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21 Sep 1998

Volume 73, Issue 12, pp. 1607-1747

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High-frequency beam steering induced by switching of high-order transverse modes in vertical cavity surface emitting lasers

A. Valle

Appl. Phys. Lett. 73, 1607 (1998); http://dx.doi.org/10.1063/1.122221 (3 pages) | Cited 3 times

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Selection over a wide current range of high-order transverse modes in vertical cavity surface emitting lasers is achieved by using appropriate current profiling. High-frequency beam steering in the azimuthal direction is then obtained by alternate current modulation of two orthogonal high-order transverse modes. Alternate modulation of these modes can double the pulse repetition frequency obtained by modulating just one high-order transverse mode, without increasing injected current density levels. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

Optical parametric oscillation out to 6.3 μm in periodically poled lithium niobate under strong idler absorption

L. Lefort, K. Puech, G. W. Ross, Y. P. Svirko, and D. C. Hanna

Appl. Phys. Lett. 73, 1610 (1998); http://dx.doi.org/10.1063/1.122222 (3 pages) | Cited 20 times

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The very high gains, achieved when using mode-locked pulses to synchronously pump an optical parametric oscillator based on periodically poled lithium niobate, permit oscillation even with strong idler absorption. Oscillation has been achieved at idler wavelengths out to 6.3 μm. Idler power was directly measured, out to 5.41 μm. Beyond this, idler generation was inferred from the observed signal. We present an analysis of operation in the presence of strong idler absorption. © 1998 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization

Comparison study of photoluminescence from InGaN/GaN multiple quantum wells and InGaN epitaxial layers under large hydrostatic pressure

W. Shan, P. Perlin, J. W. Ager, W. Walukiewicz, E. E. Haller, M. D. McCluskey, N. M. Johnson, and D. P. Bour

Appl. Phys. Lett. 73, 1613 (1998); http://dx.doi.org/10.1063/1.122266 (3 pages) | Cited 5 times

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We report the results of a comparison study of photoluminescence (PL) from an In0.15Ga0.85N/GaN multiple-quantum-well (MQW) sample and an In0.11Ga0.89N thick epitaxial-layer sample, which have very similar band-gap energies. Large hydrostatic pressures were used for our investigations. The PL emissions in both samples were found to shift linearly to higher energy with applied pressure. In the MQW sample, the pressure response of the InGaN is dominated by the GaN layers, which leads to a significantly weaker pressure dependence as compared to the epilayer sample. Our results yield a pressure coefficient of 2.8×10−3 eV/kbar for the In0.15Ga0.85N/GaN MQW sample and 4.0×10−3 eV/kbar for the In0.11Ga0.89N epilayer. An abrupt decrease of PL intensity in both samples was observed at pressures above 100 kbar, indicating the carriers involved in the radiative recombination processes in the samples originate primarily from the adjacent GaN layers. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
78.55.Cr III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

An electro-optic device based on field-controlled anchoring of a nematic liquid crystal

P. Jägemalm, L. Komitov, and G. Barbero

Appl. Phys. Lett. 73, 1616 (1998); http://dx.doi.org/10.1063/1.122223 (3 pages) | Cited 9 times

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A surface-controlled electro-optic device using a nematic liquid crystal enclosed between two thin spaced glass plates is presented. Modulation angles of the optic axis up to more than 70° can be achieved even for small applied voltages. The switching of the optic axis occurs with a large component in the plane of the sample even though the electric field is applied normal to the sample surfaces. The effect seems to be driven by the dielectric coupling of the liquid crystal molecules with the applied electric field. The field induced switching process is governed by the bounding surfaces that have been covered with obliquely evaporated SiOx. The mechanism of the phenomenon is briefly discussed. © 1998 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
42.70.Df Liquid crystals

Near-field scanning optical microscopy studies of V-grooved quantum wire lasers

U. Ben-Ami, R. Nagar, N. Ben-Ami, J. Scheuer, M. Orenstein, G. Eisenstein, A. Lewis, E. Kapon, F. Reinhardt, P. Ils, and A. Gustafsson

