Showing papers in "Applied Physics Letters in 1984"
TL;DR: In this paper, an extremely narrow aperture along a test object equipped with fine-line structures was used to demonstrate a resolving power of at least λ/20 which is to be compared with the values of λ 2.3 obtainable in conventional optical microscopy.
Abstract: Subwave length‐resolution optical image recording is demonstrated by moving an extremely narrow aperture along a test object equipped with fine‐line structures. Details of 25‐nm size can be recognized using 488‐nm radiation. The result indicates a resolving power of at least λ/20 which is to be compared with the values of λ/2.3 obtainable in conventional optical microscopy.
2,038 citations
TL;DR: In this article, the generation transmission and detection of extremely rapid electromagnetic pulses have been achieved using fast photoconducting materials as time-varying Hertzian dipoles, which overcomes many of the limitations imposed by transmission line structures, and due to its jitter free behavior and open geometry is ideally suited for transient electromagnetic measurements of materials.
Abstract: The generation transmission, and detection of extremely rapid electromagnetic pulses have been achieved using fast photoconducting materials as time‐varying Hertzian dipoles. This approach, which has a measured time response of 1.6 ps, overcomes many of the limitations imposed by transmission line structures, and due to its jitter‐free behavior and open geometry is ideally suited for transient electromagnetic measurements of materials.
992 citations
TL;DR: In this article, the authors confirmed greatly improved resistance to photorefractive damage in compositions of lithium niobate containing 4.5 at.m. of MgO or more.
Abstract: We have confirmed greatly improved resistance to photorefractive damage in compositions of lithium niobate containing 4.5 at. % MgO or more. Holographic diffraction measurements of photorefraction demonstrated that the improved performance is due to a hundredfold increase in the photoconductivity, rather than a decrease in the Glass current. The diffraction efficiency shows an Arrhenius dependence on temperature, with an activation energy of 0.1 eV for the damage‐resistant compositions, compared with 0.5 eV for undoped or low‐magnesium compositions. The damage‐resistant compositions are distinguished by a 2.83‐μm absorption line instead of the usual 2.87‐μm line due to the OH‐stretch vibration.
619 citations
TL;DR: In this article, it was shown that bulk specimens (0.4-4 g mass) of the alloy Pd40Ni40P20 have been undercooled consistently to the glass state with no detectable superficial crystallinity, in a molten flux of dehydrated boron oxide.
Abstract: Bulk specimens (0.4-4 g mass) of the alloy Pd40Ni40P20 have been undercooled consistently to the glass state, with no detectable superficial crystallinity, in a molten flux of dehydrated boron oxide. The minimum dimension of the most massive glass specimen, so formed, was 1.0 cm. The absence of crystallinity in the specimens was confirmed by X-ray diffraction, scanning electron microscopy, and calorimetry.
539 citations
TL;DR: In this article, a self-electro-optic effect device (SEED) was proposed, which uses the same GaAs/GaAlAs multiple quantum well material simultaneously as an optical detector and modulator.
Abstract: We report a new type of optoelectronic device, a self‐electro‐optic effect device (SEED), which uses the same GaAs/GaAlAs multiple quantum well material simultaneously as an optical detector and modulator. Using a series resistor and constant voltage bias supply the SEED shows optical bistabilty (OB) of the recently discovered type which relies on increasing absorption and requires no mirrors. OB is seen at room temperature from ∼850–860 nm, at powers as low as 670 nW or switching times as short as 400 ns (limited only by power restrictions) with ∼1‐nJ optical switching energy in a 600‐μm‐diam device. Total energies per unit area (∼18 fJ/μm2) are substantially lower than any previously reported for OB.We report a new type of optoelectronic device, a self‐electro‐optic effect device (SEED), which uses the same GaAs/GaAlAs multiple quantum well material simultaneously as an optical detector and modulator. Using a series resistor and constant voltage bias supply the SEED shows optical bistabilty (OB) of the recently discovered type which relies on increasing absorption and requires no mirrors. OB is seen at room temperature from ∼850–860 nm, at powers as low as 670 nW or switching times as short as 400 ns (limited only by power restrictions) with ∼1‐nJ optical switching energy in a 600‐μm‐diam device. Total energies per unit area (∼18 fJ/μm2) are substantially lower than any previously reported for OB.
510 citations
TL;DR: In this article, the authors explored the hard magnetic properties of melt-spun Nd-Fe-B alloys and found that the coercivity arises principally from the formation of single-domain particles.
