transfer devices have been implemented in InGaAs/InAlAs/InGaAs heterostructure material. The use of nonalloyed contacts provides excellent ohmic contacts to the channel without compromising insulation from the second conducting layer, The observed negative differential resistance has a peak-to-valley ratio that typically exceeds 100, both at room temperature and cryogenic temperatures. The highest observed peak-to-valley ratio at 300 K was 490. With increasing heating voltage, the injection current across the InAlAs barrier rises in a sequence of sharp steps. We explain this feature by an instability caused by a positive feedback between the heating field in the channel and the local real-space transfer current.
Determination of Γ electron and light hole effective masses in AlxGa1−xAs on the basis of energy gaps, band-gap offsets, and energy levels in AlxGa1−xAs/GaAs quantum wells
Authors: Hrivnák Ľ.
Published: July 2002

Experimental data of energy gaps, band offsets, and energy levels in AlxGa1−xAs/GaAs quantum wells are utilized for the determination of Γ electron and light hole effective masses in AlxGa1−xAs compounds on the basis of the author’s relations between these quantities. The temperature dependences of electron and light hole effective masses in GaAs are also obtained.
Soft x-ray lasing and its spatial characteristics in a lithium-like silicon plasma
Authors: Xu Zhi-zhan , Fan Pin-zhong , Zhang Zheng-quan , Chen Shi-shen , Lin Li-huang , Lu Pei-xiang , Wang Xiao-fang , Qian An-di , Yu Jia-jin , Sun Lan , Wu Min-chun
Published: July 2002

Experimental study of soft x-ray laser carried out on the LF12 Laser Facility of SIOM (Shanghai Institute of Optics and Fine Mechanics) is reported. Soft x-ray amplifications were observed in lithium-like silicon ions by line-focused laser irradiation of slab targets. Based on the time-integrated measurements, the gain coefficients are 1.5 and 1.4 cm−1 for the 5f–3d (88.9 Å) and the 5d–3p (87.3 Å) transitions of lithium-like silicon ions, respectively. In addition, the spatial characteristics of the laser lines are also presented.
Spatial switching, instabilities, and chaos in a three-waveguide nonlinear directional coupler
Authors: Finlayson N. , Stegeman G. I.
Published: July 2002

A numerical study is conducted of a three-waveguide nonlinear directional coupler. Markedly sharper transmittance characteristics than the well-known two-waveguide coupler are obtained at the expense of a higher switching power. Over longer distances transitions from quasi-periodic to chaotic behavior and back take place as the power is varied.
Stimulated emission from a CdTe/HgCdTe separate confinement heterostructure grown by molecular beam epitaxy
Authors: Mahavadi K. K. , Bleuse J. , Sivananthan S. , Faurie J. P.
Published: July 2002

We present the results of low-temperature photoluminescence and stimulated emission experiments performed on a CdTe/Hg0.45Cd0.55Te/Hg0.67Cd0.33Te multiquantum well separate confinement heterostructure grown by molecular beam epitaxy. The photoluminescence results suggest that because of the growth conditions, there is a strong interdiffusion in the multiquantum well region. Pulsed stimulated emission was observed from this structure up to 77 K.
Comparison of simultaneous multiple wavelength lasing in various neodymium host crystals at transitions from 4F3/2–4I11/2 and 4F3/2–4I13/2
Authors: Shen H. Y. , Zeng R. R. , Zhou Y. P. , Yu G. F. , Huang C. H. , Zeng Z. D. , Zhang W. J. , Ye Q. J.
Published: July 2002

The possibility of simultaneous multiple wavelength lasing in various neodymium host crystals such as Nd:YAG, Nd:YLF, Nd:BEL, and Nd:YAP has been analyzed by the ‘‘oscillation condition.’’ It is shown that this kind of laser can be realized in all the described crystals in pulsed state, but only achieved in the Nd:YAP crystal in continuous-wave state. On the basis of the analyzed results, we have achieved cw simultaneous multiple wavelength lasing in Nd:YAP crystal for the first time at both 1.0795 and 1.3414 μm.
Transistor-based measurements of electron injection currents in p-type GaAs doped 1018–1020 cm−3
Authors: Klausmeier-Brown M. E. , Melloch M. R. , Lundstrom M. S.
Published: July 2002

