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23 Jan 1995

Volume 66, Issue 4, pp. 399-531

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New encapsulant source for III–V quantum well disordering

E. V. K. Rao, A. Hamoudi, Ph. Krauz, M. Juhel, and H. Thibierge

Appl. Phys. Lett. 66, 472 (1995); http://dx.doi.org/10.1063/1.114060 (3 pages) | Cited 23 times

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We report here the characteristic features of a newly developed dielectric encapsulant cap layer, which after adequate thermal treatments, leads to a reproducible local alloy disorder in several III–V quantum well (QW) structures. Data are presented to demonstrate its universality, namely, its ability to promote alloy‐disorder free of charge carriers either on group III or group V sublattice depending on the type of the QW structure. © 1995 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
66.30.Ny Chemical interdiffusion; diffusion barriers
61.72.Cc Kinetics of defect formation and annealing

Characterization of reconstructed SiC(100) surfaces using soft‐x‐ray photoemission spectroscopy

V. M. Bermudez and J. P. Long

Appl. Phys. Lett. 66, 475 (1995); http://dx.doi.org/10.1063/1.114061 (3 pages) | Cited 55 times

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The surface quality of βSiC films grown on Si(100) by chemical vapor deposition has been assessed through synchrotron photoemission measurements of the valence band and of the linewidths and surface‐induced structure in Si 2p core‐level spectra. For these n‐type samples, band bending is small on the c(2×2) and (3×2) surfaces but larger on the (2×1), which also exhibits an increased Si 2p linewidth and evidence of elemental Si patches. All three reconstructions show emission from gap states extending from the valence band maximum to the Fermi level.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology

Cross‐sectional scanning tunneling microscopy study of GaAs/AlAs short period superlattices: The influence of growth interrupt on the interfacial structure

A. R. Smith, Kuo‐Jen Chao, C. K. Shih, Y. C. Shih, and B. G. Streetman

Appl. Phys. Lett. 66, 478 (1995); http://dx.doi.org/10.1063/1.114062 (3 pages) | Cited 26 times

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We report studies of GaAs/AlAs short period superlattices using cross‐sectional scanning tunneling microscopy. In particular, we investigate the role of growth interrupt time on the resulting interfacial structure. Superlattices with repeated periods of four layers of GaAs and two layers of AlAs are resolved atom by atom. Superlattices grown using a 30 s growth interrupt time are observed while those grown with a 5 s growth interrupt time are not. We also discuss residual effects of the growth interrupt process on layers grown on top of the short‐period superlattice. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology

Uncooled high‐speed InSb field‐effect transistors

T. Ashley, A. B. Dean, C. T. Elliott, G. J. Pryce, A. D. Johnson, and H. Willis

Appl. Phys. Lett. 66, 481 (1995); http://dx.doi.org/10.1063/1.114063 (3 pages) | Cited 37 times

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InSb enhancement‐mode, metal‐insulator‐semiconductor, field‐effect transistors with 1 μm gate lengths have been fabricated. When operated at room temperature with less than 0.5 V applied between the source and drain, the transistors have a static dynamic range in excess of 20 dB, a cut‐off frequency (fT) of 14 GHz and a transconductance, at 1 GHz, of 230 mS mm−1. Analysis of the parasitic capacitances indicates an intrinsic fT of about 90 GHz. The static electron mobility in the channel is 2×104 cm2 V−1 s−1, so a carrier velocity of about 3.7×107 cm s−1 should be attained. This leads to a predicted frequency response of 84 GHz, in reasonable agreement with the intrinsic microwave data.
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85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Voltage offsets in (Pb,La)(Zr,Ti)O3 thin films

G. E. Pike, W. L. Warren, D. Dimos, B. A. Tuttle, R. Ramesh, J. Lee, V. G. Keramidas, and J. T. Evans

Appl. Phys. Lett. 66, 484 (1995); http://dx.doi.org/10.1063/1.114064 (3 pages) | Cited 152 times

