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30 Sep 1991

Volume 59, Issue 14, pp. 1655-1799

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Leaky‐wave interarray coupling for coherent‐power scaling of phase‐locked diode‐laser arrays of antiguides

L. J. Mawst, D. Botez, M. Jansen, M. Sergant, G. Peterson, and T. J. Roth

Appl. Phys. Lett. 59, 1655 (1991); http://dx.doi.org/10.1063/1.106258 (3 pages) | Cited 2 times

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Long‐range coupling and phase locking of several 10‐element resonant antiguided arrays via (lateral) radiation leakage is demonstrated. Coupling occurs for interarray separations as large as 90 μm, as evidenced from far‐field patterns and spectrally resolved near‐field patterns. Diffraction‐limited‐beam operation is achieved from a 244‐μm aperture (four coupled 10‐element arrays) device. Intermodal discrimination between the in‐phase mode and adjacent higher‐order modes is shown to be maximized for a resonant ensemble.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
85.60.Jb Light-emitting devices
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Passive mode locking and Q switching of an erbium 3 μm laser using thin InAs epilayers grown by molecular beam epitaxy

K. L. Vodopyanov, A. V. Lukashev, C. C. Phillips, and I. T. Ferguson

Appl. Phys. Lett. 59, 1658 (1991); http://dx.doi.org/10.1063/1.106259 (3 pages) | Cited 13 times

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Passive mode locking and Q switching has been achieved for the first time in an Er3+:YSGG laser at λ=2.8 μm using ultrathin single‐crystal InAs epilayers grown on GaAs substrate which were subsequently bombarded with 15 keV protons at a dose of 1013 cm−2. The bleaching effect was due to a dynamic Moss–Burstein mechanism with a fast (<100 ps) recovery time. In the case of passive mode locking, pulses of 10 MW power were generated at λ=2.8 μm.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Rz Doped-insulator lasers and other solid state lasers
42.55.Px Semiconductor lasers; laser diodes

Third‐order nonlinear optical properties of poly(diphenyl amine) and poly(4‐amino biphenyl), novel processible conducting polymers

P. Chandrasekhar, Jonathan R. G. Thorne, and Robin M. Hochstrasser

Appl. Phys. Lett. 59, 1661 (1991); http://dx.doi.org/10.1063/1.106260 (3 pages) | Cited 8 times

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Off‐resonant third‐order nonlinear optical susceptibilities using degenerate four‐wave mixing measurements in solution at 1.064 μm are reported for partially doped states of the soluble, stable, reprocessible conducting polymers poly(4‐amino biphenyl) [P(4ABP)] and poly(diphenyl amine) [P(DPA)] whose synthesis and properties were reported earlier. The polymers show appreciable nonlinearities, χ(3)xxxx being (1.4±0.3)×10−10 esu for P(4ABP) and (1.3±0.3)×10−10 esu for P(DPA), with a time response faster than 40 ps.  
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.20.-e Optical properties of bulk materials and thin films
42.70.-a Optical materials

Inverted cavity GaAs/InGaAs asymmetric Fabry–Perot reflection modulator

Kezhong Hu, Li Chen, Anupam Madhukar, Ping Chen, Chris Kyriakakis, Zaheed Karim, and Armand R. Tanguay

Appl. Phys. Lett. 59, 1664 (1991); http://dx.doi.org/10.1063/1.106261 (3 pages) | Cited 7 times

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See Also: Erratum

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We report the realization of an inverted cavity (through‐substrate) reflection modulator based on an asymmetric Fabry–Perot configuration that utilizes the transparency of the GaAs substrate for operation at wavelengths appropriate for strained‐layer GaAs/InGaAs multiple quantum wells. At room temperature, a contrast ratio of 12:1 is realized along with a dynamic range of 20% at an operating wavelength of 9565 Å.
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42.79.Hp Optical processors, correlators, and modulators
78.20.-e Optical properties of bulk materials and thin films

Propagation loss measurements in silicon‐on‐insulator optical waveguides formed by the bond‐and‐etchback process

A. F. Evans, D. G. Hall, and W. P. Maszara

Appl. Phys. Lett. 59, 1667 (1991); http://dx.doi.org/10.1063/1.106262 (3 pages) | Cited 8 times

