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4 Aug 1997

Volume 71, Issue 5, pp. 563-724

Page 2 of 3 Pages Previous Page Next Page | Jump to Page

Ga vacancies in low-temperature-grown GaAs identified by slow positrons

J. Gebauer, R. Krause-Rehberg, S. Eichler, M. Luysberg, H. Sohn, and E. R. Weber

Appl. Phys. Lett. 71, 638 (1997); http://dx.doi.org/10.1063/1.119814 (3 pages) | Cited 32 times

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A systematic investigation of GaAs layers grown at low temperatures was carried out by means of positron annihilation. The vacancy defects in undoped as-grown material were identified to be mainly Ga vacancies (VGa) by comparing the annihilation parameters to those of Ga vacancies in highly Si-doped GaAs. The characteristic S parameter for positron annihilation in Ga vacancies was determined to be S(VGa) = 1.024(1). The VGa concentration increases up to 1018 cm−3 by decreasing the growth temperature to 200 °C. The vacancy concentration can account for the compensation of AsGa+ antisites as was previously assumed. © 1997 American Institute of Physics.
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61.72.J- Point defects and defect clusters
61.72.S- Impurities in crystals
61.80.Fe Electron and positron radiation effects
78.70.Bj Positron annihilation

Ultrafast intersubband photocurrent response in quantum-well infrared photodetectors

S. Ehret, H. Schneider, J. Fleissner, P. Koidl, and G. Böhm

Appl. Phys. Lett. 71, 641 (1997); http://dx.doi.org/10.1063/1.119815 (3 pages) | Cited 10 times

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We report on a high bandwidth measurement of the transient intersubband photocurrent of a GaAs/AlGaAs multiple quantum-well infrared photodetector (QWIP). The photocurrent is excited via tunable subpicosecond infrared pulses. The response time of the detector has a full width at half-maximum of 18.5 ps and a rise time of 14.5 ps, which is limited by the electrical circuit. The decay time of the photocurrent response exhibits a significant dependence on the applied voltage, with increasing decay times for increasing bias voltages. From the experimental data, we conclude that the intrinsic response time of a QWIP is less than 7 ps. © 1997 American Institute of Physics.
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73.61.Ey III-V semiconductors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors

Logarithmic normal distribution of particle size from a luminescence line-shape analysis in porous silicon

H. Yorikawa and S. Muramatsu

Appl. Phys. Lett. 71, 644 (1997); http://dx.doi.org/10.1063/1.119816 (3 pages) | Cited 28 times

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Photoluminescence spectra of porous silicon prepared with electro-chemical etching, were analyzed using a simple model based on a statistical distribution of particle size. It was found that the size of nanoparticles, obeys the logarithmic normal distribution in all the porous silicon investigated here. This model also explains the dependence of the photoluminescence spectrum on the excitation energy. © 1997 American Institute of Physics.
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78.55.Ap Elemental semiconductors
02.50.Ng Distribution theory and Monte Carlo studies
81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning
61.43.Gt Powders, porous materials
81.05.Rm Porous materials; granular materials

Ambipolar diffusion coefficient and carrier lifetime in a compressively strained InGaAsP multiple quantum well device

Daniel X. Zhu, Serge Dubovitsky, William H. Steier, Johan Burger, Denis Tishinin, Kushant Uppal, and P. Daniel Dapkus

Appl. Phys. Lett. 71, 647 (1997); http://dx.doi.org/10.1063/1.119817 (3 pages) | Cited 7 times

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By using the technique of noncollinear nearly-degenerate four-wave mixing, ambipolar diffusion coefficients and carrier lifetimes were directly determined for a compressively-strained InGaAsP multiple quantum well semiconductor optical amplifier operating at 1.3 μm. A diffusion coefficient of 8.0 cm2/s and a carrier lifetime of 1.33 ns, were obtained at the amplifier current density of 1.88 kA/cm2. The current-density dependent measurements show that the diffusion coefficient will drop with increasing amplifier pumping current, which is consistent with the prediction of the conventional semiconductor theory. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
73.61.Ey III-V semiconductors

