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14 Feb 1994

Volume 64, Issue 7, pp. 809-938

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Atomic layer epitaxy of Si on Ge(100) using Si2Cl6 and atomic hydrogen

D. D. Koleske and S. M. Gates

Appl. Phys. Lett. 64, 884 (1994); http://dx.doi.org/10.1063/1.110984 (3 pages) | Cited 20 times

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The surface composition is measured during atomic layer epitaxy (ALE) growth of Si on Ge(100) using Si2Cl6 and atomic hydrogen (Hat) at TS=400 °C. During each Si2Cl6 exposure, Si is adsorbed until Cl fully terminates the surface, making the Si deposition step self‐limiting. The terminating Cl layer is removed by Hat exposure. At 400 °C, H2 rapidly desorbs from Ge(100) and Si/Ge alloy surfaces, regenerating the surface dangling bonds for the next Si2Cl6 adsorption cycle. A thin alloy is grown epitaxially on the Ge(100) substrate, which displays a linear increase in Si content and a linear decrease in Ge content, measured over 1–20 Si ALE cycles.
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68.55.-a Thin film structure and morphology
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Reactive ion etching of GaN using BCl3

M. E. Lin, Z. F. Fan, Z. Ma, L. H. Allen, and H. Morkoç

Appl. Phys. Lett. 64, 887 (1994); http://dx.doi.org/10.1063/1.110985 (2 pages) | Cited 102 times

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Reactive ion etching with SiCl4 and BCl3 of high quality GaN films grown by plasma enhanced molecular beam epitaxy is reported. Factors such as gas chemistry, flow rate, and microwave power affecting the etching rate are discussed. The etch rate has been found to be larger with BCl3 than with SiCl4 plasma. An etch rate of 8.5 Å/s was obtained with the BCl3 plasma for a plasma power of 200 W, pressure of 10 mTorr, and flow rate of 40 sccm. Auger electron spectroscopy (AES) was used to investigate the surface of GaN films after etching. Oxygen contamination has been detected from the AES profiles of etched GaN samples.
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81.65.-b Surface treatments
82.50.Kx Processes caused by X-rays or γ-rays

Ultrafast transient absorption measurement of the electron‐LO phonon scattering time in GaAs‐Al0.33Ga0.67As multiple quantum wells

D. Collings, K. L. Schumacher, F. Raksi, H. P. Hughes, and R. T. Phillips

Appl. Phys. Lett. 64, 889 (1994); http://dx.doi.org/10.1063/1.110986 (3 pages) | Cited 8 times

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The electron‐LO phonon scattering time in GaAs‐Al0.33Ga0.67As quantum wells is determined to be 200±50 fs using transient absorption with low excitation density, a more direct method than previous measurement techniques.
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78.47.-p Spectroscopy of solid state dynamics
63.20.K- Phonon interactions
72.20.Dp General theory, scattering mechanisms
78.66.Fd III-V semiconductors

Band‐offset determination for GaInP‐AlGaInP structures with compressively strained quantum well active layers

Martin D. Dawson and Geoffrey Duggan

Appl. Phys. Lett. 64, 892 (1994); http://dx.doi.org/10.1063/1.110987 (3 pages) | Cited 11 times

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(AlGaIn)P‐on‐GaAs structures incorporating compressively strained Ga1−xInxP (x≳0.48) quantum well active layers have been studied by low‐temperature photoluminescence excitation spectroscopy. The splitting between the lowest energy heavy‐ and light‐hole excitonic transitions is observed to be only weakly dependent on well width over the range 25–300 Å, for sample sets with x=0.56 and x=0.59. Envelope function approximation fitting, based on bulk valence band dispersion calculations which include the strain‐induced interaction with the spin split‐off band, shows this splitting behavior to be a sensitive function of the heterojunction band offset. Conduction band discontinuities, ΔEc, of 0.67ΔEg (x=0.56) and 0.85ΔEg (x=0.59) provide the best fit to these and all higher lying transitions for the full range of structures examined, indicating that poor hole confinement is a limiting factor in practical compressive strain (AlGaIn)P laser device performance.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
42.55.Px Semiconductor lasers; laser diodes

