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29 Sep 1997

Volume 71, Issue 13, pp. 1747-1892

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Effects of electron–hole energy transfer on the nonlinear gain coefficients in the small-signal modulation response of semiconductor lasers

Chin-Yi Tsai, Fang-Ping Shih, Chih-Hsiung Chen, Tsu-Yin Wu, Tien-Li Sung, and Chin-Yao Tsai

Appl. Phys. Lett. 71, 1747 (1997); http://dx.doi.org/10.1063/1.119388 (3 pages) | Cited 1 time

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The effects of energy transfer between electrons and holes on the small-signal modulation response of semiconductor lasers are theoretically investigated. We calculate the electron energy relaxation time due to electron–hole scattering from the first principle. We show that its value is comparable to the electron energy relaxation time due to the electron–LO phonon scattering with the effect of nonequilibrium LO phonons. In such a case, the nonlinear gain coefficient due to carrier heating defined in the small-signal modulation response of semiconductor lasers is no longer a simple sum of the term due to electron heating and that due to hole heating. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
71.38.-k Polarons and electron-phonon interactions
72.10.Di Scattering by phonons, magnons, and other nonlocalized excitations

Low-loss hydrogenated buried waveguide coupler integrated with a four-wavelength distributive Bragg reflector laser array on InP

M. Allovon, A. Talneau, E. V. K. Rao, F. Huet, F. Alexandre, A. Ougazzaden, S. Slempkes, B. Theys, and J. Chevallier

Appl. Phys. Lett. 71, 1750 (1997); http://dx.doi.org/10.1063/1.119387 (3 pages) | Cited 6 times

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An approach is proposed to realize the integration of a 4>1 passive coupler with butt-jointed buried ridge structure distributive Bragg reflector lasers and transparent buried waveguides for Bragg section. The butt coupling facilitates an independent optimization of gain and Bragg sections and the proposed additional processing step, namely, localized hydrogenation of coupler regions, permits reducing dramatically the losses due to free holes in the p+-InP cladding layer. With a coupling efficiency of ∼90% and losses as low as ∼0.4 dB/mm, the integrated emitter with uncoated facets yielded output powers up to 0.4 mW for each wavelength at 100 mA. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Gn Optical waveguides and couplers
81.05.Ea III-V semiconductors
85.60.-q Optoelectronic devices

Halide-modified Ga–La sulfide glasses with improved fiber-drawing and optical properties for Pr3+-doped fiber amplifiers at 1.3 μm

Ji Wang, Jason R. Hector, Dominic Brady, Dan Hewak, Bill Brocklesby, Miles Kluth, Roger Moore, and David N. Payne

Appl. Phys. Lett. 71, 1753 (1997); http://dx.doi.org/10.1063/1.119389 (3 pages) | Cited 9 times

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We report Cs halide-modified Ga–La sulfide glasses, a new class of chalcohalide glasses with improved fiber-drawing and optical properties suitable for Pr3+-doped fiber amplifiers at 1.3 μm. Cs halide-modified Ga–La sulfide glasses retain the essential characteristics of low phonon-energy and good rare-earth solubility of pure Ga–La sulfide glasses. However, they transmit further into the UV/visible region of the spectrum, and can meet the need of high thermal stability for fiber fabrication. © 1997 American Institute of Physics.
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81.05.Kf Glasses (including metallic glasses)
42.70.Ce Glasses, quartz
42.55.Wd Fiber lasers
61.43.Fs Glasses

Highly efficient excitation of optical near-field on an apertured fiber probe with an asymmetric structure

T. Yatsui, M. Kourogi, and M. Ohtsu

Appl. Phys. Lett. 71, 1756 (1997); http://dx.doi.org/10.1063/1.119390 (3 pages) | Cited 28 times

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We propose and demonstrate a novel method to enhance the near-field optical intensity on the apertured probe with its foot removed asymmetrically by using a focused ion beam. The spatial distribution of the near-field optical intensity on the asymmetric probe was observed by scanning another sharpened symmetric probe over the aperture. The observed spatial distribution profile was in good agreement with a numerical result corresponding to the HE11 mode. Furthermore, compared with the symmetric apertured probe, a 10 times enhancement of the near-field optical intensity on the asymmetric apertured probe was observed. © 1997 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.60.Vg Fiber-optic instruments
42.81.Wg Other fiber-optical devices