Intrinsic modulation bandwidth of strained GaInP/AlGaInP quantum well lasers

A. Moritz, R. Wirth, S. Heppel, C. Geng, J. Kuhn, H. Schweizer, F. Scholz, and A. Hangleiter

Appl. Phys. Lett. 71, 650 (1997); http://dx.doi.org/10.1063/1.119818 (3 pages) | Cited 6 times

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We have investigated the intrinsic modulation response of GaxIn1-xP/AlGaInP quantum well lasers. The differential gain resulting from the measurement of the frequency response, is in good agreement with calculations based on a 6-band kp-theory and direct measurements of the optical gain. We find a maximum value of 3.8×10−16 cm2 for a strongly compressively strained sample, which is less than in InGaAs lasers according to the larger effective masses. The maximum bandwidth we observed is 9.3 GHz at −3 dB. We show that the bandwidth is limited by catastrophic optical damage and not by intrinsic mechanisms. © 1997 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes

Si1−yCy/Si(001) heterostructures made by sublimation of SiC during silicon molecular beam epitaxy

K. B. Joelsson, W.-X Ni, G. Pozina, H. H. Radamson, and G. V. Hansson

Appl. Phys. Lett. 71, 653 (1997); http://dx.doi.org/10.1063/1.119819 (3 pages) | Cited 7 times

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Preparation of pseudomorphic Si1−yCy/Si(001) heterostructures using Si molecular beam epitaxy with C obtained from SiC sublimation in a high-temperature cell has been studied. Thick ( ≈ 2000 Å) homogenous Si1−yCy layers, y ⩽ 1.5%, and Si1−yCy/Si multiple quantum well (MQW) structures, y ⩽ 8%, have been prepared. There is a growth temperature dependent surface roughness accumulating during the growth sequence that can lead to reduction of C induced strain. Temperature modulation during growth has been used to suppress this effect. Near band gap photoluminescence is reported from Si1−yCy/Si MQW structures. © 1997 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Hd Other semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
64.70.Hz Solid-vapor transitions
78.55.Hx Other solid inorganic materials
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
78.66.Li Other semiconductors

Higher order magnetoresistance commensurability oscillations in low aspect ratio antidot lattice and focusing structures

J. S. Moon, J. A. Simmons, and J. L. Reno

Appl. Phys. Lett. 71, 656 (1997); http://dx.doi.org/10.1063/1.119820 (3 pages) | Cited 1 time

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We observe unusually strong magnetoresistance commensurability oscillations in two different types of artificial arrays of scattering centers, multiparallel focusing slits and a square antidot lattice, both fabricated on a two-dimensional electron gas by electron-beam lithography and damageless wet etching. The strength of the magnetoresistance peaks is attributed to a high reflection specularity and a small effective antidot cross section. The absence of commensurability effects near Landau level filling factor υ = 3/2 is attributed to the composite fermion mean free path being smaller than the slit and antidot spacings. The mechanism for the observed commensurability is discussed. © 1997 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.70.Di Landau levels
81.65.Cf Surface cleaning, etching, patterning
72.70.+m Noise processes and phenomena

Microstructural evolution of {113} rodlike defects and {111} dislocation loops in silicon-implanted silicon

G. Z. Pan, K. N. Tu, and S. Prussin

Appl. Phys. Lett. 71, 659 (1997); http://dx.doi.org/10.1063/1.119821 (3 pages) | Cited 11 times