Highly polarized photoluminescence from 2‐μm‐thick strained GaAs grown on CaF2

Leandro R. Tessler, Claudine Hermann, Georges Lampel, Yves Lassailly, Chantal Fontaine, Emmanuelle Daran, and Antonio Muñoz‐Yagüe

Appl. Phys. Lett. 64, 895 (1994); http://dx.doi.org/10.1063/1.110988 (3 pages) | Cited 6 times

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Intense photoluminescence was measured in a strained 2‐μm‐thick GaAs film grown on a (100)‐oriented CaF2 substrate. Circular polarization of 77%±2% was obtained at 77 K under excitation with circularly polarized photons below 1.575 eV. For excitation above 1.610 eV the polarization is limited to 30%±2%. These results are clear indications of strain induced splitting between the Mj=‖±3/2〉 and the Mj=‖± 1/2〉 hole bands. The deduced splitting was 62.5±2.5 meV, corresponding to a stress of the order of −12 kbar. The polarization is maximum for reception energies very close to the excitation. Strained GaAs/CaF2 is thus a good candidate structure for efficient strongly polarized electron sources.
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78.55.Cr III-V semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
78.66.Fd III-V semiconductors

Novel self‐electro‐optic device using bulk Franz–Keldysh effects in an n+‐GaAlAs‐GaAs‐Ag asymmetric Fabry–Perot device structure

Parviz Tayebati and Linas Jauniskis

Appl. Phys. Lett. 64, 898 (1994); http://dx.doi.org/10.1063/1.110989 (3 pages) | Cited 1 time

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We report a novel n+‐Al0.3Ga0.7As/GaAs/Ag asymmetric Fabry–Perot optical modulator based on bulk Franz–Keldysh (FK) effects in GaAs. The modulator exhibits high on/off contrast (≳120:1) and high reflectivity (33%). Using a pair of these devices in series, we demonstrate a bistable FK self‐electro‐optic device (FK‐SEED) operating at 872.5 nm with on/off contrast ratio of 87:1 and 27% reflectivity under 11‐V bias. The negative differential responsivity necessary for SEED operation is provided through a combination of ‘‘normally off’’ mode of the Fabry–Perot and the negative electroabsorption at the wavelength of operation.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Hp Optical processors, correlators, and modulators
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Atomic hydrogen‐induced interface degradation of reoxidized‐nitrided silicon dioxide on silicon

E. Cartier, D. A. Buchanan, and G. J. Dunn

Appl. Phys. Lett. 64, 901 (1994); http://dx.doi.org/10.1063/1.110990 (3 pages) | Cited 37 times

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Remote hydrogen plasma exposure is used to study the transport of atomic hydrogen, H0, through reoxidized‐nitrided oxides and SiO2 and to quantify H0‐induced degradation of their interfaces with silicon. It is directly demonstrated that (1) H0 is extremely reactive and produces large numbers of interface states; (2) the transport of H0 to the silicon/oxide interface is strongly suppressed in reoxidized‐nitrided oxides; and (3) this suppression of the H0 transport is mainly responsible for the much slower interface degradation of reoxidized‐nitrided oxides during high‐field, hot‐electron stress as compared to thermal oxide.
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68.35.Fx Diffusion; interface formation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Epitaxial growth of p‐type ZnMgSSe

Hiroyuki Okuyama, Yuko Kishita, Takao Miyajima, Akira Ishibashi, and Katsuhiro Akimoto

Appl. Phys. Lett. 64, 904 (1994); http://dx.doi.org/10.1063/1.110991 (3 pages) | Cited 36 times

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N‐doped p‐type ZnMgSSe was grown by molecular beam epitaxy. Nitrogen was induced by electron cyclotron resonance plasma. The maximum net acceptor concentration (NA−ND) and the activation energy of the nitrogen acceptor (EN) depend on the band‐gap energy of ZnMgSSe. With increasing band‐gap energy, the maximum NA‐ND is decreased and EN is increased. The maximum NA‐ND and the EN of ZnMgSSe with a band‐gap energy of 3.05 eV at 77 K are 2.5×1016 cm−3 and 140 meV, respectively.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
42.55.Px Semiconductor lasers; laser diodes
42.70.Hj Laser materials