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We report the results of loss measurements for guided waves in silicon‐on‐insulator (SOI) optical waveguides formed by the bond‐and‐etchback process. Losses as low as 2.6 (2.0) dB/cm were found for the TE0 (TM0) mode for wavelength λ=1.319 μm. Grating coupling into these waveguides is demonstrated and discussed.
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42.79.Gn Optical waveguides and couplers
42.82.-m Integrated optics

Bistable self‐electro‐optic operation of strained In0.1Ga0.9As/GaAs asymmetric Fabry–Perot modulators

T. E. Sale, J. Woodhead, A. S. Pabla, R. Grey, P. A. Claxton, P. N. Robson, M. H. Moloney, and J. Hegarty

Appl. Phys. Lett. 59, 1670 (1991); http://dx.doi.org/10.1063/1.106263 (3 pages) | Cited 6 times

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We report bistable operation of a strained‐layer InGaAs/GaAs asymmetric Fabry–Perot optical modulator configured as a self‐electro‐optic effect device (SEED) operating in reflection mode. Bistable loops are observed from 949 to 962 nm with switching powers down to submicrowatt levels. The contrast ratio between on and off states is as large as 5:1 (7 dB) and the device will hold in either state indefinitely. A 600‐μm‐diam device has a switching time of 20 μs for 2.1 fJ μm−2 switching energy. Large optical latch arrays are envisaged using this device.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Hp Optical processors, correlators, and modulators
85.60.-q Optoelectronic devices

Measurement of nonlinear gain suppression and four‐wave mixing in quantum well lasers

S. R. Chinn

Appl. Phys. Lett. 59, 1673 (1991); http://dx.doi.org/10.1063/1.106264 (3 pages) | Cited 3 times

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We have applied a new heterodyne measurement of spontaneous emission modes of a cw, unmodulated quantum well laser operating above threshold, to observe spectrally asymmetric nonlinear gain suppression and intrinsic four‐wave mixing up to 675 GHz from the lasing frequency.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes

Integrated distributed feedback laser and optical amplifier

N. K. Dutta, J. Lopata, R. Logan, and T. Tanbun‐Ek

Appl. Phys. Lett. 59, 1676 (1991); http://dx.doi.org/10.1063/1.106419 (2 pages) | Cited 3 times

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The fabrication and performance characteristics of an integrated distributed feedback (DFB) laser and optical amplifier structure are described. The structure utilizes semi‐insulating Fe‐doped InP layers for current confinement to the active region, electrical isolation between the two sections, and for lateral index guiding. The amplified output has a slope of 1 mW/mA of laser current with the amplifier biased at 150 mA, which is a factor of 5 larger than that for a typical laser. The laser emits near 1.55 μm, and the spectral width under modulation of the amplified output is considerably smaller than that for a DFB laser for the same on/off ratio.
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42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Disk‐shaped vacuum ultraviolet light source driven by microwave discharge for photoexcited processes

K. Yoshizawa, M. Taki, K. Tachibana, and S. Moriyama

Appl. Phys. Lett. 59, 1678 (1991); http://dx.doi.org/10.1063/1.106241 (3 pages) | Cited 1 time

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An efficient vacuum ultraviolet light source of large diameter has been developed for use in photoexcited processes. It has a novel structure in which microwaves propagating through a sapphire window break down Xe gas enclosed in a disk‐shaped volume and thereby produce intense emission from Xe at a wavelength of 147 nm. By optimizing the pulse width and the repetition rate, we obtained an illuminance of more than 3 mW/cm2 at the window surface. When this lamp was used as a source for photoinduced chemical vapor deposition of hydrogenated amorphous silicon films, a deposition rate of 5 nm/min was attained.
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52.80.Yr Discharges for spectral sources (including inductively coupled plasma)
42.72.-g Optical sources and standards

Optically pumped lasing of ZnSe at room temperature

X. H. Yang, J. Hays, W. Shan, J. J. Song, E. Cantwell, and J. Aldridge

Appl. Phys. Lett. 59, 1681 (1991); http://dx.doi.org/10.1063/1.106242 (3 pages) | Cited 11 times

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Optically pumped lasing of (111) oriented bulk ZnSe grown by seeded physical vapor phase transport (SPVT) technique has been achieved at room temperature under near resonant pumping with the excitation photon energy very close to the fundamental band gap. Laser emission can be seen at a pumping intensity as low as 7 kW/cm2. The lasing mode spacings resulting from the dispersion of the index of refraction for ZnSe in a Fabry–Perot resonator‐like cavity have been observed as well. Our experimental results demonstrate that SPVT ZnSe single crystals have the quality sufficient to develop low‐threshold, high‐power output blue lasers.
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42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission