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Recent study indicated that transient enhanced diffusion in implanted silicon is attributed to {113} rodlike defects. We have used plan-view and cross-sectional transmission electron microscopy to study the microstructural evolution of {113} rodlike defects as well as their transition to {111} dislocation loops in heat treatment of Si-amorphized silicon. We found that {113} rodlike defects undergo three stages of change during postimplantation anneals; accumulation of point defects to form homogeneous circular interstitial clusters, growth of these clusters along the 〈110〉 direction in a {113} habit plane, and dissolution into the matrix. We observed that the nucleation of {111} dislocation loops at the amorphous/crystalline interface lags behind that of the {113} defects and occurs while the latter grow and/or dissolve. This suggests that there is a period when {113} defects release interstitial point defects before the {111} dislocation loops nucleate from matrix. The {113} defects were found to disappear completely at 900 °C for 120 s, but the {111} dislocation loops disappear at 1100 °C for 60 s. © 1997 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.72.J- Point defects and defect clusters
66.30.Lw Diffusion of other defects
61.72.Cc Kinetics of defect formation and annealing

Demonstration of an imide coupling reaction on a Si(100)-2×1 surface by molecular layer deposition

T. Bitzer and N. V. Richardson

Appl. Phys. Lett. 71, 662 (1997); http://dx.doi.org/10.1063/1.119822 (3 pages) | Cited 11 times

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In this letter, we report the successful growth of an ultrathin organic film on Si(100)-2×1 by reactive coupling of polyimide precursors. Using the molecular layer deposition technique, 1,4-phenylene diamine and pyromellitic dianhydride were sequentially dosed on clean Si(100)-2×1 under ultrahigh vacuum conditions. The interfacial imidization was initiated by thermal curing at 200 °C. High resolution electron energy loss spectroscopy was employed to identify surface species. The spectra show clearly, that an oligimide chain has been formed which stands upright on the substrate. The chain bonds to the silicon substrate via a Si–(NH)–C linkage. © 1997 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.65.-b Surface treatments
73.61.Ng Insulators
68.35.Ct Interface structure and roughness
68.55.-a Thin film structure and morphology
79.20.Kz Other electron-impact emission phenomena
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Model of coherent transport in metal–insulator–midband gap semiconductor–insulator–semiconductor structure

I. I. Abramov and A. L. Danilyuk

Appl. Phys. Lett. 71, 665 (1997); http://dx.doi.org/10.1063/1.119823 (3 pages) | Cited 1 time

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A kinetic model of coherent transport with self-organized carrier transfer via midband gap semiconductor states in metal–insulator–midband gap semiconductor–insulator–semiconductor structure at room temperature is proposed. The coherent transport at room temperature can be a result of continuous oscillations of charge carriers at midband gap semiconductor states. © 1997 American Institute of Physics.
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73.40.Rw Metal-insulator-metal structures
73.40.Ty Semiconductor-insulator-semiconductor structures
73.20.At Surface states, band structure, electron density of states

Electrical characterization of defects in SiCl4 plasma-etched n-GaAs and Pd Schottky diodes fabricated on it

F. D. Auret, G. Myburg, W. E. Meyer, P. N. K. Deenapanray, H. Nordhoff, S. A. Goodman, M. Murtagh, Shu-Ren Ye, and G. M. Crean

Appl. Phys. Lett. 71, 668 (1997); http://dx.doi.org/10.1063/1.119824 (3 pages) | Cited 1 time

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We employed deep-level transient spectroscopy to determine the electrical properties of defects introduced in epitaxially grown n-GaAs during dry etching in a SiCl4 plasma at different rf powers and plasma pressures. We found that SiCl4 etching introduced two prominent defects, one of which is metastable. Current–voltage measurements demonstrated that high barrier Schottky barrier diodes can be fabricated on SiCl4-etched n-GaAs surfaces for all power and plasma pressure conditions investigated. The defect concentration decreased and the diode quality improved when etching at lower rf power and higher plasma pressure. © 1997 American Institute of Physics.
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71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors
73.40.Ns Metal-nonmetal contacts
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
61.72.-y Defects and impurities in crystals; microstructure