Activator recycling in low voltage cathodoluminescent phosphors

C. Stoffers, S. Yang, F. Zhang, S. M. Jacobsen, B. K. Wagner, and C. J. Summers

Appl. Phys. Lett. 71, 1759 (1997); http://dx.doi.org/10.1063/1.119391 (3 pages) | Cited 9 times

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Cathodoluminescent phosphors excited at low voltages and high current densities often exhibit brightness saturation due to ground state depletion. A two-level model can be used to show that the luminance and saturation behavior of low voltage phosphors can be greatly improved by choosing phosphors with an activator decay time that is considerably less than the excitation dwell time. This is of considerable importance for field emission displays, where saturation due to ground state depletion has been found to be a factor limiting the achievement of the necessary luminance. Thus, fast activators may overcome ground state depletion and can lead to brighter displays. © 1997 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
85.60.Jb Light-emitting devices
42.79.Kr Display devices, liquid-crystal devices
79.70.+q Field emission, ionization, evaporation, and desorption

Highly efficient and bright organic electroluminescent devices with an aluminum cathode

G. E. Jabbour, Y. Kawabe, S. E. Shaheen, J. F. Wang, M. M. Morrell, B. Kippelen, and N. Peyghambarian

Appl. Phys. Lett. 71, 1762 (1997); http://dx.doi.org/10.1063/1.119392 (3 pages) | Cited 110 times

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The electron injection process, which limits the electroluminescent performance of organic devices, has been enhanced tremendously by inserting a layer of LiF with appropriate thickness between the cathode and a quinacridone doped organic layer. Devices with an Al/LiF cathode demonstrated a luminance in excess of 20 000 cd/m2 and an external quantum efficiency of 3%, which is comparable to devices with a Mg/LiF cathode. These devices show maximum luminance of 45 000 cd/m2 prior to failure in continuous bias operation. For the same LiF thickness, the operating voltage for devices with Al/LiF was lower than the corresponding operating voltage for devices with Mg/LiF or Mg alone. Tunneling theory is used to explain this enhancement. © 1997 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds

Autocorrelation of mode-locked laser pulses based on the synchronous drift of photogenerated carriers

Amjad T. Obeidat and Jacob B. Khurgin

Appl. Phys. Lett. 71, 1765 (1997); http://dx.doi.org/10.1063/1.119393 (3 pages)

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We show that the autocorrelation function of mode-locked laser pulses can be measured by interfering a pulse with its time-delayed replica in a conventional photoconductor to generate a pulsating grating that can be represented as a superposition of moving gratings. The resonance current peak resulting from matching the carrier drift velocity to the velocity of one of the grating components is proportional to the autocorrelation function. Unlike conventional autocorrelators, the proposed method uses no nonlinear effects and thus can be utilized for measuring weak pulses. © 1997 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Dj Gratings
72.40.+w Photoconduction and photovoltaic effects

Interferometric roughness measurement of Ohmic contact/III–V semiconductor interfaces

P. C. Montgomery, D. Benhaddou, and D. Montaner

Appl. Phys. Lett. 71, 1768 (1997); http://dx.doi.org/10.1063/1.119394 (3 pages) | Cited 4 times

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The nondestructive measurement of the internal roughness of Ohmic contacts on GaAs and InP using near-infrared interferometry through the rear of the wafer is investigated. The main difficulties were found to be associated with the thick high refractive index viewing window leading to conflicting requirements in the position of the interface along the optical axis for forming the image and the fringes. Two solutions are proposed: the first using a low numerical aperture objective, and the second using a rear surface reflecting GaAs reference mirror, giving an axial resolution of approximately 8 nm. © 1997 American Institute of Physics.
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68.35.Ct Interface structure and roughness
07.60.Ly Interferometers
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Acoustic radiation force on micrometer-size particles

K. Yasuda and T. Kamakura

Appl. Phys. Lett. 71, 1771 (1997); http://dx.doi.org/10.1063/1.119395 (3 pages) | Cited 11 times

