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30 Oct 1989

Volume 55, Issue 18, pp. 1817-1926

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Electron transport in an AlSb/InAs/GaSb tunnel emitter hot‐electron transistor

T. H. Chiu and A. F. J. Levi

Appl. Phys. Lett. 55, 1891 (1989); http://dx.doi.org/10.1063/1.102163 (3 pages) | Cited 10 times

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We report preparation of high quality AlSb/InAs/GaSb heterostructures by molecular beam epitaxy. Using this crystal growth technique we have fabricated unipolar AlSb tunnel emitter transistors and used them to explore electron transport as a function of electron injection energy Ei across a 100‐Å‐thick InAs quantum well base. A low‐energy threshold for collector current is observed for Ei>ϕbc, where ϕbc is the base/collector potential barrier. A maximum collection efficiency of ∼0.9 is obtained at Ei≂1.5 eV and at larger values of Ei, the collection efficiency decreases due to wave function symmetry and velocity mismatch across the abrupt base/collector heterointerface.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Role of interfaces on the performance and stability of amorphous silicon‐germanium alloy p‐i‐n solar cells

R. R. Arya, M. S. Bennett, K. Rajan, and A. Catalano

Appl. Phys. Lett. 55, 1894 (1989); http://dx.doi.org/10.1063/1.102164 (3 pages) | Cited 9 times

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The performance and stability of a‐SiGe:H single junction p‐i‐n solar cells with interfacial layers at the p/i and the i/n interfaces are reported. It is found that interfacial layers have a strong influence both on the initial performance as well as on the stability of these devices. The device structure, which consists of glass, conductive transparent oxide (SnO2 ), p(a‐SiC:H), a‐Si:H (buffer layer), graded interface layer (1.7 eV–1.5 eV), i (2500 Å, 1.5 eV), inverse graded interface layer (1.5 eV–1.7 eV), and n (a‐Si:H), results in the highest long‐term performance. This device structure has resulted in a conversion efficiency of 10.1% with short‐circuit current density of 20 mA/cm2 .
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84.60.Jt Photoelectric conversion
72.40.+w Photoconduction and photovoltaic effects
73.50.Pz Photoconduction and photovoltaic effects

Passivation of defects in polycrystalline superlattices and quantum well structures

Raphael Tsu, Edward H. Nicollian, and Arnold Reisman

Appl. Phys. Lett. 55, 1897 (1989); http://dx.doi.org/10.1063/1.102328 (3 pages) | Cited 6 times

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In order to broaden the available materials for superlattices and quantum well structures, well‐passivated polycrystalline semiconductors and amorphous oxides such as pc‐Si/a‐SiO2, pc‐Ge/a‐GeO2 (pc: polycrystalline; a: amorphous) are proposed. Crucial in maintaining long scattering length involves the passivation of pc‐Si (polycrystalline silicon) and pc‐Ge. Specific means to passivate grain boundaries are discussed which consist of the use of the common dangling bond teminator, hydrogen, as well as amorphous oxides and other amorphous materials. This unique procedure may be extended to the entire group III‐V semiconductors such as polycrystalline GaAs and InP.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.65.-b Surface treatments
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Dv Composition, segregation; defects and impurities

Thermal stability of Si/GexSi1−x/Si heterostructures

R. Hull and J. C. Bean

Appl. Phys. Lett. 55, 1900 (1989); http://dx.doi.org/10.1063/1.102165 (3 pages) | Cited 27 times

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The thermal stability of Si/GexSi1−x/Si (100) heterostructures is studied by in situ electron microscope observations of the thermal relaxation process. Structures are observed to relax by misfit dislocation propagation at both strained interfaces, and are stable to significantly higher temperatures than equivalent strained GexSi1−x layers at a free surface. This observed difference in thermal stability between double and single interface structures is due at least in part to much lower dislocation velocities in the double interface structures, with a measured glide activation energy approximately twice as high as single interface structures. It is argued that this difference in glide activation energies may be due to a smaller kink nucleation activation energy in the single interface structure.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
68.35.Dv Composition, segregation; defects and impurities
68.60.Dv Thermal stability; thermal effects
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Inductive current measurements in an oriented grained YBa2Cu3Ox superconductor