Measurements of electron currents injected into p+-GaAs are presented for molecular beam epitaxially grown material doped from 2×1018 to 8×1019 cm−3 with Be. The collector current versus base-emitter voltage characteristics of n-p+-n GaAs homojunction bipolar transistors are analyzed, and the results are interpreted in terms of the quantity (n0Dn), where n0 is the equilibrium minority-carrier concentration and Dn is the minority-carrier diffusion coefficient. The results are consistent with earlier measurements of (n0Dn) made using metalorganic chemical vapor deposited p+-n GaAs solar cells, Zn doped as heavily as 1×1019 cm−3. The large electron injection currents observed are interpreted as evidence for significant effective band-gap shrinkage. These effects must be accounted for in the modeling and design of GaAs-based heterojunction bipolar transistors and solar cells.
Shallow junction formation by dopant diffusion from i
n s
i
t
u doped polycrystalline silicon chemically vapor deposited in a rapid thermal processor
Authors: Hsieh T. Y. , Chun H. G. , Kwong D. L. , Spratt D. B.
Published: July 2002

Shallow n+-p junctions were formed by utilizing an in situ doped thin polycrystalline silicon layer as a diffusion source. The in situ arsenic-doped polycrystalline silicon films were deposited by rapid thermal processing chemical vapor deposition. The dopant pileup phenomena were observed at both the polycrystalline silicon/silicon interface and at the surface. The dopant concentrations were higher when the deposition temperatures were lower. The observed pileup phenomena at the polycrystalline silicon/silicon interface were temperature dependent and mainly due to the segregation of arsenic at the grain boundary. The dopant distribution was mainly due to the grain boundary diffusion and grain growth mechanisms. Extremely shallow n+-p junctions were achieved and laterally uniform delineated junctions were observed. The dopant concentration in the Si substrate drops two orders of magnitude in less than 500 Å.
Laser-induced fluorescence imaging of laser-ablated barium
Authors: Cappelli M. A. , Paul P. H. , Hanson R. K.
Published: July 2002

We have applied laser-induced fluorescence diagnostics to expanding recombining barium plasmas produced by laser ablation. For relatively modest ablation laser energy fluences (∼102–103 W cm−2), we have measured neutral barium leading edge density gradients of 1012–0.5×1013 cm−3 cm−1 and cloud expansion velocities of ∼106 cm s−1, consistent with recent results of ablation studies in copper [R. J. von Gutfeld and D. W. Dreyfus, Appl. Phys. Lett. 54, 1212 (1989)].
1.5 μm GaInAsP/InP buried-heterostructure laser diode fabricated by reactive ion etching using a mixture of ethane and hydrogen
Authors: Matsui Teruhito , Ohtsuka Ken-ichi , Sugimoto Hiroshi , Abe Yuji , Ohishi Toshiyuki
Published: July 2002

A 1.5 μm GaInAsP/InP buried-heterostructure laser diode was fabricated by reactive ion etching using a mixture of ethane and hydrogen for the formation of mesa stripe. Blocking layers were regrown on the dry etched wafers by liquid phase epitaxy. Continuous-wave operation was obtained at room temperature. A threshold current as low as 15 mA was achieved, which is superior to that of the same structure laser diode fabricated by conventional chemical etching.
Formation of single-phase PtAs2 films on GaAs by selective oxidation and etching
Authors: Weiss Eliezer , Keller Robert C. , Kniffin Margaret L. , Helms C. R.
Published: July 2002

The oxidation of prereacted Pt films on (100) oriented n-GaAs substrates was studied in the temperature range between 550 and 750 °C using Auger electron spectroscopy and Xe+ ion profiling. The GaPt/PtAs2/GaAs structure formed during annealing in hydrogen was oxidized using a mixture of water vapor and hydrogen. The GaPt phase can be oxidized completely, whereas the inner PtAs2 and GaAs interfaces are left unoxidized. The oxidation of the platinum-gallium phase is self-limited by the diffusion of the Ga through the gallium oxide overlayer. The oxide can be etched off to leave a structure consisting only of platinum-arsenide on the GaAs substrate.
High transport critical currents and flux jumps in bulk YBa2Cu3Ox superconductors
Authors: Chen K. , Hsu S. W. , Chen T. L. , Lan S. D. , Lee W. H. , Wu P. T.
Published: July 2002