Effect of growth phase on intrinsic Stark effect in CdS–ZnSe superlattices

I. V. Bradley, J. P. Creasey, K. P. O’Donnell, B. Neubauer, and D. Gerthsen

Appl. Phys. Lett. 71, 671 (1997); http://dx.doi.org/10.1063/1.119825 (3 pages) | Cited 1 time

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The operation of the intrinsic Stark effect at visible wavelengths is reported, for both cubic and wurtzite type-II CdS–ZnSe strained layer superlattices grown on CdS buffer layers on (111)A GaAs. An observed increase of the effective piezoelectric coefficient from the measured cubic bulk value is attributed to a nonlinear effect, as previously reported for CdTe quantum wells [R. André, J. Cibert, Le Si Dang, J. Zeman, and M. Zigone, Phys. Rev. B 53, 6951 (1996)]. Exciton peak shifts of 70 meV per decade change of excitation intensity are similar in magnitude to those found in CdS–CdSe superlattices of similar period. These shifts are attributed to screening of the internal piezoelectric fields by photoexcited carriers. Exciton peak shifts that are smaller by an order of magnitude appear in CdS–ZnSe samples, grown on (100) ZnSe buffers and therefore predicted to exhibit no piezoelectric effects of any order. These small shifts, which we attribute to space charge buildup, are a characteristic feature of type-II superlattices. © 1997 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.20.Jq Electro-optical effects
77.65.-j Piezoelectricity and electromechanical effects
73.50.Pz Photoconduction and photovoltaic effects
77.22.Jp Dielectric breakdown and space-charge effects

Photocurrent from photocorrosion of aluminum electrode in porphyrin/Al Schottky-barrier cells

Kazuhiko Murata, Shoji Ito, Kohshin Takahashi, and Brian M. Hoffman

Appl. Phys. Lett. 71, 674 (1997); http://dx.doi.org/10.1063/1.119826 (3 pages) | Cited 11 times

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Current–voltage characteristics under illumination of monochromatic light for metal-free tetrabenzporphyrin, metal-free triazatetrabenzporphyrin, and metal-free phthalocyanine in (indium–tin–oxide)/porphyrin/Al sandwich cells seem to show high-energy conversion efficiencies of 14%, 7.7%, and 5.5%, respectively. However, according to the simultaneous measurement of both short-circuit photocurrent and transmittance of the aluminum electrode with time, the transmittance of Al linearly increases as the photocurrent flows into the external circuit. It is concluded that all photocurrents in the above cells arise from photoaccelerated corrosion of aluminum electrode and do not originate from conversion of light energy to electrical energy. © 1997 American Institute of Physics.
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84.60.Jt Photoelectric conversion
72.80.Le Polymers; organic compounds (including organic semiconductors)
73.40.Ns Metal-nonmetal contacts
85.30.Kk Junction diodes
73.30.+y Surface double layers, Schottky barriers, and work functions

Surface-reconstruction-enhanced solubility of N, P, As, and Sb in III-V semiconductors

S. B. Zhang and Alex Zunger

Appl. Phys. Lett. 71, 677 (1997); http://dx.doi.org/10.1063/1.119827 (3 pages) | Cited 48 times

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We show that surface reconstructions may play an essential role in determining the equilibrium solubilities of N, P, As, and Sb in various III-V compounds. In particular, anion–anion dimerization of the (001)-β2(2×4) surface can enhance the solubility of N near the surface in GaAs, GaP, and InP by five, three, and two orders of magnitudes, respectively, at 1000 K. With certain assumptions on the growth kinetics, this high concentration of N may be frozen in as the crystal grows. © 1997 American Institute of Physics.
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64.75.-g Phase equilibria
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.30.Nr Association, addition, insertion, cluster formation

Far-infrared spectroscopic, magnetotransport, and x-ray study of athermal annealing in neutron-transmutation-doped silicon