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The acoustic radiation force on micrometer-sized polystyrene spheres was measured through observation of the sphere movement in a 500 kHz ultrasonic standing wave. The known spatial distribution of the force allowed verification of the correlation between the sphere velocity and the force. It was found that the linear dependency of the force on the cube of the sphere radius, as predicted by Yosioka, began to fail when the sphere radius was below 5 μm. This can be accounted for by the presence of a shell layer surrounding the sphere, which increased the effective radius of the sphere. This may point to applications of the acoustic radiation force in the handling of moicrospheres smaller than hitherto thought possible. © 1997 American Institute of Physics.
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43.25.Nm Acoustic streaming

Evolution of ion charge states in vacuum arc plasmas

O. Demokan

Appl. Phys. Lett. 71, 1774 (1997); http://dx.doi.org/10.1063/1.120021 (3 pages)

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A model, based on ion transport along the plasma in vacuum arcs, is proposed to explain the evolution of charge states. Physical arguments implementing such a model are given, and the charge state fluxes are evaluated. The systematic trends of the particle current fractions are seen to be alike for the theoretical and experimental values, and good quantitative agreement is found for electron temperatures, higher than the generally accepted values. Comments regarding the future work and the effect of a magnetic field are stated. © 1997 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.25.-b Plasma properties

Influence of reactive gas on ion energy distributions in filtered cathodic vacuum arcs

M. M. M. Bilek, M. Chhowalla, and W. I. Milne

Appl. Phys. Lett. 71, 1777 (1997); http://dx.doi.org/10.1063/1.119428 (3 pages) | Cited 18 times

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The energy with which depositing species impinge on a growth surface is one of the main factors influencing the microstructure and properties of the thin films fabricated in plasma deposition processes. In this letter, we examine the effects of a variety of deposition parameters on the ion energy distribution beyond the magnetic filter in a filtered cathodic vacuum arc (FCVA). The results indicate that the ion energy distributions do not vary significantly with the magnetic field strength, magnetic field configuration, lateral position in the beam, or bias on the filter duct wall in the ranges studied. The energy distribution was however strongly affected by the presence of a reactive background gas. A reduction of 10 eV was recorded for a background pressure of 10−3 Torr of N2 gas in a carbon FCVA. This result has implications for all FCVA depositions carried out in a gas atmosphere and is consistent with the view that ion transport in the magnetic filter occurs due to an electrostatic guiding potential well. © 1997 American Institute of Physics.
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68.55.-a Thin film structure and morphology
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Sz Deposition technology
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Experimental demonstration of complete photonic band gap in graphite structure

F. Gadot, A. Chelnokov, A. De Lustrac, P. Crozat, J.-M. Lourtioz, D. Cassagne, and C. Jouanin

Appl. Phys. Lett. 71, 1780 (1997); http://dx.doi.org/10.1063/1.119396 (3 pages) | Cited 21 times

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We experimentally demonstrate the existence of complete photonic band gap in graphite-type photonic crystals, thereby confirming theoretical predictions reported in previous studies. Experiments are performed at microwave frequencies from 27 to 75 GHz using hexagonal lattices of alumina rods. Transmission spectra measured for E (TM) and H (TE) polarizations and for different orientations of the two-dimensional lattice are found to be in excellent agreement with numerical calculations. The complete photonic band gap results from the overlap of E7 and H5 forbidden bands. Attenuations larger than 30 dB are measured for structures comprised of only four rows of alumina rods. © 1997 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics

Thin-film channel waveguide electro-optic modulator in epitaxial BaTiO3

D. M. Gill, C. W. Conrad, G. Ford, B. W. Wessels, and S. T. Ho

Appl. Phys. Lett. 71, 1783 (1997); http://dx.doi.org/10.1063/1.119397 (3 pages) | Cited 42 times

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We report on a thin-film channel waveguide electro-optic modulator fabricated in epitaxial BaTiO3 on MgO. Films had an effective dc electro-optic coefficient of reff∼50±5 pm/V and reff∼18±2 pm/V at 5 MHz for λ∼1.55 μm light. Extinction ratios of 14 dB were obtained. The electro-optic effect decreases to ∼60% of the dc value at 1 Hz, 50% of the dc value at 20 kHz, and ∼37% of the dc value at 5 MHz. © 1997 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Wc Optical coatings
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Et Waveguides, couplers, and arrays
42.86.+b Optical workshop techniques
42.79.Gn Optical waveguides and couplers
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Energy conversion with Zr-rich lead zirconate/titanate ceramics