A preferentially oriented bulk YBa2Cu3Ox superconductor was prepared by the liquid phase method. A continuous dc current carrying capacity exceeding 120 A with current density higher than 37 300 A/cm2 at 77 K has been obtained. The high current effects causing fracture of the sample were studied in relation to the thermal diffusion properties. In magnetization measurements, flux jumps were observed for currents in the sample a-b plane below the temperature of about 20 K. The jumps are more closely spaced with decreasing temperature or increasing field sweep rates.
Electrical characterization of chemically modified YBa2Cu3O7−x surfaces
Authors: Hunt B. D. , Foote M. C. , Vasquez R. P.
Published: July 2002

Results on electrical characterization of YBa2Cu3O7−x thin-film surfaces treated with a Br/ethanol chemical etch are presented. Electrical measurements of YBa2Cu3O7−x/Au/Nb device structures fabricated using polycrystalline, post-annealed YBa2Cu3O7−x films with Br-etched surfaces, show improvements of approximately one or two orders of magnitude in current densities and resistivities (resistance-area products) relative to unetched devices. The existence of supercurrents in these structures has been confirmed by observation of the ac Josephson effect, and by magnetic field and temperature studies of the critical currents. The Br-etch process has produced 10×10 μm2 devices with critical current densities greater than 400 A/cm2 and resistivities as low as 4×10−7 Ω cm2.
TE/TM mode selective channel waveguides in GaAs/AlAs superlattice fabricated by SiO2 cap disordering
Authors: Suzuki Yasuhiro , Iwamura Hidetoshi , Mikami Osamu
Published: July 2002

Novel structure TE/TM mode selective optical channel waveguides are proposed and fabricated in GaAs/AlAs superlattices (SLs) using impurity-free disordering induced by SiO2 cap annealing. The disordered SL regions are found to be useful as low-loss waveguides even at a wavelength close to the absorption edge of the as-grown SL. By observing the near-field patterns, it is confirmed that these channel waveguides could selectively confine TE or TM polarized light.
Tunneling measurements on superconductor/insulator/superconductor junctions using single-crystal YBa2Cu3O7−x thin films
Authors: Hirata K. , Yamamoto K. , Iijima K. , Takada J. , Terashima T. , Bando Y. , Mazaki H.
Published: July 2002

We have, for the first time, made quasi-particle tunneling measurements on a YBa2Cu3O7−x(001)/Y2O3 (001)/YBa2 Cu3 O7−x (001)junction, which was epitaxially grown on a MgO(100) substrate in an in-situ process. Both layers of YBa2 Cu3 O7−x showed the same superconducting transition of Tc end =86 K with ΔT(R=10–90%)=1.5 K. Quasi-particle tunneling in the direction perpendicular to the Cu-O planes was measured. A gap parameter Δ(4.5 K) of 9.0±0.2 meV and a value of 2Δ/kTc of 3.5+0.4−0.6 were obtained.
Selective epitaxial growth with oxide-polycrystalline silicon-oxide masks by rapid thermal processing chemical vapor deposition
Authors: Hsieh T. Y. , Jung K. H. , Kwong D. L. , Spratt D. B.
Published: July 2002

We have used rapid thermal processing chemical vapor deposition for Si selective epitaxial growth using a mask consisting of a sandwich structure of SiO2 on doped polycrystalline Si on SiO2. Lateral polycrystalline Si growth from the sidewalls of the polycrystalline Si layer was also observed and resulted in polycrystalline ‘‘bumps’’ along the mask sidewalls. Otherwise, the epitaxial Si layer was defect-free.
Deep Ti donor in GaAs
Authors: Scheffler H. , Korb W. , Bimberg D. , Ulrici W.
Published: July 2002

Ti-doped GaAs crystals grown by the liquid-encapsulated Czochralski method were investigated by using the observation of direct capacitance transients. The charge transfer transitions to the deep Ti donor level close to midgap are unambiguously identified in both n-type and p-type material. The energy position of Ti3+/Ti4+ is determined with high precision of Ec−(0.87±0.01) eV at 300 K and the respective cross sections are σn∞=(7±3)×10−15 cm2 for electron capture and σp∞=(10±5)×10−16 cm2 for hole capture. The position of the Ti2+/Ti3+ acceptor is confirmed to be at Ec−(0.19±0.01) eV. Its cross section for electron capture is σn∞=(3±1)×10−16 cm2.
Room-temperature excitonic saturation in CdZnTe/ZnTe quantum wells
Authors: Lee D. , Zucker J. E. , Johnson A. M. , Feldman R. D. , Austin R. F.
Published: July 2002

