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Applied Physics Letters

Issue 1 • Date Jan 1986

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Displaying Results 1 - 25 of 28
  • Monolithic integration of a laser diode and an optical waveguide modulator having a GaAs/AlGaAs quantum well double heterostructure

    Page(s): 1 - 3
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    This letter describes the monolithic integration of a laser diode and an optical waveguide modulator that have the same GaAs/AlGaAs quantum well double heterostructure grown on the same substrate. The intensity of the light emitted from the laser diode is modulated by the modulator, utilizing the effect of an electric field on exciton absorption. The absorption loss coefficient of the modulator waveguide with no applied voltage was estimated to be 60 cm-1. This value is much smaller than the previously reported corresponding value of a veguide having a conventional GaAs double heterostructure. The modulation depth achieved was 7 dB for a driving voltage of 2.3 V; the cut‐off modulation frequency was 0.88 GHz. A prospect for improving these characteristics is also presented. View full abstract»

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  • Continuous wave operation of ridge waveguide AlGaAs/GaAs distributed feedback lasers with low threshold current

    Page(s): 4 - 6
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    Ridge waveguide AlGaAs/GaAs distributed feedback lasers were fabricated by a two‐step molecular beam epitaxial growth technique. A threshold current as low as 42 mA, which is the lowest ever reported, was obtained under a continuous wave condition at room temperature. Stable single longitudinal mode oscillation was observed in the temperature range from -20 to 30 °C without any suppression of the Fabry–Perot mode. View full abstract»

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  • Highly efficient multiple emitter index guided array lasers fabricated by silicon impurity induced disordering

    Page(s): 7 - 9
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    We describe the fabrication of closely spaced arrays of buried heterostructure semiconductor lasers by the process of silicon impurity induced disordering. These devices have the low threshold currents which are associated with buried heterostructure lasers, as well as high overall device efficiency. The device we have analyzed for this letter exhibits a threshold current of 53 mA, differential quantum efficiency of 62%, and a total power conversion efficiency of 43% when operating at a power output level of 250 mW. These numbers indicate that this technology is quite promising for the fabrication of high power semiconductor laser arrays. View full abstract»

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  • Electro‐optical response of a liquid‐crystalline fiber coupler

    Page(s): 10 - 12
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    The electro‐optical properties of a thin layer of nematic liquid crystal, sandwiched between two side‐polished single‐mode optical fibers and flanked by electrodes, are investigated by documenting the response of the resulting fiber coupler to electric fields of different frequencies and amplitudes. It is found that similar coupling states (corresponding to similar states of the liquid crystal) are created at every driving frequency if the correct voltage level (above a threshold dependent on the coupling state) is selected. The presence of certain resonance peaks in the frequency response of the liquid crystal (to our knowledge not before observed) is explained phenomenologically in terms of orientational standing‐wave patterns between the electrodes. View full abstract»

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  • Vapor diffused optical waveguides in strontium barium niobate (SBN: 60)

    Page(s): 13 - 15
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    Single mode planar and channel waveguides have been produced in Sr0.6Ba0.4Nb2O6 (tungsten bronze structure) by sulfur diffusion in a sealed ampule, followed by oxidation in an open tube. Losses in channel waveguides were ∼15–20 dB/cm for TM polarization and ∼27–32 dB/cm for the TE polarization in z‐cut substrates. Electro‐optic modulation was observed after poling of the substrate. The experimentally determined value of the effective electro‐optic coefficient was slightly greater than reported earlier for bulk samples of SBN:60, and about 15 times greater than for LiNbO3. Based on measurements with the S35 radioisotope, the average atomic sulfur concentration was estimated to be about 4×1017/cm3 in the region extending from the surface to a depth of 2.5 μm, and a significant background concentration (∼5×1016/cm3) was present to depths in excess of 20 μm. View full abstract»

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  • Eigenmode analysis of phase‐locked semiconductor laser arrays

    Page(s): 16 - 18
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    A self‐consistent model of phased‐array diode lasers, which takes into account the interaction of the carrier and the field, is presented with numerical simulations on both ideal dielectric coupled waveguides and active phased arrays. While essential agreement between the results of this model and those of coupled mode analysis is obtained for passive waveguides, important differences are found for active arrays. Our results show the development of patterns for the various array modes in the active regions. View full abstract»

