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9 Dec 1991

Volume 59, Issue 24, pp. 3075-3191

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Electron waveguide coupler: A four‐terminal device

Jian Wang, Hong Guo, and R. Harris

Appl. Phys. Lett. 59, 3075 (1991); http://dx.doi.org/10.1063/1.106400 (3 pages) | Cited 29 times

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We model the electron waveguide coupler as a four‐terminal device, by considering the scattering at the interaction region between the electron waveguides. Transmission and reflection coefficients are evaluated for a variety of system parameters. Periodic switching of the electron wave between the waveguides are observed. Complete electron transfer occurs at a transfer length as short as 400 Å. This value is much smaller than that predicted by coupled‐mode theory and the device is thus experimentally realizable.
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85.30.-z Semiconductor devices

Suppression of beam steering in an injection‐locked laser diode array

Laurence R. Brewer

Appl. Phys. Lett. 59, 3078 (1991); http://dx.doi.org/10.1063/1.105794 (3 pages)

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Experimental measurements were made to demonstrate that the degree of beam steering in an injection‐locked laser diode array is related to the divergence of the master laser beam. For a collimated master laser beam the beam steering was suppressed. The injection‐locked laser diode array beam steers with the master laser wavelength because only a portion of the divergent master laser beam satisfies the round trip mode condition.
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42.55.Px Semiconductor lasers; laser diodes

Wavelength tuning in a grating‐assisted vertical coupler filter using quantum well electrorefraction

Hajime Sakata and Shinsuke Takeuchi

Appl. Phys. Lett. 59, 3081 (1991); http://dx.doi.org/10.1063/1.105795 (3 pages) | Cited 3 times

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We present a demonstration of the electro‐optic tuning in a GaAs/AlGaAs quantum well vertical codirectional coupler filter. Tunable range over 2 nm was realized through the quantum‐confined Stark effect with a tuning rate of 0.28 nm/V2 for transverse magnetic polarization. A filter bandwidth as narrow as 1.7 nm (full width at half‐maximum) at 830 nm with a coupling region length of 490 μm was obtained.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Gn Optical waveguides and couplers

1.3 μm InGaAsP/InP multiquantum well buried heterostructure lasers grown by chemical‐beam epitaxy

W. T. Tsang, F. S. Choa, R. A. Logan, T. Tanbun‐Ek, M. C. Wu, Y. K. Chen, A. M. Sergent, and K. W. Wecht

Appl. Phys. Lett. 59, 3084 (1991); http://dx.doi.org/10.1063/1.105796 (3 pages) | Cited 3 times

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High performance InGaAsP/InP multiquantum well (MQW) buried heterostructure lasers emitting around 1.3 μm were prepared for the first time by chemical‐beam epitaxy. At 20 °C, continuous‐wave (cw) threshold currents were 5–8 mA and quantum efficiencies were 0.35–0.45 mW/mA for 250 μm long lasers having one facet ∼85% reflective coated. At 80 °C, the cw threshold currents remained low, 23 mA, quantum efficiency stayed high, 0.22 mW/mA, and output power of ∼10 mW was achieved. cw power output as high as 125 mW was achieved with 750 μm long lasers having AR–HR (∼5%–85%) coatings. Lasers with bulk active were also studied for comparison. Though they also have excellent device performance, in general, they are somewhat inferior to MQW lasers.
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42.55.Px Semiconductor lasers; laser diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

1.55 μm high‐power large optical cavity lasers

J. C. Zhong, B. R. Zhu, R. H. Li, Y. J. Zhao, and R. Pillai

Appl. Phys. Lett. 59, 3087 (1991); http://dx.doi.org/10.1063/1.105797 (3 pages) | Cited 1 time

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A high‐power 1.55 μm large optical cavity (LOC) laser structure is successfully prepared for the first time by reasonably designing its configuration and by using a proper single step liquid phase epitaxy (LPE) so as to realize lasers with peak output power higher than 2 W per facet in pulsed operation at room temperature. The devices are also characterized by their lower threshold current ( Jth≤2.7 KA/cm2 for broad area contact structure) and high‐temperature stability (T0≊130 K). At the same time they are of long‐lived operation and are an ideal source of light in this spectral region.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Energy relaxation and dephasing dynamics of colored filter glasses

H. Nakano, Y. Ishida, and T. Yanagawa

Appl. Phys. Lett. 59, 3090 (1991); http://dx.doi.org/10.1063/1.105798 (3 pages) | Cited 6 times