Ning Duan, Noé Cereceda, Beatriz Noheda, José Raúl Fernandez-del-Castillo, and Julio A. Gonzalo

Appl. Phys. Lett. 71, 1786 (1997); http://dx.doi.org/10.1063/1.119398 (3 pages) | Cited 4 times

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The conversion efficiency and power output to convert thermal energy to electrical energy by means of a ferroelectric–ferroelectric phase transition has been investigated. The material used was the ceramic mixed system lead zirconate/titanate (PZT) with a very Zr-enriched composition (Zr/Ti=97/3%). We have studied the performance dependence on sample thickness and working frequency, the main relevant parameters for a given PZT composition. The observed optimum values of efficiency and power output are analyzed in terms of the two main characteristic relaxation times of the process, the thermal time (sample thickness dependent) and the electric time (thickness independent). Possible ways of improving the overall performance are discussed. © 1997 American Institute of Physics.
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77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Gm Dielectric loss and relaxation
84.60.Rb Thermoelectric, electrogasdynamic and other direct energy conversion
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Stress mapping of chemical-vapor-deposited diamond film surface by micro-Raman spectroscopy

I. I. Vlasov, V. G. Ralchenko, E. D. Obraztsova, A. A. Smolin, and V. I. Konov

Appl. Phys. Lett. 71, 1789 (1997); http://dx.doi.org/10.1063/1.119399 (3 pages) | Cited 21 times

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A confocal Raman spectroscopy was used to measure intrinsic stress distribution on the growth surface within individual grains of chemical-vapor-deposited diamond film. Polarization analysis of the Raman line shape revealed that even in high quality (2.8 cm−1 linewidth), free-standing film of 0.6 mm thickness, small regions exist where high local stresses (both compressive and tensile) develop. The stressed regions tend to appear near crystal edges and grain boundaries. A strong gradient in defect or impurity concentrations is supposed to cause the stress fluctuations observed. © 1997 American Institute of Physics.
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81.05.ub Fullerenes and related materials
68.60.Bs Mechanical and acoustical properties
78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators

Nanocrystals synthesized by electron-beam induced fragmentation of vacancy-containing metals microspheres

Q. Ru

Appl. Phys. Lett. 71, 1792 (1997); http://dx.doi.org/10.1063/1.119400 (3 pages) | Cited 3 times

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Dynamic behavior of gold spheres ranging from 5 to 50 μm in diameter under pulsed electron beam irradiation was observed in situ by a scanning and transmission electron microscope. Unusually large amounts of dropletlike fragments were found to be ejected out from spheres containing vacancies such as voids or holes. Crystals ranging from 1 nm to 1 μm in size were formed on a carbon substrate from the fragments. The ejection phenomenon may offer an alternative to laser ablation as a means of forming small particles. © 1997 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
61.80.Fe Electron and positron radiation effects

Simplified evaluation method for light-biased effective lifetime measurements

F. M. Schuurmans, A. Schönecker, A. R. Burgers, and W. C. Sinke

Appl. Phys. Lett. 71, 1795 (1997); http://dx.doi.org/10.1063/1.119401 (3 pages) | Cited 9 times

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In this letter, we present a simplified evaluation method for light-biased photoconductance decay measurements. The measured effective lifetime is shown to be a differential quantity τeff,d, which may differ significantly from the actual effective lifetime τeff. However, the actual effective lifetime can be approximated by integrating τeff,d directly over the incident power density of the bias light. The quality of the approximation depends mainly on the surface recombination velocity and the wavelength of the used bias light. However, the inaccuracy remains well below 10% for most practical cases. © 1997 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors
72.40.+w Photoconduction and photovoltaic effects

Phonon-boundary scattering in thin silicon layers

M. Asheghi, Y. K. Leung, S. S. Wong, and K. E. Goodson

Appl. Phys. Lett. 71, 1798 (1997); http://dx.doi.org/10.1063/1.119402 (3 pages) | Cited 79 times

