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4 Sep 1989

Volume 55, Issue 10, pp. 927-1046

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High‐field transport in semiconductors based on eigenvalue solution to Boltzmann equation

Srinivasan Krishnamurthy, A. Sher, and A.‐B. Chen

Appl. Phys. Lett. 55, 1002 (1989); http://dx.doi.org/10.1063/1.101717 (3 pages) | Cited 7 times

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The Boltzmann equation is solved by expanding the distribution function in terms of a finite number of basis functions. The zero eigenvalue of the resulting matrix is solved for the hot‐electron distribution. This method arrives at the solution at least two orders of magnitude faster than the commonly used Monte Carlo method. Using the scattering rates due to ionized impurities, phonons, alloy disorder, and intervalley scattering calculated from a realistic band structure, we obtain velocity‐field curves for various semiconductor alloys and compounds without any adjustable parameters. The results are in good agreement with experiments.
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72.20.Ht High-field and nonlinear effects
72.20.Dp General theory, scattering mechanisms
72.80.Ey III-V and II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance

Role of gas phase reactions in silicon chemical vapor deposition from monosilane

B. A. Scott and R. D. Estes

Appl. Phys. Lett. 55, 1005 (1989); http://dx.doi.org/10.1063/1.101718 (3 pages) | Cited 6 times

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A simple flow reactor experiment is described which measures the gas phase reaction contribution to silicon chemical vapor deposition from SiH4. The approach uses the fact that the rate constant for SiH4 homogeneous decomposition exhibits a linear total pressure dependence in the low‐pressure chemical vapor deposition (LPCVD) regime. Gas phase reaction channels are found to be significant even under silicon LPCVD conditions.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Rapid heteroepitaxial growth of Ge films on (100) GaAs by pulsed supersonic free‐jet chemical beam epitaxy

Djula Eres, Douglas H. Lowndes, and Jon Z. Tischler

Appl. Phys. Lett. 55, 1008 (1989); http://dx.doi.org/10.1063/1.102261 (3 pages) | Cited 18 times

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Very high epitaxial growth rates (0.25 μm/s), not attainable by conventional vapor phase film growth methods, have been obtained using a pulsed supersonic free jet to supply digermane (Ge2H6) for thermal decomposition at a heated (100)GaAs surface. Double‐crystal x‐ray diffractometry and scanning electron microscopy show that highly planar, smooth, and commensurate epitaxial Ge films are grown on (100)GaAs using gas pulses of 250 ms duration at 1–3 atm (0.1–0.3 MPa) pressure for substrate temperatures of 480–680 °C. It is believed that the very high growth rates effectively ‘‘freeze’’ the Ge‐GaAs interface resulting in minimal interfacial diffusion and reduced incorporation of impurities from the surrounding growth environment.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
68.35.Fx Diffusion; interface formation

Reaction of trimethylgallium in the atomic layer epitaxy of GaAs (100)

Ming L. Yu, Ulrich Memmert, and Thomas F. Kuech

Appl. Phys. Lett. 55, 1011 (1989); http://dx.doi.org/10.1063/1.101719 (3 pages) | Cited 41 times

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The initial reaction of the As‐rich c(2×8) GaAs(100) surface with trimethylgallium (TMGa) has been studied by x‐ray and ultraviolet photoemission. TMGa was found to chemisorb dissociatively at temperatures below 300 °C with many of the methyl radicals remaining on the surface. Bonding requirements and steric effects limit the saturation coverage to about 0.1 monolayer. At temperatures above 300 °C, TMGa was observed to dissociate on the surface, release all the methyl groups, and deposit Ga up to a self‐limiting coverage. This process is most effective at high temperatures. We propose a model for the temperature dependence of the chemisorption which explains and unites many reported observations in the atomic layer epitaxy of GaAs using TMGa and arsine.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
81.65.-b Surface treatments

Silicon selective epitaxial growth at 800 °C using SiH4/H2 assisted by H2/Ar plasma sputter

Tri‐Rung Yew and Rafael Reif

Appl. Phys. Lett. 55, 1014 (1989); http://dx.doi.org/10.1063/1.101720 (3 pages) | Cited 11 times

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This letter presents the results of silicon selective epitaxial growth at 800 °C by ultralow pressure chemical vapor deposition using SiH4 /H2 assisted by H2 /Ar plasma sputter. By utilizing growth‐sputter cycles, selective epitaxial layers can be grown on exposed silicon windows of silicon wafers with oxide patterns to the thickness needed. The growth process was carried out by flowing SiH4 (3.5 mTorr)/H2 (7 mTorr), while the sputter step was performed by using H2 (7 mTorr)/Ar(1.5 mTorr) plasma at a susceptor dc bias from −100 to −300 V. Characterized by cross‐sectional transmission electron microscopy, Nomarski optical microscopy, and spreading resistance profiling, the epitaxial films were found of high structural and electrical quality.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Cd Deposition by sputtering
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors

Mg diffusion during metalorganic vapor phase epitaxy of InP

E. Veuhoff, H. Baumeister, R. Treichler, and O. Brandt

Appl. Phys. Lett. 55, 1017 (1989); http://dx.doi.org/10.1063/1.101721 (3 pages) | Cited 13 times

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The diffusion mechanism of Mg has been studied during low‐pressure metalorganic vapor phase epitaxy of InP. The Mg dopant profiles were measured by secondary‐ion mass spectroscopy. The analysis reveals that abrupt Mg dopant profiles are possible; the Mg diffusion, however, strongly depends on the Mg concentration in the crystal lattice. Simultaneous doping with Si leads to a distinct decrease of the Mg diffusion. This behavior is consistent with a model assuming that Mg diffuses as a complex involving a deep donor.
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66.30.J- Diffusion of impurities
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ey III-V semiconductors

Synchrotron radiation induced metal deposition on semiconductors: Mo(CO)6 on Si (111)

R. Zanoni, M. N. Piancastelli, J. McKinley, and G. Margaritondo

Appl. Phys. Lett. 55, 1020 (1989); http://dx.doi.org/10.1063/1.101722 (3 pages) | Cited 17 times

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We found that unmonochromatized soft x‐ray synchrotron radiation stimulates the dissociation of molecular Mo(CO)6 adsorbed on silicon, producing a metallic overlayer. The process, which is interesting for potential applications, was studied using soft x‐ray photoemission spectroscopy.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
79.60.Jv Interfaces; heterostructures; nanostructures
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light

Magnetoreflectivity study of excitons in (Zn,Co)Se epilayers

X. Liu, A. Petrou, B. T. Jonker, G. A. Prinz, J. J. Krebs, and J. Warnock

Appl. Phys. Lett. 55, 1023 (1989); http://dx.doi.org/10.1063/1.102262 (3 pages) | Cited 3 times

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The reflectivity spectra from single‐crystal epilayers of the diluted magnetic semiconductor Zn1−x Cox Se(x=0.0076, x=0.0104) have been studied as functions of magnetic field and temperature. The excitonic spin splitting in these crystals saturates for magnetic fields B>5 T, indicating that (Zn,Co)Se is a Brillouin paramagnet, in agreement with magnetization and electron‐paramagnetic‐resonance studies on the same samples. The magnetoreflectivity data yield a value for the exchange parameter difference N0 (α−β)=2420±40 meV, significantly larger than the values obtained for either Fe‐ or Mn‐based diluted magnetic semiconductors studied to date.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
71.35.-y Excitons and related phenomena
73.20.At Surface states, band structure, electron density of states

Weighted Monte Carlo for electron transport in semiconductors

P. Poli, L. Rota, and C. Jacoboni

Appl. Phys. Lett. 55, 1026 (1989); http://dx.doi.org/10.1063/1.101723 (3 pages) | Cited 5 times

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A new powerful method, the weighted Monte Carlo method, for the solution of electron transport problems in semiconductors is presented. The method is formally derived from an iterative expansion of the integral form of the Boltzmann equation and results in a simulation of electron dynamics where arbitrary probabilities for the various events which generate electron trajectories are used. It is much more flexible than the standard algorithm that can be derived by it as a very special case. The method is applied here to study the tail of the distribution function in a simple silicon model.
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72.20.Dp General theory, scattering mechanisms
72.20.Ht High-field and nonlinear effects

High Q coplanar transmission line resonator of YBa2Cu3O7−x on MgO

A. A. Valenzuela and P. Russer

Appl. Phys. Lett. 55, 1029 (1989); http://dx.doi.org/10.1063/1.101576 (3 pages) | Cited 22 times

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We present the first coplanar waveguide transmission line resonator patterned from a perovskite high Tc superconducting film at 9 GHz. At 77 K the unloaded quality factor Q0 of the resonator patterned from a YBa2Cu3O7−x film on a MgO substrate is 1300, that is, 14 times higher than that of the copper resonator and 17 times higher than that of the gold resonator at the same temperature. At 4.2 K a Q0 factor of 3300 was measured for the YBa2Cu3O7−x /MgO resonator. Simple calculations of the quality factor show that values of 10 000 at 77 K should be possible using better substrates, films, and etching techniques. This resonator could form the basic structure of more complex microwave filter systems operating at liquid‐nitrogen temperatures.
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
74.25.-q Properties of superconductors