We present the first measurements of room-temperature excitonic absorption saturation in a II-VI semiconductor quantum well. Strong room-temperature excitonic absorption in CdZnTe/ZnTe quantum wells is found to saturate at an incident optical intensity that is considerably higher than that for III-V quantum wells. We show that this phenomenon can be interpreted in terms of the smaller excitonic Bohr radius characteristic of wide-gap II-VI compounds.
Anisotropic proximity coupling in small YBa2Cu3O7-normal-Pb junctions
Authors: Lee Mark , Lew D. , Eom C. B. , Geballe T. H. , Beasley M. R.
Published: July 2002

We report results of current-voltage measurements made on small-area YBa2Cu3O7-N-Pb thin-film junctions (N=Au, Ag) where the orientation of the Cu-O plane has been varied from (001) to (103) to (100) to study the effects of anisotropy. For (001) and (103) oriented junctions there is no well defined supercurrent despite very low contact resistances. By contrast, (100) junctions do display a well defined supercurrent. We compare these results to recent Josephson work and discuss implications for tunnellng and device work.
Isoelectronic bound exciton emission from Si-rich silicon-germanium alloys
Authors: Modavis R. A. , Hall D. G. , Bevk J. , Freer B. S. , Feldman L. C. , Weir B. E.
Published: July 2002

We report the observation and characterization of luminescence in the wavelength range 1.1 μm<λ< 1.4 μm from silicon-rich silicon-germanium alloys, grown by molecular beam epitaxy, implanted with beryllium atoms. The luminescence originates with the radiative decay of an exciton bound to an isoelectronic impurity complex. The wavelength of this emission can be controlled by varying the Ge concentration.
Confinement of light hole valence-band states in pseudomorphic InGaAs/Ga(Al)As quantum wells
Authors: Reithmaier J.-P. , Höger R. , Riechert H. , Hiergeist P. , Abstreiter G.
Published: July 2002

Pseudomorphic InGaAs/Ga(Al)As multiple quantum well structures with In content ranging from 7% to 25% and barriers with and without Al were grown by molecular beam epitaxy and investigated by optical absorption spectroscopy and photoluminescence excitation spectroscopy with linearly polarized light. A comparison of the absorption spectra between samples with and without Al content in the barriers shows that the light hole state is weakly bound in the InGaAs/GaAs quantum well at least for the lower In concentrations. Photoluminescence excitation with different linear polarization definitely distinguishes between the optical transitions of heavy or light hole to electron transitions. Several weak additional peaks appear in the spectra which are identified as forbidden optical transitions.
Device quality In0.4Ga0.6As grown on GaAs by molecular beam epitaxy
Authors: Ribas P. , Krishnamoorthy V. , Park R. M.
Published: July 2002

A novel approach to growing device quality In0.4Ga0.6As epilayers on GaAs is reported which involves the controlled propagation of dislocations via a carefully designed multistage strain-relief buffer system. Cross-sectional transmission electron microscopy analysis revealed the In0.4Ga0.6As epilayers to be threading dislocation free in contrast to the heavily dislocated material obtained by growing In0.4Ga0.6As directly on GaAs. Hall effect measurements performed on unintentionally doped buffered In0.4Ga0.6As epilayers indicated the room-temperature electron concentrations in the epilayers to be around 1×1015 cm−3 while electron mobilities were around 4700 cm2 V−1 s−1. In addition, strong band-edge photoluminescence was recorded from the buffered epilayers, the luminescence peak occurring at 1304 nm having a linewidth around 7 meV at 13 K.
Tunneling spectroscopic study of finite superlattices
Authors: Aggarwal R. J. , Reed M. A. , Frensley W. R. , Kao Y.-C. , Luscombe J. H.
Published: July 2002

We present a tunneling density of states study of the transition from a superlattice miniband to a sequential coupled well structure. We have observed by tunneling spectroscopy the eigenstates of a finite superlattice system far below the Stark localization threshold. The transition from an indistinguishable miniband to a coupled well structure is experimentally found to be 2.5 meV ≤W(miniband width)/n(♯ periods) ≤10.5 meV.
Observation of large magneto-optical effects in amorphous UxSb1−x films
Authors: McElfresh M. W. , Plaskett T. S. , Gambino R. J. , McGuire T. R.
Published: July 2002