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  • Silver ion‐exchanged, buried, glass optical waveguides with symmetric index profile

    Page(s): 19 - 20
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    Symmetrical buried waveguides with fiberlike refractive index profiles using Ag+‐Na+ exchange have been realized in soda‐lime‐silicate glass substrates. A simple scanning electron microscope technique to determine the silver ion (refractive index) profile is also reported. View full abstract»

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  • Zeeman effect polarimetry of Ti XVII 3834 Å line in the Texas Experimental Tokamak

    Page(s): 21 - 23
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    We present the first measurement of a tokamak plasma internal magnetic field based on the analysis of polarization of Zeeman components of a magnetic dipole transition in heavy impurity ion. The circular polarization of the Ti XVII 3834 Å line is studied. The values of the component of the toroidal magnetic field in the direction of observation are measured for several observation angles and good agreement with expected values is found. The result indicates that the method may be useful for measuring the local magnetic field and in particular, the poloidal component of the field, in a tokamak. View full abstract»

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  • X‐ray refractive index: A tool to determine the average composition in multilayer structures

    Page(s): 24 - 26
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    We present a novel and simple method to determine the average composition of multilayers and superlattices by measuring the x‐ray refractive index. Since these modulated structures exhibit Bragg reflections at small angles, by using a triple axis x‐ray spectrometer we have accurately determined the peak shifts due to refraction in GaAs/AlxGa1-xAs and Nb/Ta superlattices. Knowledge of the refractive index provides the average fractional composition of the periodic structure since the refractive index is a superposition of the refractive indices of the atomic constituents. We also present a critical discussion of the method and compare the values of the average fractional composition obtained in this manner to the values obtained from the lattice parameter change in the GaAs/AlxGa1-xAs superlattices due to the Al. View full abstract»

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  • Oxidation resistant sol‐gel derived silicon oxynitride thin films

    Page(s): 27 - 29
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    Silicon oxynitride films, made by reacting porous, sol‐gel derived silicon dioxide with ammonia, were oxidized in dry O2 between 800 and 1000 °C. Film oxidation was characterized by ellipsometry and secondary ion mass spectrometry. Increasing the nitrogen content of the film increased oxidation resistance of the film. View full abstract»

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  • New laterally selective growth technique by metalorganic chemical vapor deposition

    Page(s): 30 - 32
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    Laterally selective growth of III‐V compounds has been successfully demonstrated by metalorganic chemical vapor deposition. This was achieved by using a specially designed growth chamber and susceptor that allows the substrate to move with respect to a stationary GaAs or Si mask. We have used this technique to selectively deposit GaAs1-xPx with different values of x and a GaAs‐GaAsP superlattice on a single GaAs substrate. We have also selectively grown multiple color light‐emitting diodes on a GaAs substrate. View full abstract»

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  • Hydrogen radical assisted chemical vapor deposition of ZnSe

    Page(s): 33 - 35
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    Hydrogen radicals are employed in the growth of ZnSe. They react with starting gases to form long‐lifetime precursors for deposition. The major advantages of hydrogen radical assisted chemical vapor deposition over the existing methods include (1) low‐temperature growth, (2) plasma‐free substrate, (3) selective precursor formation, (4) substrate cleaning effect, (5) rearrangement of atoms on the growing surface, and (6) passivation of grain boundaries or dangling bonds. Highly (111) axis oriented ZnSe films have been prepared on glass substrates at 200 °C. The temperature dependence of the electrical conductivity in the dark and the photoconductive response suggest low density of traps. Epitaxial ZnSe films on GaAs substrates have been obtained at 200 °C. View full abstract»

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  • AlGaAs/GaAs(111) heterostructures grown by molecular beam epitaxy

    Page(s): 36 - 37
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    We have grown AlGaAs/GaAs heterostructures on (111) oriented GaAs substrates by molecular beam epitaxy. Materials with good optical and electrical properties, including mobility enhancement in two‐dimensional electron and hole gases, have been obtained for the first time. View full abstract»

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  • Relationship between secondary defects and electrical activation in ion‐implanted, rapidly annealed GaAs

