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1 Dec 1983

Volume 54, Issue 12, pp. 6811-7206

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Growth by molecular beam epitaxy and characterization of high purity GaAs and AlGaAs

M. Heiblum, E. E. Mendez, and L. Osterling

J. Appl. Phys. 54, 6982 (1983); http://dx.doi.org/10.1063/1.332015 (7 pages) | Cited 63 times

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We report on the growth by molecular beam epitaxy of high‐quality GaAs and AlxGa1−xAs (x≲0.43), and discuss the effect of system parameters on material quality. The highest Hall mobility in GaAs at 77 °K was 144 000 cm2/V sec, and the photoluminescence spectra of undoped layers exhibited a strong free exciton line and a much reduced carbon peak with no carbon‐related defects. A slow growth process at a substrate temperature of 600 °C produced excellent AlxGa1−xAs whose luminescence spectrum showed a distinct excition peak 4 meV wide. This AlxGa1−xAs is compared to layers grown at a faster rate at substrate temperatures of 700 °C.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
78.40.Fy Semiconductors

Dielectric function for a quasi‐two‐dimensional semiconducting system

Johnson Lee and Harold N. Spector

J. Appl. Phys. 54, 6989 (1983); http://dx.doi.org/10.1063/1.332016 (6 pages) | Cited 16 times

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We present a calculation of the dielectric function for a quasi‐two‐dimensional electron gas (Q2D) and compare our results with those obtained for two‐dimensional (2D) and three‐dimensional (3D) electron gases. We also compare our results to those obtained using the Thomas–Fermi approximation. We find that for a Q2D system with an active layer of thickness 100 Å, the use of the 2D and Thomas–Fermi approximations overestimate the dielectric function and the amount of screening except for small wave vector disturbances. We also compare our approach to that of Stern and Howard [Phys. Rev. 163, 816 (1967)] and find that the approaches agree if we make the Thomas–Fermi approximation. When we apply our results to the problem of the calculation of the momentum relaxation rate from a screened Coulomb potential due to scattering from ionized impurities, we find that our approach leads to a larger scattering rate than that using the Thomas–Fermi approximation because of the latter’s overestimate of the effect of screening.
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71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
77.55.-g Dielectric thin films
73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors

Impurity scattering limited mobility in a quantum well heterojunction

Johnson Lee, Harold N. Spector, and Vijay K. Arora

J. Appl. Phys. 54, 6995 (1983); http://dx.doi.org/10.1063/1.331963 (10 pages) | Cited 56 times

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We calculate the mobility of carriers in a quantum well structure when they are scattered by ionized impurities in the size‐quantum limit (SQL) where the carriers are assumed to populate only the lowest quantized energy level. It is found that the probability of scattering due to ionized impurities decreases with the well thickness in contrast to the case of acoustic phonon scattering where the scattering probability is enhanced under the conditions of the SQL. The temperature and thickness dependence of the mobility depends critically on the screening of the Coulomb potential due to the presence of the ionized impurities.
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72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.10.Di Scattering by phonons, magnons, and other nonlocalized excitations

Raman instability in longitudinally magnetized n‐type piezoelectric semiconductors

S. Ghosh and S. Khan

J. Appl. Phys. 54, 7005 (1983); http://dx.doi.org/10.1063/1.331964 (7 pages) | Cited 3 times

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Raman instability of the Stoke’s component of the scattered electromagnetic wave has been investigated analytically in an n‐type nondegenerate piezoelectric semiconductor plasma subjected to a large longitudinal magnetostatic field. The general dispersion relation has been obtained following the coupled mode theory and considering that the scattering is due to both the molecular vibrations produced due to the pump wave at a frequency equal to that of the transverse optical phonons and the electron plasma wave. The dispersion relation has been solved for both cases of scattered electromagnetic waves (i.e., in the cases of left‐hand and right‐hand circularly polarized waves). The threshold value of the pump amplitude necessary for the onset of instability and the growth rate of the unstable mode well above the threshold have been obtained analytically for both the modes. The relevant experiment has not been reported. It is observed that with the increase in the longitudinal magnetostatic field, the threshold value of the pump amplitude increases while the growth rate decreases in both cases. Numerical estimates have been made for n‐type InSb at 77 K irradiated with a pulsed 10.6‐μm CO2 laser to obtain the necessary electric field. The analytical as well as numerical results have been compared with those of Ghosh [J. Appl. Phys. 52, 4667 (1981)] while studying the Brillouin instability in longitudianally magnetized n‐type semiconductors.
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72.20.Ht High-field and nonlinear effects
72.30.+q High-frequency effects; plasma effects
78.45.+h Stimulated emission
77.65.-j Piezoelectricity and electromechanical effects