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The energy relaxation and the dephasing time constants of colored filter glass are measured as functions of temperature and the wavelength of the incident light by degenerate four‐wave mixing. To investigate the influence of the photodarkening effect on the relaxation time constants, fresh and photodarkened samples are measured. The two samples have almost the same dephasing time constants but their energy relaxation time constants are quite different.
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42.70.Ce Glasses, quartz
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.47.-p Spectroscopy of solid state dynamics

New integrated acousto‐optic matrix algebra processor architecture

A. Kar‐Roy and C. S. Tsai

Appl. Phys. Lett. 59, 3093 (1991); http://dx.doi.org/10.1063/1.105799 (3 pages) | Cited 1 time

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A new integrated optic matrix algebra processor architecture that utilizes guided‐wave multifrequency acoustooptic (AO) Bragg diffractions is proposed. The architecture is potentially capable of performing matrix‐vector multiplications faster than any AO architecture reported heretofore, and matrix‐matrix multiplications at rates comparable to the fastest bulk‐wave AO architecture. An integrated AO processor module has been realilzed in a Y‐cut LiNbO3 substrate 1.0×10.0×28.0 mm3 in size to demonstrate the multiplication of a 4×4 matrix with a 4‐element vector at the optical wavelength of 0.6328 μm.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.82.-m Integrated optics
85.30.-z Semiconductor devices

Holographic Bessel beam amplification

Hee S. Lee, B. W. Stewart, D. Will, and Henry Fenichel

Appl. Phys. Lett. 59, 3096 (1991); http://dx.doi.org/10.1063/1.105800 (3 pages) | Cited 1 time

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The generation of a diffraction‐free Bessel beam from a beam that is originally Gaussian is accompanied by substantial power loss. We employed the technique of holographic intensity amplification to enhance the conversion from a Gaussian beam to a Bessel beam with conversion efficiency approaching 50%. In addition the maximum propagation distance was extended.
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42.40.My Applications
42.72.-g Optical sources and standards

Optically addressed asymmetric Fabry–Perot modulator

A. Larsson and J. Maserjian

Appl. Phys. Lett. 59, 3099 (1991); http://dx.doi.org/10.1063/1.105805 (3 pages) | Cited 13 times

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A low power, high contrast optically addressed modulator, operating with normal incidence, has been fabricated. Optically controlled reflection modulation is achieved through optically induced absorption modulation in a periodically δ‐doped InGaAs/GaAs multiple quantum well structure inserted in an integrated asymmetric Fabry–Perot resonator. A contrast ratio≳60:1 was measured using a spectrally matched low power InGaAs/GaAs quantum well laser to generate the write (control) signal. The insertion loss for the normally off modulator is 4.6 dB at the highest write signal power (30 mW) used. The device lends itself to the fabrication of arrays for optically addressed spatial light modulation.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
07.60.-j Optical instruments and equipment
42.79.-e Optical elements, devices, and systems
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Perturbation of the cathode fall in direct‐current glow discharges by particulate contamination

Seung J. Choi, Michael J. McCaughey, Timothy J. Sommerer, and Mark J. Kushner

Appl. Phys. Lett. 59, 3102 (1991); http://dx.doi.org/10.1063/1.105777 (3 pages) | Cited 6 times

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Particulate (or ‘‘dust’’) contamination of plasma materials processing discharges is known to reduce yields of the product and to perturb electron transport. Dust preferentially accumulates near the cathode sheath‐plasma boundary where energetic electrons accelerated in the cathode fall emanate into the negative glow. In this letter, we theoretically investigate the penetration of the electron flux generated in dc cathode falls through the particulate ‘‘barriers’’ formed by dust contamination. We find that at constant current densities, the plasma responds to the reduction in ionization rate coefficients caused by the particulates by increasing the electric field in the cathode fall. In doing so, the cathode fall voltage increases and cathode fall thickness decreases.
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52.80.Hc Glow; corona
52.25.Fi Transport properties
52.65.-y Plasma simulation

Formation of monolithic masks for 0.25 μm x‐ray lithography

G. K. Celler, L. E. Trimble, J. Frackoviak, C. W. Jurgensen, R. R. Kola, A. E. Novembre, and G. R. Weber

Appl. Phys. Lett. 59, 3105 (1991); http://dx.doi.org/10.1063/1.105778 (3 pages) | Cited 4 times

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We have constructed monolithic masks for proximity x‐ray lithography by forming 1 μm thick polycrystalline Si membranes directly on glass support frames. Finished masks are 78 mm in diameter and ∼5 mm thick, with the Si membrane spanning 27 mm. The monolithic design provides simple processing and unprecedented flatness of 30 nm across the membrane and <500 nm across the entire disk. Mask blanks were metallized with 500 nm of W that was sputter deposited under conditions that hold the film stress <50 MPa. Tungsten was patterned by reactive ion etching to form features as small as 0.25 μm.
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85.40.Hp Lithography, masks and pattern transfer
68.60.-p Physical properties of thin films, nonelectronic
78.66.-w Optical properties of specific thin films