    Page(s): 38 - 40
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    The removal of lattice damage and consequent activation by rapid thermal annealing of implanted Si, Se, Zn, and Be in GaAs was investigated by capacitance‐voltage profiling, Hall measurements, transmission electron microscopy (TEM), secondary ion mass spectrometry, and Rutherford backscattering. The lighter species show optimum electrical characteristics at lower annealing temperatures (∼850 °C for Be, ∼950 °C for Si) than the heavier species (∼900 °C for Zn, ∼1000 °C for Se), consistent with the amount of lattice damage remaining after annealing. TEM reveals the formation of high densities (107 cm-2) of dislocation loops after 800 °C, 3 s anneals of high dose (1×1015 cm-2) implanted GaAs, which are gradually reduced in density after higher temperature anneals (∼1000 °C). The remaining loops do not appear to affect the electrical activation or carrier mobility in the implanted layer, the latter being comparable to bulk values. View full abstract»

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  • Effect of organic contaminants on the oxidation kinetics of silicon at room temperature

    Page(s): 41 - 43
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    The oxidation kinetics of HF‐etched n‐ and p‐doped silicon in air at room temperature have been studied by electron spectroscopy for chemical analysis. No great differences have been found between the n‐ and p‐type oxidation kinetics at the low doping level of the studied samples. The rate of oxide growth on the HF‐etched surface is much lower than that on a silicon surface obtained by fracture in air of a silicon monocrystal. The behavior of a silicon sample fractured in de‐ionized water and then oxidized in air at room temperature is intermediate. The above findings have been interpreted on the basis of surface reactions involving the plasticizers of the HF and water containers. These reactions produce carbon‐rich hydrophobic surfaces which retard the silicon oxide growth. A mechanism for the involved surface reactions is proposed. View full abstract»

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  • Diffusion of Ag and Hg at the Ag/(Hg, Cd)Te interface

    Page(s): 44 - 46
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    The room‐temperature Ag/(Hg, Cd)Te interface has been studied in ultrahigh vacuum with x‐ray and ultraviolet photoelectron spectroscopy. The Ag evaporated onto (Hg, Cd)Te diffuses 102–103 Å into the bulk of the semiconductor, displacing Hg as it does so. The bands bend 0.05–0.1 eV upward at low coverage. No significant chemical reaction is observed. View full abstract»

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  • Morphological studies of oval defects in GaAs epitaxial layers grown by molecular beam epitaxy

    Page(s): 47 - 49
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    The detailed morphology of defects occurring in GaAs layers grown by molecular beam epitaxy (MBE) was determined by high resolution scanning electron microscopy and scanning Auger spectroscopy under various substrate preparation and MBE growth conditions. It was observed that surface defects commonly identified as oval defects are of two varieties: particulate‐originated defects and liquid‐gallium‐originated defects. The former type was shown to be sensitive to the cleanliness of the surface, while the latter type was shown to be determined primarily by the growth conditions. In addition, we found the use of an arsenic cracking source eliminated the liquid‐gallium‐originated defects. View full abstract»

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  • Characterization of beam‐recrystallized Si films and their Si/SiO2 interfaces in silicon‐on‐insulator structures

    Page(s): 50 - 52
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    A technique equivalent to the conventional C(V) measurement is developed for silicon‐on‐insulator technology. A depletion mode transistor is used. The ID(VG) characteristic and its derivative, i.e., the transconductance, allow the determination of the doping of the Si film, the oxide thickness, the fixed oxide charge at both Si/SiO2 interfaces. The device can be used in process control without any extra process steps. View full abstract»

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  • Raman scattering study of disordering and alloying of GaAs‐AlAs superlattice by As implantation and rapid thermal annealing

    Page(s): 53 - 55
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    Disordering and alloying of the GaAs‐AlAs superlattice by high‐dose implantation of As ions and rapid thermal annealing were studied by Raman scattering. It was found that the superlattice was disordered by ion implantation, and the spectrum of the resulting amorphous phase was identical to the spectrum of amorphous AlxGa1-xAs alloy. It consisted of GaAs‐ and AlAs‐type bands which had the same energies as corresponding bands in amorphous GaAs and AlAs. The ratio of intensities of the bands reflected the Al content. After annealing, the crystalline AlxGa1-xAs alloy was formed with composition dependent on actual thickness of the superlattice layers. View full abstract»

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  • Stability of semiconductor strained‐layer superlattices