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Cooling (Pb,La)(Zr,Ti)O3 films from their pulsed laser deposition temperature in a reducing ambient yields a voltage offset in the polarization–voltage characteristics. Reversing the as‐processed polarization at 120 °C nearly removes the offset. By reversing the polarization at room temperature and either heating the film at zero voltage or illuminating the film with UV light, the offset can be partially changed. All changes are recoverable using the same processes with opposite polarity polarization. This behavior is explained by a process‐induced accumulation of oxygen vacancies at one interface, oxygen vacancy defect‐dipole complexes throughout the film, and trapping of free electrons at the interface of positive polarization. Voltage offset and shift effects are not observed in films cooled in 1 atm of oxygen © 1995 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Fg Pulsed laser ablation deposition

Surfactants in Si(111) homoepitaxy

M. Horn‐von Hoegen, J. Falta, M. Copel, and R. M. Tromp

Appl. Phys. Lett. 66, 487 (1995); http://dx.doi.org/10.1063/1.114065 (3 pages) | Cited 19 times

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Si epitaxy is strongly affected by the presence of an adsorbate (surfactant). We have examined both film quality and dopant incorporation in homoepitaxy for Sb, As, and Ga terminated Si(111). The efficency of site exchange between Si and adsorbate depends sensitively on binding energy and binding geometry of the adsorbate. For a weakly bound adsorbate (Ga or Sb), there is no inhibition of epitaxy, but a strongly bound adsorbate (As) kinetically inhibits growth. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

On the local structure of optically active Er centers in Si

H. Przybylinska, G. Hendorfer, M. Bruckner, L. Palmetshofer, and W. Jantsch

Appl. Phys. Lett. 66, 490 (1995); http://dx.doi.org/10.1063/1.114066 (3 pages) | Cited 32 times

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We report high resolution (<0.05 cm−1) photoluminescence (PL) spectra of erbium implanted float‐zone (FZ) and Czochralski grown (CZ) silicon. We show that the PL spectrum of cubic Er centers observed in CZ‐Si annealed at 900°C is the dominant emission in FZ‐Si for the same annealing conditions. We assign it to isolated, interstitial erbium. We observe also two other kinds of optically active Er centers with lower than cubic site symmetry: (i) O‐related (found only in CZ Si) and (ii) those related to radiation defects. We conclude that coimplantation with light elements does not lead to the formation of Er‐codopant complexes, but rather to Er forming complexes with implantation induced lattice defects. © 1995 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.uf Ge and Si
78.55.Hx Other solid inorganic materials

Excitation and relaxation of Yb3+ in InPAs and InP

M. Godlewski, A. Kozanecki, J. P. Bergman, and B. Monemar

Appl. Phys. Lett. 66, 493 (1995); http://dx.doi.org/10.1063/1.114067 (3 pages) | Cited 4 times

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Excitation and relaxation mechanisms of Yb3+ ions in InP and InP0.93As0.07 alloy have been studied based on optically detected cyclotron resonance (ODCR), temperature dependent photoluminescence (PL), and PL decay measurements. It is shown with use of ODCR that charge carriers, most probably electrons, are captured by Yb3+ ions. PL transients show that the decay rate of the Yb3+ PL decreases with increasing As contents. Evidence is presented proving that the excited state of the Yb3+ ion decays by transfer of energy to the band states of InP, while in the case of InPAs, the energy may also be transferred to an exciton bound at the Yb3+ ion. © 1995 American Institute of Physics.
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71.55.Eq III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.55.Cr III-V semiconductors

Measurement of adsorbed F atoms on a HF treated Si surface using infrared reflection absorption spectroscopy

Yoshiyasu Yamada, Tadashi Hattori, Tsuneo Urisu, and Hisayoshi Ohshima

Appl. Phys. Lett. 66, 496 (1995); http://dx.doi.org/10.1063/1.114068 (3 pages) | Cited 6 times