D. W. Donnelly, B. C. Covington, J. Grun, C. A. Hoffman, J. R. Meyer, C. K. Manka, O. Glembocki, S. B. Qadri, and E. F. Skelton

Appl. Phys. Lett. 71, 680 (1997); http://dx.doi.org/10.1063/1.119828 (3 pages) | Cited 7 times

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We present evidence that the energy introduced by a short laser pulse focused to high intensity on a small spot on the surface of neutron-transmutation-doped silicon electrically activates impurities far away from the focal spot. The activation of the impurities is measured by far-infrared spectroscopy of shallow donor levels and by magnetotransport characterization. Electrical activity is comparable to that obtained with conventional thermal annealing. X-ray rocking curve measurements show strain in the area of the focal spot, but none at large distances from the focal spot. © 1997 American Institute of Physics.
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72.80.Cw Elemental semiconductors
61.72.uf Ge and Si
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.80.Hg Neutron radiation effects
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
78.30.Am Elemental semiconductors and insulators
81.05.Cy Elemental semiconductors
61.72.S- Impurities in crystals
71.55.Cn Elemental semiconductors

Extremely high-mobility two dimensional electron gas: Evaluation of scattering mechanisms

V. Umansky, R. de-Picciotto, and M. Heiblum

Appl. Phys. Lett. 71, 683 (1997); http://dx.doi.org/10.1063/1.119829 (3 pages) | Cited 50 times

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We report on the characterization of selectively doped GaAs/AlGaAs heterostructures, grown by an extremely clean molecular beam epitaxy system, which exhibit a Hall mobility of a two dimensional electron gas exceeding 10×106 cm2/Vs for a wide range of undoped spacer layer thickness (50–100 nm). A maximum electron mobility of 14.4×106 cm2/Vs was measured at 0.1 K in a structure with a 68 nm spacer thickness and an areal carrier density of 2.4×1011 cm−2. This is the highest electron mobility ever reported, leading to a momentum relaxation mean-free path of ∼ 120 μm. We present experiments that enable us to distinguish between the main scattering mechanisms. We find that scattering due to background impurities limits electron mobility in our best samples, suggesting that further improvement in structure quality is possible. © 1997 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

An aluminum-wire grid polarizer fabricated on a gallium–arsenide photodiode

Tohru Doumuki and Hitoshi Tamada

Appl. Phys. Lett. 71, 686 (1997); http://dx.doi.org/10.1063/1.119830 (3 pages) | Cited 9 times

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An aluminum-wire grid polarizer fabricated directly on a gallium–arsenide photodiode is used to realize a polarization-selective photodetector. Since all of the light transmitted through the wire grid, including higher-order diffraction components, can be detected at the photodiode and since a resonance of incident electromagnetic waves is utilized, the required grid period can be significantly larger. With a grid period of 600 nm and normal incident light at 715 nm, an extinction ratio of 16 can be obtained both for light detected at the photodiode and light reflected from the surface. If light detected at the photodiode is to be optimized, a higher extinction ratio of 30 and a loss of 30% have been experimentally obtained as well. These experimental results are in good agreement with our theoretical simulation. © 1997 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors

Ideal Ohmic contact to n-type 6H-SiC by reduction of Schottky barrier height

T. Teraji, S. Hara, H. Okushi, and K. Kajimura

Appl. Phys. Lett. 71, 689 (1997); http://dx.doi.org/10.1063/1.119831 (3 pages) | Cited 15 times

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We formed ideal Ti Ohmic contacts on an n-type 6H-SiC epitaxial layer by reducing Schottky barrier heights. The ideal contacts were realized by utilizing ideal SiC surfaces formed under processes that intend to lower the density of surface states. As the first process to form the ideal surfaces, SiC surfaces were flattened by oxidation followed by HF etching. Further, the ideal SiC surfaces in terms of passivation of surface states were formed by immersing the flat SiC surfaces in boiling water. Ti electrodes thus formed had Ohmic properties with excellent I–V characteristic linearity without the use of heavy doping and high-temperature annealing. © 1997 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.At Surface states, band structure, electron density of states
81.65.Mq Oxidation
81.05.Hd Other semiconductors