Effective conductivity of regular conducting channeling textures in two dimensions

Mitsunobu Nakamura

J. Appl. Phys. 54, 7012 (1983); http://dx.doi.org/10.1063/1.331965 (4 pages) | Cited 2 times

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Composite materials exist, which are composed of elongated conductors and granular insulators. For the effective conductivity of such materials, the ordinary effective medium theory and the random resistor network models cannot be efficiently applied. As an approach to the problem, we compute by the finite element method the effective conductivity of triangular, square, and hexagonal channeling textures, composed of continuous conductive channels and islands of insulators. As shown by the results, the effective conductivities of the three patterns are nearly equal when the channel widths of the textures are the same. And compared with a granular conductor‐insulator composite material, the three textures have a very conductive geometrical configuration, because neither island nor dead end conducting regions exist in the three patterns. If we accumulate such data for the effective conductivity of materials with a definite composite structure, we can predict the outline of the geometrical configuration of a composite material or inhomogeneous medium by measurement of the conductivity and volume components.
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72.90.+y Other topics in electronic transport in condensed matter (restricted to new topics in section 72)

Fourier transform approach to materials characterization with the acoustic microscope

J. A. Hildebrand, K. Liang, and S. D. Bennett

J. Appl. Phys. 54, 7016 (1983); http://dx.doi.org/10.1063/1.331966 (4 pages) | Cited 7 times

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A general method is presented for characterization of elastic properties of materials with the reflection acoustic microscope. The material acoustic reflectance function and the acoustic microscope focus curve [V(z)] are shown to be a Fourier transform pair. By measurement of both phase and amplitude, the complex V(z) curve can be recorded. These data can then be inverted to obtain an estimate of the reflectance function. This method allows calibration of individual acoustic lenses and is experimentally demonstrated with a 50‐MHz acoustic microscope and a synchronous phase detection system.
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72.90.+y Other topics in electronic transport in condensed matter (restricted to new topics in section 72)
43.58.+z Acoustical measurements and instrumentation

Temperature dependence of the electrical characteristics in Au‐n‐type InP Schottky diodes

K. Hattori, T. Yamasaki, Y. Uraoka, and T. Fujii

J. Appl. Phys. 54, 7020 (1983); http://dx.doi.org/10.1063/1.331967 (5 pages) | Cited 5 times

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The current‐voltage (I‐V) and capacitance‐voltage (C‐V) characteristics of Au‐n‐type InP Schottky diodes are measured over the temperature range 120–300 K. It is found that apparent barrier heights qϕB obtained from I‐V curves increase linearly with increasing temperature. The intercept voltage V0 of the 1/C2 vs V curve is observed to decrease with increasing temperature. The quantity q(V0+Vn+kT/q) shows a linear temperature variation, where qVn denotes the semiconductor Fermi level. Theoretical analysis is also developed, including the effects of an interfacial layer between the metal and semiconductor. Increase in qϕB with temperature is due to the presence of the electron tunneling barrier in the interfacial layer. It is shown that the temperature variation of the barrier height qϕB0 is closely related to that of q(V0+Vn+kT/q)@B: for a sufficiently thin interfacial layer, we have dqϕB0/dT ≊dq(V0+Vn +kT/q)/dT<0. As the interfacial layer is thick, ‖dqϕB0/dT‖ becomes small, and we have dq(V0+Vn+kT/q) /dT<dqϕB0/dT<0.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

The capacitance of rf sputtered hydrogenated amorphous silicon, Schottky barrier diodes