Influence of delta‐doping profile and interface roughness on the transport properties of pseudomorphic heterostructures

S. Fernández de Avila, J. L. Sánchez‐Rojas, F. González‐Sanz, E. Calleja, E. Muñoz, P. Hiesinger, K. Köhler, and W. Jantz

Appl. Phys. Lett. 64, 907 (1994); http://dx.doi.org/10.1063/1.110992 (3 pages) | Cited 9 times

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Thickness effects of the InGaAs channel on photoluminescence and transport properties of δ‐doped Al0.3Ga0.7As/In0.3Ga0.7As heterostructures are investigated. The spreading of the Si δ‐doping layer is deduced from a comparison of the measured charge with self‐consistent calculations assuming a Gaussian Si distribution profile and a definite ionization probability of the Si‐related DX centers. With decreasing channel thickness below 80 Å, the effect of the spreading on the sheet carrier concentration increases and the low temperature mobility decreases due to roughness scattering at the In0.3Ga0.7As/GaAs interface. In channels thicker than 80 Å the thickness‐independent alloy scattering process dominates.
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72.20.Fr Low-field transport and mobility; piezoresistance
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.55.Cr III-V semiconductors
85.30.Tv Field effect devices

Ultrashallow p‐type layer formation by rapid vapor‐phase doping using a lamp annealing apparatus

Yukihiro Kiyota, Masaru Matsushima, Yutaka Kaneko, Masafumi Kanetomo, Youichi Tamaki, Kazuhiko Muraki, and Taroh Inada

Appl. Phys. Lett. 64, 910 (1994); http://dx.doi.org/10.1063/1.110993 (2 pages) | Cited 5 times

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Ultrashallow p‐type layers below 30 nm were formed by a rapid vapor‐phase doping involving a lamp annealing system. A new one‐wafer‐type apparatus with tungsten lamps has been developed for use in this process. Temperatures at five different points on a 4‐in. wafer are in situ monitored by infrared radiative thermometers with optical fibers to maintain a uniform temperature profile across the wafer. By using hydrogen and B2H6 gas, an ultrashallow boron‐doped layer of below 30 nm with the surface boron concentration of 5.8×1019 cm−3 was formed after 10 s of 900 °C annealing with a B2H6 flow rate of 100 ml/min.
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61.72.uf Ge and Si
66.30.J- Diffusion of impurities
85.40.Hp Lithography, masks and pattern transfer

Characteristics of strengthened Ag substrates for Bi2Sr2CaCu2Ox doctor‐bladed tapes

K. Nomura, J. Sato, S. Kuma, H. Kumakura, K. Togano, and N. Tomita

Appl. Phys. Lett. 64, 912 (1994); http://dx.doi.org/10.1063/1.111962 (3 pages) | Cited 7 times

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The characteristics of Ag‐(Mg,Ni) and Ag‐Mn alloys as substrate materials for Bi2Sr2CaCu2Ox (Bi‐2212) tapes and their influence on the superconducting properties were studied. Alloying with Mg+Ni or Mn drastically decreased the grain size of Ag after heat treatment. The additives in Ag‐(Mg,Ni) and Ag‐Mn alloys were oxidized during heat treatment in air. Both the fine grain structure and the internal oxidation of the additives increased the mechanical strength of the Ag alloys. Both alloys were 3–6 times stronger than pure Ag. The superconducting properties of Bi‐2212 prepared on these Ag alloys were slightly degraded; however the critical current densities at 4.2 K in 8 T were still well over 104 A/cm2.
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84.71.Mn Superconducting wires, fibers, and tapes
74.72.-h Cuprate superconductors

Broadband response of the quasiparticle current in a superconducting tunnel junction

