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6 Jun 1988

Volume 52, Issue 23, pp. 1933-2003

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Optically controlled GaAs/AlAs multiple quantum well modulators employing integrated dielectric reflectors

W. Kowalsky, Th. Hackbarth, and K. J. Ebeling

Appl. Phys. Lett. 52, 1933 (1988); http://dx.doi.org/10.1063/1.99602 (3 pages) | Cited 3 times

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We investigate all‐optical switching in GaAs/AlAs multiple quantum well devices with integrated dielectric reflector. A 7 mW control beam at λc=790 nm wavelength produces a 15% reflection change for a test beam at λt=858 nm which is close to the lowest energy transition in the quantum wells (λ=868 nm). Switching dynamics are shown to be limited by excess carrier lifetimes of τ≊4 ns corresponding to a 3 dB frequency of 70 MHz. A basic analysis in terms of carrier‐induced absorption change by dynamic band filling provides a good description of the experiments.
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42.82.-m Integrated optics
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.79.Hp Optical processors, correlators, and modulators
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Distributed feedback laser line narrowing with external fiber resonators

M. Fuchs and W. Hoppe

Appl. Phys. Lett. 52, 1936 (1988); http://dx.doi.org/10.1063/1.99603 (3 pages)

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A simple distributed feedback (DFB) laser line narrowing arrangement consisting of an adapted coupler and a cleaved fiber end resonator has been realized. Linewidths below 100 kHz have been obtained for different commercial 1300 nm and 1550 nm DFB lasers.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
42.81.Qb Fiber waveguides, couplers, and arrays

Induced‐frequency shift of copropagating ultrafast optical pulses

P. L. Baldeck, R. R. Alfano, and Govind P. Agrawal

Appl. Phys. Lett. 52, 1939 (1988); http://dx.doi.org/10.1063/1.99604 (3 pages) | Cited 29 times

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The combined effects of cross‐phase modulation and pulse walk‐off on copropagating optical pulses are investigated. It is shown that ultrafast pulses which overlap in a nonlinear dispersive medium undergo a substantial shift of their carrier frequencies. This new coherent phenomenon of induced‐frequency shift has been demonstrated using strong infrared picosecond pulses which shift the frequency of weak green picosecond pulses propagating in a 1‐m‐long single‐mode optical fiber.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.50.-p Quantum optics
42.81.Dp Propagation, scattering, and losses; solitons

Investigations of the preparation process for efficient second‐harmonic generation in optical fibers

Arūnas Krotkus and Walter Margulis

Appl. Phys. Lett. 52, 1942 (1988); http://dx.doi.org/10.1063/1.99605 (3 pages) | Cited 5 times

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Experiments were carried out to elucidate aspects of the preparation process, which enables glass fibers to efficiently frequency‐double infrared laser light. A picture is described which is consistent with most of the observations.
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42.81.Gs Birefringence, polarization
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Effect of doping on the optical gain and the spontaneous noise enhancement factor in quantum well amplifiers and lasers studied by simple analytical expressions

Kerry J. Vahala and C. E. Zah

Appl. Phys. Lett. 52, 1945 (1988); http://dx.doi.org/10.1063/1.99584 (3 pages) | Cited 47 times

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The maximum optical gain and the spontaneous noise enhancement factor in quantum well structures are expressed as extremely simple functions that are accurate over a wide range of carrier densities. These expressions are used to study the effect of doping on the optical gain and the noise enhancement factor in a 100 Å InGaAs/InP quantum well structure. n‐type doping is most effective in reducing the transparency excitation level (laser threshold) and the noise enhancement factor (amplifier noise figure), whereas p‐type doping enables increased gain at a given excitation level.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Linear electro‐optic effect in β‐BaB2O4

Chris A. Ebbers

Appl. Phys. Lett. 52, 1948 (1988); http://dx.doi.org/10.1063/1.99585 (2 pages) | Cited 6 times

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The linear electro‐optic (EO) coefficients of beta‐barium borate (β‐BaB2O4) have been measured. The clamped and unclamped values of ryyy and rc are ‖rTyyy‖ =2.5 pm/V, ‖rTc‖ =0.17 pm/V, ‖rSyyy‖=0.24rSxyz (KDP), and ‖rSc‖=0.013rSxyz (KDP). The magnitude of the EO coefficient is due mainly to the electronic nonlinearity.
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78.20.Jq Electro-optical effects
42.65.-k Nonlinear optics