Abstract: We have explored the hard magnetic properties of melt‐spun Nd‐Fe‐B alloys. A maximum energy product of 14.1 MG Oe has been observed, the highest value ever reported for a light rare earth‐iron material. X‐ray analyses indicate that the alloys exhibiting optimum characteristics are comprised of roughly spherical crystallites of an equilibrium Nd‐Fe‐B intermetallic phase. The observed grain sizes are in or near the estimated single‐domain range, suggesting that the coercivity arises principally from the formation of single‐domain particles.
442 citations
TL;DR: In this article, the energy levels of defect states in amorphous silicon nitride have been calculated and the results are used to identify the nature of trap states responsible for charge trapping during transport and the charge storage leading to memory action.
Abstract: The energy levels of defect states in amorphous silicon nitride have been calculated and the results are used to identify the nature of trap states responsible for charge trapping during transport and the charge storage leading to memory action. We argue that the Si dangling bond is the memory trap in chemical vapor deposited memory devices and is also the center in plasma‐deposited nitride responsible for hopping at low electric fields and for charge‐trapping instabilities in amorphous silicon‐silicon nitride thin‐film transistors.
402 citations
TL;DR: In this paper, the authors studied Raman scattering from 〈100〉 GaAs samples implanted with 270-keV As+ ions with various fluences up to 3.2×1014 cm−2, and observed a softening and asymmetric broadening of the allowed LO phonon while the small symmetry forbidden TO phonon remains almost unchanged.
Abstract: We have studied Raman scattering from 〈100〉 GaAs samples implanted with 270‐keV As+ ions with various fluences up to 3.2×1014 cm−2. In addition to phonon density of states effects, we observe a softening and asymmetric broadening of the allowed LO phonon while the small symmetry forbidden TO phonon remains almost unchanged. The behavior of the LO and TO modes can be explained quantitatively on the basis of a ‘‘spatial correlation’’ model related to q‐vector relaxation induced by the damage. Our interpretation is quite general and makes it possible to use Raman spectra to evaluate an average size of undamaged regions in semiconductors.
378 citations
TL;DR: In this article, high resolution Si 2p photoelectron spectra obtained with synchrotron radiation were used to determine the distribution of oxidation states in the intermediary layer at the SiO2Si interface.
Abstract: High resolution Si 2p photoelectron spectra obtained with synchrotron radiation are used to determine the distribution of oxidation states in the intermediary layer at the SiO2‐Si interface. A ratio of 0.4:0.3:0.3 is found for the Si3+:Si2+:Si1+ intensities independent of Si surface orientation and oxide thickness. The interface is not completely abrupt (5±1 A width).
376 citations
TL;DR: In this paper, a new type of high-speed optical modulator is proposed and demonstrated, where an electric field is applied perpendicular to GaAs/GaAlAs multiple quantum well layers using a diode doping structure of 4μm total thickness.
Abstract: A new type of high‐speed optical modulator is proposed and demonstrated An electric field is applied perpendicular to GaAs/GaAlAs multiple quantum well layers using a ‘‘p‐i‐n’’ diode doping structure of 4‐μm total thickness The optical absorption edge, which is particularly abrupt because of exciton resonances, shifts to longer wavelengths with increasing field giving almost a factor of 2 reduction in transmission at 857 nm with an 8‐V reverse bias The shifts are ascribed to changes in carrier confinement energies in the wells The observed switching time of 28 ns is attributed to RC time constant and instrumental limitations only, and fundamental limits may be much faster
371 citations
TL;DR: In this article, a chiral-doped nematic layer with tilted boundaries and a twist angle of ∼270° was used for a 120×240 dot matrix panel multiplexed at a 1/120 duty cycle.
Abstract: A new, highly multiplexable liquid crystal display is described, which has a superior image quality than a twisted nematic display multiplexed at the same high level. The display cell consists of a chiral‐doped nematic layer with tilted boundaries and a twist angle of ∼270°. It operates in a birefringent optical mode between two ‘‘nonconventionally’’ oriented polarizers. Performance characteristics presented for a 120×240 dot matrix panel multiplexed at a 1/120 duty cycle include driving voltages compatible with complementary‐metal‐oxide‐semiconductor technology, 300‐ms response times, a contrast ratio of 10:1 at normal incidence, and ≥4:1 inside a viewing cone of 45° from the vertical.
