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15 May 1998

Volume 83, Issue 10, pp. 5019-5595

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Electrical properties of lightly doped p-type silicon–germanium single crystals

P. Gaworzewski, K. Tittelbach-Helmrich, U. Penner, and N. V. Abrosimov

J. Appl. Phys. 83, 5258 (1998); http://dx.doi.org/10.1063/1.367348 (6 pages) | Cited 16 times

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Experimental results are presented on the electrical properties of lightly boron doped bulk Si1−xGex as a function of the Ge content x in the range 0<x<0.13. Calculations of the hole mobility in Si and in Si1−xGex and comparison with experimental results allow us to estimate the averaged scattering potential of the randomly distributed Ge atoms to be 0.55 eV. From Hall effect and capacitance–voltage measurements, a Hall factor around 0.8 at T = 300 K is derived. Hall effect measurements in the temperature range 20–300 K enable us to determine the boron acceptor activation energy, which decreases from 45 meV at x = 0 down to 32 meV for x = 0.13, and to estimate the hole effective masses to be meff/m0 ≈ 0.45. © 1998 American Institute of Physics.
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72.80.Jc Other crystalline inorganic semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.My Galvanomagnetic and other magnetotransport effects
71.55.Ht Other nonmetals
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Thermoelectric power, specific heat, and giant magnetoresistance of La0.85MnO3

R. Suryanarayanan, J. Berthon, I. Zelenay, B. Martinez, X. Obradors, S. Uma, and E. Gmelin

J. Appl. Phys. 83, 5264 (1998); http://dx.doi.org/10.1063/1.367349 (6 pages) | Cited 6 times

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Magnetization, thermoelectric power (TEP), specific heat (Cp), and magnetoresistance (MR) of the as prepared (AP) and oxidized (OX) polycrystalline La0.85MnO3 are reported. Both the samples have rhombohedral symmetry. The magnetization of the OX sample showed a sharper rise as a function of temperature with a Tc ∼ 270 K and a well defined peak of Cp close to Tc. The TEP of the AP sample was positive between 10<T<300 K with a maximum located near Tc, but the OX sample showed a negative value between 240 and 300 K. A maximum of 75% in MR was observed for the OX sample in a field of 5 T at 270 K. The data were analyzed in light of similar data obtained on divalent (Sr,Ca) substituted LaMnO3 and the existing models. © 1998 American Institute of Physics.
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72.20.Pa Thermoelectric and thermomagnetic effects
65.40.-b Thermal properties of crystalline solids
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
75.50.Dd Nonmetallic ferromagnetic materials
72.20.My Galvanomagnetic and other magnetotransport effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Structural and electronic transport properties of polycrystalline p-type CoSb3

H. Anno, K. Hatada, H. Shimizu, K. Matsubara, Y. Notohara, T. Sakakibara, H. Tashiro, and K. Motoya

J. Appl. Phys. 83, 5270 (1998); http://dx.doi.org/10.1063/1.367350 (7 pages) | Cited 34 times

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The structural and electronic transport properties of polycrystalline p-type CoSb3 with different grain sizes (about 3 and 3×102 μm) were investigated. The magnetic susceptibility was also measured. Samples were characterized by x-ray diffractometry, electron-probe microanalysis, and optical microscope observation. Samples were found to be stoichiometric and homogeneous. The Hall carrier concentration of the samples is of the order of 1018 cm−3 and weakly dependent on the temperature. The temperature dependence of the Hall mobility suggests that the predominant scattering mechanism drastically changes depending on grain size: for large grain size a combination of the neutral impurity scattering and the acoustic phonon scattering, and for small grain size the ionized impurity scattering. The magnetic susceptibility was found to be essentially diamagnetic independently of grain size, and to vary slightly with temperature. The weak temperature dependence of the susceptibility can be explained by taking into account the three contributions of ion cores, conduction electrons, and trace amounts of magnetic impurities. From the analysis of the susceptibility due to conduction electrons, the band gap energy was determined to be about 70–80 meV, consistent with a recent band structure calculation. Although the effects of nonmagnetic impurity phases segregated (Sb, etc.) on the scattering mechanism are not clear, the grain size is one of the key factors determining the transport properties of polycrystalline CoSb3. © 1998 American Institute of Physics.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Jc Other crystalline inorganic semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
61.66.Fn Inorganic compounds
71.20.Nr Semiconductor compounds
75.20.Ck Nonmetals