Stationary chaotic states in linear magnetohydrodynamic generators

S. W. Simpson and C. A. Schmidt‐Harms

Appl. Phys. Lett. 52, 1950 (1988); http://dx.doi.org/10.1063/1.99586 (3 pages) | Cited 2 times

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In linear magnetohydrodynamic generators operating with a slag layer coating the electrode walls, highly nonuniform electrical characteristics are often observed. It is proposed that the voltage patterns in these channels are an example of chaos in a discrete spatial system. An idealized model is presented, based on the Hall effect and nonlinear resistance in the slag layer. The model, which correctly predicts observed features, exhibits complex chaotic behavior.
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52.75.Fk Magnetohydrodynamic generators and thermionic convertors; plasma diodes
05.45.-a Nonlinear dynamics and chaos
52.30.-q Plasma dynamics and flow
84.60.Lw Magnetohydrodynamic conversion

Real‐time measurements of plasma/surface interaction by plasma‐amplified photoelectron detection

G. S. Selwyn, B. D. Ai, and J. Singh

Appl. Phys. Lett. 52, 1953 (1988); http://dx.doi.org/10.1063/1.99587 (3 pages) | Cited 10 times

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A new method, based on the photoelectric effect, is described for real‐time, in situ monitoring of metal or semiconductor surfaces during plasma exposure. As an example of the application of this technique, the effect of both sputter and reactive gas plasma exposure is studied for graphite, silicon, and aluminum surfaces. Results are consistent with the formation of a surface‐passivating layer of fluoride on aluminum and penetration of fluorine into the silicon bulk during exposure to the CF4+Ar etching plasma. An application of this technique for endpoint detection monitoring is described.
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81.65.-b Surface treatments
79.20.Ds Laser-beam impact phenomena
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Production of a low‐pressure processing plasma with ion beam injection for thin‐film preparation

Hiroharu Fujita and Shinya Yagura

Appl. Phys. Lett. 52, 1956 (1988); http://dx.doi.org/10.1063/1.99588 (3 pages) | Cited 1 time

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A low‐pressure processing plasma production with an ion beam injection is presented by applying microwave and rf discharges in a low‐pressure gas for thin‐film preparation. Electrostatic ion energy analyzer and emissive probe techniques are used in the plasma of a nonreactive gas to get plasma characteristics. The measurement reveals that an energy of ion beam injected into a reactor is controllable by adjusting a bias potential applied between the two plasmas, and electric fields at the steady state are affected by a configuration of a magnetic field applied for an enhancement of a microwave plasma production.
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81.15.Rs Spray coating techniques

Photolytic decomposition of adsorbed tellurium and cadmium alkyl species at 295 K upon 193 nm photon irradiation

C. D. Stinespring and A. Freedman

Appl. Phys. Lett. 52, 1959 (1988); http://dx.doi.org/10.1063/1.99589 (3 pages) | Cited 9 times

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The photolytic decomposition of adspecies formed by the adsorption of tellurium and cadmium alkyls at 295 K under ultrahigh‐vacuum conditions has been studied using x‐ray photoelectron spectroscopy. Dimethyl tellurium adsorbed at submonolayer coverages on a polycrystalline gold substrate has been observed to undergo nearly quantitative photolytic decomposition at 193 nm to form metallic tellurium. The hydrocarbon photofragments produced in the decomposition lead to negligible carbon contamination on the gold surface. Dimethyl cadmium adsorbed on amorphous SiO2 both desorbs and decomposes to form the metal adspecies. In this case, most of the carbon remains as hydrocarbon and carbidic contaminants. Monomethyl adspecies of both metals formed on Si(100) and GaAs(100) surfaces are inactive with respect to decomposition at the low fluences (0.25 mJ cm−2) used in these experiments; however, substantial desorption is observed.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light

Reduction of interface hydrogen content by partially ionized beam deposition technique