New technique for investigating ferroelectric phase transitions: The photoacoustic effect

Jorge O. Tocho, Rafael Ramírez, and J. A. Gonzalo

Appl. Phys. Lett. 59, 1684 (1991); http://dx.doi.org/10.1063/1.106243 (3 pages) | Cited 5 times

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Measurements of the photoacoustic (PA) effect in properly oriented triglycine sulfate (TGS) crystals from 30 to 60 °C show clearly the ferroelectric phase transition in this crystal manifested by the pronounced thermal expansion anomalies. The same method is generally applicable to similar phase transitions.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
07.90.+c Other topics in instruments, apparatus, and components common to several branches of physics and astronomy (restricted to new topics in section 07)
62.65.+k Acoustical properties of solids

Positron annihilation study of low pressure chemical vapor deposited silicon nitride films

R. A. Hakvoort, H. Schut, A. van Veen, W. M. Arnold Bik, and F. H. P. M. Habraken

Appl. Phys. Lett. 59, 1687 (1991); http://dx.doi.org/10.1063/1.106218 (3 pages) | Cited 9 times

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Doppler S‐parameter measurements have been performed on low‐pressure chemical vapor deposited (LPCVD) Si3N4 samples. Annealing of the samples at 1000 °C for times up to 1 h resulted in a decrease of both the S parameter and the positron diffusion length of the silicon nitride. The diffusion length recovers after reimplantation of deuterium, but the S parameter remains low. The data are discussed using a model also applied to understand some electrical properties of the LPCVD nitride.
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78.70.Bj Positron annihilation
73.61.Ng Insulators
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Photodarkening and microcrystallite size in colored filter glasses

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

Appl. Phys. Lett. 59, 1690 (1991); http://dx.doi.org/10.1063/1.106219 (3 pages) | Cited 9 times

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It is demonstrated for the first time that photodarkening in colored filter glasses is associated with apparent growth of CdSxSe1−x microcrystallites. This is thought to be due to the attraction of impurity ions around the microcrystallites. Both a Q‐switched Nd3+:YAG laser and a hybrid mode‐locked dye laser are used as the light sources. Microcrystallite growth is directly observed by transmission electron microscopy and by field‐emission scanning electron microscopy. Growth is also inferred from local changes in color and measured absorption spectra.
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78.20.-e Optical properties of bulk materials and thin films
81.40.Tv Optical and dielectric properties related to treatment conditions
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

Columnar growth in combustion deposited diamond thin films

H. A. Hoff, C. J. Craigie, E. Dantsker, and C. S. Pande

Appl. Phys. Lett. 59, 1693 (1991); http://dx.doi.org/10.1063/1.106220 (3 pages) | Cited 3 times

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The morphology of the nucleation and growth surfaces of oxygen‐acetylene combustion deposited diamond thin films has been studied using scanning electron microscopy. The diameters of both nucleation cells and growth surface grains have been measured and analyzed statistically. The general shape of the distributions is found to change from nucleation to growth surface for each film. The frequency distribution of cells is generally normal, whereas, the distribution for the growth surface is found to be always lognormal. The change in shape of the distributions from normal for the nucleation surface to lognormal for the growth surface can be explained from a stochastic theory of growth.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
64.60.Q- Nucleation
61.72.Mm Grain and twin boundaries
68.35.B- Structure of clean surfaces (and surface reconstruction)

Initial stages of sputtering on Au(111) as seen by scanning tunneling microscopy

C. A. Lang, C. F. Quate, and J. Nogami

Appl. Phys. Lett. 59, 1696 (1991); http://dx.doi.org/10.1063/1.106221 (3 pages) | Cited 20 times

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We have studied the evolution of the surface topography of neon‐bombarded gold films, from the initial stages of sputter damage to the removal of several layers. Energy‐dependent sputter yields and crater size distributions are derived from scanning tunneling microscope (STM) images which show the progressing surface erosion. A surprising duality in the behavior of surfaces prepared by deposition of atoms (growth) and ‘‘deposition of vacancies’’ (erosion) is revealed.  
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81.15.Cd Deposition by sputtering
68.35.B- Structure of clean surfaces (and surface reconstruction)
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Energy level of the nitrogen dangling bond in amorphous silicon nitride