Appl. Phys. Lett. 73, 1619 (1998); http://dx.doi.org/10.1063/1.122224 (3 pages) | Cited 4 times

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Detailed near-field scanning optical microscopy studies of GaAs/AlGaAs V-grooved quantum wire lasers at room temperature were performed. We measured the spectrally resolved near-field intensity distributions, emitted from the complex epitaxially grown optical waveguide in the V groove with a spatial resolution of ∼0.1 μm. Distinct regions emitting at different wavelengths were identified, and a heart shaped modal distribution of less than 0.5 μm in diameter was measured and well matched the calculated light distribution of this structure. © 1998 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.)

Optical activation of Be implanted into GaN

C. Ronning, E. P. Carlson, D. B. Thomson, and R. F. Davis

Appl. Phys. Lett. 73, 1622 (1998); http://dx.doi.org/10.1063/1.122225 (3 pages) | Cited 29 times

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Single crystalline (0001) gallium nitride layers were implanted with beryllium. Photoluminescence (PL) measurements were subsequently performed as a function of implantation dose and annealing temperature. One new line in the PL spectra at 3.35 eV provided strong evidence for the presence of optically active Be acceptors and has been assigned to band–acceptor (eA) recombinations. The determined ionization energy of 150±10 meV confirmed that isolated Be has the most shallow acceptor level in GaN. Co-implantation of nitrogen did not enhance the activation of the Be acceptors. © 1998 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Luminescence quenching in Er-doped BaTiO3 thin films

G.-C. Yi, B. A. Block, G. M. Ford, and B. W. Wessels

Appl. Phys. Lett. 73, 1625 (1998); http://dx.doi.org/10.1063/1.122226 (3 pages) | Cited 12 times

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Luminescence quenching in Er-doped epitaxial BaTiO3 thin films was investigated. From transient photoluminescence, nonradiative decay processes were measured, and a nonradiative resonant energy transfer model was developed. The nonradiative transition rate is linearly proportional to the OH impurity concentration in the films, indicating it is responsible for the observed quenching behavior. © 1998 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Highly sensitive photopolymerizable dry film for use in real time holography

S. Blaya, R. Mallavia, L. Carretero, A. Fimia, and R. F. Madrigal

Appl. Phys. Lett. 73, 1628 (1998); http://dx.doi.org/10.1063/1.122227 (3 pages) | Cited 13 times

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A photopolymerizable holographic material has been obtained and characterized using agent N,N′-dihydroxiethylenbisacrylamide as crosslinking. A sensitivity of 5 mJ/cm2 and a diffraction efficiency around of 70% have been reached for holograms recorded at 633 nm with a spatial frequency of 1000 lines/mm. High sensitivities can be obtained with low intensities, and this is important in applications such as holographic interferometry and the fabrication of holographic optical elements. © 1998 American Institute of Physics.
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42.70.Jk Polymers and organics
42.70.Ln Holographic recording materials; optical storage media
42.40.Kw Holographic interferometry; other holographic techniques
82.35.-x Polymers: properties; reactions; polymerization
82.50.-m Photochemistry
42.40.Eq Holographic optical elements; holographic gratings
42.79.Wc Optical coatings

Anisotropic apertures for polarization-stable laterally oxidized vertical-cavity lasers

C. L. Chua, R. L. Thornton, D. W. Treat, and R. M. Donaldson

Appl. Phys. Lett. 73, 1631 (1998); http://dx.doi.org/10.1063/1.122228 (3 pages) | Cited 9 times

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We disclose a method of eliminating the polarization instability in laterally oxidized vertical-cavity surface-emitting lasers. By employing an appropriately shaped device aperture, we are able to make the lasers operate in a single polarization direction through their entire L–I curve. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
85.40.Hp Lithography, masks and pattern transfer

