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Applied Physics Letters

Issue 17 • Date Apr 1992

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Displaying Results 1 - 25 of 44
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Blue and green diode lasers in ZnSe‐based quantum wells

    Page(s): 2045 - 2047
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    Laser diode operation has been obtained from (Zn,Cd)Se/ZnSe and (Zn,Cd)Se/Zn(S,Se) quantum well structures in the blue and the green. The devices, prepared on p‐ and n‐type (In,Ga)As or GaAs buffer layers for lattice matching purposes to control the defect density, have been operated at near‐room‐temperature conditions and briefly at room temperature with uncoated end facets. Quasi‐continuous wave operation has been obtained at T=77 K. View full abstract»

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  • High frequency magnetic field sensors based on the Faraday effect in garnet thick films

    Page(s): 2048 - 2050
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    The Faraday effect in the thick epitaxial films of magnetic garnets of the type used in magneto‐optic isolators can be used as the basis for a fiber‐optic magnetic field sensor. These films have uniaxial anisotropy perpendicular to the surface and they contain bismuth to enhance the Faraday rotation. The typical magnetic domain pattern of meandering stripes changes in response to an applied field perpendicular to the film and this changes the polarization of infrared light propagating perpendicular to the film. Theory and experiment show that the speed of operation is limited by relaxation or resonance effects to upper frequencies between 106 and 109 Hz. Maximum sensitivity requires low magnetic moment and large thickness, in conflict with the requirements for high speed. View full abstract»

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  • Characterization of recombination processes in multiple narrow asymmetric coupled quantum wells based on the dependence of photoluminescence on laser intensity

    Page(s): 2051 - 2053
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    Continuous‐wave intensity‐dependent photoluminescence spectra of multiple narrow asymmetric coupled quantum wells at room temperature have been measured. At low laser intensity, the total photoluminescence intensity is primarily proportional to the square of the laser intensity due to dominant nonradiative recombination of free carriers at nearly saturated interface traps. At high laser intensity, however, the total photoluminescence intensity approaches a level proportional to the laser intensity due to radiative recombination of free carriers. Based on this transition behavior, which has been observed for the first time to the best of our knowledge, and our simple theory, the transition intensity, the nonradiative decay time of the carriers, and the intensity‐dependent carrier density and photoluminescence quantum efficiency have been determined. View full abstract»

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  • Separate confinement electroabsorption modulator for 633 nm light

    Page(s): 2054 - 2056
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    A novel guided‐wave electroabsorption modulator, based on separate confinement of the optical modes and the applied electric field, is described. When demonstrated for 633 nm light using AlGaAs waveguide technology, the concept provides low insertion loss and extinction ratios as great as 100:1 (20 dB) while operating at less than 10 V. Other advantages include polarization insensitivity and low capacitance. View full abstract»

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  • Epitaxial surface‐emitting laser on a lattice‐mismatched substrate

    Page(s): 2057 - 2059
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    We have demonstrated continuous‐wave, room‐temperature, photopumped operation of a vertical‐cavity surface‐emitting laser having a 0.8% lattice mismatch with its GaAs substrate. Such mismatch provides flexibility in designing resonators with new lasing wavelengths. The laser resonator comprises lattice‐matched In0.12Ga0.88As and In0.10Al0.90As quarter‐wave layers for mirrors and a strained‐layer superlattice of In0.23Ga0.77As/Al0.35Ga0.65As for an active region. The structure lases in the range 1.05–1.10 μm under continuous‐wave photoexcitation in the wavelength range 900–950 nm. The differential power efficiency is as high as 68% and the threshold is 2 kW/cm2 (1.8 kA/cm2 injection current‐density equivalent). Dislocation line densities observed by photoluminescence microscopy are about 6×102/cm in both the active region and the uppermost mirror layers. The lines predominate along one 〈110〉 direction along which the laser light is preferentially polarized. These observations suggest a way of polarizing surface‐emitting lasers by intentional patterning of grating lines on the wafer surface. View full abstract»

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  • Third harmonic generation from MOx‐PbO‐GaO1.5 ternary glasses