Amorphous films with the compositions UxSb1−x (for x between 0.2 and 0.8) prepared by magnetron sputtering show ferromagnetic properties with Curie temperatures as high as 135 K (for x=0.45) and ordered magnetic moments of about 1.5μB. Large positive Faraday rotation values of over 2×106 deg/cm and large negative Kerr rotation values of over 3° are reported. The values of Faraday rotation are correlated with a large Hall effect, having corresponding Hall angles of up to θH=17°.
Rectifying metal-polymer contacts formed by melt processing
Authors: Sundberg M. , Gustafsson G. , Inganäs O.
Published: July 2002

Rectifying contacts between aluminum, indium, or titanium and a solution and melt processable conducting polymer, poly(3-octylthiophene) have been formed by melt processing. The contacts are formed by heating a metal/polymer/metal structure to the melting point of the polymer and then pressing the metals to the melted polymer until adhesion is achieved, whereupon the whole structure is cooled to room temperature. Comparison of the current-voltage and capacitance-voltage characteristics of a melt processed device and a device manufactured by metal sputtering shows that no significant differences exist between these structures.
Near-infrared emission in a chemically excited oxygen system
Authors: Yoshida S. , Tokuda T. , Shimizu K. , Ogasawara K. , Sawano T.
Published: July 2002

Near-infrared emission has been observed in a chemically generated singlet oxygen system. Spectrum peaks observed at 1090, 1275, and 1550 nm appear to correspond to O2(1Δ)O2(3Σ) dimer transitions to ground state accompanied by vibrational changes. The experimental result suggests that the previously observed visible emission which accompanies the present infrared emission is also due to an excited oxygen dimer. The possibility of lasing at the infrared wavelengths is discussed.
Observation of electron velocity overshoot in AlxGa1−xAs/GaAs heterostructure insulated-gate field-effect transistors
Authors: Sun C. C. , Xu J. M. , Hagley A. , Surridge R. , SpringThorpe A.
Published: July 2002

The factor γ=1+(RS+RD)/Rds is suggested to modify the expression of effective electron velocity in field-effect transistors (FETs), where RS and RD are the source and drain resistances, respectively, and Rds is the intrinsic drain-to-source resistance. Based on this modified expression ν′eff = 2πLfTγ, where L is the gate length and fT is the cut-off frequency, velocity overshoots were observed clearly at room temperature in AlxGa1−xAs/GaAs heterostructure insulated-gate FETs with both undoped and doped channels.
Tests of a superconducting rf quadrupole device
Authors: Delayen J. R. , Shepard K. W.
Published: July 2002

High surface electric fields have been obtained in the first tests of a superconducting rf quadrupole device. The rf quadrupole fields were generated between niobium vanes 6.5 cm in length, with an edge radius of 2 mm, and with a beam aperture of 6 mm diameter. In tests at 4.2 K, the 64 MHz device operated cw at peak surface electric fields of 128 MV/m. Virtually no electron loading was observed at fields below 100 MV/m. It was possible to operate at surface fields of 210 MV/m in pulses of 1 ms duration using a 2.5 kW rf source. For the vane geometry tested, more than 10 square centimeters of surface support a field greater than 90% of the peak field. The present result indicates that electric fields greater than 100 MV/m can be obtained over an appreciable area, sufficient for some accelerator applications. It also shows that superconducting rf technology may provide an extended range of options for rf quadrupole design.
Ion implanted confinement layer for an InP/InGaAs/InP:Fe heterojunction field-effect transistor
Authors: Lauterbach Ch. , Römer D. , Treichler R.
Published: July 2002

A p-doped confinement layer was fabricated by Be implantation for an InP/InGaAs/InP:Fe heterojunction field-effect transistor (HFET). The epitaxial layers were grown by metalorganic vapor phase epitaxy and were suitable for the integration with a pin photodiode. The pn junction of the gate was formed by Zn diffusion that is not influenced by the preceding ion implantation. In the output characteristics of the HFET the pinch-off voltage changes from Vp=−7 V without to Vp=−3.5 V with confinement layer. No degradation of the maximum transconductance was observed. The gate leakage current is 80 nA at a gate source voltage of Vgs=−5 V.
Photorefractive gain enhancement in InP:Fe using band-edge resonance and temperature stabilization
Authors: Millerd James E. , Koehler Steffen D. , Garmire Elsa M. , Partovi Afshin , Glass Alastair M. , Klein Marvin B.
Published: July 2002