Formation of V-shaped pits in InGaN/GaN multiquantum wells and bulk InGaN films

Ig-Hyeon Kim, Hyeong-Soo Park, Yong-Jo Park, and Taeil Kim

Appl. Phys. Lett. 73, 1634 (1998); http://dx.doi.org/10.1063/1.122229 (3 pages) | Cited 64 times

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InGaN/GaN multiquantum well structures and bulk InGaN films grown on (0001) sapphire substrate were investigated by cross-sectional transmission electron microscopy and double crystal x-ray diffraction. Highly strained InGaN layers with a high In mole fraction were found to contain V-shaped surface pits with (10–11) facet planes on pure or mixed screw treading dislocations. Phase separation was also found on thick InGaN/GaN superlattices and bulk InGaN layers. The mechanism of the surface pit formation was discussed in terms of strain energy and surface mobility of InGaN. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.-a Thin film structure and morphology
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.60.Wm Other nonelectronic physical properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Time resolved photoluminescence investigations of polyacetylene derivatives

Hui Wang and Kam Sam Wong

Appl. Phys. Lett. 73, 1637 (1998); http://dx.doi.org/10.1063/1.122230 (3 pages) | Cited 4 times

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Time resolved photoluminescence dynamics of poly(phenylacetylene)(PPA) and poly(1-phenyl-1-butyl)(PPB) were investigated by using femtosecond luminescence upconversion spectroscopy technique. An ultrafast initial luminescence decay (∼5 ps) was observed for PPA, but it was absent for PPB. The transient luminescence spectrum of PPA exhibits a much larger red-shift (∼140 meV) than that of PPB (∼60 meV). PPB shows a much higher luminescence efficiency than that of PPA. The influence of the substitution on the photoluminescence behaviors of PPA and PPB is discussed. © 1998 American Institute of Physics.
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42.70.Jk Polymers and organics
78.55.Kz Solid organic materials
78.47.-p Spectroscopy of solid state dynamics
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Excitation of higher harmonics in transient laser gratings by an ablative mechanism

Y.-C. Shen, A. Lomonosov, A. Frass, and P. Hess

Appl. Phys. Lett. 73, 1640 (1998); http://dx.doi.org/10.1063/1.122231 (3 pages) | Cited 2 times

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Laser-induced transient gratings were excited at the surface of an aluminum film by picosecond laser pulses. The counterpropagating surface acoustic waves with a fundamental frequency of 70 MHz that were launched were monitored outside the source region by laser probe beam deflection. The second and third harmonics were observed for ablative interaction of the laser radiation with the aluminum surface. A simple model is presented that describes the effects on the basis of nonlinear photoacoustic signal generation at the source due to a nonsinusoidal driving force. © 1998 American Institute of Physics.
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43.25.Fe Effect of nonlinearity on acoustic surface waves
42.79.Dj Gratings
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.35.Pt Surface waves in solids and liquids
68.35.Gy Mechanical properties; surface strains
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Control of antenna coupling in high-density plasma production by m = 0 helicon waves

Y. Sakawa, T. Takino, and T. Shoji

Appl. Phys. Lett. 73, 1643 (1998); http://dx.doi.org/10.1063/1.122232 (3 pages) | Cited 9 times

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Antenna coupling has been controlled in high-density plasma production by m = 0 helicon waves using multiple-loop antennas and varying the phase and the distance between antennas. When two single-loop antennas are connected in series with the phase between the two being zero, threshold power for the density jump Pth is reduced by a factor of 2–3 compared with that of the one-turn loop antenna. This reduction in Pth is caused by the increase in antenna coupling at the lower plasma density. The observed differences in antenna coupling among different antennas have been examined by using a two-dimensional wave code. © 1998 American Institute of Physics.
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52.50.Dg Plasma sources
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.25.Kn Thermodynamics of plasmas
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Temperature dependence of the growth rate for nanocrystalline diamond films deposited from an Ar/CH4 microwave plasma