H. L. Fernandez‐Canque, J. Allison, and M. J. Thompson

J. Appl. Phys. 54, 7025 (1983); http://dx.doi.org/10.1063/1.331968 (9 pages) | Cited 8 times

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A generalized interpretation of the capacitance/conductance behavior in a hydrogenated amorphous silicon Schottky barrier is introduced. This approach takes into account the influence of voltage, temperature, frequency, and light intensity on the capacitance and conductance characteristics of a Schottky barrier junction and on a complete device. From the various different considered cases it is possible to obtain information on the barrier profile, depletion width of the barrier, and density of states in the gap. The model proposed provides a method of obtaining the ‘‘active’’ charge that effectively determines the capacitance in the barrier. Comparison of theoretical predictions based on the model with experimental data from capacitance and conductance measurements of reactively sputtered, hydrogenated a‐Si:H‐metal Schottky barrier structures as a function of temperature voltage, frequency, and illumination shows good agreement.
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.De Semiconductor-device characterization, design, and modeling
85.30.Hi Surface barrier, boundary, and point contact devices

Quantitative model for current‐voltage characteristics of metal point contacts on silicon rectifying junctions

J. J. Marchand and Van Khiem Truong

J. Appl. Phys. 54, 7034 (1983); http://dx.doi.org/10.1063/1.331969 (7 pages) | Cited 12 times

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Metal point contacts on semiconductors result in rectifying contacts whose current‐voltage characteristics do not obey the Schottky diode formula. However, the curves under loads varying from 20 to 100 g have been found to be described by a constriction resistance in series with a rectifying device whose law is of the form I=I0 (exp αV−1). The α exponent varies with load and would correspond, as compared to a Schottky diode, to high values of the idealization factor. A brief synthesis of the existing surface mechanic models shows that the real area of contact Ar must be proportional to the load. This is checked with the classical formulation for constriction resistances and so we obtain the measure of Ar . These results allow us to conclude that the deformations of silicon at the interface are mostly plastic. A great number of dislocations appear and cause the existence of many traps which are responsible for a tunneling effect through the metal–semiconductor barrier. This enables us to explain the low values of α and to determine the barrier height. Furthermore, we obtain the formula relating α and I0 to Ar and a plot of Ar versus the load agrees well with the mechanical theory.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential

Low‐resistance contacts to p‐type Li‐diffused CdTe

Chun‐teh Lee and Richard H. Bube

J. Appl. Phys. 54, 7041 (1983); http://dx.doi.org/10.1063/1.331970 (6 pages) | Cited 10 times

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Reproducible low‐resistance contacts to p‐type CdTe single crystals have been made by diffusion of Li into the CdTe surface before evaporation of Au as the contact metal. Diffusion produces a surface hole density of about 1019 cm−3 at room temperature; this results in a contact resistivity of the order of 0.01 Ω cm2, the lowest value reported to date for p‐type CdTe. The high diffusivity of Li results in a degradation of the contacts even at room temperature, with the degradation rate critically dependent on the temperature used for Li diffusion. The optimum temperature appears to be about 280 °C; contacts formed on surfaces diffused with Li at this temperature show a contact resistivity of 0.025 Ω cm2 after 5 months.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
73.40.Gk Tunneling
72.80.Ey III-V and II-VI semiconductors

Temperature dependence of structural and electrical properties of Ta‐Si thin alloy films

T. Tien, G. Ottaviani, and K. N. Tu

J. Appl. Phys. 54, 7047 (1983); http://dx.doi.org/10.1063/1.331971 (11 pages) | Cited 20 times

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In situ electrical resistivity measurement and structural analysis methods including MeV 4He+ ion backscattering, x‐ray diffraction, Auger electron spectroscopy combined with Ar+ sputtering, scanning and transmission electron microscopies have been used to investigate the properties and characteristics of the Ta‐Si thin alloy film system as a function of temperature. Stoichiometric TaSi2 films were deposited by double electron‐gun coevaporation on Si, oxidized Si, and sapphire substrates. A distinct drop in resistivity near 300 °C has been determined to be a transformation of the amorphous to crystalline phase. The kinetics of the transformation has been obtained by isothermal treatment over the temperature interval of 240–280 °C. The results are interpreted in terms of a classical solid‐state phase transformation model with a t4 (time) dependence and an apparent activation energy of 1.85 eV. Subsequent annealing causes further decrease of resistivity. The microstructures of films at various stages of annealing have been studied by x‐ray diffraction and transmission electron microscopy. Correlation between the resistivity and microstructure is given and discussed. In situ resistivity of annealed films below room temperature has been measured. Crystalline TaSi2 thin films do not become superconductive at 1.5 °K. Ion‐beam mixed, coevaporated TaSi2 film and films varying in composition from TaSi3.4 to TaSi1.2 prepared by cosputtering have also been studied. The results are compared and discussed.
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73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
68.55.-a Thin film structure and morphology