Preparation and growth of (Bi,Pb)‐Sr‐Ca‐Cu‐O superconductor fibers

Wilder Carrillo‐Cabrera, Wolfgang Göpel, Germán F. de la Fuente, and Horacio R. Verdún

Appl. Phys. Lett. 55, 1032 (1989); http://dx.doi.org/10.1063/1.102455 (3 pages) | Cited 7 times

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The laser floating zone (LFZ) method has been used to grow (Bi,Pb)‐Sr‐Ca‐Cu‐O superconductor fibers from solution‐derived ceramic precursors (nominal Bi1.8Pb0.35Sr1.87Ca2Cu3Ox), prepared under different sintering conditions. The as‐grown LFZ fibers were semiconducting. After annealing at 855 and 800 °C in air, the fibers were metallic. A second anneal at these temperatures optimized the superconducting properties of the fibers [Tc (midpoint)=111 K and Tc (zero)=106 K]. The LFZ‐grown fibers contain highly oriented superconductor grains their electrical properties depend strongly on precursor thermal processing.
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74.70.-b Superconducting materials other than cuprates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.40.Rs Electrical and magnetic properties related to treatment conditions
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)

Effect of a declination angle of substrate position on magnetron sputter deposition from a YBa2Cu3O7−x target

Yasuyuki Kageyama and Yasunori Taga

Appl. Phys. Lett. 55, 1035 (1989); http://dx.doi.org/10.1063/1.102456 (3 pages) | Cited 9 times

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Thin‐film deposition by magnetron sputtering of a multielement target was carried out with respect to the geometrical factors between a target and the substrates. The thin films were deposited on substrates which were located semicircularly over a YBa2Cu3O7−x target in several declination angles measured from the normal to the target surface. The deposition rate decreased to about one‐third with the change in the angle from 0° to 90°. In the angles of 45°, 60°, and 75°, films showed significant instability in the atmosphere, which appeared to be caused by an excessive concentration of Ba atoms in the films. Target composition was almost reproduced in the films deposited in the angle of 90°.
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81.15.Cd Deposition by sputtering
74.78.-w Superconducting films and low-dimensional structures
68.55.Nq Composition and phase identification
74.70.-b Superconducting materials other than cuprates

Correlation of thermally stimulated luminescence with radio frequency surface resistance of high‐temperature superconductors

D. W. Cooke, B. Bennett, E. R. Gray, R. J. Houlton, W. L. Hults, M. A. Maez, A. Mayer, J. L. Smith, and M. S. Jahan

Appl. Phys. Lett. 55, 1038 (1989); http://dx.doi.org/10.1063/1.101724 (3 pages) | Cited 10 times

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We recently demonstrated that insulating surface impurity phases in high‐temperature superconductors can be detected by thermally stimulated luminescence. Moreover, we suggested that the intensity of luminescence is related to the magnitude of the rf surface resistance. In this work we show that a quantitative correlation exists between these two quantities, and that luminescence can be a very useful technique for estimating rf surface resistance.
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74.25.N- Response to electromagnetic fields
78.60.Kn Thermoluminescence
74.70.-b Superconducting materials other than cuprates
68.35.Dv Composition, segregation; defects and impurities

Nature of in situ superconducting film formation

Q. Y. Ying, H. S. Kim, D. T. Shaw, and H. S. Kwok

Appl. Phys. Lett. 55, 1041 (1989); http://dx.doi.org/10.1063/1.101725 (3 pages) | Cited 31 times

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The resistivity of a Y‐Ba‐Cu‐O film was monitored during laser deposition in real time. Both deposition parameters leading to in situ films and those requiring high‐temperature (850 °C) post‐annealing were examined. It was found that in both cases, the resistivity was dependent on the oxygen partial pressure during deposition, and that filling the chamber with oxygen immediately after deposition was crucial to the formation of the superconducting phase. Oxygen outdiffusion during deposition at high temperature (600 °C) was found to be the major obstacle to true in situ film formation.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Laser patterning and critical current measurements of submicrometer lines of Y‐Ba‐Cu‐O

J. P. Zheng, H. S. Kim, Q. Y. Ying, R. Barone, P. Bush, D. T. Shaw, and H. S. Kwok

Appl. Phys. Lett. 55, 1044 (1989); http://dx.doi.org/10.1063/1.101726 (3 pages) | Cited 20 times

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Superconducting strips of 0.6 μm width were fabricated by direct laser writing on mirror‐like Y‐Ba‐Cu‐O thin films on various substrates. These films were grown by laser deposition without post‐annealing. Laser ablation etching had no effect on the Tc and Jc until the lines were <1 μm wide. The 0.6‐μm‐wide strip showed some degradation of Tc. The critical current densities for all patterned lines were measured to be ∼4×106 A/cm2 at 20 ° K.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
74.25.Sv Critical currents
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