Showing papers in "Applied Physics Letters in 1983"
TL;DR: In this paper, X-ray diffraction was used to follow the progress of the mechanical alloying which eventually produced "amorphous" diffraction patterns similar to those for liquid quenched amorphous Ni60Nb40.
Abstract: ‘‘Amorphous’’ Ni60Nb40 has been prepared by mechanical alloying of elemental nickel and niobium powders in a laboratory ball mill in controlled environments. X‐ray diffraction was used to follow the progress of the mechanical alloying which eventually produced ‘‘amorphous’’ diffraction patterns similar to those for liquid quenched amorphous Ni60Nb40. Crystallization behavior was measured by differential scanning calorimetry for the mechanically alloyed and liquid quenched material. The differences that were observed in this behavior, and in the products of crystallization, may be attributed to impurities (especially oxygen) introduced during mechanical alloying.
1,001 citations
TL;DR: In this paper, a single quantum well of GaAs has been observed, and the current singularity and negative resistance region are dramatically improved over previous results, and detecting and mixing have been carried out at frequencies as high as 2.5 THz.
Abstract: Resonant tunneling through a single quantum well of GaAs has been observed. The current singularity and negative resistance region are dramatically improved over previous results, and detecting and mixing have been carried out at frequencies as high as 2.5 THz. Resonant tunneling features are visible in the conductance‐voltage curve at room temperature and become quite pronounced in the I‐V curves at low temperature. The high‐frequency results, measured with far IR lasers, prove that the charge transport is faster than about 10−13 s. It may now be possible to construct practical nonlinear devices using quantum wells at millimeter and submillimeter wavelengths.
900 citations
TL;DR: In this article, a reproducible process for growing a thick single-crystal layer of cubic SiC on a singlecrystal Si wafer by chemical vapor deposition is described, where a buffer layer, grown in situ, is used between the SiC and the Si substrate to minimize the effect of lattice mismatch.
Abstract: A reproducible process is described for growing a thick single-crystal layer of cubic SiC on a single-crystal Si wafer by chemical vapor deposition. A buffer layer, grown in situ, is used between the cubic SiC and the Si substrate to minimize the effect of lattice mismatch. Layers of up to 34 microns thick and several sq cm in area have been grown. Wafers are obtained by chemically removing the Si substrates from the grown layers. Excellent electron channeling patterns produced by these wafers indicate very good crystal quality. Preliminary electrical measurements have yielded electron mobilities up to 380 sq cm/Vs.
862 citations
TL;DR: In this article, well-resolved sharply structured luminescence spectra at 1.54 μm were observed in erbium-implanted GaP, GaAs, InP, and Si. The optical transitions occur between the weakly crystal field split spin-orbit levels, 4I13/2→4I15/2, of Er3+(4f11).
Abstract: Well‐resolved sharply structured luminescence spectra at 1.54 μm were observed in erbium‐implanted GaP, GaAs, InP, and Si. The optical transitions occur between the weakly crystal field split spin‐orbit levels, 4I13/2→4I15/2, of Er3+(4f11). Typical spectral linewidths in GaAs are 2 cm−1(0.25 meV) at 6 K and 11 cm−1(1.36 meV) at room temperature.
538 citations
TL;DR: In this paper, high quality all-refractory Josephson tunnel junctions based on Nb/Al−oxide−Nb and Nb−Al−Ooxide−Al/Nb structures are reported.
Abstract: Preparation of high quality all‐refractory Josephson tunnel junctions based on Nb/Al‐oxide‐Nb and Nb/Al‐oxide‐Al/Nb structures is reported. Critical currents up to 1300 A/cm2 and Vm values up to 35 mV were obtained. The specific capacitance of these junctions is 0.06±0.02 pF/μm2. Junctions were fabricated using standard photolithography and a new plasma etching process coupled with anodization of Nb.
530 citations
TL;DR: In this paper, the electrical and luminescent properties of GaN epitaxial films grown on AlN•coated sapphire by reactive molecular beam epitaxy have been studied.
Abstract: The electrical and luminescent properties of the GaN epitaxial films grown on AlN‐coated sapphire by reactive molecular beam epitaxy have been studied. The GaN films on AlN epitaxial films have larger Hall mobilities and show more intense cathodoluminescence peaks at a wavelength of 360 nm than those of the GaN films grown directly on sapphire, which suggests that the crystal qualities of GaN films are improved by use of AlN‐coated sapphire as substrates. The lattice matching and small difference of the thermal expansion coefficients between GaN and AlN are considered to result in the improvements.