Characterization of plasma‐enhanced chemically‐vapor‐deposited silicon‐rich silicon dioxide/thermal silicon dioxide dual dielectric systems

S. Yokoyama, D. W. Dong, D. J. DiMaria, and S. K. Lai

J. Appl. Phys. 54, 7058 (1983); http://dx.doi.org/10.1063/1.331972 (8 pages) | Cited 16 times

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Plasma enhanced chemically‐vapor‐deposited silicon‐rich oxides (200 Å and 500 Å in thickness) of various excess silicon content were deposited onto thermal silicon dioxide (SiO2) layers (103, 207, and 530 Å in thickness) grown on a p‐type silicon (Si) substrate. The dielectric constant, electron injection efficiency, current‐voltage (I‐V) reproducibility, and breakdown property of these composite structures were examined. The dielectric constants of Si‐rich oxide were observed to increase with Si content from 3.8 for films deposited at a gas phase ratio (R0) of the concentration of nitrous oxide (N2O) to silane (SiH4) of 150 to ∼10 for films deposited with R0=0. The Si‐rich oxides with R0≤5 were found to work as electron injectors. The average oxide field needed to induce a current of 4.8×10−7 A/cm2 through the SiO2 (530 Å in thickness) decreased about 40% in magnitude by adding a Si‐rich oxide layer with the optimized R0(=1) compared to that of a control sample which had no Si‐rich oxide layer. For thin SiO2 (103 Å and 207 Å in thickness) samples, the decrease of the average field was only 2% and 10% in magnitude with the optimized R0 (=2) layer, respectively, due to the relatively large voltage drop (≊−1 V) across the Si‐rich oxide compared to that across the thermal oxide layer. The voltage drop across the oxide is discussed in terms of a dual dielectric model. The yeild, which was defined as the percentage of capacitors that required a field larger than 2 MV/cm to obtain a current of 9.6×10−4 A/cm2, on as‐fabricated samples was larger than 90% for all samples with Si‐rich oxide. The samples were not destroyed by the passage of a relatively high current density (1.21×10−2 A/cm2) through the oxide and subsequent measurements resulted in approximately the same field to produce the specified current as for the first measurement. The yield was found to have a maximum at R0=1–10 depending on the thickness of Si‐rich oxides and SiO2. Current‐voltage reproducibility was also found to be improved by the deposition of Si‐rich oxide.
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73.61.Ng Insulators
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films

Ar ion bombardment effects of NbN/Pb Josephson junctions with plasma oxidized barriers

Makoto Hikita, Koji Takei, and Masaru Igarashi

J. Appl. Phys. 54, 7066 (1983); http://dx.doi.org/10.1063/1.331973 (7 pages) | Cited 10 times

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Details of the relation between Ar ion bombardment effects on NbN surface and I‐V characteristics of NbN/Pb junctions with plasma oxidized barriers have been studied. NbN base electrodes, which behave as a strong coupling superconductor (Tc>15 K, 2Δ/kTc=4.2–4.3), were prepared onto substrates at 300 °C by reactive dc magnetron sputtering. In the NbN/Pb junction fabrication, cathode self‐bias voltage VCSB during Ar sputter cleaning strongly influences the subgap leakage current value, which increases with VCSB . The VCSB also influences normalized normal tunnel resistance ARNN. It is found, in reflection electron diffraction and x‐ray photoelectron spectroscopy studies, that the Ar ion bombardment at VCSB> 200 V on a NbN surface produces an amorphous structure in the surface layer. It is also found that the thickness of amorphous layer increases with Ar ion energy. Based on the experimental results, low subgap leakage current junctions, where Vm exceeds 100 mV at 4.2 K, were fabricated under low energy plasma oxidation conditions, where Vm is the product of Josephson critical current and subgap resistance. Sputter cleaning and plasma oxidation conditions for obtaining high quality junctions are also discussed.
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74.50.+r Tunneling phenomena; Josephson effects
81.40.Rs Electrical and magnetic properties related to treatment conditions
74.78.-w Superconducting films and low-dimensional structures
61.80.Jh Ion radiation effects