A method for determining microinhomogeneities in semiconductors

I. Chaikovsky and L. Alperovich

J. Appl. Phys. 83, 5277 (1998); http://dx.doi.org/10.1063/1.367351 (5 pages) | Cited 2 times

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A method is suggested for determining random irregularities in semiconductors. The method is based on the anomalous sensitivity of the effective electrical conductivity of semiconductors with weak random irregularities to an applied strong magnetic field. The primary advantage of this method is the possibility to control the sensitivity of measurements of small values of concentration of random weak inhomogeneities changing an external magnetic field. Preliminary results are presented here of experiments with Si:B thin layers at He temperatures under a broad range of magnetic fields (0–30 kOe). The experimentally determined measure of the sample inhomogeneity was found to be close to the theoretical predicted value. © 1998 American Institute of Physics.
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68.55.Nq Composition and phase identification
72.80.Cw Elemental semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Thermal stability of epitaxial aluminum on In0.53Al0.47As Schottky diodes grown by molecular beam epitaxy

S. J. Pilkington and M. Missous

J. Appl. Phys. 83, 5282 (1998); http://dx.doi.org/10.1063/1.367352 (7 pages) | Cited 2 times

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Current–voltage and capacitance–voltage techniques have been used to characterize the electrical properties of annealed epitaxial aluminum contacts to In0.53Al0.47As grown by molecular beam epitaxy. These as-deposited diodes were found to have electrical characteristics that were dominated by thermionic emission, with an ideality factor of 1.06–1.08 and a barrier height of 0.55–0.56 eV. As the anneal temperature is increased, there is a slight increase in the value of the barrier height, which is believed to be related to an increasing interfacial reaction occurring, promoting the formation of AlAs. For anneals above 400 °C, the electrical characteristics start to degrade rapidly. For comparison, conventionally evaporated Au/InAlAs diodes were also characterized. These diodes had an ideality factor of 1.14–1.18 and a barrier height of 0.63–0.67 eV. Although the electrical characteristics showed little variation in the forward direction, the reverse characteristics exhibited a significant variation between diodes. Upon annealing, the characteristics show variations between diodes, with the characteristics significantly degraded for anneals of 300 °C, showing the poor thermal stability exhibited by conventionally evaporated contacts. The observed characteristics for the epitaxial aluminum contacts to InAlAs, compared with those from conventionally evaporated gold contacts, have implications for the Schottky gate contact in the manufacture of InAlAs–InGaAs high electron mobility transistors. © 1998 American Institute of Physics.
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85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes
81.40.Gh Other heat and thermomechanical treatments
73.30.+y Surface double layers, Schottky barriers, and work functions
68.35.Ct Interface structure and roughness
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

A model for minority carrier lifetime variation in the oxide–silicon structure following 253.7 nm ultraviolet irradiation

Z. Y. Cheng and C. H. Ling

J. Appl. Phys. 83, 5289 (1998); http://dx.doi.org/10.1063/1.367353 (6 pages) | Cited 3 times

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The effective minority carrier lifetime, in the silicon wafer covered with different oxides, is found to increase, or decrease, or decrease and then increase, following ultraviolet (UV) light irradiation. Evidence is presented of injection of UV-generated electrons from the silicon substrate into the oxide. Subsequent trapping occurs at the outer oxide surface for dry or native oxides, but mainly in the bulk of the oxide, in the case of wet or chemical vapor deposited oxides. Recognizing that the lifetime is determined predominantly by carrier recombination at the silicon–silicon oxide interface, and that this recombination rate is controlled by silicon surface band bending, a simple model, based on the postirradiation shift in the location of the Fermi level in the silicon at the interface, is shown to be able to reconcile the apparently conflicting reports in the lifetime behavior. The location of the pre-irradiation Fermi level is determined by the initial oxide charge, assumed to be positive, and also by the interface states. © 1998 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Cw Elemental semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.20.At Surface states, band structure, electron density of states

Experimental and computer simulation studies of diffusion mechanisms on the arsenic sublattice of gallium arsenide