Ion dependent interstitial generation of implanted mercury cadmium telluride

B. L. Williams, H. G. Robinson, and C. R. Helms

Appl. Phys. Lett. 71, 692 (1997); http://dx.doi.org/10.1063/1.119832 (3 pages) | Cited 13 times

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The creation of Hg interstitials during ion implantation of mercury cadmium telluride is found to strongly depend on the preferred lattice position of the element implanted. Elements that substitute onto the cation sublattice create significantly more interstitials than elements that sit interstitially or on the anion sublattice. In particular, implants of column II elements Mg and Zn produced much larger interstitial concentrations than implants of column VI elements S and Se. Implants of B, which resides mostly as an interstitial, produced Hg interstitial concentrations intermediate between the column II and column VI ions. Recoils from implant damage also contributed to Hg interstitial formation in heavier mass implants (Zn and Se), but appear to have negligible influence on interstitial generation in implants of lighter ions. © 1997 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.J- Point defects and defect clusters
61.72.S- Impurities in crystals

The effect of surface reconstructions on the surface morphology during in situ etching of GaAs

M. Ritz, T. Kaneko, and K. Eberl

Appl. Phys. Lett. 71, 695 (1997); http://dx.doi.org/10.1063/1.119921 (3 pages) | Cited 5 times

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The influence of surface reconstructions on the surface morphology during in situ layer-by-layer etching of GaAs(001) has been studied based on the observation of reflection high-energy electron-diffraction measurements. For the etching, AsBr3 is used as a reactive source etchant under solid source molecular beam epitaxy conditions, focusing on a high temperature region in which the etching rate is limited by a supply rate of AsBr3 resulting in a constant value. Despite the fact that the etching starts on a layer-by-layer basis, an initially smooth surface turns considerably rougher depending on the stoichiometry associated with the surface reconstruction. The best morphology after a removal of 250 nm is obtained in the Ga-rich (3×1) reconstruction region close to the phase transition boundary to the As-rich (2×4). This is also verified by the measurement of scanning electron microscopy and atomic force microscopy. © 1997 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)

Intense violet-blue photoluminescence in as-deposited amorphous Si:H:O films

Song Tong, Xiang-na Liu, Ting Gao, and Xi-mao Bao

Appl. Phys. Lett. 71, 698 (1997); http://dx.doi.org/10.1063/1.119833 (3 pages) | Cited 21 times

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Three photoluminescence (PL) bands at 340–370, 400–430, and 740 nm were observed at room temperature in a-Si:H:O films fabricated by plasma enhanced chemical vapor deposition without any postprocessing. The violet-blue emission is very strong and stable, and its intensity is closely related to the oxygen content in the films, which can be controlled by the applied dc biases on the sample substrates during deposition. The first two PL peaks are ascribed to Si–O related species, and the last one to the quantum size effect of the nanocrystallites embedded in the a-Si:H:O matrix. © 1997 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.46.-w Structure of nanoscale materials

Lattice relaxation of GaAs islands grown on Si(100) substrate

Koyu Asai, Kazuhito Kamei, and Hisashi Katahama

Appl. Phys. Lett. 71, 701 (1997); http://dx.doi.org/10.1063/1.119834 (3 pages) | Cited 5 times

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Initial stage of lattice relaxation of GaAs islands grown on Si(100) substrate were investigated by combination of reflection high-energy electron diffraction and molecular beam epitaxy. In addition to the lattice constants in horizontal direction (a∥) to the substrate surface, we first measured directly those in vertical one (a⊥). At the beginning of the growth, the rapid increase of a∥ and the larger Poisson’s ratios than that of bulk were observed. Atomic bond flexibility and extension induced by surface effects might cause this rapid increase of a∥ and large Poisson’s ratios. © 1997 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
62.20.D- Elasticity