Thomas G. McCauley, Dieter M. Gruen, and Alan R. Krauss

Appl. Phys. Lett. 73, 1646 (1998); http://dx.doi.org/10.1063/1.122233 (3 pages) | Cited 61 times

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We have investigated the effect of substrate temperature on the growth rate and properties of nanocrystalline diamond thin films prepared by microwave plasma-assisted chemical vapor deposition on (100) Si from a 1% methane (CH4) precursor in argon (Ar). In previous work we have shown that the carbon dimer C2 is the dominant growth species for this CH4/Ar system without the addition of molecular hydrogen. In the present work, the apparent activation energy for this growth process from C2 was determined from a standard Arrhenius-type analysis of the growth rate data for substrate temperatures between 500 and 900 °C. The measured value of 5.85±0.438 kcal/mol (0.254±0.019 eV/atom) is shown to be in close agreement with the results of recent modeling studies of the energetics of C2 addition to the diamond (110)–(1×1):H surface. These results have important implications for low-temperature diamond coating of nonrefractory materials such as glasses. © 1998 American Institute of Physics.
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81.05.ub Fullerenes and related materials
81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.07.-b Nanoscale materials and structures: fabrication and characterization
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
61.46.-w Structure of nanoscale materials

Dielectric anomaly in strontium bismuth tantalate thin films

Koichi Takemura, Takehiro Noguchi, Takashi Hase, and Yoichi Miyasaka

Appl. Phys. Lett. 73, 1649 (1998); http://dx.doi.org/10.1063/1.122234 (3 pages) | Cited 15 times

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The authors have succeeded in observing the dielectric anomaly in ferroelectric strontium bismuth tantalate (SBT) thin films, and studied how it varies with film composition. For a stoichiometric SBT film, the dielectric anomaly was diffused, and the Curie temperature (Tc) was approximately 260 °C, which is lower than that for the bulk ceramic. A SBT film with excess Bi composition showed Tc of approximately 300 °C, and Tc for Sr deficient SBT films was higher than 340 °C. The composition dependence of remanent polarization and coercive field near room temperature for the SBT films reflects the composition dependence of the Tc values. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films

Composition and crystal structure of carbon nitride films prepared by the electron cyclotron resonance plasma sputtering method

Youji Tani, Yoshifumi Aoi, and Eiji Kamijo

Appl. Phys. Lett. 73, 1652 (1998); http://dx.doi.org/10.1063/1.122235 (3 pages) | Cited 24 times

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Carbon nitride films were prepared on a Si(100) substrate by an electron cyclotron resonance plasma sputtering method using a carbon target and a nitrogen atmosphere. The maximum value of the N/C ratio in the film deposited at a substrate bias potential of about −55 V and ambient temperature was 1.35, which is close to the stoichiometric composition of C3N4. The surface morphology observed with scanning electron microscopy of the film deposited at 600 °C showed a crystalline structure with a 500 nm average grain diameter. The x-ray diffraction pattern of the film deposited at 600 °C and a substrate bias potential of −50 V indicates no amorphous phase in the film, which is composed of β- and α-C3N4 phases containing an unidentified C–N phase. © 1998 American Institute of Physics.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
68.35.B- Structure of clean surfaces (and surface reconstruction)

Real-time x-ray diffraction to examine elastic–plastic deformation in shocked lithium fluoride crystals

P. A. Rigg and Y. M. Gupta

Appl. Phys. Lett. 73, 1655 (1998); http://dx.doi.org/10.1063/1.122236 (3 pages) | Cited 33 times

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An experimental method was developed to obtain quantitative, x-ray diffraction data in laboratory plate impact experiments. This method was used to examine lattice compression accompanying elastic and elastic–plastic deformation in shocked LiF single crystals by imposing well-characterized, macroscopic uniaxial strain along the [111] and [100] axes, respectively. The [111] results reveal that the unit cell undergoes a one-dimensional compression; in contrast, the [100] results reveal an isotropic compression of the unit cell. The implications of the present results and the ability to make quantitative measurements are discussed. © 1998 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
61.05.cp X-ray diffraction
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
81.40.Jj Elasticity and anelasticity, stress-strain relations

