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19 Dec 1988

Volume 53, Issue 25, pp. 2465-2568

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Transverse magnetic field dependence of the current‐voltage characteristics of double‐barrier quantum well tunneling structures

S. Ben Amor, K. P. Martin, J. J. L. Rascol, R. J. Higgins, A. Torabi, H. M. Harris, and C. J. Summers

Appl. Phys. Lett. 53, 2540 (1988); http://dx.doi.org/10.1063/1.100202 (3 pages) | Cited 31 times

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We report the effects of a transverse magnetic field (J⊥B) on the conductivity of quantum well tunneling structures based on AlGaAs/GaAs/AlGaAs quantum wells. The current‐voltage characteristics in the positive differential resistance regime show negative magnetoconductance for all values of B. The peak bias voltage increases monotonically with increasing B. For B<6 T there is a decrease in the peak tunneling current, but then it increases for B>6 T. The data also show dramatic magnetic field induced changes in the negative differential resistance (NDR) features. The behavior of the NDR changes from sharp hysteretic bistable‐like transitions to astable NDR transitions. Both the valley current and its bias voltage position increase with increasing magnetic field. This behavior is described by a simple model that includes magnetic field effects across the barriers.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Limitations in low‐temperature silicon epitaxy due to water vapor and oxygen in the growth ambient

J. A. Friedrich, G. W. Neudeck, and S. T. Liu

Appl. Phys. Lett. 53, 2543 (1988); http://dx.doi.org/10.1063/1.100530 (3 pages) | Cited 13 times

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Basic chemical equilibrium data for the Si/SiO2/O2/H2O system have been employed to compute critical epitaxial preclean and growth parameters. Preclean and growth experiments were conducted and compared with predicted behavior. A procedure is given that allows for the design of an epitaxial deposition process for most commercially available epitaxy reactor systems. Following this scheme, good crystal quality silicon was deposited at temperatures as low as 890 °C and at a deposition pressure of 150 Torr. For current commercially available reduced pressure reactor systems, a practical low‐temperature limit of about 810 °C is predicted.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Effect of local alloy disorder on emission kinetics of deep donors (DX centers) in AlxGa1−xAs of low Al content

P. M. Mooney, T. N. Theis, and S. L. Wright

Appl. Phys. Lett. 53, 2546 (1988); http://dx.doi.org/10.1063/1.100203 (3 pages) | Cited 78 times

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We report measurements by deep level transient spectroscopy of electron emission from the deep donor level (DX center) in Si‐doped GaAs and AlxGa1−xAs of very low Al content. For the first time, discrete emission rates corresponding to different local configurations of Ga and Al atoms around the Si donor are resolved. The large change in emission kinetics previously observed between GaAs and AlxGa1−xAs (x≥0.14) is thus shown to arise from the local alloy disorder which is absent in GaAs.
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71.55.Eq III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Angled etching of GaAs/AlGaAs by conventional Cl2 reactive ion etching

Takeshi Takamori, Larry A. Coldren, and James L. Merz

Appl. Phys. Lett. 53, 2549 (1988); http://dx.doi.org/10.1063/1.100204 (3 pages) | Cited 11 times

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Angled etching of GaAs and GaAs/AlGaAs double heterostructures was achieved in a conventional Cl2 reactive ion etching system. A new angled holder, which has a recessed groove structure where the substrate is positioned, was used to eliminate bending of the ion trajectory around the substrate. The facet angle is accurately determined by the angle of the groove wall. Equal etching rates and smooth facets were obtained by using a load‐locked system and trilevel photoresist masking. This simple dry etch process is suitable for the formation of optoelectronic integrated circuits such as surface‐emitting lasers.
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
85.40.Hp Lithography, masks and pattern transfer

High‐power GaAs/AlGaAs diode lasers grown on a Si substrate by metalorganic chemical vapor deposition

J. Connolly, N. Dinkel, R. Menna, D. Gilbert, and M. Harvey

Appl. Phys. Lett. 53, 2552 (1988); http://dx.doi.org/10.1063/1.100205 (3 pages) | Cited 4 times

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High‐power GaAs/AlGaAs double‐heterostructure lasers have been fabricated on Si substrates using a single‐step metalorganic chemical vapor deposition process. An output power of 130 mW (per facet) and a slope efficiency of 38% have been obtained under pulsed operation. The peak emission wavelength of the laser was 8823 Å and the beam full width at half power for the parallel and perpendicular far‐field radiation patterns were 6° and 41°, respectively.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Cooperative growth phenomena in silicon/germanium low‐temperature epitaxy