We report photorefractive two beam coupling gain coefficients as high as Γ=19 cm−1 and net gains of Γ-α=14 cm−1 in InP:Fe at around 970 nm. This enhancement was achieved by combining band-edge resonant nonlinearities with a second resonant enhancement derived from the bipolar transport in this material. Measurements of gain as a function of pump intensity, applied field, grating spacing, wavelength, and temperature are presented. No moving gratings were required.
High transconductance and large peak-to-valley ratio of negative differential conductance in three-terminal InGaAs/InAlAs real-space transfer devices
Authors: Mensz Piotr M. , Garbinski Paul A. , Cho Alfred Y. , Sivco Deborah L. , Luryi Serge
Published: July 2002

Three-terminal real-space transfer devices with improved room-temperature characteristics have been implemented in InGaAs/InAlAs/InGaAs heterostructures lattice matched to InP. The devices exhibit extremely sharp charge injection, characterized by a transconductance exceeding 23 S/mm and a negative differential conductance with a peak-to-peak ratio of over 7000. Our experiments suggest that both of these characteristics are limited only by the dielectric strength of the InAlAs barrier layer.
Growth of YBa2Cu3O7−δ on vicinally polished MgO substrates
Authors: Streiffer S. K. , Lairson B. M. , Bravman J. C.
Published: July 2002

YBaCu3O7−δ thin films were grown on vicinally polished MgO [001] substrates. The orientation of the films is strongly influenced by the substrate surface normal, with only very weak alignment to the substrate [001] crystallographic direction. Vicinal angles of 1°, 2.5°, and 5° toward [010] produced films with large mosaic spread parallel to the vicinal angle [as high as 4° full width half maximum (FWHM) for the 5° sample] and with critical current densities as high as films grown on on-axis substrates (e.g., 4.4×107 A/cm2). Samples on 10° and 20° vicinal substrates showed a reduction in mosaic spread but still alignment to the surface normal, and weak and strong reductions of the critical current density, respectively.
Fission-fragment-excited lasing at 585.3 nm in He/Ne/Ar gas mixtures
Authors: Hebner G. A. , Hays G. N.
Published: July 2002

Fission-fragment-excited lasing is reported for the 3p′(1/2)0–3s′(1/2)01 neon transition (λ=585.3 nm) in mixtures of He/Ne/Ar. The laser power efficiency peaks at a He/Ne/Ar ratio of approximately 50/2/1 for a laser cell pressure of 1.9 atmospheres. Laser parameters for pump rates from 70 to 1200 W/cm3 are presented for three cavity configurations.
New approach to projection-electron lithography with demonstrated 0.1 μm linewidth
Authors: Berger S. D. , Gibson J. M.
Published: July 2002

We present a new approach to projection-electron lithography which allows sub-0.1 μm resolution to be achieved with short exposure times and a parallel illumination system. We have printed a grating pattern into PMMA with 0.1 μm linewidths. Our new technique consists of using an angularly limiting filter which differentiates electrons that have traversed a transparent mask in terms of the degree of scattering between the patterned and unpatterned regions.
InAs/InP strained single quantum wells grown by atmospheric pressure organometallic vapor phase epitaxy
Authors: Schneider R. P. , Wessels B. W.
Published: July 2002

Strained InAs/InP single quantum wells of nominal thickness 1–11 monolayers have been prepared using organometallic vapor phase epitaxy in an atmospheric pressure reactor. For wells of thickness 1–3 ML grown using optimal flow modulation parameters, the surface morphology was specular and narrow single-line photoluminescent emission was observed. For thicker wells, the evolution of additional PL features and the appearance of island-like features on the sample surface was attributed to the onset of three-dimensional (island) growth.
Realization of low defect density, ultrathick, strained InGaAs/GaAs multiple quantum well structures via growth on patterned GaAs (100) substrates
Authors: Madhukar A. , Rajkumar K. C. , Chen Li , Guha S. , Kaviani K. , Kapre R.
Published: July 2002