TL;DR: In this paper, hyperfine control of the interface structure and composition between GaAs and AlAs films grown by molecular beam epitaxy has been achieved by deposition on vicinal (100) GaAs substrates.
Abstract: Hyperfine control of the interface structure and composition between GaAs and AlAs films grown by molecular beam epitaxy has been achieved by deposition on vicinal (100) GaAs substrates. This control is demonstrated by producing (GaAs)m‐(AlAs)n submonolayer (m and/or n<1) superlattices over a wide temperature range. Analysis of these submonolayer superlattices by transmission electron microscopy shows that the layer growth regime is dominant and that layer nucleation is initiated preferentially at the step edges on the (100) vicinal surface. Potential applications of submonolayer superlattices including the growth of superlattice layers perpendicular to the substrate surface are described.
TL;DR: In this article, a coupledmode analysis has been developed to describe the output of phase-locked injection laser arrays, showing that an array of emitters with weak coupling can only operate in a set of discrete modes determined by the number and the spacing of the emitters.
Abstract: A coupled‐mode analysis has been developed to describe the output of phase‐locked injection laser arrays. We show that an array of emitters with weak coupling can only operate in a set of discrete modes determined by the number and the spacing of the emitters. The interaction between emitters leads to a splitting of the common frequency of operation that can be estimated from the coupling strength. The coupled‐mode analysis is compared to calculations based on simple diffraction theory. A consequence of the analysis is an explanation for the commonly observed discrepancy between experimentally observed far‐field lobe(s) widths and those predicted by simple diffraction theory.
TL;DR: In this article, the first observation of the modulation doping effect in Si/Ge0.2Si0.8 heterojunctions grown by molecular beam epitaxy was reported, and a hole effective mass of 0.30±0.02mo has been derived.
Abstract: We report the first observation of the modulation doping effect in Si/Ge0.2Si0.8 heterojunctions grown by molecular beam epitaxy. Peak hole mobilities of ∼3300 cm2 V−1 s−1 have been observed at 4.2 K. These values, although nonoptimum, are comparable to the best reported values for holes in Si/SiO2 inversion layers. Low temperature, angular dependent, Shubnikov–de Haas measurements have demonstrated the two‐dimensional nature of the hole gas and yield a surface carrier density of 3.5×1011 cm−2. From the temperature dependence of the Shubnikov–de Haas amplitudes a hole effective mass of 0.30±0.02mo has been derived. Identical measurements on n‐type heterojunctions having the same Ge content (x=0.2) have failed to show a sustained enhancement of mobility at low temperatures, indicating that ΔEv≫ΔEc.
TL;DR: In this paper, the electrical properties of thin-film CuInSe2 deposited by coevaporation of the elements have been measured by different techniques as a function of material composition, and a correlation between the Cu/In and Se/metal ratios versus majority carrier concentration is established.
Abstract: The electrical properties of thin‐film CuInSe2 (<4 μm thick) deposited by coevaporation of the elements have been measured by different techniques as a function of material composition. A correlation between the Cu/In and Se/metal ratios versus majority‐carrier concentration is established. A qualitative scheme is developed, based on experiments, which predicts the majority‐carrier type and concentration in relation to the stoichiometry of the material.
TL;DR: In this article, the authors compared the performance of XeF2 and F•atom etching under conditions typical of those used in plasma etching and showed that physisorption can limit silicon etching.
Abstract: Silicon gasification by XeF2 is compared with F‐atom etching under conditions typical of those used in plasma etching. Temperatures ranged from −17 to 360 °C and XeF2 pressures were between 0.05 and 2 Torr. Silicon etching by XeF2 shows a sharply different etch rate/temperature dependence than the Si/F or Si/F2 reaction systems; there is no detectable reaction between XeF2 and SiO2 in contrast to the F‐atom/SiO2 system. These data indicate that physisorption can limit silicon etching by XeF2 and show that basic studies which use XeF2 as a model compound for the etching of silicon and SiO2 by F atoms should be interpreted with caution.
TL;DR: In this article, double barrier resonant tunneling structures have been used to increase the tunneling current density by a factor of nearly 100, with the attendant increase in gain and improved impedance match to the resonant circuit.
Abstract: Oscillations have been observed for the first time from double barrier resonant tunneling structures. By eliminating impurities from the wells, we have been able to increase the tunneling current density by a factor of nearly 100. With the attendant increase in gain and improved impedance match to the resonant circuit, the devices oscillated readily in the negative resistance region. Oscillator output power of 5 μW and frequencies up to 18 GHz have been achieved with a dc to rf efficiency of 2.4% at temperatures as high as 200 K. It is shown that higher frequencies and higher powers can be expected.