W. L. Warren, J. Kanicki, J. Robertson, and P. M. Lenahan

Appl. Phys. Lett. 59, 1699 (1991); http://dx.doi.org/10.1063/1.106222 (3 pages) | Cited 19 times

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The composition dependence and room‐temperature metastability of the paramagnetic nitrogen dangling‐bond center is amorphous silicon nitride suggest that its energy level lies close to the N pπ states, in agreement with theoretical calculations.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ng Insulators
77.55.-g Dielectric thin films
76.30.Lh Other ions and impurities

Oscillatory instability in the heterostructure hot‐electron diode

A. Wacker and E. Schöll

Appl. Phys. Lett. 59, 1702 (1991); http://dx.doi.org/10.1063/1.106223 (3 pages) | Cited 14 times

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Vertical electrical transport in the heterostructure hot‐electron diode is considered theoretically. We present a simple dynamical model which consistently explains the measured S‐shaped negative differential conductivity in the current‐voltage characteristics. The model predicts a new type of self‐sustained 60 GHz voltage oscillations between tunneling and thermionic emission if the sample is driven by a dc voltage source having a resistor in series and a capacitor in parallel.
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72.20.Ht High-field and nonlinear effects
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Hi Surface barrier, boundary, and point contact devices

Photoluminescence of hydrogenated SimGen superlattices

V. Arbet‐Engels, M. A. Kallel, and K. L. Wang

Appl. Phys. Lett. 59, 1705 (1991); http://dx.doi.org/10.1063/1.106224 (3 pages) | Cited 14 times

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The effect of hydrogen passivation on the photoluminescence of Si‐rich superlattices is investigated. The as‐grown samples show many defect‐related luminescence signals and several additional luminescence peaks believed to originate from the superlattice. The background luminescence along with the dislocation and defect lines are found to be passivated by the hydrogen atoms. The intensity of the superlattice peak increases after passivation and its phonon replica, initially submerged in the background and defect luminescence signals, is highlighted. After a subsequent temperature annealing in N2, the background luminescence is increased as hydrogen outdiffuses but the superlattice main peak decreases, perhaps due to the change of the carrier lifetime.
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78.66.-w Optical properties of specific thin films
78.55.Hx Other solid inorganic materials
81.40.Tv Optical and dielectric properties related to treatment conditions
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors

Nonlinear transport phenomena in a triangular quantum well

A. Kastalsky, F. Peeters, W. K. Chan, L. T. Florez, and J. P. Harbison

Appl. Phys. Lett. 59, 1708 (1991); http://dx.doi.org/10.1063/1.106225 (3 pages) | Cited 8 times

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We have measured transport properties in an AlGaAs/AlxGa1−xAs, triangular quantum well whose energy spectrum has been varied by means of gate bias. We have observed several nonlinear effects in the lateral conductance arising at positive gate voltages as the increasing Fermi level is moved toward the lowering energy positions of the excited subbands in the quantum well. We interpret our results in terms of electron population of the excited subbands in which electrons possess low mobility. Finally, we find new features at high lateral voltages which are considered to be an evidence of previous predicted electrophonon resonance.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.10.Di Scattering by phonons, magnons, and other nonlocalized excitations
72.80.Ey III-V and II-VI semiconductors

Electrooptic modulation in polar growth axis InGaAs/GaAs multiple quantum wells

I. H. Campbell, D. E. Watkins, D. L. Smith, S. Subbanna, and H. Kroemer

Appl. Phys. Lett. 59, 1711 (1991); http://dx.doi.org/10.1063/1.106226 (3 pages) | Cited 15 times

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We present electrooptic modulation results on [100], [211]A and [211]B oriented InGaAs/GaAs multiple quantum wells. Internal electric fields are generated by a combination of strain, due to lattice mismatch, and the piezoelectric properties of III‐V semiconductors in the [211] structures. These fields have opposite orientation in the [211]A and [211]B samples. They do not occur in the [100] samples. The total electric field is a superposition of the strain‐generated field, the built‐in field from the p‐n junction and any externally applied field. We show that whereas in the conventional [100] structures the exciton energy is a quadratic function of applied field, the strain‐generated fields cause a linear shift in the exciton resonance with applied field in the [211] structures. In addition, the direction of the excitonic shift is opposite in the [211]A and [211]B samples, because the sign of the strain‐generated fields are opposite for these samples.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.20.Jq Electro-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Thermionic emission of Γ and L electrons in the GaSb/InAs hot‐electron transistors