Experimental investigation of the magnetic behavior of superconducting‐normal‐superconducting Josephson junctions

K. Bures, S. E. Barnes, and K. Baberschke

J. Appl. Phys. 54, 7073 (1983); http://dx.doi.org/10.1063/1.331974 (5 pages) | Cited 3 times

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We have measured the magnetic field dependence of the supercurrent in micron‐size medium and high current density superconducting‐normal‐superconducting Nb–Au–Nb Josephson junctions. We find good quantitative agreement between the experiment and a theory for the distributed Josephson effect in such junctions. For finite bias voltages, high current density junctions show a monotonic decrease in the effective critical current with increasing field in sharp contrast to the resistively shunted junction model which predicts the well‐known Fresnel‐type behavior. Our medium current density junctions represent an intermediate case, residual Fresnel behavior is observed at small bias voltages, but a monotonic decrease with the field is observed for higher bias voltages.
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74.50.+r Tunneling phenomena; Josephson effects
85.25.-j Superconducting devices

Far infrared frequency response of a Josephson junction in a self‐pumped mixer

J‐C. Henaux, G. Vernet, and R. Adde

J. Appl. Phys. 54, 7078 (1983); http://dx.doi.org/10.1063/1.331975 (5 pages) | Cited 1 time

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A continuous measurement of the far‐infrared frequency response of a point contact Josephson junction is performed between 0.7 and 2 THz. The response at increasing frequencies present three characteristic regions with variations proportional to f−2, f−4, f−6. They illustrate the losses introduced successively at increasing frequencies by the resistively shunted junction model, the junction RC time constant and the attenuation of the Josephson current above the gap frequency.
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74.50.+r Tunneling phenomena; Josephson effects
85.25.-j Superconducting devices

Influence of ternary additions and precipitation on the critical current density and other superconducting properties in Nb‐65 wt. %Ti

M. Panek, D. Pattanayak, R. Meier‐Hirmer, and H. Küpfer

J. Appl. Phys. 54, 7083 (1983); http://dx.doi.org/10.1063/1.331976 (6 pages) | Cited 6 times

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The superconducting behavior of Nb‐65 wt. %Ti and their ternary alloys with 1 wt. % Mo, Re, Si, Ta, V, and Zr was studied with regard to precipitation. Transmission electron microscopy studies were carried out to determine the size and distribution of the precipitates. In contrast to the commerical Nb‐Ti superconductor the alloys show a quadratic dependence of the pinning force on the field close to the upper critical field. With a suitable precipitate size distribution but without workhardening these alloys display high current densities which are comparable with commercial Nb‐Ti.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
81.30.Mh Solid-phase precipitation

Magnetic properties of sputtered Co‐Pt thin films

Masahiro Kitada and Noboru Shimizu

J. Appl. Phys. 54, 7089 (1983); http://dx.doi.org/10.1063/1.331977 (6 pages) | Cited 25 times

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Magnetic properties of sputtered Co‐Pt thin films, and the relation between the properties and the film microstructures were studied. Thin films obtained by sputtering a Co‐Pt alloy containing 5–35 at. % Pt exhibited high coercivity. A coercivity of 1800 Oe was obtained as the maximum value for a composition of Co‐20 at. % Pt, while the remanence of the film was about 9500 G. Thin film coercivity was affected by ultimate vacuum pressure before the introduction of sputtering gas. Film coercivity also increased with an increase in the average grain diameter of the films.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
68.60.-p Physical properties of thin films, nonelectronic

Dielectric properties of plasma polymerized styrene film

S. Nakamura, T. Murata, and G. Sawa

J. Appl. Phys. 54, 7095 (1983); http://dx.doi.org/10.1063/1.331978 (4 pages) | Cited 1 time

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The dielectric loss tangent tan δ for the plasma polymerized styrene film has been investigated between room temperature and 250 °C over a frequency range of 102–104 Hz. As‐polymerized films exhibited a noticeable peak on the tan δ temperature characteristic in vacuo. The temperature giving the maximum of tan δ shifted to a higher temperature with descending frequency and the peak disappeared once the sample was heated to 250 °C. These behaviors can not be understandable from the usual dielectric relaxation. As a candidate for their origin, the process of further polymerization of the residual low molecular moieties containing oxidized products by heating has been considered.
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77.22.Gm Dielectric loss and relaxation
77.55.-g Dielectric thin films