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Si(111) surface treated with HF solution was studied using Fourier transform infrared reflection absorption spectroscopy for the observation of Si–Fx bond absorption and x‐ray photoelectron spectroscopy for the identification of the adsorbates on the Si surface. Two absorption peaks were observed in the range of 905–925 cm−1, and they were assigned to Si–F2 symmetric stretching mode at 918 cm−1 and Si–H2 bending mode at 910 cm−1. The absorption peak of Si–F2 distinctly decreased with de‐ionized water rinse, though the Si–H2 peak hardly changed. The absorption peak of Si–F was not observed in all spectra. This result indicates that F atoms selectively adsorbed at a step region rather than on a terrace region on Si(111) surface after HF treatment. © 1995 American Institute of Physics.
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81.65.-b Surface treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.Dv Composition, segregation; defects and impurities

Nucleation of misfit dislocations in In0.2Ga0.8As epilayers grown on GaAs substrates

Y. Chen, Z. Liliental‐Weber, J. Washburn, J. F. Klem, and J. Y. Tsao

Appl. Phys. Lett. 66, 499 (1995); http://dx.doi.org/10.1063/1.114069 (3 pages) | Cited 10 times

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Misfit dislocation arrays in In0.2Ga0.8As epilayers grown on GaAs substrates tilted 2°–10° away from exact (001) toward varied directions have been studied by transmission electron microscopy. A method has been developed to determine the glide plane and the Burgers vector of each misfit dislocation in the tilted InGaAs/GaAs interfaces. Based on experimental observations and theoretical analyses, it is proposed that a stacking fault surrounded by a 30° partial is at first generated by a growth error, followed by thermally activated nucleation of a 90° partial dislocation that removes the stacking fault and forms a 60° dislocation. From the frequency of nucleation events versus the dislocation glide force, the energy barrier for dislocation nucleation of α and β 90° partial dislocations was determined to be equal to 1.5 and 1.4 eV, respectively. © 1995 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Schottky barrier contacts of titanium nitride on n‐type silicon

C. A. Dimitriadis, S. Logothetidis, and I. Alexandrou

Appl. Phys. Lett. 66, 502 (1995); http://dx.doi.org/10.1063/1.114070 (3 pages) | Cited 29 times

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Schottky contacts of TiNx thin films on n‐type Si(100) were fabricated by reactive magnetron sputtering at room temperature. In situ spectroscopic ellipsometry was used to determine the stoichiometry of the TiNx films. Dark forward bias current–voltage as well as dark reverse bias capacitance–voltage techniques was used to characterize the diodes in the temperature range from 77 to 300 K. The electrical characteristics of the contacts (i.e., barrier height, ideality factor, and leakage current) as well as the inhomogeneity of the spatial distribution of the barrier heights at the interface are improved drastically for overstoichiometric TiNx films obtained by using low negative bias voltage and/or high N2 flow rates during the TiNx deposition. © 1995 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
81.15.Cd Deposition by sputtering

Negative magnetoresistance in parallel magnetic fields in InGaAs quantum wells with a δ‐doped layer close to the quantum well

J. Herfort, K.‐J. Friedland, H. Kostial, and R. Hey

Appl. Phys. Lett. 66, 505 (1995); http://dx.doi.org/10.1063/1.114071 (3 pages) | Cited 1 time

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The magnetotransport properties in pseudomorphic GaAs/InGaAs/GaAs and AlGaAs/InGaAs/GaAs quantum wells with a Si δ‐doped layer in the barrier close to the quantum well have been investigated. In the GaAs/InGaAs/GaAs system, a giant negative magnetoresistance is observed in the parallel magnetic field configuration. The effect is less pronounced if the doping is performed in the AlGaAs barrier. We attribute this giant negative magnetoresistance to the reduction of an additional impurity scattering process between two‐dimensional states in the quantum well and inhomogeneously distributed donor states in the δ‐doped layer. The experimental results in the GaAs/InGaAs/GaAs system are found to be in excellent agreement with a model that takes into account an oscillation between two‐dimensional states and the δ‐doped layer including an additional momentum in parallel magnetic fields. © 1995 American Institute of Physics.
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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
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Electronic subband studies in In0.52Al0.48As/InxGa1−xAs one‐side‐modulation‐doped asymmetric coupled double quantum wells