S. Verghese, C. Karadi, C. A. Mears, J. Orenstein, P. L. Richards, and A. T. Barfknecht

Appl. Phys. Lett. 64, 915 (1994); http://dx.doi.org/10.1063/1.110994 (3 pages) | Cited 2 times

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We have measured the linear response of the quasiparticle current in a Nb/AlOx/Nb junction from 75–200 GHz. Picosecond pulses of millimeter wave radiation were generated by illuminating a photoconductive switch with a mode‐locked laser. The pulses were coupled to the junction through an impedance‐mismatched, planar lithographed antenna. The broadband response of the superconductor‐insulator‐superconductor junction was measured by monitoring changes in the dc current induced by interfering two electrical pulses at the junction as a function of the time delay between them. The data are in agreement with the linear theory of photon‐assisted tunneling.
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74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
74.50.+r Tunneling phenomena; Josephson effects
85.25.Cp Josephson devices

Spatially resolved critical current limitations in YBa2Cu3O7 multilayer structures

C. A. Hollin, J. S. Abell, S. W. Goodyear, N. G. Chew, and R. G. Humphreys

Appl. Phys. Lett. 64, 918 (1994); http://dx.doi.org/10.1063/1.110995 (3 pages) | Cited 3 times

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Current flow in YBa2Cu3O7/PrBa2Cu3O7 multilayer structures has been studied using low temperature, scanning electron microscope, beam‐induced voltage contrast. Specialized data acquisition has been used to limit thermalization effects and improve resolution. For both via hole contacts and crossovers, the lowest critical current densities were found at steps where the superconductor tracks climb up or down over patterned edges of the insulator.
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74.78.Fk Multilayers, superlattices, heterostructures
74.25.Sv Critical currents
74.78.-w Superconducting films and low-dimensional structures

Photon‐assisted tunneling in double‐barrier superconducting tunnel junctions

M. M. Th. M. Dierichs, P. Dieleman, J. J. Wezelman, C. E. Honingh, and T. M. Klapwijk

Appl. Phys. Lett. 64, 921 (1994); http://dx.doi.org/10.1063/1.110996 (3 pages) | Cited 1 time

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Double‐barrier Nb/Al2O3/Al/Al2O3/Nb tunnel junctions are used as mixing elements in a 345 GHz waveguide mixer. Noise temperatures (double side band) down to 720 K at 3.0 K are obtained without the need to apply a magnetic field to suppress the Josephson current. It is shown that the composite barrier acts as a single barrier for photon‐assisted tunneling. Surprisingly, at these frequencies the capacitance of two stacked tunnel barriers is only determined by one barrier.    
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
74.78.Fk Multilayers, superlattices, heterostructures
74.50.+r Tunneling phenomena; Josephson effects
74.25.N- Response to electromagnetic fields

Comparative study of Jc‐H characteristics for silver‐sheathed superconducting Bi(2:2:1:2) and Bi(2:2:2:3) tapes

K. Shibutani, H. J. Wiesmann, R. L. Sabatini, M. Suenaga, S. Hayashi, R. Ogawa, Y. Kawate, L. Motowidlo, and P. Haldar

Appl. Phys. Lett. 64, 924 (1994); http://dx.doi.org/10.1063/1.110997 (3 pages) | Cited 17 times

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Critical current densities Jc of silver sheathed Bi2Sr2CaCu2O8 and Bi2Sr2Ca2Cu3O10 composite tapes fabricated by a partial melt and a powder‐in‐tube process, respectively, were measured at 4.2, 27, and 64 K as a function of applied magnetic field and the angle between the tape face and the direction of applied magnetic field. These measurements indicate that (1) the fraction of the grain boundaries, which are strongly coupled, are greater in the Bi(2:2:1:2)/Ag tapes than in the Bi(2:2:2:3)/Ag tapes; (2) the alignment of the Bi cuprate platelets with the c‐axis perpendicular to the tape face is significantly greater for the Bi(2:2:1:2) than for the Bi(2:2:2:3)/Ag tapes; and (3) the E‐J curves for both kinds of the tapes are described well by an expression, E∼exp[−(J0/J)μ], where μ and J0 are constants below their transition magnetic fields H∗g.
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84.71.Mn Superconducting wires, fibers, and tapes
74.72.-h Cuprate superconductors
74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)