Effect of nonparabolicity on amplification of eigenmode acoustic waves in piezoelectric semiconductor films

Chhi‐Chong Wu and Jensan Tsai

J. Appl. Phys. 54, 7099 (1983); http://dx.doi.org/10.1063/1.331979 (11 pages) | Cited 1 time

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Amplification characteristics of eigenmode acoustic waves in piezoelectric semiconductor films have been investigated quantum mechanically in the GHz frequency region. The energy‐band structure of piezoelectric semiconductors is assumed to be nonparabolic. Numerical results show that the amplification coefficient oscillates with the frequency according to the mode of acoustic waves and the thickness of semiconductor films. Moreover, the amplification coefficient depends on the band structure of materials, the electronic screening effect, the temperature, and the applied electric field.
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77.65.-j Piezoelectricity and electromechanical effects
73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
43.35.Ns Acoustical properties of thin films
43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
72.50.+b Acoustoelectric effects
73.50.Rb Acoustoelectric and magnetoacoustic effects
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics

Optical absorption of liquid phase epitaxial garnet films at 1.3‐μm wavelength for magneto‐optic application

Taketoshi Hibiya and Junichiro Nakajima

J. Appl. Phys. 54, 7110 (1983); http://dx.doi.org/10.1063/1.331980 (4 pages) | Cited 2 times

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Optical absorption of liquid phase epitaxial magneto‐optic Gd0.2Y2.8Fe5O12 films was measured at 1.3‐μm wavelength using a waveguide technique. An optical absorption coefficient of α=0.2 cm−1 at 1.3 μm was obtained. This is the smallest value which has ever been reported for a garnet film and corresponds to 230 deg/dB in the figure of merit for Gd:YIG with the Faraday rotation coefficient of 200 deg/cm. α≤0.6 cm−1 is obtained, when garnet films are grown under the supercooling temperature of less than 10 °C. The supercooling temperature dependence of the α value is more insensitive for films grown from melts poor in B2O3 than for films from B2O3 rich melts. A mechanism of increase in optical absorption is discussed from the viewpoint of lead ion condensation at the solid/liquid interface and of incorporation into garnet films.
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75.20.Ck Nonmetals
85.70.Sq Magnetooptical devices
68.55.-a Thin film structure and morphology
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Optical evaluation of indium gallium arsenide phosphide double‐heterostructure material for injection lasers

J. Degani, P. Besomi, D. P. Wilt, R. J. Nelson, and R. B. Wilson

J. Appl. Phys. 54, 7114 (1983); http://dx.doi.org/10.1063/1.331981 (5 pages) | Cited 4 times

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Optical methods used for evaluation of InGaAsP double‐heterostructure (DH) material are described. The photoluminescence (PL) efficiency of the active layer in DH wafers and its spatial variation are shown to be correlated with the threshold current density of the broad area lasers processed from the corresponding wafers. The simultaneous measurement of the PL signal and the transmitted intensity of the excitation source through the active layer is a useful technique for monitoring imperfection in the active layer. The sheet conductivity of the epitaxial p layers and p‐n junction misplacement can be determined from the variation of the PL signal as a function of the power of the optical pump source. In addition, conventional spectrally and spatially resolved PL indicates the compositional homogeneity and the doping concentration of the active layer. In general, we find the 1.06‐μm yttrium aluminum garnet (YAG) laser to be a most convenient tool for evaluation of InGaAsP DH material.
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78.55.Hx Other solid inorganic materials
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.50.Nw Crystal stoichiometry
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Sputtering of a polymer layer deposited on metal substrates