374 citations
TL;DR: In this paper, the direct etching of polyethylene terephthalate (PET) film using a XeCl laser has been investigated and is shown to be consistent with a thermal model for degradation.
Abstract: The direct etching of polyethylene terephthalate film using a XeCl laser has been investigated and is shown to be consistent with a thermal model for degradation. Microstructure revealed by deep etching suggests the UV laser may prove useful for studying polymeric materials. Polyimide and photoresist film has also been directly etched.
355 citations
TL;DR: In this article, the light output was 1.3 times larger than that of the best Bi4Ge3O12, and the decay constant was 60 ns at room temperature.
Abstract: Cerium‐activated phosphors are characterized by their fast luminescence decay. Gadolinium orthosilicate (Gd2SiO5) is a material possessing a high atomic number, and can also play host to the cerium activator. Cerium‐doped Gd2SiO5 single crystals were grown by the Czochralski technique, and their luminescence properties were examined. The light output was 1.3 times larger than that of the best Bi4Ge3O12, and the decay constant was 60 ns at room temperature.
342 citations
TL;DR: In this article, the optical gap depends linearly on hydrogen content and Eopt can be varied between 0.8 and 1.8 eV, where sp3 (single) and sp2 (double) C-C bonds dominate.
Abstract: Hydrogenated amorphous (a‐C:H) films were prepared by rf‐plasma deposition from benzene vapor. Complete optical absorption spectra from the UV to the IR (0.2–20.0 μm) have been measured. The optical gap depends linearly on hydrogen content and Eopt can be varied between 0.8 and 1.8 eV. For energies below Eopt the films are almost transparent and absorption is especially low in the 2–6‐μm region (e.g., α=15 cm−1 at λ=2.8 μm). Sharp C–H stretch absorption bands occur near 3.4 μm, giving insight into the microstructure of the films. A newly reported weak band at 3.03 μm is first evidence for C–C triple bonds (sp1 hybridization) in a‐C:H, where sp3 (single) and sp2 (double) C–C bonds dominate.
327 citations
TL;DR: The most important instability mechanism in amorphous silicon-silicon nitride thin-film transistors is charge trapping in the silicon nitride layer, which leads to a threshold voltage shift (ΔVT).
Abstract: The most important instability mechanism in amorphous silicon‐silicon nitride thin‐film transistors is charge trapping in the silicon nitride layer, which leads to a threshold voltage shift (ΔVT). We have measured the time, temperature, and gate voltage dependence of ΔVT and conclude that the rate limiting process, in the charge transfer from semiconductor to insulator, is the conduction in the nitride by variable‐range hopping. The threshold shift (under positive bias) is temperature dependent with an activation energy of 0.3 eV. This activation energy is identified with the mean hop energy required to inject charge deep into the silicon nitride at the low applied fields appropriate to transistor operation.
308 citations
TL;DR: The transition from the crystalline to the amorphous phase can be explained in terms of a "chemical frustration" effect as discussed by the authors, and the transition can be confirmed using X-ray diffraction patterns, density measurements, and superconducting properties.
Abstract: Noncrystalline metallic hydrides can be formed from certain crystalline Zr3Rh intermetallic phases by hydrogenation. X-ray diffraction patterns, density measurements, and superconducting properties confirmed the transition from the crystalline to the amorphous phase by this solid state reaction. The transition can be explained in terms of a "chemical frustration" effect.
TL;DR: In this article, the authors measured the heat of crystallization, ΔHac, to be 11.9±0.7 kJ/mol, substantially less than the value predicted by scaling ΔHAC of a•Ge.
Abstract: Thin layers of amorphous silicon (a‐Si) were produced by noble gas ion implantation of (100) substrates held at 77 K. Rutherford backscattering and channeling, and differential scanning calorimetry were used to measure the heat of crystallization, ΔHac, to be 11.9±0.7 kJ/mol, substantially less than the value predicted by scaling ΔHac of a‐Ge. The crystal growth velocity is found to have the form v=v0 exp(−2.24 eV/kT). We obtain a new estimate, 1420 K, for the melting temperature of a‐Si.
TL;DR: In this paper, two new experiments were presented which suggest that the "bulk-compensating donor" phenomenon observed in pSi is probably a deactivation process of the boron acceptor by hydrogen with the formation of a B−H+ pair.
