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24 Mar 1997

Volume 70, Issue 12, pp. 1491-1630

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High efficiency photoemission from Cs–K–Te

D. Bisero, B. M. van Oerle, G. J. Ernst, J. W. J. Verschuur, and W. J. Witteman

Appl. Phys. Lett. 70, 1491 (1997); http://dx.doi.org/10.1063/1.118362 (3 pages)

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Cs–K–Te films have been fabricated under ultrahigh vacuum by vapor deposition of Te, K, and Cs onto a Mo substrate into the preparation chamber of the free electron laser of the University of Twente. Their photoemission properties are reported in this letter. The average quantum efficiency at 259 nm measured on 5 evaporated Cs–K–Te photocathodes is 22.5%, whereas the best quantum efficiency obtained at 259 nm is 23.4%. To our knowledge, this is the highest quantum efficiency at 259 nm reported so far, being about twice that of Cs2Te photocathodes. The reported results demonstrate that Cs–K–Te photocathodes are very promising for the use in photoinjectors. © 1997 American Institute of Physics.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
85.60.Ha Photomultipliers; phototubes and photocathodes

Transfer of temporal fluctuations in photorefractive two-beam coupling

S. Juul Jensen and M. Saffman

Appl. Phys. Lett. 70, 1494 (1997); http://dx.doi.org/10.1063/1.118640 (3 pages)

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Transfer of temporal fluctuations between the signal and pump beams in diffusion dominated photorefractive two-beam coupling is studied experimentally. The dependence on the gain, beam intensity ratio, and frequency of the fluctuations is found to agree well with a linearized analysis. The transfer of perturbations is frequency dependent at low frequencies, and becomes constant at frequencies large compared to the inverse material time constant. We discuss the possibility of pump noise suppression when amplifying weak signals. © 1997 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.20.-e Optical properties of bulk materials and thin films
42.50.Lc Quantum fluctuations, quantum noise, and quantum jumps

Short-pulse, extreme-ultraviolet continuum emission from a table-top laser plasma light source

O. Meighan, A. Gray, J.-P. Mosnier, W. Whitty, J. T. Costello, C. L. S. Lewis, A. MacPhee, R. Allott, I. C. E. Turcu, and A. Lamb

Appl. Phys. Lett. 70, 1497 (1997); http://dx.doi.org/10.1063/1.118364 (3 pages) | Cited 5 times

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We have observed extreme-ultraviolet (XUV) “line-free” continuum emission from laser plasmas of high atomic number elements using targets irradiated with 248 nm laser pulses of 7 ps duration at a power density of ∼ 1013 W/cm2. Using both dispersive spectroscopy and streak camera detection, the spectral and temporal evolution of XUV continuum emission for several target atomic numbers has been measured on a time scale with an upper limit of several hundred picoseconds limited by amplified spontaneous emission. © 1997 American Institute of Physics.
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42.72.Bj Visible and ultraviolet sources
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Mechanical resonance behavior of near-field optical microscope probes

Fred F. Froehlich and Tom D. Milster

Appl. Phys. Lett. 70, 1500 (1997); http://dx.doi.org/10.1063/1.118365 (3 pages) | Cited 9 times

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The mechanical resonance behavior of near-field optical microscope probes is examined with a simple experiment on a flat pyrex sample. While our tapered-fiber probe is locked on the second resonance for servo control, the vibration characteristics around the first resonance are investigated. We find that the overwhelming cause of decreased vibration amplitude as the tip approaches the sample is an increase in damping presumably due to a fluidlike layer on the sample. A small additional effect is also observed that could be due to force derivatives. © 1997 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.79.Lh Atomic force microscopes
07.60.Vg Fiber-optic instruments
42.81.Wg Other fiber-optical devices
07.07.Tw Servo and control equipment; robots

Metal complex polymer for second harmonic generation and electroluminescence applications

X. T. Tao, H. Suzuki, T. Watanabe, S. H. Lee, S. Miyata, and H. Sasabe

Appl. Phys. Lett. 70, 1503 (1997); http://dx.doi.org/10.1063/1.118366 (3 pages) | Cited 18 times