Electron microscopy study of C60

J. Q. Li, Z. X. Zhao, D. B. Zhu, Z. Z. Gan, and D. L. Yin

Appl. Phys. Lett. 59, 3108 (1991); http://dx.doi.org/10.1063/1.105779 (2 pages) | Cited 13 times

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The microstructural features of the powder C60 material have been studied by using scanning microscopy, electron diffraction, and high resolution electron microscopy. Scanning electron microscopy observation reveals that the grains in the samples are packed by extensively disordered crystallites as well as amorphous granules. Electron diffraction measurements have identified that the crystals of C60 have two kinds of structure, one is face‐centered‐cubic (fcc) with unit cell parameter a=1.41 nm, and the other has the hexagonal closest packed (hcp) structure with cell parameters a=0.958 nm and c=1.63 nm. High resolution electron microscopy as well as electron diffraction observations clearly show the random crystallites packing in the C60 grains.
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61.05.J- Electron diffraction and scattering
61.66.Fn Inorganic compounds

Structural investigation of aromatic polyimide films modified by ion beams: A comparative study

Dong Xu, Xinglong Xu, and Shichang Zou

Appl. Phys. Lett. 59, 3110 (1991); http://dx.doi.org/10.1063/1.105780 (3 pages) | Cited 6 times

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X‐ray photoelectron (XPS) and Raman spectroscopy were employed in the structural investigation of the modified polyimide films irradiated with boron ion beams. XPS discloses the formation of graphite bonding especially when irradiation comes up to a dose around 3×1016 B+/cm2. Raman spectroscopy, together with the calculation of its reduced spectra as well as the one‐phonon state density of amorphous graphite, is inclined to demonstrate a structural similarity between modified polyimide films and amorphous graphite in short range order. The degree of this similarity depends on the irradiation condition. From this view point, the effects of dose and beam current density upon the final microstructures of the irradiated polyimide films were also investigated.
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61.80.Jh Ion radiation effects
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Dynamic thermal expansion under transient laser‐pulse heating

D. W. Tang, B. L. Zhou, H. Cao, and G. H. He

Appl. Phys. Lett. 59, 3113 (1991); http://dx.doi.org/10.1063/1.105755 (2 pages) | Cited 8 times

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An infrared radiation pyrometer for transient temperature measurement and a photoelectric installation for micrometric length‐change measurement were developed. After being heated by a CO2 laser pulse of 0.1 μs, the transient temperature‐rise history and length change of thermal expansion of 20–50 μm Al films during tens of microseconds were recorded. Nonsynchronous change of temperature and thermal expansion under transient heating was observed.
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65.40.De Thermal expansion; thermomechanical effects
63.20.Ry Anharmonic lattice modes
62.50.-p High-pressure effects in solids and liquids

Molecular beam epitaxial growth and characterization of CoAl on AlAs/GaAs

M. Tanaka, H. Sakakibara, and T. Nishinaga

Appl. Phys. Lett. 59, 3115 (1991); http://dx.doi.org/10.1063/1.105756 (3 pages) | Cited 4 times

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We study molecular beam epitaxial growth and structural properties of intermetallic compound CoAl on AlAs/GaAs III‐V semiconductors. CoAl has a CsCl structure whose lattice constant is nearly half the lattice constant of GaAs and AlAs, hence, it is a good candidate for the constituent material in epitaxial metal/semiconductor heterostructures. We investigate the dependence of crystallinity of Co1−xAlx epitaxial layers on Al composition x and on growth temperature Ts, by in situ reflection high‐energy electron diffraction and ex situ x‐ray measurements. It is found that the single‐crystalline CoAl with high quality can be obtained at x=0.5 and Ts=350 °C. Under appropriate growth procedures and conditions, the epitaxial growth orientation is (001)[110]CoAl on (001)[110]AlAs/GaAs.  
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Nature of the mechanism of interface state creation on electrically stressed metal‐oxide‐semiconductors structures

Dominique Vuillaume

Appl. Phys. Lett. 59, 3118 (1991); http://dx.doi.org/10.1063/1.105757 (3 pages) | Cited 6 times