Abstract: Two new experiments are presented which suggest that the ‘‘bulk‐compensating donor’’ phenomenon observed in p‐Si is probably a deactivation process of the boron acceptor by hydrogen with the formation of a B−H+ pair. The two experiments are (i) avalanche hole injection in Al‐gate metal‐oxide‐silicon capacitor from boron‐diffused n‐Si substrate and (ii) 5‐keV electron irradiation of Al/p‐Si Schottky diodes. Atomic hydrogen may be released by the avalanche injected energetic electrons or holes or keV electrons from the Al–H, AlO–H, Si–H, and SiO–H sites in the Al gate and the SiO2 film as well as at the Al/SiO2 and SiO2/Si interfaces, which may then migrate to the boron acceptor sites to form the B−H+ pair. Observed hydrogen bond breaking rate by holes is as much as two orders of magnitude larger than by electrons, which is consistent with the thermal hole capture and energetic electron impact bond‐breaking models.
TL;DR: In this article, the double magneto-optical Kerr effect was measured at room temperature on the Heusler alloy PtMnSb in the wavelength range 280-2000 nm.
Abstract: Results are reported of polar magneto‐optical Kerr effect measurements performed at room temperature on the Heusler alloy PtMnSb in the wavelength range 280–2000 nm. The double Kerr rotation has a maximum in excess of 2.5° at 720 nm, which is to our knowledge the highest room‐temperature Kerr rotation reported thus far for any material in the wavelength range under consideration. In order to assess the influence of composition the related materials PdMnSb, NiMnSb, and PtMnSn were also investigated. Here the Kerr effect was considerably lower.
TL;DR: In this paper, the birefringence of polymethylmethacrylate and silicon nitride gratings was measured at 632.8 nm and found to agree closely with the theory.
Abstract: Gratings of dielectric material can act as homogeneous birefringent materials if the wavelength of the incident radiation is greater than twice the period of the grating. For the case of square profile gratings, simple equations predict the birefringence versus linewidth‐to‐period ratio of the gratings. By using x‐ray lithography and reactive ion etching, 240‐nm period gratings of polymethylmethacrylate and silicon nitride were fabricated with various linewidths. The birefringence of these was measured at 632.8 nm and found to agree closely with the theory. Silicon nitride gratings which act as half‐wave and quarter‐wave plates in the visible were made.
TL;DR: In this paper, the cavity mode enhanced frequency modulation (CME-FM) was proposed for direct frequency modulation using the newly developed cleaved-coupled-cavity (C3) semiconductor laser.
Abstract: We report a new mechanism of direct frequency modulation, the cavity‐mode enhanced frequency modulation (CME‐FM), using the newly developed cleaved‐coupled‐cavity (C3) semiconductor laser. In this operation, one of the diode of the C3 laser was operated as a laser, while the other diode was operated as a frequency modulator. It was shown that a very large frequency excursion of 150 A and frequency tuning rate of 10 A/mA have been obtained with a C3 GaInAsP crescent laser operating at 1.3 μm. Time‐resolved spectral and spectral‐resolved pulse response measurements also showed that such C3 lasers operated in highly stable single‐longitudinal mode at all times even under high‐speed direct frequency modulation. In addition to the important application as the optical source in FM optical communication systems, the present CME‐FM C3 laser can also be used as the optical source in wavelength‐division multiplexing systems. Further, it opens the possibility of ultrahigh capacity multilevel optical FM information t...
TL;DR: In this paper, a theory of the amplitude and phase modulation characteristic of a single mode semiconductor laser is presented, where the amplitude modulation couples through the complex susceptibility of the gain medium to the phase.
Abstract: A theory of the amplitude and phase modulation characteristic of a single mode semiconductor laser is presented. In this model the amplitude modulation couples through the complex susceptibility of the gain medium to the phase. We show that this coupling constant can be obtained by a high‐frequency modulation experiment. This measured coupling constant is used to infer the linewidth enhancement factor α as discussed by Henry, and Vahala and Yariv. Experiments confirmed the model and we measured a linewidth enhancement factor ‖α‖=4.6±1.0 for a GaAlAs buried optical guide laser.
TL;DR: In this paper, a sufficient condition was established that an amorphous binary alloy will be formed by ion mixing of multilayered samples when the two constituent metals are of different crystalline structure, regardless of their atomic sizes and electronegativities.