Noise study of a high‐Tc Josephson junction under near‐millimeter‐wave irradiation

R. Gupta, Qing Hu, D. Terpstra, G. J. Gerritsma, and H. Rogalla

Appl. Phys. Lett. 64, 927 (1994); http://dx.doi.org/10.1063/1.110974 (3 pages) | Cited 5 times

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Noise studies of both the dc and ac Josephson effects have been performed on a high‐Tc ramp‐type Josephson junction irradiated at 176 GHz. Well‐established analytical results for noise in overdamped RSJs are used to model the measured I‐V characteristics, and their agreement is excellent. Noise‐rounded I‐V curves at the critical current and the first and second Shapiro steps under coherent 176 GHz radiation have been studied in detail at several temperatures and rf power levels. The noise temperatures inferred from these simulations are close to the physical temperatures. An increase of noise temperatures at high radiation power levels is a result of radiation heating, which could be due to a bolometric effect.
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85.25.Cp Josephson devices
74.78.-w Superconducting films and low-dimensional structures
74.40.-n Fluctuation phenomena
74.50.+r Tunneling phenomena; Josephson effects

Mode‐mixing in an x‐ray thin‐film waveguide

Y. P. Feng, H. W. Deckman, and S. K. Sinha

Appl. Phys. Lett. 64, 930 (1994); http://dx.doi.org/10.1063/1.110975 (3 pages) | Cited 9 times

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Mode‐mixing in a thin‐film x‐ray waveguide with 4–6 Å interfacial roughness was analyzed using a formalism based on the coupled power theory for optical waveguides. The mode mixing was found to occur between nearest‐neighbor modes with a uniform probability of ∼1.1% per bounce. The small mixing probability and the nearest‐neighbor selection rule are consistent with a mixing mechanism arising from diffuse scattering, which at subcritical angles of incidence displays dramatically different behavior in x‐ray waveguides than in optical counterparts.
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07.85.-m X- and γ-ray instruments
41.50.+h X-ray beams and x-ray optics
78.70.-g Interactions of particles and radiation with matter

Shock wave velocity and shock pressure for low density powders: A novel approach

D. K. Dijken and J. Th. M. De Hosson

Appl. Phys. Lett. 64, 933 (1994); http://dx.doi.org/10.1063/1.110976 (3 pages) | Cited 1 time

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A novel approach is presented to predict the shock wave velocity as well as the shock wave pressure in powder materials. It is shown that the influence of the specific volume behind the shock wave on shock wave velocity and shock pressure decreases with decreasing initial powder density. The new model is compared with experimental data of various materials: Fe, Cu, Al, C, UO2, Ce2O3, SiO2 (quartz), NaCl, and polystyrene. It is concluded that the model holds in particular for initial powder densities less than 50% and for flyer plate velocities up to 5 km/s.
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62.50.-p High-pressure effects in solids and liquids
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
62.20.M- Structural failure of materials

Ultraviolet laser‐projection patterning of polymeric materials for electrochemical gas sensors

P. Tejedor and F. Briones

Appl. Phys. Lett. 64, 936 (1994); http://dx.doi.org/10.1063/1.110950 (3 pages) | Cited 2 times

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ArF laser ablation has been successfully applied to maskless pattern by projection lithography of two polymeric materials, polysiloxane and polyHEMA (2‐hydroxy‐ethyl methacrylate), to be used as gas diffusion membranes in electrochemical gas sensors. Etch rates up to 0.65 μm/s with smooth surface morphology, high edge definition, and a resolution of ∼5 μm were obtained using laser fluences between 250 and 400 mJ/cm2 and repetition rates between 1 and 10 Hz in air for polyHEMA films and in nitrogen for polysiloxane films.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
79.20.Ds Laser-beam impact phenomena
82.47.-a Applied electrochemistry
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