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Temperature fields in microdevices made from silicon-on-insulator (SOI) wafers are strongly influenced by the lateral thermal conductivity of the silicon overlayer, which is diminished by phonon scattering on the layer boundaries. This study measures the thermal conductivity of single-crystal silicon layers in SOI substrates at temperatures between 20 and 320 K using Joule heating and electrical-resistance thermometry in microfabricated structures. Data for layers of thickness between 0.4 and 1.6 μm demonstrate the large reduction resulting from phonon-boundary scattering, particularly at low temperatures, and are consistent with predictions based on the phonon Boltzmann transport equation. © 1997 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.10.Di Scattering by phonons, magnons, and other nonlocalized excitations
71.38.-k Polarons and electron-phonon interactions
68.35.Ja Surface and interface dynamics and vibrations

Theory of menisci and its applications

Chao Gao

Appl. Phys. Lett. 71, 1801 (1997); http://dx.doi.org/10.1063/1.119403 (3 pages) | Cited 14 times

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A theory for liquid menisci formed at an arbitrary interface is developed including surface interactions and liquid evaporation. Its applications to scanning probe techniques and laser textured magnetic disks are also given. The meniscus force is shown to be proportional to meniscus size for none-spherical contacts, but nearly independent for spherical contacts. Stronger surface interactions on the liquid film result in the formation of smaller menisci, whereas a thicker liquid film causes larger menisci. The theory predicts that the meniscus (adhesion) force can be effectively reduced when using the same surface material for the interface that can be wetted by the liquid film. Analytical formulae for meniscus forces are derived for widely encountered spherical/conical tips. Comparisons with existing experiments and macroscopic theories are also discussed. © 1997 American Institute of Physics.
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68.08.Bc Wetting
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
64.70.F- Liquid-vapor transitions
68.03.Fg Evaporation and condensation of liquids
68.35.Gy Mechanical properties; surface strains

Hydrogen induced silicon surface layer cleavage

Xiang Lu, Nathan W. Cheung, Michael D. Strathman, Paul K. Chu, and Brian Doyle

Appl. Phys. Lett. 71, 1804 (1997); http://dx.doi.org/10.1063/1.119404 (3 pages) | Cited 34 times

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Physical mechanisms of hydrogen induced silicon surface layer cleavage were investigated using a combination of microscopy and spectroscopy techniques. The evolution of the silicon cleavage phenomenon is recorded by a series of microscopic images. The underlying hydrogen profiles under (between 250 and 500 °C) annealing are characterized by secondary-ion-mass spectroscopy and hydrogen forward scattering experiments. An idea gas law model calculation suggests that internal pressure of molecular hydrogen filled microcavities is in the range of Giga-Pascal, high enough to break silicon crystal bond. A dose threshold, which prevents cleavage, is observed at 1.6×1017 cm−2 for 40 kV hydrogen implantation. © 1997 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.S- Impurities in crystals
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.50.Lt Crystal binding; cohesive energy
61.72.uf Ge and Si

Luminescence enhancement in AlN(Er) by hydrogenation

S. J. Pearton, C. R. Abernathy, J. D. MacKenzie, U. Hömmerich, X. Wu, R. G. Wilson, R. N. Schwartz, J. M. Zavada, and F. Ren

Appl. Phys. Lett. 71, 1807 (1997); http://dx.doi.org/10.1063/1.119405 (3 pages) | Cited 20 times

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Room-temperature Er3+ photoluminescence increases of a factor of 5 are observed for AlN(Er) samples treated in a 2H plasma at 200 °C for 30 min. The atomic deuterium passivates defects in the AlN, which normally provide alternative carrier recombination routes. Postdeuteration annealing at 300 °C for 20 min removes the luminescence enhancement by depassivating the nonradiative centers. The AlN(Er) provides a high degree of resistance to thermal quenching of luminescence as a function of temperature because of its wide band gap (6.2 eV), and hydrogenation is a simple method for maximizing the optical output in this materials system. © 1997 American Institute of Physics.
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78.55.Cr III-V semiconductors
71.55.Eq III-V semiconductors
81.65.Rv Passivation
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
81.05.Ea III-V semiconductors
71.20.Nr Semiconductor compounds
61.72.Cc Kinetics of defect formation and annealing