K. Funato, K. Taira, F. Nakamura, and H. Kawai

Appl. Phys. Lett. 59, 1714 (1991); http://dx.doi.org/10.1063/1.106227 (3 pages) | Cited 2 times

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We have fabricated GaSb/InAs hot‐electron transistors with base widths of 30 to 200 Å. The barrier height of thermionic emission was evaluated with two techniques; deducing from values of collector current density itself, and from its temperature dependence. The difference between the two results reveals that electrons are emitted from both Γ and L valleys of the GaSb conduction band. From the measured barrier height, the energy of the ground quantum level formed in InAs base was also deduced. Its dependence on the base width was compared with simple calculation where nonparabolicity of the InAs conduction band was considered. It indicates electron density in the InAs base is enhanced due to electron’s transfer from GaSb to InAs.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.40.+z Thermionic emission
85.30.Tv Field effect devices

Image potentials and the dry etching of submicron trenches with low‐energy ions

Robert J. Davis

Appl. Phys. Lett. 59, 1717 (1991); http://dx.doi.org/10.1063/1.106228 (3 pages) | Cited 11 times

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The image potential between an ion and an etched sidewall is shown to be important in the dry etching of high‐aspect ratio features. Low‐energy ions are attracted to the walls of an etched trench, resulting in wall collisions which can lead to loss of etch directionality and slow vertical etch rates. Estimates are given for the depth at which one‐half of the ion flux into an etched trench is lost to one of the etched walls, as a function of trench width and ion energy. The effect is particularly important in the etching of quarter‐micron features and smaller using ion energies less than 200 eV.
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85.40.Hp Lithography, masks and pattern transfer
81.65.-b Surface treatments

Improvement of the optical and photoelectric properties of hydrogenated amorphous silicon‐carbon alloys by using trisilylmethane as a feedstock

Y.‐M. Li and B. F. Fieselmann

Appl. Phys. Lett. 59, 1720 (1991); http://dx.doi.org/10.1063/1.106229 (3 pages) | Cited 23 times

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Hydrogenated amorphous silicon‐carbon alloys (a‐SiC:H) with band gaps around 1.9 eV have been prepared using trisilylmethane (TSM) as the carbon source by plasma‐enhanced chemical vapor deposition. Compared to a‐SiC:H alloys prepared from the conventional CH4/SiH4 mixture, the TSM‐based films show sharper optical‐absorption edge, weaker defect‐related optical absorption, lower methyl group concentration, longer ambipolar diffusion length, and higher photoconductivity.
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72.40.+w Photoconduction and photovoltaic effects
73.50.Pz Photoconduction and photovoltaic effects
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors

Thermal annealing of light−induced metastable defects in hydrogenated amorphous silicon nitride

E. D. Tober, J. Kanicki, and M. S. Crowder

Appl. Phys. Lett. 59, 1723 (1991); http://dx.doi.org/10.1063/1.106230 (3 pages) | Cited 19 times

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Exposure to ultraviolet light induces paramagnetic, metastable defects in hydrogenated amorphous silicon nitride (a‐SiN1.6:H) thin films. The thermally induced decay of the light‐induced paramagnetic defects follows a stretched exponential dependence on annealing time, exp [−(t/τ)β], and displays a temperature‐dependent β and τ. These results indicate that a multiple trapping or a trap‐controlled hopping mechanism is involved in the annealing process with an apparent activation energy of 0.43 eV.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
73.61.Ng Insulators
76.30.Lh Other ions and impurities

Identification of nonambipolar transport in the application of a photocarrier grating to hydrogenated amorphous silicon

I. Balberg and S. Z. Weisz

Appl. Phys. Lett. 59, 1726 (1991); http://dx.doi.org/10.1063/1.106231 (3 pages) | Cited 5 times

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Thus far the many reports concerning the utilization of the photocarrier grating (PCG) method have assumed that ambipolar transport takes place in such a PCG when it is imposed on hydrogenated amorphous silicon (a‐Si:H). This assumption, which is decisive in the interpretation of the experimental results in terms of the ambipolar diffusion length, has not been tested thus far. In this letter a corresponding testing criterion is proposed, and it is demonstrated that whenever ambipolarity is lost, the PCG‐derived diffusion lengths may be wrong. The finding that ambipolarity is maintained in device quality a‐Si:H is shown to confirm the theoretical suggestion that, whenever observed, the ambipolarity in a‐Si:H is due to shallow trapping effects.
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72.40.+w Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ng Disordered solids
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
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