H. Küpfer, C. Keller, K. Salama, and V. Selvamanickam

Appl. Phys. Lett. 55, 1903 (1989); http://dx.doi.org/10.1063/1.102329 (3 pages) | Cited 13 times

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The critical current of grain aligned YBa2 Cu3Ox bulk material was investigated by inductive flux profile and ac susceptibility measurements. The induced current was directed perpendicular to the a‐b plane oriented grains where high values of the transport current, have been previously reported. In spite of the unfavorable geometry of the investigated shielding current, no features of granularity were observed. The results yield a uniform bulk critical current density jc of 3×104 A/cm2 at zero field and 77 K. Field and temperature dependences of this jc are discussed and compared with those in a granular Y‐Ba‐Cu‐O material.
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74.25.Sv Critical currents
74.70.-b Superconducting materials other than cuprates
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors

Organometallic chemical vapor deposition of superconducting, high Tc Pb‐doped Bi‐Sr‐Ca‐Cu‐O thin films

J. M. Zhang, H. O. Marcy, L. M. Tonge, B. W. Wessels, T. J. Marks, and C. R. Kannewurf

Appl. Phys. Lett. 55, 1906 (1989); http://dx.doi.org/10.1063/1.102330 (3 pages) | Cited 13 times

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Highly oriented films of the high Tc Bi‐Pb‐Sr‐Ca‐Cu‐O (BPSCCO)superconductor have been prepared by two organometallic chemical vapor deposition (OMCVD) approaches. In the first approach, Pb is introduced by alternate deposition of BSCCO and PbOx films using the volatile metalorganic precursors Cu(acetylacetonate)2, Sr(dipivaloylmethanate)2, Ca(dipivaloylmethanate)2, triphenyl bismuth, and tetraphenyl lead. In the second approach, Pb is incorporated into an OMCVD‐derived BSCCO film by vapor diffusion using PbO as the source. X‐ray diffractometry and scanning electron microscopy reveal that Pb doping significantly improves the crystalline orientation and the film morphology. Films deposited by both methods on [100] single‐crystal MgO consist predominantly of the Bi2(Sr,Ca)3Cu2Ox phase and have a high preferential orientation of the crystallite c axes perpendicular to the substrate surface. Four‐probe resistivity measurements indicate the onset of film superconductivity at ∼110 K and zero resistance by 80 K.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
74.70.-b Superconducting materials other than cuprates

Superconducting InGaAs junction field‐effect transistors with Nb electrodes

A. W. Kleinsasser, T. N. Jackson, D. McInturff, F. Rammo, G. D. Pettit, and J. M. Woodall

Appl. Phys. Lett. 55, 1909 (1989); http://dx.doi.org/10.1063/1.102166 (3 pages) | Cited 32 times

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We describe the design, fabrication, and characterization of superconducting In0.47Ga0.53As junction field‐effect transistors (JFETs) with Nb source and drain electrodes. In0.47Ga0.53As has the advantage of combining large coherence length and high Schottky barrier transmission, making it a very attractive material on which to base superconducting FETs. At large voltages these devices behave as normal FETs in either enhancement or depletion modes, while at small voltages they act as Josephson junctions or super‐Schottky diodes. Both normal and super‐ currents are controlled by the gate.
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
85.30.Tv Field effect devices
74.50.+r Tunneling phenomena; Josephson effects
73.30.+y Surface double layers, Schottky barriers, and work functions

Gold contacts on superconducting crystals of YBa2Cu3O7 with very low contact resistivity

T. W. Jing, Z. Z. Wang, and N. P. Ong

Appl. Phys. Lett. 55, 1912 (1989); http://dx.doi.org/10.1063/1.102167 (3 pages) | Cited 21 times

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By cleaving crystals of YBa2Cu3O7 in high vacuum and evaporating Au in situ, we have fabricated Au‐YBa2Cu3O7 junctions with very low contact resistance. Below Tc, the specified contact resistivity drops by three decades to an estimated value 2×10−9 Ω cm2 at 87.3 K. We emphasize the importance of correcting for spreading resistance in such studies. We also discuss the ideal contact resistivity, and possible contributions to the measured resistance very near Tc.
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73.40.Cg Contact resistance, contact potential
74.70.-b Superconducting materials other than cuprates
73.40.Jn Metal-to-metal contacts
85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices

Ion beam thinning and polishing of YBa2Cu3O7 films

A. F. Hebard, R. M. Fleming, K. T. Short, A. E. White, C. E. Rice, A. F. J. Levi, and R. H. Eick

Appl. Phys. Lett. 55, 1915 (1989); http://dx.doi.org/10.1063/1.102331 (3 pages) | Cited 20 times

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Successive ion beam milling at grazing angles of a 2400‐Å‐thick, c‐axis‐oriented YBa2Cu3O7 film is shown to give smooth films which superconduct at thicknesses on the order of tens of angstroms. The thinning and polishing process is characterized at successive milling stages using resistance transitions, x‐ray analysis, scanning electron microscopy, and Rutherford backscattering and channeling analysis of composition and surface quality. As thinning proceeds, scanning electron microscopy and diffraction features associated with a‐axis texture are removed and crystalline quality, as measured by x rays and channeling, markedly improves.
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74.78.-w Superconducting films and low-dimensional structures
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
74.70.-b Superconducting materials other than cuprates
81.40.Rs Electrical and magnetic properties related to treatment conditions

Anomalous field dependence of magnetoresistance in Fe/Gd multilayered ferrimagnets

Y. Kamiguchi, Y. Hayakawa, and H. Fujimori

Appl. Phys. Lett. 55, 1918 (1989); http://dx.doi.org/10.1063/1.102277 (2 pages) | Cited 28 times

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The magnetoresistance of Fe/Gd ferrimagnetic multilayered films prepared by sputtering was investigated. The longitudinal magnetoresistance ρl increases first, followed by a deep decrease, and then increases again, with an increasing applied field. The transverse magnetoresistance ρt behaves in an opposite manner such that ρl and ρt play a crossover at an intermediate field. This new type of field dependence of ρl and ρt can be explained in terms of the spin flop of artificial ferrimagnetism which gives rise to an anomalous up‐turn curve in magnetization versus field.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Gg Ferrimagnetics
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.80.+q Magnetomechanical effects, magnetostriction

Origin of inverted‐in‐sense and constricted near‐surface hysteresis loops of magnetic plates

M. Tejedor, H. Rubio, and A. Fernández

Appl. Phys. Lett. 55, 1920 (1989); http://dx.doi.org/10.1063/1.102168 (3 pages) | Cited 5 times

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New types of magnetic hysteresis loops, inverted‐in‐sense and crossed, have been observed in some directions of the surface of METGLAS 2605SC circular plates (Allied Chemical Corp.) The origin of these kinds of loops and other constricted ones observed in the surface of magnetic plates is explained. They appear because the internal field that acts on surface and inside the sample is mainly determined by the bulk properties of the sample. The validity of this interpretation is tested with additional measurements in METGLAS 2605SC.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
75.30.Gw Magnetic anisotropy
75.50.Kj Amorphous and quasicrystalline magnetic materials

Tungsten metal film formed by spin‐coating amorphous peroxopolytungstic acid

Hiroshi Okamoto and Akira Ishikawa

Appl. Phys. Lett. 55, 1923 (1989); http://dx.doi.org/10.1063/1.102332 (3 pages) | Cited 3 times

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A homogeneous, amorphous peroxopolytungstic acid film can be formed easily with the spin‐coating method. The film is found to provide a homogeneous tungsten metal film after reduction with hydrogen at ∼400 °C. Although the electric resistivity (∼450 μΩ cm) is higher than that for the bulk (5.65 μΩ cm), this method has an advantage in addition to spin coatability: tungsten metal films with fine patterns can be easily obtained because the starting material is photosensitive.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
73.61.At Metal and metallic alloys
81.05.Bx Metals, semimetals, and alloys
81.40.Rs Electrical and magnetic properties related to treatment conditions
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Erratum: Manipulation of Si nucleation on artificial sites of SiNx (x<4/3) over SiO2 [Appl. Phys. Lett. 55, 636 (1989)]

N. Sato and T. Yonehara

Appl. Phys. Lett. 55, 1926 (1989); http://dx.doi.org/10.1063/1.102379 (1 page)

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Abstract Unavailable
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Dv Composition, segregation; defects and impurities
68.55.Nq Composition and phase identification
68.35.Fx Diffusion; interface formation
99.10.Cd Errata
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