    Page(s): 2060 - 2061
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    Third harmonic generation from nonconventional MOx‐PbO‐GaO1.5 (M=Ti,Nb,W) glasses have been measured. The nonlinear susceptibility, χ(3), of these glasses at 0.635 μm are about 30 times higher than that of SiO2 glass at the same wavelength. It has been found that TiO2 is most effective in increasing refractive index and χ(3).   View full abstract»

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  • Observation of screening effect in large‐area, cold‐cathode diodes

    Page(s): 2062 - 2064
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    In this work we report the first observation of the screening effect in large‐area, cold‐cathode diodes. A framing camera was used to observe the formation of emission centers (ECs) on a 200 cm2 velvet emitter. The density of ECs increased as a function of applied magnetic field as predicted. The current per EC decreased as the magnetic field was increased. These phenomena suggest methods of increasing the spatial and temporal uniformity of high‐power electron beams. View full abstract»

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  • Analysis of field emission from three‐dimensional structures

    Page(s): 2065 - 2067
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    An analysis of the field emission from emitter tips with the geometry of a prolate ellipsoid of revolution indicates that the field enhancement factor, β, and effective emission area, α, are not constant but instead depend on the applied field. The added complexity of a materials related limit on the minimum time for transition of an electron from the solid into the vacuum is also examined in the analysis. The calculated variations of α and β are as large as 35%, and in some instances could result in erroneous interpretation of measured current‐voltage (I‐V) characteristic data.   View full abstract»

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  • Hydrogen assisted heat transfer during diamond growth using carbon and tantalum filaments

    Page(s): 2068 - 2070
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    Much of the previous work on the role of atomic hydrogen in diamond growth has been focused on its formation on various refractory metal filaments, its reaction in the gas phase and its role in the growth mechanism. In contrast, the effect of atomic hydrogen recombination on substrate heating is addressed in this letter. Experiments were conducted in vacuum, helium, and hydrogen environments. Tantalum and carbon filaments were used to vary atomic hydrogen generation rates. Furthermore, methane was added in some experiments to determine its effect on hydrogen assisted ‘‘chemical’’ heating of the substrate. The results indicate that when substantial amounts of atomic hydrogen are generated at the filament, reactions of atomic hydrogen at the diamond growth surface have a pronounced effect on the substrate temperature. Use of carbon filaments lead to significantly diminished atomic hydrogen generation rates and much lower substrate temperatures. Additions of small amounts of methane to hydrogen also resulted in reduced atomic hydrogen generation rates and, consequently, lower substrate temperatures. View full abstract»

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  • New insight into the structure and growth of CaF2/Si(111)

    Page(s): 2071 - 2073
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    We have used transmission electron microscopy and x‐ray crystal truncation rod measurements to investigate thin (≪50 Å) CaF2 films grown on Si(111) substrates by molecular beam epitaxy. The results indicate that CaF2/Si can be structurally as perfect as NiSi2/Si and CoSi2/Si, and that a reconstructed layer is present at the CaF2/Si(111) interface. View full abstract»

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  • Effect of thermal treatment of passivation integrity of chemical vapor deposition silicon nitride

    Page(s): 2074 - 2076
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    The relationship between the pinhole density in silicon nitride layers deposited on oxide‐silicon structures and etching in buffered hydrofluoric acid is investigated in relation to the cooling down rate after Si3N4 deposition and subsequent annealing conditions. Si3N4 layers were deposited using a high temperature atmospheric pressure chemical vapor deposition technique on SiO2 patterned silicon substrates additionally covered with a thin SiO2 layer. Average numbers of pinholes per chip, as function of etch time, are presented both for differently treated wafers and for the specific locations on chips. The phenomenon is attributed to the preferential etching of Si3N4 in locations under stress. View full abstract»

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  • Inhibition of hydrogen plasma erosion and enhancement in wear resistance of tungsten implanted glassy carbon

    Page(s): 2077 - 2079
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    The hydrogen plasma erosion and abrasive wear resistance of glassy carbon implanted with tungsten has been studied as a function of ion dose. It was found that the onset of hydrogen plasma erosion inhibition occurred at a dose of ∼6.5×1015 ion/cm2. In addition, the tungsten implanted material exhibits an increase in wear resistance similar in magnitude to that obtained with nitrogen and other nonmetallic ions. Carbon ion implantation does not significantly inhibit erosion in a hydrogen plasma. Hence, the resistance to such erosion observed with tungsten implanted glassy carbon is believed to be due to a chemical effect specific to certain metallic ions. In contrast, increased wear resistance is a defect driven effect not specific to the ion used. View full abstract»