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We report the second harmonic generation and electroluminescent (EL) properties of a soluble metal complex polyurethane (PU). The PU was prepared by the reaction of a zinc Schiff base with 4,4′-diphenylmethane-diisocyanate. The polymer film has been effectively poled under a corona field and its linear and nonlinear optical (NLO) properties were characterized. The results indicated that the NLO effects of the polymer are mainly originated in the distorted coordination tetragonals formed by the central zinc atoms and coordination atoms. The polymer shows strong photoluminescence under a ultraviolet-lamp illumination and can be used as a luminescent material for EL devices. © 1997 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.60.Fi Electroluminescence
61.41.+e Polymers, elastomers, and plastics
78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds
42.70.Jk Polymers and organics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.40.Me Organic compounds and polymers

Spectrally and temporally resolved gain dynamics in mode locked semiconductor quantum well lasers

P. Miltényi, M. Koch, M. Hofmann, H. Jung, and W. Elsässer

Appl. Phys. Lett. 70, 1506 (1997); http://dx.doi.org/10.1063/1.118363 (3 pages) | Cited 2 times

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We perform measurements of the differential gain of modelocked semiconductor quantum well lasers over a wide spectral range employing a modified “electrical pump-optical probe” technique. We find that the two-dimensional density of states expresses itself significantly in the spectral dependence and value of the differential gain. Contributions of the second electronic level are observed in the high-energy range with an increasing in the differential gain, whereas a slightly decreasing differential gain with decreasing wavelength is observed in spectral regimes, where only the first quantized level contributes. © 1997 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Temperature measurements using pulsed photothermal radiometry and silver halide infrared optical fibers

O. Eyal, V. Scharf, and A. Katzir

Appl. Phys. Lett. 70, 1509 (1997); http://dx.doi.org/10.1063/1.118602 (3 pages) | Cited 7 times

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A novel technique for measuring temperature, based on pulsed photothermal radiometry and analysis of the spectral and temperature dependence of Planck’s blackbody equation, is described. In this technique a body is irradiated by a laser pulse and its temperature inferred from the time dependence of the emitted infrared signal curve. This technique was used for near ambient temperature measurements using a CO2 laser, an infrared detector, and infrared transmitting silver halide optical fibers. The experimental results are consistent with theory. This technique is independent of changes in emissivity or geometric factors and it will be useful for accurate and fast noncontact temperature measurements. © 1997 American Institute of Physics.
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07.20.Dt Thermometers
07.60.Dq Photometers, radiometers, and colorimeters
42.81.Pa Sensors, gyros
07.60.Vg Fiber-optic instruments

Linewidth broadening by 1/f noise in wavelength-tunable laser diodes

M.-C. Amann, R. Hakimi, B. Borchert, and S. Illek

Appl. Phys. Lett. 70, 1512 (1997); http://dx.doi.org/10.1063/1.118603 (3 pages) | Cited 3 times

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The excess linewidth broadening of continuously tunable InGaAsP/InP laser diodes at 1.5 μm wavelength is investigated. Terminal electrical and FM noise measurements indicate that the recombination processes in the forward biased tuning region produce significant 1/f carrier noise. Below 1 MHz the 1/f noise dominates yielding a noise enhancement of about 30 dB at 1 kHz. The discrepancy observed so far between theoretically expected and measured spectral linewidth can be well resolved by taking into account this additional noise source. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
72.70.+m Noise processes and phenomena

High performance photorefractive polymer with improved stability

A. Grunnet-Jepsen, C. L. Thompson, R. J. Twieg, and W. E. Moerner

Appl. Phys. Lett. 70, 1515 (1997); http://dx.doi.org/10.1063/1.118604 (3 pages) | Cited 69 times

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A novel photorefractive polymer composite is reported which exhibits a high two-beam coupling gain coefficient (Γ=200 cm−1 at 120 V/μm, fast response time (τg=50 ms at 1 W/cm2), overmodulation of diffraction efficiency, and high sensitivity. The composition and processing have been altered to yield greatly improved material stability. © 1997 American Institute of Physics.
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42.70.Jk Polymers and organics
42.70.Gi Light-sensitive materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
61.66.Bi Elemental solids
61.66.Dk Alloys