T. W. Kim, M. Jung, T. H. Park, Keon‐Ho Yoo, Kyung‐Hwa Yoo, and G. Ihm

Appl. Phys. Lett. 66, 508 (1995); http://dx.doi.org/10.1063/1.114072 (3 pages) | Cited 11 times

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Shubnikov–de Haas (SdH) and van der Pauw Hall effect measurements on In0.52Al0.48As/InxGa1−xAs coupled double quantum wells grown by metalorganic chemical vapor deposition have been carried out to investigate the magnetotransport properties of an electron gas and to determine the subband energies and wave functions in the coupled quantum wells. Transmission electron microscopy measurements showed that In0.8Ga0.2As and In0.53Ga0.47As quantum wells were separated by an In0.25Ga0.75As potential barrier in an active region. The SdH measurements at 1.5 K demonstrated clearly the existence of a quasi‐two‐dimensional electron gas in the quantum wells. The fast Fourier transformation results for the SdH data clearly indicate the occupation of three subbands in the In0.52Al0.48As/InxGa1−xAs coupled quantum wells. Electron subband energies and wave functions in the quantum wells were calculated by a self‐consistent method taking into account exchange‐correlation effects. The first and second excited subband wave functions in the asymmetric quantum well are strongly coupled over both In0.8Ga0.2As and In0.53Ga0.47As wells. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Nb/Al–AlOx–Al/Ta/Nb Josephson junctions for x‐ray detection

Shin’ichi Morohashi, Kohtaroh Gotoh, and Naoki Yokoyama

Appl. Phys. Lett. 66, 511 (1995); http://dx.doi.org/10.1063/1.114073 (3 pages) | Cited 2 times

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Nb/Al–AlOx–Al/Ta/Nb Josephson junctions for use as energy resolving x‐ray detectors have been fabricated. The junctions have been designed to raise both creation and collection efficiency of quasiparticles. The current–voltage characteristics of the junctions have been investigated on the Al deposition dependence, and found that the characteristics are strongly dependent on the Al deposition rate during the fabrication. The subgap leakage current of those junctions fabricated at higher Al deposition rates exhibit very low leakage current (less than 200 nA at a bias voltage of 100 μV measured at 0.5 K). © 1995 American Institute of Physics.
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85.25.Cp Josephson devices
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
74.50.+r Tunneling phenomena; Josephson effects

Effect of lattice mismatch on surface morphology of (110) thin films of 214‐type superconductors

H. Sato, M. Naito, S. Kinoshita, T. Arima, and Y. Tokura

Appl. Phys. Lett. 66, 514 (1995); http://dx.doi.org/10.1063/1.114074 (3 pages) | Cited 2 times

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We characterized the surface morphology of (110) thin films of 214‐type superconductors epitaxially grown on substrates of 214‐type materials with various degrees of lattice mismatch. By reactive co‐evaporation, (110) thin films of La1.85Sr0.15CuO4 and Pr1.85Ce0.15CuO4 are grown on (110) substrates of La2CuO4 and Pr2CuO4. Reflection high energy electron diffraction, scanning electron microscopy, and atomic force microscopy show the roughness of the film surface is reduced by decreasing mismatch. The surface roughness of La1.85Sr0.15CuO4 (110) thin films on La2CuO4 substrates is comparably small to that of (001) films on SrTiO3(001) substrates. © 1995 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
68.55.-a Thin film structure and morphology

Buffer layer/film interactions in the growth of Tl2Ba2Ca1Cu2Ox films on CeO2 buffered sapphire

A. P. Bramley, S. M. Morley, C. R. M. Grovenor, and B. Pecz

Appl. Phys. Lett. 66, 517 (1995); http://dx.doi.org/10.1063/1.114075 (3 pages) | Cited 13 times