TL;DR: In this paper, a beam epitaxial growth technique, chemical beam epitaxy (CBE), was demsonstrated and investigated with the growth of InP and GaAs.
Abstract: A new epitaxial growth technique, chemical beam epitaxy (CBE), was demsonstrated and investigated with the growth of InP and GaAs. In this technique, all the sources were gaseous group III and group V alkyls. The In and Ga were derived by the pyrolysis of either trimethylindium or triethylindium and trimethylgallium or triethylgallium at the heated substrate surface, respectively. The As2 and P2 were obtained by thermal decomposition of triethylphosphine and trimethylarsine in contact with heated Ta or Mo at 950–1200 °C, respectively. Unlike conventional vapor phase epitaxy, in which the chemicals reach the substrate surface by diffusing through a stagnant carrier gas boundary layer above the substrate, the chemicals in CBE were admitted into a high vacuum growth chamber and impinged directly light of sight onto the heated substrate surface in the form of molecular beams. The beam nature of CBE resulted in efficient use of the impinging chemicals and allowed the utilization of mechanical shutters. A gas h...
TL;DR: In this paper, a new mode of IR detection using photoemission from a single quantum well is proposed and optimization of the device performance by the proper choice of parameters is discussed.
Abstract: A new mode of IR detection using photoemission from a single quantum well is proposed and optimization of the device performance by the proper choice of parameters is discussed. Despite the very thin device structures, theoretical calculations show large absorption at wavelengths near cutoff. The largest photoemissive response is found by adjusting the well parameters so that an excited virtual state lies just above threshold.
TL;DR: In this paper, the authors studied Raman scattering from CdTe surfaces subjected to various surface treatments and showed that 0.1% Br/methanol etch or chemomechanical polish leaves a thin residual layer of polycrystalline Te of thickness 10-40 A (under a tensile stress of about 8 kbar).
Abstract: We have studied Raman scattering from CdTe 〈100〉, 〈110〉, and 〈111〉 surfaces subjected to various surface treatments. Our investigation shows that 0.1% Br/methanol etch or chemomechanical polish leaves a thin residual layer of polycrystalline Te of thickness 10–40 A (under a tensile stress of about 8 kbar) and that this Te film can be removed by a rinse in a 1 N KOH in methanol solution.
TL;DR: In this article, the Raman line from the Si layers of the strained-layer superlattices is indistinguishable from that from single-crystalline Si in both linewidth and frequency.
Abstract: Raman spectroscopy has been used to determine built‐up deformation in GexSi1−x/Si strained‐layer superlattice grown by molecular beam epitaxy. By comparing peak positions in commensurate superlattices and single layers with those from incommensurate thick layers of the same composition we can obtain a quantitative determination of strain. Linewidths are affected by the presence of inhomogeneous strain, dislocations, and disorder. Lines are always narrower in superlattice samples, indicating better crystalline quality. In particular, the Raman line from the Si layers of the strained‐layer superlattices is indistinguishable from that from single‐crystalline Si in both linewidth and frequency. This is consistent with the expectation that the entire lattice mismatch is accommodated as a homogeneous tetragonal strain in the alloy layers only.
TL;DR: In this paper, the epitaxial growth of GaAs and AlGaAs on (100) oriented Si substrates by molecular beam epitaxy was studied in situ by reflection high-energy electron diffraction.
Abstract: We have grown GaAs and AlGaAs on (100) oriented Si substrates by molecular beam epitaxy. The epitaxial growth was studied in situ by reflection high‐energy electron diffraction. Low‐temperature photoluminescence, Raman scattering, and scanning electron microscopy were used to characterize the epitaxial layers. It is shown for the first time that antiphase disorder could be suppressed. The doped AlGaAs grown directly on Si substrates exhibited PL efficiency similar to that of AlGaAs grown on GaAs substrates.
TL;DR: In this article, the same impurity is compared in different crystals, referring them to the vacuum level through the use of the photothreshold reveals a remarkable material invariance of the levels in III-V and II-VI semiconductors.
Abstract: Whereas the conventional practice of referring binding energies of deep donors and acceptors to the band edges of the host semiconductor does not produce transparent chemical trends when the same impurity is compared in different crystals, referring them to the vacuum level through the use of the photothreshold reveals a remarkable material invariance of the levels in III-V and II-VI semiconductors. It is shown that this is a consequence of the antibonding nature of the deep gap level with respect to the impurity atom-host orbital combinations.