An analysis of the anisotropic and topographic gratings in a side-chain liquid crystalline azobenzene polyester

N. C. R. Holme, L. Nikolova, P. S. Ramanujam, and S. Hvilsted

Appl. Phys. Lett. 70, 1518 (1997); http://dx.doi.org/10.1063/1.118605 (3 pages) | Cited 60 times

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We have examined in detail the formation of surface relief structures in azobenzene polyesters formed by polarization holography with orthogonally circularly polarized laser beams. We show that it is possible to separate the contribution to the diffraction efficiency into an anisotropic part and a surface relief part by examining the polarization content of the first order diffracted beam. By studying the dynamics of the growth of the grating, we show that the gratings due to anisotropy and surface relief appear at the same time. Atomic force microscopic investigations of the film after irradiation reveal a strongly polarization dependent surface relief pattern. © 1997 American Institute of Physics.
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42.40.Eq Holographic optical elements; holographic gratings
42.70.Ln Holographic recording materials; optical storage media
42.70.Df Liquid crystals
42.70.Jk Polymers and organics

Electric field measurement in the cathode fall region of a glow discharge in helium

M. M. Kuraica and N. Konjević

Appl. Phys. Lett. 70, 1521 (1997); http://dx.doi.org/10.1063/1.118606 (3 pages) | Cited 13 times

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Spatial distribution of electric field strength in the cathode fall region of an analytical glow discharge in helium and helium-hydrogen mixture is determined from the Stark splitting and shifting of three visible helium lines and their forbidden components. For this diagnostic technique the basic theory is outlined. The results in gas mixture agree well with electric fields determined from the shape of Hβ line. © 1997 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Hc Glow; corona
32.60.+i Zeeman and Stark effects
52.25.Fi Transport properties
32.30.Jc Visible and ultraviolet spectra

Measurement of two-photon absorption cross sections of dye molecules doped in thin films of polymethylmethacrylate

N. Mukherjee, A. Mukherjee, and B. A. Reinhardt

Appl. Phys. Lett. 70, 1524 (1997); http://dx.doi.org/10.1063/1.118638 (3 pages) | Cited 4 times

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Two-photon absorption cross sections of two dye molecules, doped in thin films of polymethylmethacrylate, are measured by comparing fluorescence intensities induced by single- and two-photon excitations. Ratio of the single- and two-photon absorption cross sections is related to the ratio of the single- and two-photon pumped fluorescence intensities. Using this sensitive and background-free detection technique, dispersion of the nonlinearity is measured over a wavelength range of 700–800 nm. © 1997 American Institute of Physics.
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33.50.Dq Fluorescence and phosphorescence spectra
33.80.Wz Other multiphoton processes
42.70.Jk Polymers and organics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Low temperature plasma process based on CO-rich CO/H2 mixtures for high rate diamond film deposition

Joungchel Lee, R. W. Collins, R. Messier, and Y. E. Strausser

Appl. Phys. Lett. 70, 1527 (1997); http://dx.doi.org/10.1063/1.118607 (3 pages) | Cited 22 times

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A low temperature process (350 °C<T<500 °C) for nanocrystalline diamond film growth by microwave plasma-enhanced chemical vapor deposition has been developed that yields high rates (up to 2.5 μm/h) at relatively low plasma powers (0.5 kW). In contrast to the widely used H2-rich mixtures of CH4 or CO and H2 that exhibit monotonic decreases in the diamond growth rate as T is reduced from 800 to 400 °C, CO-rich mixtures of CO and H2 exhibit an increase and sharp maximum as T is reduced. The results suggest a different diamond growth mechanism from the CO-rich mixtures. © 1997 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Cy Elemental semiconductors

A nondiamond phase at the interface between oriented diamond and Si(100) observed by confocal Raman spectroscopy

Mikka Nishitani-Gamo, Toshihiro Ando, Kazuo Yamamoto, Kenji Watanabe, Paul A. Dennig, Yoichiro Sato, and Masami Sekita

Appl. Phys. Lett. 70, 1530 (1997); http://dx.doi.org/10.1063/1.118608 (3 pages) | Cited 21 times