High quality large-area CdTe(211)B on Si(211) grown by molecular beam epitaxy

S. Rujirawat, L. A. Almeida, Y. P. Chen, S. Sivananthan, and David J. Smith

Appl. Phys. Lett. 71, 1810 (1997); http://dx.doi.org/10.1063/1.119406 (3 pages) | Cited 35 times

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We describe the growth of high quality CdTe(211)B layers by molecular beam epitaxy on nominal Si(211) substrates. Prior to CdTe deposition, thin ZnTe(211)B buffer layers were grown to preserve the homo-orientation. Large-area CdTe(211)B layers were routinely obtained by optimizing the growth parameters. From x-ray diffraction, we observed the presence of twin-free CdTe(211)B layers. One 8 μm thick CdTe epilayer had a near-surface etch pit density of 1.5×105 cm−2, which surpassed the best value reported for CdTe(211)B grown on GaAs(211)B, GaAs/Si(211), or Si(211) substrates. © 1997 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.35.Ct Interface structure and roughness
68.55.-a Thin film structure and morphology

Raman scattering studies on Si-doped GaAs grown by hydrogen-assisted molecular beam epitaxy

J. M. Zhang, M. Cardona, Z. L. Peng, and Y. Horikoshi

Appl. Phys. Lett. 71, 1813 (1997); http://dx.doi.org/10.1063/1.119407 (3 pages)

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The surfactant effect of atomic hydrogen on the incorporation of silicon into (100)-, (111)A-, and (311)A-oriented GaAs grown by hydrogen-assisted molecular beam epitaxy has been studied with Raman spectroscopy. Local vibrational modes (LVMs) of SiGa and SiAs impurities are observed for excitation nearly resonant with the E1 energy gap. Site switch of the doping Si atoms from Ga to As lattice sites due to the surfactant effect of H during growth of the high-index doped layers was directly monitored by changes of the normalized intensity of the LVMs. An increase of the free carrier concentration in p-type samples and a decrease in n-type samples resulting from this site switch were also observed in the plasmon-phonon coupled modes as observed in Raman scattering. Similar changes in carrier concentrations were observed by means of electrical transport measurements. © 1997 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors

GaN and AlxGa1−xN molecular beam epitaxy monitored by reflection high-energy electron diffraction

N. Grandjean and J. Massies

Appl. Phys. Lett. 71, 1816 (1997); http://dx.doi.org/10.1063/1.119408 (3 pages) | Cited 57 times

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GaN and AlxGa1−xN alloys were grown by gas source molecular beam epitaxy using NH3. High quality GaN layers with smooth surfaces being obtained, reflection high-energy electron diffraction (RHEED) can be used to monitor the growth. The oscillations of the specular beam intensity indicate a layer-by-layer growth which allows one to precisely measure the deposition rate and the composition of AlxGa1−xN alloys. The transition from two dimensional nucleation to step flow growth mode when increasing the substrate temperature is also evidenced. Finally, RHEED is used to investigate the relaxation processes which take place during the growth of AlN on GaN and GaN on AlN. © 1997 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Study of dynamic space charge in SrS:Ce thin-film electroluminescent devices by tunable laser excitation

Manuela Peter, Yukinori Kashio, Satoru Nishimura, Koutoku Ohmi, Shosaku Tanaka, and Hiroshi Kobayashi

Appl. Phys. Lett. 71, 1819 (1997); http://dx.doi.org/10.1063/1.119409 (3 pages) | Cited 4 times

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The origin of the dynamic space charge in SrS:Ce ac-driven thin-film electroluminescent devices is studied using photoinduced current measurements. Field assisted photoionization of Ce3+ centers and of intrinsic electron traps is observed. The results show that about 50% of the dynamic space charge in SrS:Ce originates from cerium ionization. The remaining 50% results from the ionization of crystal imperfections. © 1997 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.60.Fi Electroluminescence
77.22.Jp Dielectric breakdown and space-charge effects
78.66.Li Other semiconductors
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