Abstract: We formulate a rule which establishes a sufficient condition that an amorphous binary alloy will be formed by ion mixing of multilayered samples when the two constituent metals are of different crystalline structure, regardless of their atomic sizes and electronegativities. The rule is supported by the experimental results we have obtained on six selected binary metal systems, as well as by the previous data reported in the literature. The amorphization mechanism is discussed in terms of the competition between two different structures resulting in frustration of the crystallization process.
TL;DR: The first application of optical enhancement to thin-film (∼0.75 μm) amorphous silicon solar cells was described in this paper, where the authors defined cell geometries which maximize enhancement effects.
Abstract: We describe the first application of optical enhancement to thin‐film (∼0.75 μm thick) amorphous silicon solar cells and define cell geometries which maximize enhancement effects. We observed that due to the improved infrared absorption the external AM1 short circuit current increases by 3.0 mA/cm2 in cells constructed in accordance with the principles of optical enhancement.
TL;DR: In this paper, the hyperfine spectrum associated with unpaired electrons at the (111) Si/SiO2 interface (Pb centers) is reported for the first time, and an analysis of this hyperfine interaction firmly establishes many of the details in the structure of this interface defect.
Abstract: The hyperfine spectrum associated with unpaired electrons at the (111) Si/SiO2 interface (Pb centers) is reported for the first time. Electron paramagnetic resonance measurements indicate that the hyperfine interaction S↘⋅A⋅I↘ arises from the 29Si isotope and is characterized by A∥=146.(±5.)×10−4 cm−1 and A⊥=85.(±8.)×10−4 cm−1. An analysis of this hyperfine interaction firmly establishes many of the details in the structure of this interface defect.
TL;DR: In this article, the conduction-band discontinuity ΔEc was measured for molecular beam epitaxial grown N−n In0.52Al0.48As/In0.53Ga0.47As heterojunction using the C-V profiling technique outlined by Kroemer et al.
Abstract: We report the first measurement of the conduction‐band discontinuity ΔEc for molecular beam epitaxial grown N‐n In0.52Al0.48As/In0.53Ga0.47As heterojunction using the C‐V profiling technique outlined by Kroemer et al. We find ΔEc=(0.50±0.05) eV @297 K corresponding to (71±7)% ΔEg. An interface charge density σi of (4.0±0.8)×1011 cm−2 was also obtained. A knowledge of ΔEc is of importance for quantifying carrier confinement in double heterostructure lasers fabricated from these ternary compounds.
TL;DR: In this paper, optical absorption measurements on fine-grain polycrystalline-silicon thin films indicate that the singly occupied dangling silicon bond lies 0.65±0.15 eV below the conduction band minimum in the grain boundary.
Abstract: The results of optical absorption measurements on fine‐grain polycrystalline‐silicon thin films indicate that the singly occupied dangling silicon bond lies 0.65±0.15 eV below the conduction‐band minimum in the grain boundary. The grain boundary band gap is ∼1.0 eV and there is evidence for exponential tailing of the band edges. The optical absorption was determined by photothermal deflection spectroscopy. The dangling silicon bond density has been measured on polycrystalline‐silicon thin films as a function of hydrogen passivation of the grain boundaries and on silicon‐on‐saphhire films. The optical absorption exhibits a defect shoulder which varies as the dangling bond density.
TL;DR: In this paper, a quantitative comparison of the trapping rates of carriers at charged and neutral dangling bonds in hydrogenated amorphous silicon (aSi:H) is reported, based on time-of-flight photoconductivity studies of doped and undoped samples.
Abstract: We report a quantitative comparison of the trapping rates of carriers at charged and neutral dangling bonds in hydrogenated amorphous silicon (a‐Si:H) The data are obtained from time‐of‐flight photoconductivity studies of doped and undoped samples The temperature dependence of the trapping rates, as well as the effect of boron doping on the hole drift mobility, is also reported
TL;DR: In this paper, the recovery kinetics of a stress induced dichroism in the 9-μm oxygen infrared absorption band were determined from the recovery process of a diffusion matrix. And they combined their data for well dispersed oxygen (i.e., crystals heat treated at 1350 °C for 20 h), with Mikkelsen's recent mass transport work at higher temperature to obtain the diffusivity, D=0.17 exp (−2.54/kT), for the range 330-1240
Abstract: We present data on oxygen diffusivity in silicon for the temperature range 270–400 °C. The diffusivity is determined from the recovery kinetics of a stress induced dichroism in the 9‐μm oxygen infrared absorption band. We combine our data for well dispersed oxygen (i.e., crystals heat treated at 1350 °C for 20 h), with Mikkelsen’s recent mass transport work at higher temperature to obtain the diffusivity, D=0.17 exp (−2.54/kT), for the range 330–1240 °C. We have also found that the oxygen atomic hopping times can be as much as 100 times faster in crystals that have not received the 1350 °C heat treatment.