A. S. Yapsir, T.‐M. Lu, and W. A. Lanford

Appl. Phys. Lett. 52, 1962 (1988); http://dx.doi.org/10.1063/1.99590 (3 pages) | Cited 20 times

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Hydrogen content at the Al/Si interface of samples with Al films deposited by conventional means and by a partially ionized beam (PIB) was measured using 1H(15N,αγ)12C nuclear resonance reaction. We observed that samples with PIB‐deposited Al film exhibited significantly lower hydrogen concentration at the Al/Si in interface than that of the sample deposited by conventional means. The results demonstrated the ability of the PIB technique to perform interface self‐cleaning, at least for hydrogen contaminant.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.Nq Composition and phase identification
68.35.Dv Composition, segregation; defects and impurities

Pulsed laser processing of ceramics in water

Noboru Morita, Shuichi Ishida, Yasutomo Fujimori, and Ken Ishikawa

Appl. Phys. Lett. 52, 1965 (1988); http://dx.doi.org/10.1063/1.99591 (2 pages) | Cited 20 times

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A new method for defect‐free processing of ceramics is presented. This method consists of processing ceramics in water with a Q‐switched yttrium aluminum garnet (YAG) laser. In laser machining, a recast layer and cracks are usually formed in the machined part. Using this method, these defects are not formed.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
61.72.Bb Theories and models of crystal defects

Photocurrent spectroscopy in a sawtooth doping superlattice

B. Ullrich, C. Zhang, H. Fronius, and K. v. Klitzing

Appl. Phys. Lett. 52, 1967 (1988); http://dx.doi.org/10.1063/1.99592 (3 pages) | Cited 4 times

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We report an investigation of photocurrent response in a sawtooth doping superlattice which is composed of alternating n(Si) and p(Be) δ‐doping layers with undoped GaAs layers (7–15 nm) between them. A selective contact method is used to measure the interesting behavior of the subband gap compared with the gap of the host semiconductor. The photocurrent is finite even when the photon energy is below the gap of GaAs and can be varied by applying a bias voltage between the n and p contacts. The observed phenomena can be explained by a generalized Franz–Keldysh model which takes into account the finite voltage drop inside the sample.
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73.50.Pz Photoconduction and photovoltaic effects
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.-r Electrical properties of specific thin films

Oval defects in Ga1−xAlxAs molecular beam epitaxy layers: A Raman scattering and photoluminescence combined study

J. Sapriel, J. Chavignon, and F. Alexandre

Appl. Phys. Lett. 52, 1970 (1988); http://dx.doi.org/10.1063/1.99593 (3 pages) | Cited 9 times

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Oval defects in Ga1−xAlxAs molecular beam epitaxy layers are characterized by spatially resolved Raman and photoluminescence studies performed at room temperature with a Raman microprobe. Changes in the crystallographic orientation and chemical composition are evidenced by Raman scattering. The modification of the Ga concentration which occurs inside the oval defect is confirmed by photoluminescence investigation.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.55.Cr III-V semiconductors
78.30.Fs III-V and II-VI semiconductors

Charge state controlled short‐ and long‐range defect motions in GaAs

H. Kamada and K. Ando

Appl. Phys. Lett. 52, 1973 (1988); http://dx.doi.org/10.1063/1.99594 (3 pages) | Cited 2 times

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We report the charge state dependent annealing reactions for a defect (H2, 0.4 eV) in p‐type GaAs following room‐temperature electron irradiation. Using deep level transient spectroscopy, it is shown that one of two absolutely different defect reaction branches is chosen depending on the junction bias condition. The ranges of defect motion involved in these two reactions are markedly different: When the H2 center is emptied of hole it disappears near room temperature by several defect jumps to the near neighbor sites, whereas when it is occupied with hole it annihilates at 370–380 K by long‐range defect motion. The observed defect motions are well described by the simple charge state effect upon the defect which has two distinct reaction branches.
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61.72.Bb Theories and models of crystal defects
71.55.Eq III-V semiconductors
61.72.J- Point defects and defect clusters
66.30.Lw Diffusion of other defects