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We have characterized bias-assisted chemical vapor deposition diamond using the nondestructive technique of confocal Raman spectroscopy to investigate the interfacial structures and the variation in structure and quality with depth. The spectral depth profiles of oriented diamond showed that a band centered at 1210 cm−1 and the diamond peak at 1332 cm−1 coexisted at the interface between the oriented diamond and Si substrate. The relative intensity of the 1210 cm−1 band compared to that of the diamond peak varied with depth. The intensity of the band decreased and that of the diamond peak increased from the interface to the diamond surface. The quality of the oriented diamond improved with the growth time. In contrast, for the case of a randomly oriented diamond, a band centered at 1550 cm−1 was observed, the diamond peak was shifted between −6 and 6 cm−1 from the single crystal diamond peak at 1332.5 cm−1, and the spectral profile did not change with depth. No band at 1210 cm−1 was seen in this case. We conclude that a nondiamond phase with a Raman band at 1210 cm−1 and a diamond phase coexist at the interface between the oriented diamond and the Si substrate, and that this 1210 cm−1 phase is therefore a characteristic feature of the nature of the diamond-substrate bonding in oriented films. © 1997 American Institute of Physics.
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68.55.Nq Composition and phase identification
68.55.-a Thin film structure and morphology
78.30.Am Elemental semiconductors and insulators
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.ub Fullerenes and related materials
78.30.Na Fullerenes and related materials
78.66.Db Elemental semiconductors and insulators
78.66.Tr Fullerenes and related materials

Role of oxygen in the formation of voids at the SiC–Si interface

A. Leycuras

Appl. Phys. Lett. 70, 1533 (1997); http://dx.doi.org/10.1063/1.118609 (3 pages) | Cited 9 times

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The purpose of this letter is to observe voids at the SiC–Si interface beneath the SiC layers grown by chemical vapor deposition at high temperature. It is shown in this letter that the volume of the voids per unit area is proportional to the oxygen concentration in the Si substrate over seven orders of magnitude. In situ dynamical reflectivity measurements show that the voids are formed during the carbonization step and especially when the carbon, which has diffused deeply into the Si substrate, diffuses back toward the SiC layer just completed at the substrate surface. This back diffusion is due to the inversion of the carbon concentration gradient sign at that moment. It is accompanied by the formation of CO, resulting either from the reduction of SiO or SiO2 dissolved in the Si substrate. Diffusion of carbon in silicon might improve the methods of purification for the removal of oxygen which remains the main impurity of the purest silicon material. © 1997 American Institute of Physics.
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68.35.Ct Interface structure and roughness
61.72.Qq Microscopic defects (voids, inclusions, etc.)
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
81.20.Ym Purification
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Db Elemental semiconductors and insulators

Spatial resolution of the molecular alignment in electroclinic liquid crystals

J. R. Lindle, F. J. Bartoli, S. R. Flom, A. T. Harter, B. R. Ratna, and R. Shashidhar

Appl. Phys. Lett. 70, 1536 (1997); http://dx.doi.org/10.1063/1.118610 (3 pages) | Cited 6 times

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Field induced deformations of the bookshelf geometry in electroclinic liquid crystals are investigated by means of spatially resolved phase retardation experiments. It is found that the triangular deformation model does not adequately describe the optical data, and underestimates the achievable device contrast ratios. To more correctly model the smectic layer deformation, it is necessary to consider a distribution of molecular directors within a stripe domain. © 1997 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

The role of hydrogen in nitrogen-containing diamondlike films studied by photoelectron spectroscopy

S. Souto and F. Alvarez

Appl. Phys. Lett. 70, 1539 (1997); http://dx.doi.org/10.1063/1.118611 (3 pages) | Cited 42 times