    Page(s): 56 - 58
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    The criteria for strained‐layer growth of semiconductor superlattices are discussed. It is shown that to avoid misfit dislocations, careful attention has to be paid to the composition, geometry, and dimensions of the quantum well structure. Two critical thicknesses are found to apply to strained‐layer superlattice growth, one relating to the thickness of individual layers and one relating to the overall thickness of the superlattice. We derive the relationship between these two critical values. Experimental studies of the GexSi1-x/Si on Si and GexSi1-x/Ge on Ge systems using electron microscopy, Raman scattering, and ion channeling show that exceeding the critical superlattice thickness results in a network of dislocations between the substrate and first superlattice layer. View full abstract»

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  • Observation of new common emissions in GaAs produced by ion implantation of four acceptor impurities

    Page(s): 59 - 61
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    Photoluminescence studies of C+, Mg+, Zn+, and Cd+ ion‐implanted GaAs layers were carried out at 2 K. Two conspicuous emissions denoted by g and [g‐g] were observed to be situated between bound exciton and band to acceptor emissions. It was found that these two are common emissions among the above acceptor impurities, and that they can be explicitly observed only when the background impurity concentration is extremely small. View full abstract»

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  • Light‐induced metastable defects in amorphous silicon: The role of hydrogen

    Page(s): 62 - 64
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    The role of hydrogen in the creation and annealing kinetics of the light‐induced metastable defects in hydrogenated amorphous silicon is investigated using electron spin resonance. Deuterated and hydrogenated films exhibited the same defect creation rate and nearly identical distributions of annealing energies. Implications of these results for various microscopic models for the creation of metastable defects are discussed. View full abstract»

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  • High resolution electron microscopic and spectroscopic characterization of semi‐insulating polycrystalline silicon and its interface with single‐crystal silicon

    Page(s): 65 - 67
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    A combination of high resolution electron microscopy (HREM), electron energy loss spectroscopy (EELS), energy dispersive x‐ray analysis (EDXA), and scanning transmission electron microscopy (STEM) techniques has been employed to characterize the structure and composition of vapor‐deposited thin films of semi‐insulating polycrystalline silicon (SIPOS) and their interfaces with Si. SIPOS layers containing ∼30 at. % of oxygen are amorphous when deposited at Si substrate temperature of 625 °C. Upon annealing at 900 °C in N2 for 30 min, Si crystallites up to ∼100 Å in size appear throughout the SIPOS layer, the microstructure of which appears to be a dispersion of Si crystallites in an amorphous matrix. The plasmon‐loss spectra show a characteristic energy for each material: 16.7 eV for Si, 17.6 eV for SIPOS, and 23.2 eV for SiO2, which correlate empirically with increasing oxygen content in these materials. A combination of HREM and STEM revealed the existence of a 25–30‐Å native oxide layer between the SIPOS and Si substrate. This native oxide yields a plasmon loss at 22 eV using a 10‐Å probe in the STEM. View full abstract»

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  • Nondestructive depth profiling of carrier lifetimes in full silicon wafers

    Page(s): 68 - 70
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    We demonstrate for the first time that the phase shift associated with amplitude modulated, near band‐edge photoluminescence from Si at room temperature can be used to map defects and carrier lifetimes over full wafers with depth sensitivity. View full abstract»

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  • High‐frequency amplification and generation in charge injection devices

    Page(s): 71 - 73
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    Room‐temperature high‐frequency measurements on a three‐terminal amplifying device based on real‐space hot‐electron transfer between two conducting layers separated by a potential barrier have been performed. The devices grown by organometallic chemical vapor deposition utilize a novel undoped GaAs/AlGaAs heterostructure which, through its dramatically reduced parasitic leakage compared to previous structures, permits, for the first time, operation as a charge injection transistor. The charge injection transistor exhibits true three‐terminal amplification due to real‐space hot‐electron transfer controlled by electron temperature in a high mobility channel. The device demonstrates power and current gains with cut‐off frequencies of 9.8 and 29 GHz, respectively, with maximum current gain of 39 dB. In the negative resistance transistor mode, the same device was found capable of microwave generation up to 7.7 GHz. The frequency response of our device is shown to be limited by RC in the output circuit and methods for improvement of the cut‐off frequency are discussed. View full abstract»

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Applied Physics Letters, published by the American Institute of Physics, features concise, up-to-date reports on significant new findings in applied physics.

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Nghi Q. Lam
Argonne National Laboratory