TL;DR: In this paper, the relaxation oscillation corner frequency fr and linewidth enhancement factor alpha for both a quantum well and a quantum wire semiconductor laser were calculated and compared to those of a conventional double heterostructure device.
Abstract: We calculate the relaxation oscillation corner frequency fr and the linewidth enhancement factor alpha for both a quantum well and a quantum wire semiconductor laser. A comparison of the results to those of a conventional double heterostructure device indicates that fr can be enhanced by 2× in the quantum well case and 3× in the quantum wire case while alpha is reduced in both cases.
TL;DR: In this paper, the lattice mismatch between the GexSi1−x and Si layers can be accommodated by lattice distortion rather than by misfit dislocation formation.
Abstract: GexSi1−x layers are grown on Si substrates over the full range of alloy compositions at temperatures from 400–750 °C by means of molecular beam epitaxy. At a given growth temperature films grow in a smooth, two‐dimensional manner up to a critical germanium fraction xc. Beyond xc growth is rough. xc increases from 0.1 at 750 °C to 1.0 at ∼550 °C. Rutherford ion backscattering measurements indicate good crystallinity over a wide range of growth conditions. Transmission electron microscopy reveals that in thin films, the lattice mismatch between the GexSi1−x and Si layers can be accommodated by lattice distortion rather than by misfit dislocation formation. This pseudomorphic growth condition can persist to alloy thicknesses as large as l/4 μm.
TL;DR: In this article, a new type of hydrogen sensor is reported in which an optical fiber is used as the sensing element and the fiber is coated with palladium which expands on exposure to hydrogen.
Abstract: A new type of hydrogen sensor is reported in which an optical fiber is used as the sensing element. The fiber is coated with palladium which expands on exposure to hydrogen. This changes the effective optical path length of the fiber, which is detected by interferometric techniques. Preliminary experiments have demonstrated the effect and suggest a high sensitivity and a wide dynamic range for this kind of sensor. The experimental results are compared to calculated optical path length changes. Application of this kind of sensor to the detection of other chemicals appears feasible.
TL;DR: In this article, a model is developed based on the formation and rapid diffusion of Si nearest neighbor donor-acceptor pairs, and results from the codiffusion of Si and Ge support this model.
Abstract: Rapid thermal processing was used to diffuse Si into GaAs from a thin elemental source. Several encapsulants were applied. The diffusion was found to be dependent on the type of encapsulant. A model is developed based on the formation and rapid diffusion of Si nearest neighbor donor‐acceptor pairs. Results from the codiffusion of Si and Ge support this model.
TL;DR: In this paper, the effective interdiffusion coefficient of metallic bilayers under ion irradiation has been correlated with the heat of mixing of corresponding binary alloys, interpreted according to Darken's theory of chemically enhanced diffusion.
Abstract: The effective interdiffusion coefficient of metallic bilayers under ion irradiation has been correlated with the heat of mixing of corresponding binary alloys. The results are interpreted according to Darken's theory of chemically enhanced diffusion.
TL;DR: In this article, the first operation of an optical parametric oscillator in a chalcopyrite crystal, AgGaS2, was reported, with a tuning range from 1.4 to 4.0 microns.
Abstract: A report is presented of the first operation of an optical parametric oscillator in a chalcopyrite crystal, AgGaS2. Tuning from 1.4 to 4.0 microns is demonstrated for 1.06-micron Nd:yttrium aluminum garnet pumping. The potential tuning range extends to the 12-micron transparency limit of the crystal.
TL;DR: In this article, the third order intermodulation distortion product in the modulation response of high speed semiconductor lasers was investigated and it was shown that at low frequencies, an increase at a rate of 40 dB/dec as the modulation frequency is increased, and a leveling off at one half of the relaxation oscillation resonance frequency.
Abstract: A most important quantity in high‐frequency analog transmission is the intermodulation distortion product. Experimental studies of the third order intermodulation distortion products in the modulation response of high‐speed semiconductor lasers give very low values (<−60 dB) at low frequencies, an increase at a rate of 40 dB/dec as the modulation frequency is increased, and a leveling off at one‐half of the relaxation oscillation resonance frequency. These experimental results can be well explained by a theory based on a perturbative analysis of laser dynamics.