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  • Fabrication of modified lead iron niobate films

    Page(s): 2080 - 2082
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    The fabrication of new ferroelectric modified lead iron niobate films having an approximate composition Pb[(Fe0.7Cr0.2Ni0.1)0.5Nb0.5]O3 is reported. A magnetron sputtering technique was used for the deposition of the films and a post‐deposition annealing at 800 °C for 5 s in a rapid thermal processing furnace crystallizes the films principally into a perovskite‐type structure. Ferroelectricity in these films was confirmed by the presence of hysteresis loops, with a remanent polarization of 15 μC/cm2, and coercive field of 100 kV/cm. The room‐temperature dielectric constant measured at 1 kHz was 640 and the dissipation factor was 0.1. View full abstract»

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  • Mechanism for diamond nucleation and growth on single crystal copper surfaces implanted with carbon

    Page(s): 2083 - 2085
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    The nucleation and growth of diamond crystals on single‐crystal copper surfaces implanted with carbon ions has been studied. Microwave plasma‐enhanced chemical vapor deposition was used for diamond growth. The single‐crystal copper substrates were implanted either at room temperature or at elevated temperature (∼820 °C) with carbon ions prior to diamond nucleation. This procedure leads to the formation of a graphite film on the copper surface which greatly enhances diamond crystallite nucleation. From our study we construct a simple lattice model for diamond growth on graphite as 〈111〉diamond parallel to 〈0001〉graphite and 〈110〉diamond parallel to 〈112¯0〉graphite. View full abstract»

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  • Raman analysis of light‐emitting porous silicon

    Page(s): 2086 - 2088
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    Porous silicon that strongly emits in the visible was analyzed using Raman scattering. The spectrum peaks near 508 cm-1, has a width of ∼40 cm-1, and is very asymmetric. Using a model of phonon confinement, this suggests that the local structure of porous silicon is more like a sphere than a rod and has a characteristic diameter of 2.5–3.0 nm. Polarization Raman measurements suggest that the structure does not consist of a series of parallel columns. View full abstract»

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  • Characterization of diamondlike carbon by infrared spectroscopy?

    Page(s): 2089 - 2091
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    Comparison of Fourier transform infrared (FTIR) absorption spectroscopy, high resolution 13C nuclear magnetic resonance spectroscopy, and hydrogen evaluation by forward recoil elastic scattering (FRES) measurements shows that FTIR cannot be used to determine the carbon hybridization or total hydrogen content of diamondlike carbon films (DLC). FTIR absorption reflects only the optically active hydrogen in the DLC and, using it together with FRES, it can provide an estimate of the unbound hydrogen contained in the films. The fraction of unbound hydrogen can reach values of up to ∼50%. View full abstract»

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  • Formation of p+n junctions by Si++B+ implantation and laser annealing

    Page(s): 2092 - 2094
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    The effects of rapid thermal annealing (RTA) and laser annealing (LA) on the activation and diffusion of ion‐implanted boron in Si substrate have been investigated. The implant and anneal regimes, forming good shallow junctions, were presented. The Si+‐preamorphized samples boron implanted with a high dosage showed largely enhanced diffusion in RTA processing. The LA process serves as an excellent scheme to effectively activate the dopant and suppress the anomalous diffusion because of its very high heating rate. A high‐quality p+/n junction with a leakage current density lower than 2 nA/cm2 and a forward ideality factor of about 1.01 was formed by laser processing. View full abstract»

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  • Adatom processes near step‐edges and evolution of long range order in semiconductor alloys grown from vapor phase

    Page(s): 2095 - 2097
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    Single and multiple adatom energetics near the [110] and [1¯10] step edges on the As (2×4) reconstructed (missing dimer) GaAs (001) surface are examined to shed light on the issue of the occurrence of long range order in III‐III‐V alloys. Semiempirical potential functions and the simulated annealing procedure are employed. Step‐induced local breaking of symmetry and the adatom‐ledge interaction are found to favor the evolution of the 〈111〉 CuPt‐B type of ordering. View full abstract»

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  • Luminescence and Raman measurements of InyGa1-yP (0.3≪y≪0.5) grown by gas‐source molecular beam epitaxy

