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24 Jun 1991

Volume 58, Issue 25, pp. 2871-2991

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Guiding‐center‐drift resonance of two‐dimensional electrons in a grid‐gate superlattice potential

C. T. Liu, D. C. Tsui, M. Shayegan, K. Ismail, D. A. Antoniadis, and Henry I. Smith

Appl. Phys. Lett. 58, 2945 (1991); http://dx.doi.org/10.1063/1.104730 (3 pages) | Cited 5 times

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We have studied the low‐field magnetoresistance of the two‐dimensional electron gas in GaAs/<m1;&33>AlxGa1−xAs in the presence of a two‐dimensional lateral surface superlattice (2D LSSL) potential, and observed, for the first time, the guiding‐center drift resonance, previously reported for one‐dimensional LSSL structures. The 2D LSSL potential is created by applying a voltage Vg to a 200 nm period grid‐gate structure fabricated on top of the sample and can be tuned continuously from being repulsive to attractive by tuning Vg.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.25.+i Surface conductivity and carrier phenomena

Highly conductive and wide optical band gap n‐type μc‐SiC prepared by electron cyclotron resonance plasma‐enhanced chemical vapor deposition

Toshiro Futagi, Masakazu Katsuno, Noboru Ohtani, Yasumitsu Ohta, Hidenori Mimura, and Kazuhiko Kawamura

Appl. Phys. Lett. 58, 2948 (1991); http://dx.doi.org/10.1063/1.104731 (3 pages) | Cited 13 times

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We have investigated the gas pressure dependence of electron cyclotron resonance (ECR) plasma‐enhanced chemical vapor deposition (PECVD) and prepared n‐type μc‐SiC:H with wide optical band gap (2.1–2.5 eV) and high dark conductivity (10−3– 1 S/cm). It has been suggested from plasma diagnoses of the ECR plasma that at low gas pressure a strong etching effect of hydrogen radicals and/or ions dominates the film growth process and the hydrogen ions impinging on the growing surface make the formation of μc‐SiC:H difficult, and that at high gas pressure, for the formation of μc‐SiC:H, there are nonemissive radicals contributing to the surface coverage or a nucleus formation mechanism which has not been taken into consideration in conventional rf‐PECVD.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ng Insulators

Analysis of cut‐off frequency roll‐off at high currents in SiGe double‐heterojunction bipolar transistors

Guang‐bo Gao, Zhi‐fang Fan, and H. Morkoç

Appl. Phys. Lett. 58, 2951 (1991); http://dx.doi.org/10.1063/1.104732 (3 pages) | Cited 3 times

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Roll‐off of the current gain cut‐off frequency in NpN double‐heterojunction bipolar transistors for large collector currents has been analyzed. The analysis includes such effects as the electron barrier formed at the collector base junction due to electron accumulation. Included in this investigation is also lateral electron diffusion before injection into the collector space‐charge region at the base‐collector heterointerface once the barrier is formed. The available data obtained in SiGe heterojunction bipolar transistors are in good agreement with this model.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling
85.30.Pq Bipolar transistors

Gas‐source molecular beam epitaxy growth of highly strained device quality InAsP/InP multiple quantum well structures

H. Q. Hou, C. W. Tu, and S. N. G. Chu

Appl. Phys. Lett. 58, 2954 (1991); http://dx.doi.org/10.1063/1.104733 (3 pages) | Cited 14 times

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InAsxP1−x/InP strained multiple quantum wells with strain as high as 2.5% were grown by gas‐source molecular beam epitaxy. Successful control of the arsenic composition over a wide range was achieved by two different growth techniques. Structural and optical studies, such as high‐resolution x‐ray rocking curve, cross‐sectional transmission electron microscopy, photoluminescence, and absorption measurement, indicate that we have obtained high quality multiple quantum wells that are suitable for optoelectronic applications.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Three‐terminal operation of the double‐heterostructure optoelectronic switching laser

G. W. Taylor, P. R. Claisse, and P. Cooke

Appl. Phys. Lett. 58, 2957 (1991); http://dx.doi.org/10.1063/1.104707 (3 pages) | Cited 10 times

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The double‐heterostructure optoelectronic switch is demonstrated as a three‐terminal laser. The basic laser structure employs a graded index single quantum well (GRIN SQW) and implements the third‐terminal injector as a self‐aligned implant to the inversion channel. The implant simultaneously serves as the optical confining layer. Threshold currents of 500 A/cm2 are obtained and complete control of the switching characteristic is obtained with an input current density of 0.8 A/cm2.
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42.55.Px Semiconductor lasers; laser diodes
85.60.-q Optoelectronic devices
42.55.Rz Doped-insulator lasers and other solid state lasers

Fabrication and characterization of deep mesa etched ‘‘anti’’‐dot superlattices in GaAs‐AlGaAs heterostructures