TL;DR: Amorphization by ion beam irradiation of multilayered samples of Al/Pt, Al /Pd, and Al/Ni has been investigated by selected area diffraction and Rutherford backscattering as discussed by the authors.
Abstract: Amorphization by ion beam irradiation of multilayered samples of Al/Pt, Al/Pd, and Al/Ni has been investigated by selected area diffraction and Rutherford backscattering. With a dose of 2×1014 Xe ions/cm2, uniform mixing is achieved in the Al/Pt system and the amorphous phase is produced over a large composition range. In the Al/Pd and Al/Ni systems, amorphous phases or the equilibrium, crystalline phases are formed depending on the composition of the films. The same results were found when the samples were annealed to form crystalline phases before bombardment. For thin films of these fcc metals, only the simplest intermetallics, NiAl and PdAl, (primitive cubic structures with 2 atoms/cell) were formed in crystalline form by ion‐beam irradiation.
TL;DR: In this article, the general principle of wavelength-selective enhancement of absorption in thin-film solar cells by a periodic grating substrate was presented, and substantial short-circuit current gains were realizable in thinfilm amorphous silicon (a•SiHx) solar cells.
Abstract: We present the general principle of wavelength‐selective enhancement of absorption in thin‐film solar cells by a periodic grating substrate. By exact numerical calculation we demonstrate that substantial short‐circuit current gains are realizable in thin‐film amorphous silicon (a‐SiHx) solar cells. In particular, for a 0.5‐μm‐thick a‐SiHx solar cell, optimal texturing of an Ag substrate to form a one‐dimensional reflective grating can yield a 2‐mA/cm2 enhancement over the flat substrate case. For a two‐dimensional cross‐hatched grating substrate the enhancement is estimated to be 3.5–4 mA/cm2.
TL;DR: In this article, a method and apparatus for thin film thickness measurements with thermal waves in which heating and detection laser beams are focused onto the film, normal to the surface of the film with the two beams parallel and non-coaxial.
Abstract: A method and apparatus for thin film thickness measurements with thermal waves in which heating and detection laser beams are focused onto the film, normal to the surface of the film, with the two beams parallel and non-coaxial.
TL;DR: In this article, the authors show that the spin density and the densities of the two DLTS peaks have the same annealing kinetics, and that spin density is approximately constant over the central region of the band gap but decreases near the band edges.
Abstract: On unannealed, thermally oxidized silicon, electron spin resonance reveals an oriented interface defect which is termed the Pb center and identified as the trivalent silicon defect. Deep level transient spectroscopy (DLTS) reveals two broad characteristic peaks in the interface‐state distribution: one ∼0.3 eV above the silicon valence‐band maximum and a second ∼0.25 eV below the conduction band. Isochronal anneals of oxidized silicon, coated with aluminum, show that the spin density and the densities of the two DLTS peaks have the same annealing kinetics. On large‐area, Al‐gated capacitors the spin density can be modulated with an applied voltage; sweeping the silicon band gap at the interface through the Fermi level reveals that the spin density is approximately constant over the central region of the band gap but decreases near the band edges. The variation of the spin density with gate voltage identifies an amphoteric center with both electronic transitions in the band gap. Both the annealing behavior ...
TL;DR: In this paper, the HgTe•CdTe superlattice was found to exhibit properties superior to those of the (Hg, Cd)Te alloy as an infrared detector material.
Abstract: The HgTe‐CdTe superlattice is found to exhibit properties superior to those of the (Hg, Cd)Te alloy as an infrared detector material. A calculation shows that the superlattice tunneling length is shorter than that of the alloy with the same band gap. For a given cutoff wavelength tolerance, we find that less fractional precision is needed in the superlattice control parameter (layer thicknesses) than in the alloy control parameter (composition). Also, p‐side diffusion currents are expected to be reduced due to the larger superlattice electron effective mass.
TL;DR: In this article, a simple model for the linewidth enhancement factor α and its frequency dependence in semiconductor lasers is presented, which is in reasonable agreement with the experimental results.
Abstract: A simple model for the linewidth enhancement factor α and its frequency dependence in semiconductor lasers is presented. Calculations based on this model are in reasonable agreement with experimental results.