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The influence of H on the local structure of N-containing amorphous diamondlike films (a-CNx:H) is reported. The samples were prepared by rf sputtering of graphite in a N2, Ar, and H2 atmosphere. The chemical bonding of C and N atoms was inferred by analyzing the C 1s and N 1s electronic core-level by x-ray photoelectron spectroscopy. Hydrogen free films present N 1s peaks with a “doublet”, located at 398.2–400.5 eV. When H is introduced in the preparation chamber, the doublet evolves to a single wider band located at 399.1 eV. This new band becomes dominant when increasing H2 partial pressure, completely hiding the original structure. High H2 partial pressure interrupts the growing network formed by N and C due to the attachment of H to N and/or C. Furthermore, the experimental results suggest that the possibility of formation of the C3N4 phaselike is inhibited by the presence of hydrogen. © 1997 American Institute of Physics.
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81.05.ub Fullerenes and related materials
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Dp Adsorbed layers and thin films
68.55.-a Thin film structure and morphology
73.20.At Surface states, band structure, electron density of states

Synthesis of (111) oriented diamond thin films by electrophoretic deposition process

Dong-Gu Lee and Rajiv K. Singh

Appl. Phys. Lett. 70, 1542 (1997); http://dx.doi.org/10.1063/1.118612 (3 pages) | Cited 17 times

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A method for (111) oriented diamond film synthesis has been developed using controlled seeding of micron-sized diamond particles by electrophoresis. Different sizes of diamond powders (0.25 and 5μm) were electrophoretically seeded on silicon substrates using diamond suspensions in organic solvents (acetone, methanol, and ethanol). The seeded samples were then consolidated by the hot filament chemical vapor deposition process. Diamond suspension in acetone was found to be the most suitable for obtaining uniform diamond seeding in electrophoresis. A preferred (111) orientation was obtained for a monolayer of 5 μm seeds. However, when smaller seeds (<1 μm) were used, randomly oriented films were obtained. The surface morphology, crystal orientation, and quality of diamond films were investigated using scanning electron microscopy, x-ray diffractometry, and Raman spectroscopy. © 1997 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.ub Fullerenes and related materials
68.55.-a Thin film structure and morphology
82.45.-h Electrochemistry and electrophoresis
81.05.Cy Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.30.Am Elemental semiconductors and insulators

New method for comprehensive phase-amplitude contrast imaging of the internal structure of matter using high-energy radiation

A. Yu. Nikulin

Appl. Phys. Lett. 70, 1545 (1997); http://dx.doi.org/10.1063/1.118613 (3 pages) | Cited 2 times

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A nondestructive method for structural imaging is proposed. The method is based on direct measurements of phase and amplitude changes in a two-dimensional x-ray image. A standing wave is formed between two separated crystals allowing high-resolution imaging of the complex refractive index. A comprehensive analysis of the amplitude-phase contrast is possible because of the precisely controlled variation of the phases between the reference and reflected beams from a crystalline mirror. © 1997 American Institute of Physics.
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07.85.-m X- and γ-ray instruments
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Lateral stiffness: A new nanomechanical measurement for the determination of shear strengths with friction force microscopy

R. W. Carpick, D. F. Ogletree, and M. Salmeron

Appl. Phys. Lett. 70, 1548 (1997); http://dx.doi.org/10.1063/1.118639 (3 pages) | Cited 138 times

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We present a technique to measure the lateral stiffness of the nanometer-sized contact formed between a friction force microscope tip and a sample surface. Since the lateral stiffness of an elastic contact is proportional to the contact radius, this measurement can be used to study the relationship between friction, load, and contact area. As an example, we measure the lateral stiffness of the contact between a silicon nitride tip and muscovite mica in a humid atmosphere (55% relative humidity) as a function of load. Comparison with friction measurements confirms that friction is proportional to contact area and allows determination of the shear strength. © 1997 American Institute of Physics.
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46.80.+j Measurement methods and techniques in continuum mechanics of solids
07.79.Sp Friction force microscopes
62.20.Qp Friction, tribology, and hardness
81.40.Pq Friction, lubrication, and wear
46.55.+d Tribology and mechanical contacts
68.35.Gy Mechanical properties; surface strains

Electrical characteristics of nearly relaxed InAs/GaP heterojunctions

E. H. Chen, T. P. Chin, J. M. Woodall, and M. S. Lundstrom

Appl. Phys. Lett. 70, 1551 (1997); http://dx.doi.org/10.1063/1.118614 (3 pages) | Cited 2 times