D. Weiss, P. Grambow, K. von Klitzing, A. Menschig, and G. Weimann

Appl. Phys. Lett. 58, 2960 (1991); http://dx.doi.org/10.1063/1.104708 (3 pages) | Cited 25 times

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By etching a periodic array of holes through a ;mobility two‐dimensional electron gas we define high‐a lateral, ‘‘anti’’‐dot‐type superlattice with periods a=200 and a=300 nm, much smaller than the electron mean free path in the unpatterned material. The devices are fabricated using electron beam lithography and reactive ion etching techniques, and characterized by magnetotransport experiments. Commensurability effects and the observed quenching of the Hall effect indicate that the electron gas between the etched holes essentially maintains its initial high electron mobility.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.Ey III-V semiconductors

Kinetics of surface reactions in very low‐pressure chemical vapor deposition of Si from SiH4

S. M. Gates and S. K. Kulkarni

Appl. Phys. Lett. 58, 2963 (1991); http://dx.doi.org/10.1063/1.104709 (3 pages) | Cited 65 times

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A steady‐state kinetic model for the chemical vapor deposition (CVD) growth of Si films from SiH4 on Si(100) is presented. The only adsorbing species is SiH4 (absence of homogeneous SiH4 dissociation is presumed). Model predictions of surface hydrogen coverage and Si film growth rate as a function of growth temperature ( T ) are compared with literature values for these quantities. The rate of each reaction step is calculated at selected T. Adsorption of SiH4 and decomposition of SiH3 control the growth rate in the high T limit. In the low T limit, SiH4 adsorption is slowest but is not a simple rate determining step. The SiH4 adsorption rate is controlled by the rate of H2 desorption from two surface SiH species, producing dangling bonds.
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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
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Criteria for the observation of one‐dimensional transport in split‐gate field‐effect quantum wires

Cristopher C. Eugster, Jesús A. del Alamo, Paul A. Belk, and Michael J. Rooks

Appl. Phys. Lett. 58, 2966 (1991); http://dx.doi.org/10.1063/1.104710 (3 pages) | Cited 1 time

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We have fabricated AlGaAs/GaAs split‐gate field‐effect quantum wires with different lengths and widths in order to study the effect of the dimensions of the confining gates on one‐dimensional (1D) transport. Two threshold voltages arise as the two‐dimensional (2D) electron gas is turned off first underneath the gates and then as the 1D electron gas is turned off in between the split‐gates through their fringing fields. In particular, our room‐temperature experiments reveal the existence of a critical width of 0.2–0.25 μm between the confining gates below which the 1D regime is not observed in 1.0‐μm‐long split‐gate quantum wires. This can be explained if the potential at the surface near the metal confining gates is influenced by the gate voltage through exchange of electrons between the metal gates and the surface states.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ey III-V semiconductors
85.30.Tv Field effect devices

Direct observation of optical anisotropy in a GaAs/AlAs quantum well wire array

H. Kanbe, A. Chavez‐Pirson, H. Ando, H. Saito, and T. Fukui

Appl. Phys. Lett. 58, 2969 (1991); http://dx.doi.org/10.1063/1.104711 (3 pages) | Cited 25 times

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Using reflectance difference spectroscopy and transmittance difference spectroscopy, optical anisotropy in a quantum well wire array is directly observed at room temperature. The quantum wire array is a fractional‐layer superlattice grown by metalorganic chemical vapor deposition on a vicinal (001)GaAs substrate. The size for quantum confinement of the wires is nominally 4×4 nm. Polarization dependence of optical absorption and refractive index is clearly observed between the directions parallel and perpendicular to the wires.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Room‐temperature exciton luminescence in II‐VI quantum wells

R. P. Stanley, B. J. Hawdon, J. Hegarty, R. D. Feldman, and R. F. Austin

Appl. Phys. Lett. 58, 2972 (1991); http://dx.doi.org/10.1063/1.104712 (3 pages) | Cited 8 times

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We observe free excitons in absorption and emission at room temperature in Cd0.25Zn0.75Te/ZnTe multiple quantum wells. A large overlap between luminescence and absorption peaks observed at 10 K is maintained up to room temperature showing that the luminescence is predominantly excitonic. From a rate equation analysis we calculate the branching ratio for free carriers relaxing into excitons to free‐carrier radiative recombination.
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78.55.Et II-VI semiconductors
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Chemistry of fluorine in the oxidation of silicon

S. R. Kasi, M. Liehr, and S. Cohen

Appl. Phys. Lett. 58, 2975 (1991); http://dx.doi.org/10.1063/1.104686 (3 pages) | Cited 23 times