Growth of low defect density highly strained InxGa1−xAs/GaAs multiple quantum well (MQW) structures of thicknesses suited for application in spatial light modulator (SLM) devices operating in infrared has been thwarted by the occurrence of strain-induced defects. Exploiting the notion of strain relief at mesa edges, we report here the first realization of very low defect density MQW structures of thickness as high as 2.38 μm at x=0.20. This has opened up the possibility of realizing a variety of reflective and transmissive SLM structures which also fruitfully exploit the transparent nature of the substrate.
Charge injection logic
Authors: Luryi Serge , Mensz Piotr M. , Pinto Mark R. , Garbinski Paul A. , Cho Alfred Y. , Sivco Deborah L.
Published: July 2002

The charge injection transistor is a semiconductor device based on transfer of hot electrons between separately contacted conducting layers. The nature of hot-electron injection by the real-space transfer allows the implementation of novel circuit elements. In particular, we propose a multiterminal single-device structure that works as a functional element with three logic inputs Xj (j=1,2,3) and one output equal to (X1∩X2∩X3)∪(X̄1∩X̄2∩X̄3). This device, called the norand, can perform both as a nor(X1,X2) and as an and(X1,X2) element, reprogrammable electrically by changing the X3 input. The operation of norand with logic gain is demonstrated experimentally by an equivalent circuit connection of discrete charge injection transistors implemented within InGaAs/InAlAs on InP technology.
Two quantitative optical detection techniques for photoacoustic Lamb waves
Authors: Noui L. , Dewhurst R. J.
Published: July 2002

The cross calibration of two optical detection techniques is described for the monitoring of laser-generated Lamb waves. Measurements of Lamb waves using an optical beam deflection technique are compared with those using a Michelson interferometer technique. Analysis shows that phase changes in acoustic waveforms relate to the physical characteristics of the two detection schemes. Results are self-consistent, and show that the beam deflection technique is capable of providing quantitative waveform analysis.
Critical currents of superconducting BiPbSrCaCuO tapes in the magnetic flux density range 0–19.75 T at 4.2, 15, and 20 K
Authors: Sato K. , Hikata T. , Iwasa Y.
Published: July 2002

Critical currents of superconducting silver-sheathed tapes of Bi1.8Pb0.4Sr2Ca2.2Cu3Ox have been measured in the magnetic flux density range 0–19.75 T at 4.2, 15, and 20 K. One tape achieved a critical current of 60.6 A at 19.75 T and 20 K; the corresponding critical current density is 551 A/mm2. In the same field, the tape has critical currents of 72.3 A (657 A/mm2) at 15 K and 94.2 A (856 A/mm2) at 4.2 K. At 77 K and in zero field, the tape carries 32.9 A (299 A/mm2). These results indicate that ‘‘high Tc’’ superconducting magnets of engineering interest may soon be feasible.
Superconducting superlattices: Verification of two-dimensional nature in high T
c Bi2Sr2(Ca1−xYx)Cu2O8 superconductors
Authors: Kanai Masaki , Kawai Tomoji , Kawai Shichio
Published: July 2002

An approach to evaluate the two-dimensional nature in a high Tc superconductor is examined on the superconducting superlattice prepared by stacking of superconductor and nonsuperconductor layers. The Bi2Sr2(Ca1−xYx)1Cu2O8-based superlattices have been formed by stacking two different unit cell layers containing different yttrium concentrations. One unit layer contains lower yttrium concentration (x=0.15) to be a superconductor, and the other contains higher concentration (x=0.5) to be a semiconductor, and these layers are periodically stacked with appropriate ratios. These superlattices exhibit the same resistance-temperature curve as the original superconducting films with x=0.15. This behavior can be explained by the strong two-dimensional character in this Bi2Sr2(Ca1−xYx)Cu2O8 high Tc superconductor.
Layer thickness calculations for silicon-on-insulator structures formed by oxygen implantation
Authors: Bussmann U. , Hemment P. L. F.
Published: July 2002

A new computer program enables the evolution of oxygen distributions in separation by implanted oxygen (SIMOX) substrates to be simulated during implantation and also after high-temperature annealing. The positions of the Si/SiO2 interfaces have been calculated for implantation energies of 150 and 200 keV. Theoretical results are in good agreement with experimental data over a wide range of fluences. It is found that the use of multiple implantation and annealing cycles, in comparison with a single implantation stage, shifts the buried oxide layer towards the surface.