Bernard S. Meyerson, Kevin J. Uram, and Francoise K. LeGoues

Appl. Phys. Lett. 53, 2555 (1988); http://dx.doi.org/10.1063/1.100206 (3 pages) | Cited 190 times

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A series of Si:Ge alloys and structures has been prepared by ultrahigh‐vacuum chemical vapor deposition. Alloys of composition 0≤Ge/Si≤0.20 are readily deposited at T=550 °C. Commensurate, defect‐free strained layers are deposited up to a critical thickness, whereupon the accumulated stress in the films is accommodated by the formation of dislocation networks in the substrate wafers. A cooperative growth phenomenon is observed where the addition of 10% germane to the gaseous deposition source accelerates silane’s heterogeneous reaction rate by a factor of 25. A model is proposed where Ge acts as a desorption center for mobile hydrogen adatoms on the Si[100] surface, accelerating heterogeneous silane pyrolysis by the enhanced availability of chemisorption sites.
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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
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Fine structure of EL2 defect absorption in GaAs

W. Kuszko, M. Jeżewski, J. M. Baranowski, and M. Kaminska

Appl. Phys. Lett. 53, 2558 (1988); http://dx.doi.org/10.1063/1.100207 (2 pages) | Cited 5 times

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High‐resolution measurements of the zero phonon line (ZPL) of the EL2 intracenter absorption were performed. Several samples, both Czochralski and Bridgman grown, have been examined. The shape and position of the ZPL were virtually identical for all the samples. No splitting of the ZPL was detected.
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71.55.Eq III-V semiconductors
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Large anisotropy in the upper critical field of sputtered thin films of superconducting Tl‐Ba‐Ca‐Cu‐O

J. H. Kang, K. E. Gray, R. T. Kampwirth, and D. W. Day

Appl. Phys. Lett. 53, 2560 (1988); http://dx.doi.org/10.1063/1.100531 (3 pages) | Cited 30 times

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The upper critical field Bc2 provides the most direct measure of the intrinsic anisotropy of a superconductor. For highly oriented, sputtered thin films of the high‐temperature superconductor Tl2Ba2CaCu2Ox, we find a Bc2 anisotropy of at least 70, which exceeds similar measurements on thin films and single crystals of the high‐temperature superconductors Bi‐Sr‐Ca‐Cu‐O and YBa2Cu3Oy. We discuss why the midpoints of the resistive transitions, used in these measurements, may be appropriate for defining the intrinsic Bc2.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.Op Mixed states, critical fields, and surface sheaths

Surface structure of Bi2Sr2CaCu2O8+δ high‐temperature superconductors studied using low‐energy electron diffraction

P. A. P. Lindberg, Z.‐X. Shen, B. O. Wells, D. B. Mitzi, I. Lindau, W. E. Spicer, and A. Kapitulnik

Appl. Phys. Lett. 53, 2563 (1988); http://dx.doi.org/10.1063/1.100532 (3 pages) | Cited 30 times

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The surface structure of Bi2Sr2CaCu2O8+δ has been studied using low‐energy electron diffraction (LEED). Sharp diffraction spots indicative of a well‐ordered surface are observed. The LEED patterns unequivocally show that this type of material preferentially cleaves along the a‐b planes of the nearly tetragonal unit cell. A superstructure extending along one of the axes in the a‐b plane (b) is found to have a periodicity of 27±0.5 Å, in good agreement with earlier studies of the three‐dimensional crystal structure. We conclude that the superstructure at the surface is nonlocal in character and reflects the long‐range superlattice of the bulk along the b axis. Intensity modulations of the diffraction spots oriented along the b axis are also reported and discussed in terms of the cell dimension of the unit cell along the b axis.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
74.70.-b Superconducting materials other than cuprates
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Thickness and annealing dependence of the superconducting transition temperature of YBa2Cu3O7−x thin films on oxidized silicon and polycrystalline alumina substrates

A. Mogro‐Campero, L. G. Turner, and G. Kendall

Appl. Phys. Lett. 53, 2566 (1988); http://dx.doi.org/10.1063/1.100533 (3 pages) | Cited 26 times

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Superconducting thin films of YBa2Cu3O7−x in the thickness range of 0.2–0.9 μm were tested in this study. A zirconia buffer layer was used to minimize interdiffusion on oxidized silicon and polycrystalline alumina substrates. The highest zero resistance transition temperatures (85 K for oxidized silicon and 86 K for polycrystalline alumina) were obtained for the thicker films; these are the highest values reported for thin films of this superconductor on these substrates. The thickness and annealing dependence of the transition temperature suggests that interdiffusion limits the performance of the thinner samples.
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74.78.-w Superconducting films and low-dimensional structures
68.55.-a Thin film structure and morphology
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
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