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The chemical environment of fluorine in the oxide layer of metal‐oxide‐semiconductor (MOS) structures has been examined by surface analytical spectroscopies. HF treatment of Si(100) results in subsurface SiF formation. Upon oxidation, oxyfluoride moieties are formed with a significant accumulation of fluorine throughout the oxide layer. These changes are correlated to the electrical integrity of MOS interfaces by performing Fowler–Nordheim electron injection studies.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.-b Surface treatments

Optical anisotropy in mismatched InGaAs/InP heterostructures

Brian R. Bennett and Jesús A. del Alamo

Appl. Phys. Lett. 58, 2978 (1991); http://dx.doi.org/10.1063/1.104687 (3 pages) | Cited 14 times

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Epitaxial layers of InxGa1−xAs (0.35<x<0.85) were grown on (001)InP and characterized by double‐crystal x‐ray diffraction (DCXRD) and a new technique, variable azimuthal angle ellipsometry (VAAE), in which ellipsometric measurements are taken in various crystallographic directions on the wafer. VAAE reveals significant optical anisotropy in many samples. The degree of this anisotropy is shown to be a function of lattice mismatch and relaxation as measured by DCXRD. The VAAE results exhibit a consistent cosine‐shape pattern with respect to the [110] and [110] directions. We explain these observations by the presence of misfit dislocations which form in an asymmetric network. Ellipsometry emerges as a potentially powerful tool for the characterization of mismatched zinc‐blende heterostructures.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Microwave properties of EuBa2Cu3O7−x thin films on MgO

Hidefumi Asano, Makoto Satoh, and Tsuneo Konaka

Appl. Phys. Lett. 58, 2981 (1991); http://dx.doi.org/10.1063/1.104688 (3 pages) | Cited 7 times

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We have measured the microwave surface resistance of sputtered EuBa2Cu3O7−x superconducting films on MgO in a gold‐plated Invar host cavity at 50 GHz. Low surface resistance of 2 mΩ was achieved even at 77 K and 50 GHz for highly c‐axis oriented films with good in‐plane epitaxy together with a Tc of 93 K and a Jc of 1.4×106 A/cm2 at 90 K. This surface resistance value is slightly lower than that for a classical superconductor of Nb at the same frequency at the same reduced temperature (T/Tc) of 7.7 K.
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74.25.N- Response to electromagnetic fields
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures

Strongly enhanced critical current density in Nb 47 wt. % Ti having a highly aligned microstructure

L. D. Cooley, P. D. Jablonski, P. J. Lee, and D. C. Larbalestier

Appl. Phys. Lett. 58, 2984 (1991); http://dx.doi.org/10.1063/1.104689 (3 pages) | Cited 10 times

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The transport critical current density increased from 2610 to 5200 A/mm2 at 5 T, 4.2 K, when a round monofilament Nb 47 wt. % Ti composite was rolled to an aspect ratio of 9.7 and was tested with the broad face of the tape parallel to the field. This value exceeds the previous maximum of 3700 A/mm2 by about 50%. Transmission electron micrographs show that more than 90% of the α‐Ti precipitates in the optimum‐rolled filament are aligned within 10° of the broad face of the tape, whereas the precipitates had a random azimuthal orientation prior to rolling. The strong alignment caused the elementary pinning force to be greatly enhanced in the parallel‐field orientation; however, in the orthogonal orientation the Jc fell to low values characteristic of conventional wires having no α‐Ti flux pinning centers.
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74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)

High‐temperature neutron diffraction study of the melting behavior of Bi2CaSr2Cu2Ox

Mary F. Garbauskas, Ronald H. Arendt, James D. Jorgensen, and Richard L. Hitterman

Appl. Phys. Lett. 58, 2987 (1991); http://dx.doi.org/10.1063/1.105226 (2 pages) | Cited 2 times

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High‐temperature neutron powder diffraction has been used to study the melting, and subsequent reformation, behavior of Bi2CaSr2Cu2Ox (2122), the 80 K transition temperature oxide superconductor. It was found that the (2122) substantially reforms upon return to a temperature just below the peritectic melting point of the material. This finding implies that difficulties encountered in melt processing this material may be due largely to gross segregation of the constituents while the material is partially molten, as opposed to slow formation kinetics for this species.
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74.70.-b Superconducting materials other than cuprates
61.05.fm Neutron diffraction
61.66.Fn Inorganic compounds

Bistable behavior of a vibrating tip near a solid surface

P. Gleyzes, P. K. Kuo, and A. C. Boccara

Appl. Phys. Lett. 58, 2989 (1991); http://dx.doi.org/10.1063/1.104690 (3 pages) | Cited 67 times

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Experiments using a vibrating tip close to a solid surface have shown a bistable behavior of the motion. These measurements have been interpreted in terms of perturbed harmonic oscillators both numerically and analytically.  
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
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