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The defects generated at the Si‐SiO2 interface by electron injection across the oxide under high electric‐field stress conditions are studied as a function of the stressing temperature in the range 100–450 K. After stress at temperatures below 300 K, the interface state creation during isochronal annealing at room temperature is analyzed. The defect formation is readily explained by the diffusion of neutral hydrogen‐related species and a simple model allows the determination of its diffusion coefficients to be in the range of 1.0×10−14–4.2×10−14 cm2 s−1 at 200 K to 1.6–6.6×10−12 cm2 s−1 at 275 K. These values are in good agreement with the extrapolated values from the known data for the hydrogen diffusion in SiO2 determined at higher temperatures.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.20.Hb Impurity and defect levels; energy states of adsorbed species
66.30.Lw Diffusion of other defects

Thermal stability of Schottky barriers at Au and Ag/InP(110) interfaces with Sb interlayers

Masao Yamada, Albert M. Green, Alberto Herrera‐Gomez, Tom Kendelewicz, and William E. Spicer

Appl. Phys. Lett. 59, 3121 (1991); http://dx.doi.org/10.1063/1.105758 (3 pages) | Cited 4 times

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Schottky barriers at Au and Ag/InP(110) interfaces with Sb interlayers show an unusually low Fermi level pinning position of about 0.52 eV above the valence‐band maximum (VBM) at room temperature using photoemission spectroscopy. Thermal stability of these interfaces have been first studied. Strong clustering is observed by annealing these interfaces, suggesting less reaction between overlayers and substrates. Change in Fermi level positions due to annealing is <0.1 eV up to 300 °C at these interfaces including measurement errors. However, segregation of In atoms into the Ag overlayer is observed above 300 °C for 10 min at Ag/Sb/InP interfaces, and a small pinned component with a level 0.9 eV above the VBM appears above 200 °C for 10 min at Au/Sb/InP interfaces. These Schottky barriers are stable up to at least 200 °C.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Hot hole effects in single barrier p‐type GaAs/(AlGa)As/GaAs tunnel structures

M. Alikacem, D. K. Maude, L. Eaves, M. Henini, G. Hill, and M. A. Pate

Appl. Phys. Lett. 59, 3124 (1991); http://dx.doi.org/10.1063/1.105759 (3 pages) | Cited 3 times

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Oscillatory structure in the low‐temperature current‐voltage characteristics of Be‐doped p‐type GaAs/(AlGa)As/GaAs single barrier tunneling devices is observed. The oscillations have period ΔV=39 mV, close to ℏωL/e, where ℏωL is the longitudinal optic (LO) phonon energy in GaAs. They result from energy relaxation of hot holes injected through the tunnel barrier. The oscillatory amplitude varies as exp(Ea/2kT), where Ea is the ionization energy of the Be acceptors.
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72.80.Ey III-V and II-VI semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling

Effect of doping on electron traps in metalorganic molecular‐beam epitaxial GaxIn1−xP/GaAs heterostructures

E. C. Paloura, A. Ginoudi, G. Kiriakidis, and A. Christou

Appl. Phys. Lett. 59, 3127 (1991); http://dx.doi.org/10.1063/1.105760 (3 pages) | Cited 23 times

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The formation of trap centers in GaxIn1−xP/GaAs epitaxial layers grown by metal‐organic molecular‐beam epitaxy (MOMBE) is investigated by deep‐level transient spectroscopy (DLTS). The undoped epitaxial layers are characterized by a deep electron trap with an activation energy that depends on the Ga mole fraction and takes values in the range 820 to 875 meV. This trap center is suppressed by S and Si doping, and a new trap at 300–345 meV appears in the doped samples with a capture cross section of 1×10−13–2×10−15 cm2, while the trap concentration increases with the dopant concentration. Persistent photoconductivity (PPC), which is present in all samples investigated, appears to be suppressed only by Si doping.
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71.55.Eq III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors

Study of the microstructure of low energy (70 keV) oxygen implanted silicon

Y. Li, J. A. Kilner, P. L. F. Hemment, A. K. Robinson, J. P. Zhang, K. J. Reeson, C. D. Marsh, and G. R. Booker

Appl. Phys. Lett. 59, 3130 (1991); http://dx.doi.org/10.1063/1.105761 (3 pages) | Cited 6 times

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Device grade (100) single crystal silicon wafers have been implanted with 70 keV oxygen ions over a dose range from 3.3×1017 /cm2 to 10×1017/cm2 at a temperature of 680 °C. The wafers were subsequently annealed at 1320 °C for 6 h. Transmission electron microscopy and ion channeling studies show that both the as‐implanted microstructure and the damage distribution play an important role in determining the final microstructure of the annealed wafer. As the dose increases so does both the values of χmin for both as‐implanted and annealed wafers, and the threading dislocation density in the silicon overlayer of the annealed wafers. For the wafer implanted with 70 keV oxygen ions at the lowest dose (3.3×1017/cm2), the threading dislocation density in the silicon overlayer after annealing was less than 105/cm2.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Accurate measurement of the vacancy equilibrium concentration in silicon