Heteroepitaxy of GaAs on Si: The effect of in situ thermal annealing under AsH3

A. Freundlich, J. C. Grenet, G. Neu, A. Leycuras, and C. Vèrié

Appl. Phys. Lett. 52, 1976 (1988); http://dx.doi.org/10.1063/1.99595 (3 pages) | Cited 28 times

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This letter shows that an in situ thermal annealing step in AsH3/H2 during the metalorganic vapor phase epitaxy of GaAs on Si(001) improves the crystalline quality. The dislocation density is reduced (below 107 cm−2) without affecting the Si diffusion across the heterointerface or the strain level in the epilayer. The nature of the various near‐band‐gap recombinations present in the unannealed and annealed samples is discussed in light of selective photoluminescence experiments.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Negative differential photoconductance in an alternately doped multiple quantum well structure

K. K. Choi, B. F. Levine, C. G. Bethea, J. Walker, and R. J. Malik

Appl. Phys. Lett. 52, 1979 (1988); http://dx.doi.org/10.1063/1.99596 (3 pages) | Cited 21 times

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We have measured the infrared photoconductivity of an alternately doped multiple quantum well structure. From this measurement, the density of the electrons dynamically stored in the undoped wells, which is critically important in the theory of tunneling, can be deduced at different external biases. A striking negative differential photoconductance feature is observed which is fully consistent with the theory of sequential tunneling.
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73.50.Pz Photoconduction and photovoltaic effects
73.40.Gk Tunneling
73.61.Ey III-V semiconductors

Lateral resonant tunneling field‐effect transistor

S. Y. Chou, J. S. Harris, and R. F. W. Pease

Appl. Phys. Lett. 52, 1982 (1988); http://dx.doi.org/10.1063/1.99656 (3 pages) | Cited 9 times

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A lateral resonant tunneling field‐effect transistor (RTFET) is proposed. The RTFET has three closely spaced, but independent gate electrodes. The two outer gates create lateral double potential barriers in the channel, and control the barrier heights. The inner gate controls the potential of the quantum well between the barriers. These gates are capacitively coupled to the barriers and well; therefore, very small gate currents and high input impedences result. Modeling and computer simulations show that when the potential of the quantum well is scanned, the RTFET should have a better peak‐to‐valley ratio, narrower current peak widths, and more uniform distribution of peak and valley currents than that of a resonant tunneling diode with the same barriers and well. The independent control of the barrier heights allows us to adjust continuously the peak‐to‐valley ratio, amplitude, and position of current peaks. Furthermore, using an additional back gate, the peak‐to‐valley ratio and amplitude of peak current can also be adjusted by changing the carrier concentration next to the double barriers.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
73.40.Gk Tunneling

Nondestructive measurement of layer thicknesses in double heterostructures by x‐ray diffraction

A. T. Macrander, S. Lau, K. Strege, and S. N. G. Chu

Appl. Phys. Lett. 52, 1985 (1988); http://dx.doi.org/10.1063/1.99597 (2 pages) | Cited 9 times

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Double‐crystal rocking curves for an InP/InGaAsP/InP double heterostructure grown by hydride vapor phase epitaxy have been obtained which reveal fringes corresponding to both the top InP layer and to the buried InGaAsP layer thickness. Fourier transform spectra of the rocking curves are shown to be very useful in extracting the thicknesses. We believe this to be the first report of a measurement of the thickness of a buried layer using only x‐ray fringe spacings.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Y‐Ba‐Cu‐O superconducting film on oxidized silicon

Ram P. Gupta, W. S. Khokle, R. C. Dubey, Seema Singhal, K. C. Nagpal, G. S. T. Rao, and J. D. Jain

Appl. Phys. Lett. 52, 1987 (1988); http://dx.doi.org/10.1063/1.99743 (2 pages) | Cited 9 times

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We report thick superconducting films of Y‐Ba‐Cu‐O on oxidized silicon substrates. The critical temperatures for onset and zero resistance are 96 and 77 K, respectively. X‐ray diffraction analysis predicts 1, 2, 3 composition and orthorhombic phase of the film.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
61.66.Fn Inorganic compounds
81.15.Jj Ion and electron beam-assisted deposition; ion plating

High transition temperature superconductor LaBa2Cu3O7−y with zero resistance at 92 K