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Tl2Ba2Ca1Cu2Ox thin films have been grown on highly textured CeO2 layers deposited onto R‐plane sapphire substrates. The Tl2Ba2Ca1Cu2Ox films have critical temperature (Tc) values around 95 K and current density (Jc) values up to 8×104 A/cm2. The films are c‐axis oriented even though we have identified the formation of a polycrystalline BaCe(Tl)O3 layer by reaction between the buffer layer and the superconducting precursor during the thalliation process. © 1995 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
68.55.-a Thin film structure and morphology
68.35.Fx Diffusion; interface formation

Effect of Cr doping on the magnetoresistance and saturation field of epitaxial Fe1−xCrx(001)/Cr(001) multilayers

B. J. Daniels and B. M. Clemens

Appl. Phys. Lett. 66, 520 (1995); http://dx.doi.org/10.1063/1.114076 (3 pages) | Cited 7 times

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The effect of Cr doping of the Fe layer on the magnetoresistance and saturation field of epitaxial, sputter‐deposited Fe1−xCrx(001)/Cr(001) multilayers was examined. Films with a composition of 100 Å Cr/[14 Å Fe1−xCrx/8 Å Cr]50, where x was varied from 0 to 0.5, were deposited onto single crystal MgO(001). The room temperature magnetoresistance was constant at approximately 31% for x≤0.2 and decreased with higher Cr concentrations. The saturation field decreased linearly with increasing Cr concentration over the entire range. Doping the Fe layer with Cr results in an increase of the spin‐dependent scattering (Δρ) for 0.1≤x≤0.2 and an increase in the sensitivity of these films for all Cr concentrations. © 1995 American Institute of Physics.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Raman scattering from LiF cluster‐based nanophase film

Fengqi Liu, Min Han, Jijun Zhao, Xiaoshuang Chen, Qun Wang, and Guanghou Wang

Appl. Phys. Lett. 66, 523 (1995); http://dx.doi.org/10.1063/1.114077 (3 pages) | Cited 5 times

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Raman scattering spectra are used to investigate LiF cluster‐based nanophase films. The experiments confirm the existence of multi‐order‐like Raman scattering and surface phonon modes. Good agreement is achieved between the observed spectral lines and the calculated results if the Raman scattering lines are attributed to an appropriate linear combination of primary modes and surface optical modes. The fine structure observed in the case of the smaller cluster has reflected the intensity of the cluster‐substrate interaction, which may result in the splitting of Raman peaks. © 1995 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
63.20.Pw Localized modes
78.30.Hv Other nonmetallic inorganics

Lateral force curve for atomic force/lateral force microscope calibration

Satoru Fujisawa, Eigo Kishi, Yasuhiro Sugawara, and Seizo Morita

Appl. Phys. Lett. 66, 526 (1995); http://dx.doi.org/10.1063/1.114078 (3 pages) | Cited 17 times

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In this letter, a method to calibrate sensitivity for the three‐dimensional displacement of X, Y, and Z directions by using the novel force curve, namely lateral force curve, as well as vertical force curve in atomic force/lateral force microscope (AFM/LFM) measurement is described. Furthermore, from quantized friction measurement based on the two‐dimensional stick–slip model, it is experimentally confirmed that this lateral force curve calibration is reasonable. © 1995 American Institute of Physics.  
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
07.79.Lh Atomic force microscopes

Anisotropic conductivity of silver thin films grown on silicon (100) vicinal surfaces

T. López‐Ríos, A. Briggs, S. Guillet, A. M. Baro, and M. Luna

Appl. Phys. Lett. 66, 529 (1995); http://dx.doi.org/10.1063/1.114079 (3 pages) | Cited 1 time

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The electrical conductivity between 4 and 300 K of Ag thin films (up to 30 nm grown at room temperature on Si(100) vicinal surfaces has been measured and their morphology imaged with an atomic force microscope. A noticeable anisotropy of the resistivity of the films which is related to the structure of the films has been found. © 1995 American Institute of Physics.  
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73.61.At Metal and metallic alloys
71.55.Ak Metals, semimetals, and alloys
68.55.-a Thin film structure and morphology
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