Operation of high-sensitivity radio frequency superconducting quantum interference device magnetometers with superconducting coplanar resonators at 77 K

Y. Zhang, W. Zander, J. Schubert, F. Rüders, H. Soltner, M. Banzet, N. Wolters, X. H. Zeng, and A. I. Braginski

Appl. Phys. Lett. 71, 704 (1997); http://dx.doi.org/10.1063/1.119835 (3 pages) | Cited 35 times

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We have developed a novel coplanar resonator serving as a tank circuit for radio frequency washer superconducting quantum interference devices (SQUIDs). Two coplanar lines surrounded the circular flux concentrator washer, 13.4 mm in diameter. The SQUID, 3.5 mm in diameter, was coupled to the concentrator in the flip-chip configuration. All parts were fabricated from single-layer epitaxial YBa2Cu3O7 films on LaAlO3 substrates. In this layout, the resonant frequency could be set between 600 and 850 MHz. With SQUID loops of 100×100 μm2 (SQUID) inductance Ls = 150 pH or 10×500 μm2 (Ls = 260 pH), we determined at 77 K white flux noise levels Sϕ1/2 of 1.0×10−5 and 1.5×10−5ϕ0/math, respectively. Both figures corresponded to the field resolution of about 30 fT/math. © 1997 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
07.55.Ge Magnetometers for magnetic field measurements
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits
84.40.Az Waveguides, transmission lines, striplines
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
84.40.Lj Microwave integrated electronics

Mixing at terahertz frequency band using YBa2Cu3O7−δ bicrystal Josephson junctions

J. Chen, H. Myoren, K. Nakajima, T. Yamashita, and P. H. Wu

Appl. Phys. Lett. 71, 707 (1997); http://dx.doi.org/10.1063/1.119836 (3 pages) | Cited 15 times

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Using high-Tc Josephson junctions made of YBa2Cu3O7−δ deposited across MgO bicrystal boundary, at terahertz (THz) frequency band, we demonstrated both fundamental and harmonic mixing. Radiation from a far-infrared laser was coupled to the junction, which was integrated with a planar bow-tie antenna, via an extended hyperhemispherical silicon lens. Fundamental mixing manifested itself in the junction’s dc current–voltage (I–V) curve as a third Shapiro step in addition to those two induced by the THz laser lines from a slightly misaligned resonator. In harmonic mixing between a THz laser line and a microwave local oscillator, the highest harmonic number we could get was 490 with a signal-to-noise ratio of 9 dB at the intermediate frequency. © 1997 American Institute of Physics.
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85.25.Cp Josephson devices
74.72.-h Cuprate superconductors
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
84.40.-x Radiowave and microwave (including millimeter wave) technology

Using phthalocyanine precursors to prepare oxide thin films: Decoupling the growth rate from the evaporation rate

E. Mächler, F. Arrouy, E. Fritsch, J. G. Bednorz, H. Berke, J. R. Huber, and J.-P. Locquet

Appl. Phys. Lett. 71, 710 (1997); http://dx.doi.org/10.1063/1.119837 (3 pages)

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Major challenges concerning the use of chemical beam epitaxy deposition techniques are posed by the lack of reliable in situ composition control and well-behaved metal–organic precursors. To circumvent these shortcomings, we propose the use of a different type of metal–organic precursors, namely molecules resistant to high temperatures, for the growth of thin films. As these molecules cannot be decomposed by the substrate temperature, they are subjected to a chemical reaction with a beam of activated species. The major advantages of this novel deposition process are listed and illustrated by the growth of CuO and YBa2Cu3O7 thin films. © 1997 American Institute of Physics.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Nq Composition and phase identification
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
82.39.Wj Ion exchange, dialysis, osmosis, electro-osmosis, membrane processes
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