T. Wada, N. Suzuki, T. Maeda, A. Maeda, S. Uchida, K. Uchinokura, and S. Tanaka

Appl. Phys. Lett. 52, 1989 (1988); http://dx.doi.org/10.1063/1.99744 (3 pages) | Cited 33 times

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Samples of LaBa2 Cu3 O7−y have been synthesized, which show a superconducting transition above 90 K. One of the samples shows a superconducting transition with an onset at 93 K and a zero resistivity at 92 K. These temperatures are the highest among those reported so far on this system and even higher than those in YBa2 Cu3 O7−y. The magnetic susceptibility measurement also shows that it has a superconducting transition with onset at around 93 K. To synthesize such good LaBa2 Cu3 O7−y requires two important procedures. First is sintering above 950 °C in N2 gas atmosphere and the second is annealing at 300 °C in dried O2 gas atmosphere.
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74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.25.Ha Magnetic properties including vortex structures and related phenomena
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Bi‐Sr‐Ca‐Cu‐oxide superconducting thin films deposited by dc magnetron sputtering

Brian T. Sullivan, N. R. Osborne, W. N. Hardy, J. F. Carolan, B. X. Yang, P. J. Michael, and R. R. Parsons

Appl. Phys. Lett. 52, 1992 (1988); http://dx.doi.org/10.1063/1.99598 (3 pages) | Cited 19 times

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Thin films of the high‐temperature superconductor Bi‐Sr‐Ca‐Cu‐oxide were deposited by dc magnetron sputtering onto various substrates. Films deposited on (100) MgO substrates achieved zero resistance between 78 and 82.5 K depending upon the annealing conditions. The best films were produced with a quick post‐anneal in oxygen at 870 °C followed by a slower anneal in air at the same temperature. The composition of the sputtered films was uniform within ±3% over an area 40 mm in radius, and films deposited at 15 and 40 mm from the center of deposition both exhibited high Tc transitions.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Cd Deposition by sputtering
68.55.Nq Composition and phase identification
74.70.-b Superconducting materials other than cuprates

Preparation of high Tc and Jc films of Ba2YCu3O7 using laser evaporation of a composite target containing BaF2

A. M. DeSantolo, M. L. Mandich, S. Sunshine, B. A. Davidson, R. M. Fleming, P. Marsh, and T. Y. Kometani

Appl. Phys. Lett. 52, 1995 (1988); http://dx.doi.org/10.1063/1.99745 (3 pages) | Cited 19 times

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High Tc and Jc superconducting films of Ba2YCu3O7 are prepared on SrTiO3 〈100〉 substrates using pulsed excimer laser evaporation of a composite target containing BaF2, Y2O3, and CuO, followed by annealing in wet oxygen. High transition temperatures (R=0 from 89.5 to 91 K) and high critical current densities (Jc≥7×105 A cm−2) are obtained. The electrical transport properties of these films are significantly better than films previously grown via laser ablation of Ba‐Y‐Cu‐O targets.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Observation of first‐order Freedericksz transition in a nematic film induced by electric and optical fields

Shu‐Hsia Chen and J. J. Wu

Appl. Phys. Lett. 52, 1998 (1988); http://dx.doi.org/10.1063/1.99599 (3 pages) | Cited 22 times

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The observation of optical and electric first‐order Freedericksz transitions in a homeotropically aligned nematic liquid crystal film induced by electric and optical fields, respectively, is reported. The experimental results are in good agreement with theoretical predictions.
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78.20.Jq Electro-optical effects
42.65.Pc Optical bistability, multistability, and switching, including local field effects
FREE

Comment on ‘‘Low‐frequency excess noise in Nb‐Al2O3‐Nb Josephson tunnel junctions’’ [Appl. Phys. Lett. 50, 1757 (1987)]

T. G. M. Kleinpenning

Appl. Phys. Lett. 52, 2001 (1988); http://dx.doi.org/10.1063/1.99600 (1 page) | Cited 4 times

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The 1/f noise in a josephson junction as measured by Savo et al. can b terpreted in terms of transparency fluctuations induced by Nyquist noise i n th aluminium oxide layer. (AIP)
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85.25.Cp Josephson devices
74.50.+r Tunneling phenomena; Josephson effects
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