    Page(s): 2098 - 2100
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    We have measured the luminescence, luminescence excitation, and Raman spectra of undoped InyGa1-yP (0.3≪y≪0.5) films grown by gas‐source molecular beam epitaxy on GaAs substrates. We observe strong excitonic luminescence over the entire composition range investigated. The band gap derived from the luminescence excitation spectra corresponds to that of a fully relaxed InGaP film with no residual strain, which is confirmed by the Raman measurements. The dependencies of the Raman modes on alloy composition and ordering effects are discussed. View full abstract»

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  • Modeling the cycling degradation of silicon‐oxide‐nitride‐oxide‐semiconductor transistors

    Page(s): 2101 - 2103
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    A model has been developed to predict cycling‐induced threshold voltage shifts of silicon‐oxide‐nitride‐oxide‐semiconductor transistors. The model is based on the mechanism of hole transport through the tunnel oxide. It has been experimentally demonstrated that the model accurately predicts cycling behavior for a wide range of cycling parameters. Only two simple experiments are required to determine the model parameters. View full abstract»

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  • Electrical properties of InP grown by gas‐source molecular beam epitaxy at low temperature

    Page(s): 2104 - 2106
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    InP grown by gas‐source molecular beam epitaxy at low temperature has been studied by Hall effect and admittance spectroscopy measurements. Contrary to GaAs, InP grown at low temperature is n‐type and has low resistivity. The electron concentration of InP increases dramatically with decreasing growth temperature. A deep level at Ec-ED=320±50 meV is found to be the dominant donor in InP grown at low temperature. View full abstract»

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  • Uniform β‐SiC thin‐film growth on Si by low pressure rapid thermal chemical vapor deposition

    Page(s): 2107 - 2109
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    β‐SiC thin films have been grown on Si by rapid thermal chemical deposition at reduced pressures (LP‐RTCVD) as low as 5 Torr. The growth process involved the carbonization of the (100)Si surface by reaction with propane. Reducing the pressure resulted in a monotonic increase in growth rate. At a reaction temperature of 1300 °C, using 100 sccm of C3H8 (diluted to 5% in H2) and 0.9 lpm H2 carrier gas yielded a growth rate of 0.45 Å/s at 760 Torr and 18 Å/s at 5 Torr. A substantial increase in film thickness uniformity was observed at low pressure. At 5 Torr, the average thickness and standard deviation measured over the area of a 7.5 cm diam wafer were 1602 and 46 Å, respectively. This low standard deviation for LP‐RTCVD, equivalent to 2.87% of the average thickness, is the result of uniform growth over the entire specimen, including the edge region. In contrast, atmospheric pressure RTCVD results in severely nonuniform growth in the vicinity of the wafer edge. View full abstract»

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  • Photoreflectance study of photovoltage effects in GaAs diode structures

    Page(s): 2110 - 2112
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    Photoreflectance measurements of a GaAs p‐i‐n diode as a function of temperature (50–450 K) are reported. The photovoltage in the structure is obtained from the electric field strength which is determined from the Franz–Keldysh oscillations in the photoreflectance spectrum. The results are compared to those from an n‐GaAs structure where the Fermi level is pinned at the surface. In this case the photovoltage can be determined only by fixing the energy of the Fermi pinning level. The theoretical photovoltages are also calculated from the ideal p‐n and Schottky diode equations. This study clearly shows the importance of the photovoltage effects in the photoreflectance measurements. View full abstract»

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  • Observation of negative persistent photoconductivity in an n‐channel GaAs/AlxGa1-xAs single heterojunction

    Page(s): 2113 - 2115
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    We report the first observation of negative persistent photoconductivity at 4.2 K in an n‐channel modulation doped GaAs/Al0.33Ga0.67As single heterostructure, where two‐dimensional electrons have a mobility of ∼550 000 cm2/V s when density is ∼3.0×1011 cm-2. Based on extensive magnetotransport measurements, we conclude that the negative persistent photoconductivity effect comes from the time dependence of (1) the annihilation of two‐dimensional electrons by photoexcited holes, and (2) the trapping and de‐trapping of photoexcited electrons by shallow donors in doped Al0.33Ga0.67As. A model that quantitatively explains the nonexponential recovery time is presented. 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