M. Schultz, U. Egger, R. Scholz, O. Breitenstein, U. Gösele, and T. Y. Tan

J. Appl. Phys. 83, 5295 (1998); http://dx.doi.org/10.1063/1.367354 (7 pages) | Cited 22 times

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Interdiffusion experiments with GaAsP/GaAs and GaAsSb/GaAs superlattice samples were performed at various temperatures and arsenic vapor pressures. From the depth-concentration profiles effective diffusion coefficients were calculated. The dependence of these effective diffusion coefficients on the ambient arsenic pressure led to the conclusion that the interdiffusion process is governed by a substitutional-interstitial diffusion mechanism. The good agreement of the effective diffusion coefficients of the GaAsP/GaAs and GaAsSb/GaAs samples with each other and the agreement with arsenic self-diffusion data from the literature is an indication that phosphorus and antimony have good tracer properties to investigate arsenic self diffusion. Comparing our results with sulfur in-diffusion experiments from the literature we conclude that the kick-out mechanism governs self-diffusion on the arsenic sublattice in GaAs. Our results are in contradiction to arsenic self-diffusion experiments which indicated a vacancy mechanism. © 1998 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

The influence of the critical current spread on the frequency locking of Josephson junctions in two-dimensional arrays

A. Laub, M. Keck, T. Doderer, R. P. Huebener, T. Traeuble, R. Dolata, T. Weimann, and J. Niemeyer

J. Appl. Phys. 83, 5302 (1998); http://dx.doi.org/10.1063/1.367355 (5 pages) | Cited 4 times

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Two-dimensional arrays of overdamped Josephson junctions under microwave irradiation have been examined experimentally. We show that the shape of the Shapiro steps in the current–voltage curve of the array is closely related to the critical current spread of the junctions and that its dynamic resistance is closely related to the number of frequency locked junctions which are visualized by low-temperature scanning electron microscopy. © 1998 American Institute of Physics.
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85.25.Cp Josephson devices
74.50.+r Tunneling phenomena; Josephson effects
74.25.Sv Critical currents
78.70.Gq Microwave and radio-frequency interactions
74.25.N- Response to electromagnetic fields

Critical-state model for intermodulation distortion in a superconducting microwave resonator

J. McDonald, J. R. Clem, and D. E. Oates

J. Appl. Phys. 83, 5307 (1998); http://dx.doi.org/10.1063/1.367356 (6 pages) | Cited 10 times

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A model is presented for the treatment of intermodulation distortion in a superconducting transmission line caused by vortex penetration and hysteresis. An analytical framework is developed, and numerical results are presented for center conductors of both circular and rectangular thin-film cross section. © 1998 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
85.25.Am Superconducting device characterization, design, and modeling
74.78.-w Superconducting films and low-dimensional structures

Effect of surface roughness on magnetic properties of Co films on plasma-etched Si(100) substrates

M. Li, G.-C. Wang, and H.-G. Min

J. Appl. Phys. 83, 5313 (1998); http://dx.doi.org/10.1063/1.367357 (8 pages) | Cited 53 times

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Magnetic and morphological properties of ∼ 970-Å-thick Co films, deposited simultaneously on ten plasma-etched Si(100) substrates, were measured through the magneto-optic Kerr effect (MOKE) technique, ferromagnetic resonance (FMR), magnetic force microscopy (MFM), and atomic force microscopy. As the etch time t increased from 0 to 100 min, the vertical interface width w of Co films increased from ∼ 5 to ∼ 1400 Å; the lateral correlation length ξ, from ∼ 300 to ∼ 10 500 Å. The MOKE and FMR measurements gave the in-plane azimuthal angular dependence of the hysteresis loops and the ferromagnetic resonance absorption spectra, respectively. From MOKE and FMR, the smoother films showed uniaxial magnetic anisotropy (t ⩽ 40 min). The uniaxial anisotropy decreased with the increase of the surface roughness and disappeared for the roughest films (t = 60 and 100 min). The MOKE hysteresis loop measurements suggested that, with the increasing surface roughness, the magnetization reversal changed gradually from magnetization rotation dominated for the smoothest films to domain-wall motion dominated for the roughest films. The MFM images of the films showed anisotropic magnetic domain contrasts for the smooth film, and the subsequent fragmentation of these domains as the roughness parameters increased. This supports the results of the MOKE and FMR measurements. © 1998 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.20.Ls Magneto-optical effects
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.70.Rf Surface magnetism

Direct observation of magnetization reversal processes in micron-sized elements of spin-valve material