Rapid imaging of calcite crystal growth using atomic force microscopy with small cantilevers

George T. Paloczi, Bettye L. Smith, Paul K. Hansma, Deron A. Walters, and Mark A. Wendman

Appl. Phys. Lett. 73, 1658 (1998); http://dx.doi.org/10.1063/1.122237 (3 pages) | Cited 28 times

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Using a 26 μm cantilever with a resonant frequency of 100 kHz in water, we were able to obtain sequential images of calcite crystal steps growing from a screw dislocation. The small cantilever permitted acquisition of 250 nm images at scan rates of 104 lines/s (1.2 s/image). From this sequence we directly measured critical step lengths (the length of the shortest step that can advance) of 6–21 nm. These values provided a rough estimate of (0.25±0.13 J/m2) for the step energy per unit length per unit step height on the (104) face of calcite. © 1998 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
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Self-defined AlAs-oxide–current-aperture buried heterostructure vertical cavity surface-emitting laser

Won-Jin Choi and P. Daniel Dapkus

Appl. Phys. Lett. 73, 1661 (1998); http://dx.doi.org/10.1063/1.122238 (3 pages) | Cited 2 times

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We demonstrate a promising technique to fabricate self-defined AlAs-oxide–current-apertures for vertical cavity surface-emitting lasers (VCSELs). A self-defined AlAs-oxide–current-aperture buried heterostructure VCSEL was fabricated using a three-step growth sequence. The active region mesa size was 10 μm×10 μm. The lowest threshold current of the lasers was 0.7 mA under continuous-wave operation at room temperature. The differential quantum efficiency was 32%. The lasers operate at temperatures of up to 50 °C. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems

A normal incidence p-type strain layer quantum well infrared photodetector with 19.2 μm peak detection wavelength

J. Chu, Sheng S. Li, A. Singh, and P. Ho

Appl. Phys. Lett. 73, 1664 (1998); http://dx.doi.org/10.1063/1.122267 (3 pages)

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A normal incidence p-type compressively strained layer superlattice (SL) In0.27Ga0.73As/Al0.15Ga0.85As quantum well infrared photodetector with a spectral response peak at 19.2 μm and a cutoff wavelength λc>20 μm under moderate background illumination have been demonstrated in this work. A responsivity of 50 mA/W and a gain-quantum efficiency product (ηg) of 0.32% at Vb = 20 mV and T = 40 K were obtained for this device. The device layer structure consists of four InGaAs/AlGaAs SL-absorber layers sandwiched by wide GaAs barrier layers. Results of the responsivity, dark current, noise, background photocurrent measurements, and analysis of the device performance are discussed. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
72.40.+w Photoconduction and photovoltaic effects
85.30.De Semiconductor-device characterization, design, and modeling
81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Theory of linear electro-optic effect near the E1 and the E1+Δ1 energies

Y. H. Chen and Z. Yang

Appl. Phys. Lett. 73, 1667 (1998); http://dx.doi.org/10.1063/1.122239 (3 pages) | Cited 6 times

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A theoretical k∗p model for the linear electro-optic (LEO) spectrum near the E1/E1+Δ1 energies is presented. The calculated spectrum reproduces the important features of the experimental ones. In particular, it explains the observed energy shifts of the resonance near the E1/E1+Δ1 energies, and the predicted LEO coefficient agrees well with the experimental one. The predicted linewidth, on the other hand, is about twice that of the observed one. The LEO strength is found to be dominated by the excitons. This is qualitatively consistent with the observed large change of LEO strength with temperature. © 1998 American Institute of Physics.
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78.20.Jq Electro-optical effects
71.35.-y Excitons and related phenomena

Microstructural evidence on direct contact of Au/Ge/Ni/Au ohmic metals to InGaAs channel in pseudomorphic high electron mobility transistor with undoped cap layer