B. Emmoth and G. M. Mladenov

J. Appl. Phys. 54, 7119 (1983); http://dx.doi.org/10.1063/1.331982 (5 pages) | Cited 2 times

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Substrates of Be, Si, Cr, and Mo were covered by a 400‐nm thin film of the electron lithography resist poly(methyl methacrylate) (PMMA), and irradiated by Ar+ ions. The photon emission from sputtered deexciting particles ejected during the ion bombardment was detected. The spectral scans of observed photon radiation were different for PMMA on different substrates. This supports our conclusion that excitation and ejection processes are related to the collision cascades and possibly also to collective electronic excitations. The evaluated average sputtering rates for Ar+ bombardment of PMMA at ion energies 30 and 60 keV are 320 and 375 atoms/ion, respectively, or 1.85 and 2.20 Å cm2/μC correspondingly. The erosion mechanism is discussed against this background.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Computer simulation of ion beam penetration in amorphous target

Y. Miyagawa and S. Miyagawa

J. Appl. Phys. 54, 7124 (1983); http://dx.doi.org/10.1063/1.331983 (8 pages) | Cited 15 times

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The formalism for a Monte‐Carlo computer code using a liquid model is presented. One of the characteristic features of this program is a constant free flight path length between collisions and the other is the thoroughgoing usage of the fitting formula to the nuclear scattering cross section, minimum energy transfer, and free flight path shortening. This allows for a rapid and accurate assesment of an ion’s direction and energy loss resulting from nuclear collisions. For nuclear scattering, an approximation formula derived by Kalbitzer and Oetzmann was used and the results are compared with those obtained using the formula derived by Winterbon, Sigmund, and Sanders. Both results are compared with experiments, with the results obtained using gas‐like model and also with other well‐established programs marlowe and trim.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Properties of Hg0.71Cd0.29Te and some native oxides by spectroscopic ellipsometry

H. Arwin, D. E. Aspnes, and D. R. Rhiger

J. Appl. Phys. 54, 7132 (1983); http://dx.doi.org/10.1063/1.331984 (7 pages) | Cited 22 times

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We have used spectroscopic ellipsometry to determine the complex dielectric function from 1.5 to 6.0 eV for Hg0.71Cd0.29Te and some of its native oxides. The electrochemically grown anodic oxide was found to have an absorption threshold near 3 eV and its dielectric function shows some of the features of TeO2. We found no evidence for a Te‐rich layer between the native oxide and the semiconductor. However, after stripping the oxide with HCl, a residual layer with Te‐like optical and chemical properties did appear. Thin native oxides formed by exposure to ozone‐containing oxygen had dielectric functions similar to that of the anodic oxide but with a broader absorption edge. These oxides could be stripped partly by water and totally by HCl. This confirms that they are a mixture of several oxides as also concluded in other investigations. We found no evidence for any disorder or defects induced in HgCdTe by anodization or etching.
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81.10.Fq Growth from melts; zone melting and refining
78.20.-e Optical properties of bulk materials and thin films
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
07.60.Fs Polarimeters and ellipsometers

The microstructure and critical current characteristic of a bronze‐processed multifilamentary Nb3Sn superconducting wire

I. W. Wu, D. R. Dietderich, J. T. Holthuis, M. Hong, W. V. Hassenzahl, and J. W. Morris

J. Appl. Phys. 54, 7139 (1983); http://dx.doi.org/10.1063/1.331985 (14 pages) | Cited 12 times

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The superconducting phase within a bronze‐process, multifilamentary Nb3Sn superconducting wire is formed by reaction at the interface between the Nb filaments and the bronze matrix. The maximum current that can be carried by the wire is known to depend on the time and temperature of the heat treatment as well as on the transverse magnetic field. In the work reported here a commercial Airco wire containing 2869 Nb filaments of 3–5 μm diameter in a matrix with a bronze/Nb ratio of three was given a variety of reaction heat treatments. The microstructure of the reacted layer was analyzed as a function of heat treatment, and found to be divisible into three concentric shells that are morphologically distinct. The central shell consists of fine equiaxed grains. Its areal fraction, grain size, and composition depend on the heat treatment, and appear to determine the critical current. The best combination of grain size and composition, and the highest critical current, is obtained with an intermediate reaction temperature (700–730 °C). A further improvement in both microstructure and critical current is achieved by double‐aging the wire, starting the reaction at 700 °C and finishing it at 730 °C. The relation between microstructure and heat treatment is interpreted in light of the apparent mechanism of the reaction, which is revealed by high resolution analyses of the reacted layer. The relation between microstructure and properties is consistent with current understanding of the influence of grain size and stoichiometry on the behavior of type II superconductors.
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81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
61.66.Dk Alloys
81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
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