H. Zimmermann

Appl. Phys. Lett. 59, 3133 (1991); http://dx.doi.org/10.1063/1.105762 (3 pages) | Cited 6 times

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A procedure is described which allows the measurement of the equilibrium concentration of vacancies in silicon at 800 °C. During a long lasting temperature treatment under inert and very clean conditions, the equilibrium concentration of the vacancies is established. According to the dominance of the Frank–Turnbull mechanism during platinum diffusion at 800 °C, the equilibrium concentration of vacancies C∗V can then be determined from platinum diffusion profiles. A value of 4.1×1013 cm−3 at 800 °C for C∗V is calculated using an analytical expression, which can be deduced from the equations of the Frank–Turnbull mechanism. For the vacancy diffusion coefficient in silicon, the result is 1.3×10−10 cm2 s−1. Numerical simulations show the self‐consistency of the vacancy parameters.
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61.72.jd Vacancies
61.72.jj Interstitials
66.30.J- Diffusion of impurities
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

New insights on the effect of hydrogen to tungsten hexafluoride partial pressure ratio on plasma deposited tungsten thin films

Yong Tae Kim, Jong Sung Hong, and Suk‐Ki Min

Appl. Phys. Lett. 59, 3136 (1991); http://dx.doi.org/10.1063/1.105763 (3 pages) | Cited 4 times

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Resistivities of tungsten thin films deposited by plasma enhanced chemical vapor deposition are very sensitive to the H2/WF6 partial pressure ratio, while the resistivities of tungsten films deposited by low pressure chemical vapor deposition are insensitive to the H2/WF6 ratio. The reason is investigated with x‐ray diffraction, transmission electron microscopy, Auger electron spectroscopy and optical emission spectroscopy. As a result, when the H2/WF6 partial pressure ratio is higher than 15, plasma deposited tungsten has a low resistive (11 μΩ cm) bcc structure without F impurities. However, if the H2/WF6 ratios are decreased, porous and β‐phase W films are formed due to the incomplete reduction of F concentrations.
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85.40.Ls Metallization, contacts, interconnects; device isolation
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.At Metal and metallic alloys
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Laser‐compatible InGaAs/GaAs strained layer waveguide electroabsorption modulators

D. Moss, R. L. Williams, M. Dion, and D. Landheer

Appl. Phys. Lett. 59, 3139 (1991); http://dx.doi.org/10.1063/1.105764 (3 pages) | Cited 3 times

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We report single and double quantum well electroabsorption waveguide modulators that achieve exceptional performance as both lasers and modulators. Contrast ratios of 19 and 26 dB for a 400 μm long device have been achieved for the single and double well samples, respectively. When operated as lasers, the devices exhibit broad area threshold current densities of 56 A/cm2 and 87 A/cm2 for the single and double well samples, for cavity lengths longer than 3 mm. In addition, measurements of lasing wavelength versus cavity length show that both devices can operate as lasers at wavelengths compatible with their respective modulator performance.
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42.55.Px Semiconductor lasers; laser diodes
42.79.Hp Optical processors, correlators, and modulators

Effect of structural disorder on electronic states in GaAs/AlGaAs quantum wires

Jasprit Singh

Appl. Phys. Lett. 59, 3142 (1991); http://dx.doi.org/10.1063/1.105765 (3 pages) | Cited 13 times

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Perfect quantum wire structures are attractive candidates for low threshold lasers and high speed electronic devices because of the nature of the density of states and eigenfunctions. In this letter, we discuss the effect of structural disorder on the density of states as well as on the localization length of these eigenstates. We find that significant changes in the density of states and eigenfunctions occur with a small random disorder along the wire axis. Consequences for devices based on quantum wires are discussed.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Comparative analysis of growth rate reductions on shadow masked substrates

K. De Vlamynck, G. Coudenys, and P. Demeester

Appl. Phys. Lett. 59, 3145 (1991); http://dx.doi.org/10.1063/1.105766 (3 pages) | Cited 2 times

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The growth on shadow masked substrates by atmospheric pressure metalorganic vapor phase epitaxy is investigated. An analytical description based on simple concepts for a complex geometry shows good agreement with the experimental results and enables the determination of quantum well thickness variations in optical waveguide structures. The growth rate reduction (or: ratio of growth rates) r(u) in the middle of the channel increases as the width‐to‐height ratio of the mask opening is increased.
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42.82.-m Integrated optics
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.79.Gn Optical waveguides and couplers
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