Jong-Lam Lee, Yi-Tae Kim, and Jeong Yong Lee

Appl. Phys. Lett. 73, 1670 (1998); http://dx.doi.org/10.1063/1.122240 (3 pages) | Cited 4 times

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Microstructural evidence on direct contact of Au/Ge/Ni/Au ohmic metals to a InGaAs channel in AlGaAs/InGaAs pseudomorphic high electron mobility transistor with an undoped GaAs/AlGaAs cap layer was found using transmission electron microscopy, and the results were used to interpret the electrical properties of the contact. The lowest contact resistivity of 3.8×10−6 Ω cm2, obtained at 420 °C annealing, is due to the penetration of the interfacial compounds, Au2Ga and Au2Al, into the buried InGaAs channel. The direct contact of the compounds to the channel causes the reduction of series resistances between the ohmic compounds and the channel, resulting in the low contact resistivity. © 1998 American Institute of Physics.
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85.30.Tv Field effect devices
61.72.Cc Kinetics of defect formation and annealing
73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
68.35.Ct Interface structure and roughness

Microstructuring of silicon with femtosecond laser pulses

Tsing-Hua Her, Richard J. Finlay, Claudia Wu, Shrenik Deliwala, and Eric Mazur

Appl. Phys. Lett. 73, 1673 (1998); http://dx.doi.org/10.1063/1.122241 (3 pages) | Cited 177 times

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We report that silicon surfaces develop an array of sharp conical spikes when irradiated with 500 laser pulses of 100-fs duration, 10-kJ/m2 fluence in 500-Torr SF6 or Cl2. The spikes are up to 40-μm tall, and taper to about 1-μm diam at the tip. Irradiation of silicon surfaces in N2, Ne, or vacuum creates structured surfaces, but does not create sharp conical spikes. © 1998 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors

Fabrication of midgap metal gates compatible with ultrathin dielectrics

D. A. Buchanan, F. R. McFeely, and J. J. Yurkas

Appl. Phys. Lett. 73, 1676 (1998); http://dx.doi.org/10.1063/1.122242 (3 pages) | Cited 29 times

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A process has been described which can produce a midgap tungsten gate compatible with the current and future complementary metal–oxide–semiconductor technology. The tungsten was deposited directly onto a 3.0 nm SiO2 gate dielectric without measurable degradation of any of its electrical properties. The tungsten deposition process yields no reactive or corrosive by-products that affect the gate dielectric integrity. The tungsten film is found to be pure within the limits of several analytical techniques and the resistivity of the tungsten films was found to be within a factor of 2 of the bulk value. © 1998 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.30.Tv Field effect devices
84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Nanostructure of ordering variants in (AlxGa1−x)0.52In0.48P grown on different vicinal GaAs substrates

U. Dörr, H. Kalt, W. Send, D. Gerthsen, D. J. Mowbray, and C. C. Button

Appl. Phys. Lett. 73, 1679 (1998); http://dx.doi.org/10.1063/1.122243 (3 pages) | Cited 3 times

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We have investigated the nanostructure of ordered (Al0.5Ga0.5)0.52In0.48P using conventional and high-resolution transmission electron microscopy. As in the case of ternary Ga0.52In0.48P, the morphology of the ordered material depends strongly on the substrate orientation. For a substrate orientation with equal densities of [110] and [110] steps (and, hence, no preference for one particular ordering variant) a nanostructure is found which exhibits similarities to those observed in ternary Ga0.52In0.48P with equivalent substrate orientations. For a substrate orientation which preferentially selects one ordering variant without completely suppressing the formation of the other, we have identified a new type of nanostructure. In this structure, antiphase boundaries between domains containing the preferred variant are frequently formed by thin slices of the suppressed variant. This structural form is directly deduced from high-resolution images. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
81.05.Ea III-V semiconductors
61.46.-w Structure of nanoscale materials
61.72.Mm Grain and twin boundaries
81.07.-b Nanoscale materials and structures: fabrication and characterization
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