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The electrical properties of lattice mismatched InAs/GaP heterojunctions are examined. In spite of a high dislocation density at the heterointerface, the current versus voltage characteristics show nearly ideal behavior with low reverse leakage currents and high breakdown voltages. The forward current varied exponentially with bias displaying ideal factors of 1.10 or less. Band offsets estimated from current–voltage and capacitance–voltage analysis are consistent with previous estimates based on differences in Schottky barrier heights. © 1997 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.At Surface states, band structure, electron density of states

Device length dependence of optical second-harmonic generation in AlGaAs quasiphase matched waveguides

C. Q. Xu, K. Takemasa, K. Nakamura, K. Shinozaki, H. Okayama, and T. Kamijoh

Appl. Phys. Lett. 70, 1554 (1997); http://dx.doi.org/10.1063/1.118636 (3 pages)

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Device length dependence of optical second-harmonic generation (SHG) in AlGaAs semiconductor quasiphase matched (QPM) waveguides with periodically crystal domain inverted gratings has been studied both experimentally and theoretically. It is found that the SHG power depends strongly on device length. An optimum device length for obtaining maximum SHG is shown for QPM-SHG devices with non-negligible waveguide propagation loss. It is also shown that this optimum device length can be predicted theoretically, making experimental optimization unnecessary. © 1997 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides
42.79.Dj Gratings
42.79.Gn Optical waveguides and couplers

The effect of carbon on the valence band offset of compressively strained Si1−x−yGexCy/(100) Si heterojunctions

C. L. Chang, A. St. Amour, and J. C. Sturm

Appl. Phys. Lett. 70, 1557 (1997); http://dx.doi.org/10.1063/1.118615 (3 pages) | Cited 20 times

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Capacitance–voltage measurements have been used to study the effect of carbon on the valence band offset of compressively strained Si1−x−yGexCy/(100) Si heterojunctions grown by rapid thermal chemical vapor deposition with substitutional C levels from 0% to 2.5%. The valence band offset between Si1−x−yGexCy and unstrained (100) Si decreases at a rate of 20–26 meV per % C. Our work indicates that the change in the bandgap of Si1−x−yGexCy as carbon is added is entirely accommmodated in the valence band. © 1997 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.At Surface states, band structure, electron density of states
71.20.Nr Semiconductor compounds

Ultrafast carrier trapping in oxygen-doped metal-organic vapor phase epitaxy GaAs

J. U. Kang, M. Y. Frankel, J.-W. Huang, and T. F. Kuech

Appl. Phys. Lett. 70, 1560 (1997); http://dx.doi.org/10.1063/1.118616 (3 pages) | Cited 11 times

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We have experimentally investigated the ultrafast carrier dynamics in GaAs grown by metal-organic vapor phase epitaxy with an oxygen precursor. Using a time-resolved reflection ellipsometric technique, we measured the carrier-induced refractive and absorptive index changes as a function of oxygen and aluminum doping concentrations. The free carrier trapping time is inversely proportional to the aluminum-oxygen based complex concentration and can be as short as 300 fs. The material is also highly resistive and promises to be an excellent candidate for optoelectronic applications requiring short carrier lifetime and high dark isolation. © 1997 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
72.80.Ey III-V and II-VI semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Ey III-V semiconductors

Laue x-ray diffraction from heterostructures: CdF2–CaF2 superlattices on Si(111)

R. N. Kyutt, A. Yu. Khilko, and N. S. Sokolov

Appl. Phys. Lett. 70, 1563 (1997); http://dx.doi.org/10.1063/1.118617 (3 pages) | Cited 4 times

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X-ray diffraction measurements have been carried out on epitaxial superlattices (SLs) in symmetric Laue geometry. High quality pseudomorphic CdF2/CaF2 SLs on Si(111) have been used as samples. Satellites, due to periodic variations of structural factor value, are revealed at ω-scanning rocking curves. A comparison of information about SL provided by diffraction in Bragg and Laue geometries is presented. The possibility of direct determination of SL structural parameters is discussed. © 1997 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.05.cp X-ray diffraction
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