J. N. Chapman, P. R. Aitchison, K. J. Kirk, S. McVitie, J. C. S. Kools, and M. F. Gillies

J. Appl. Phys. 83, 5321 (1998); http://dx.doi.org/10.1063/1.367358 (5 pages) | Cited 32 times

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Simple calculations suggest that when continuous films of spin-valve material are patterned into micron-sized elements the magnetic properties should change markedly, depending on the element shape and size. We have used the differential phase contrast imaging mode of transmission electron microscopy to study directly the magnetization distributions supported by such elements in zero field and when subjected to an applied field in the pinning direction. For elements whose long axis is parallel to the pinning direction a parallel alignment of the free and pinned layers is favored. When subjected to a field a complex domain structure evolves and different irreversible paths are followed as the element is taken from negative to positive saturation and back again. By contrast, when the pinning direction is parallel to the short axis an antiparallel arrangement, where the magnetostatic contribution to the energy is effectively suppressed, can be preferred and simpler reversal mechanisms, with a higher degree of reversibility, are frequently seen. © 1998 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Kw Domain structure (including magnetic bubbles and vortices)

Magnetocrystalline anisotropy of Pr2(Fe1−xCox)17−yGay compounds with a Th2Zn17-type structure

Shao-ying Zhang, Bao-gen Shen, Hong-wei Zhang, Bing Liang, Jin-yun Wang, Wen-shan Zhan, and Jian-gao Zhao

J. Appl. Phys. 83, 5326 (1998); http://dx.doi.org/10.1063/1.367359 (6 pages) | Cited 1 time

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The structure and magnetic properties of Pr2(Fe1−xCox)17−yGay compounds with 0 ⩽ x ⩽ 1 and 0 ⩽ y ⩽ 3 have been investigated using x-ray diffraction (XRD) and magnetization measurements. XRD patterns demonstrate that all samples were single phase with the rhombohedral Th2Zn17-type structure, except for Pr2Fe16.5Ga0.5 with some impurity phases. The replacement of (Fe, Co) by Ga results in an approximately linear increase in the unit cell volume, and decrease in the Curie temperature and saturation magnetization. The substitution of Co for Fe leads to a nonlinear variation in the unit cell volume, the Curie temperature and the saturation magnetization. The magnetic anisotropy phase diagrams of Pr2(Fe1−xCox)16.5Ga0.5 (0 ⩽ x ⩽ 1) and Pr2(Fe0.4Co0.6)17−yGay (0 ⩽ y ⩽ 3) compounds have been determined from the temperature dependence of magnetization and the XRD patterns of magnetically oriented powder samples. Most of the samples exhibit easy plane anisotropy. A small range exists in the magnetic anisotropy phase diagrams of Pr2(Fe1−xCox)17−yGay compounds at 300 K, in which the c axis is the easy magnetization direction, however, small amounts of Ga close the easy c-axis region at y = 1.5. The spin-reorientation temperature was found to increase with Co and Ga content for Pr2(Fe1−xCox)16.5Ga0.5 (0.5 ⩽ x ⩽ 1) and Pr2(Fe0.4Co0.6)17−yGay (0 ⩽ y ⩽ 1.5) compounds, respectively. The relationship of the magnetocrystalline anisotropy with the lattice parameters and other magnetic properties were analyzed. © 1998 American Institute of Physics.
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75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Ww Permanent magnets
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Conductance, magnetoresistance, and interlayer coupling in tunnel junctions modulated by nonmagnetic metallic interlayers

Wu-Shou Zhang, Bo-Zang Li, Xiangdong Zhang, and Yun Li

J. Appl. Phys. 83, 5332 (1998); http://dx.doi.org/10.1063/1.367360 (5 pages) | Cited 12 times

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Based on the two-band model and free-electron approximation, we study the magnetism and transport properties of tunnel junctions with nonmagnetic interlayers (NM) between the ferromagnetic electrodes and tunneling barrier. We find that properties of the junctions are intermediate between tunnel junctions and metallic magnetic multilayers. The mean conductance, tunnel magnetoresistance, and interlayer coupling are all the oscillatory functions of the thickness of NM. It suggests that weak antiferromagnetic coupling can be attained by controlling the thickness of NM. Our results have potential in designing spin-polarized tunneling devices with large field sensitivity. © 1998 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.De Giant magnetoresistance
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.At Metal and metallic alloys
75.10.Lp Band and itinerant models
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