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18 Aug 1997

Volume 71, Issue 7, pp. 861-986

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Exciton saturation in room temperature GaAs/AlGaAs multiple quantum wells

T. M. Holden, G. T. Kennedy, A. R. Cameron, P. Riblet, and A. Miller

Appl. Phys. Lett. 71, 936 (1997); http://dx.doi.org/10.1063/1.119694 (3 pages) | Cited 6 times

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We report time resolved studies of optically induced circular dichroism in room temperature GaAs/AlGaAs multiple quantum wells to resolve spin-dependent and spin-independent contributions to exciton saturation. Phase-space filling and Coulomb contributions were separated by spin dependence while the effects of broadening and screening were distinguished using different pulse bandwidths. Bound and free carrier contributions were compared by observing the temporal dependence of the circular dichroism on femtosecond timescales. The spin independent contribution to exciton saturation was found to be independent of whether the carriers were bound or free. © 1997 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.20.Fm Birefringence
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Direct observation of the amphoteric behavior of Ge in InP modified by P co-implantation

Kin Man Yu and M. C. Ridgway

Appl. Phys. Lett. 71, 939 (1997); http://dx.doi.org/10.1063/1.119695 (3 pages) | Cited 4 times

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We have investigated the preferred substitution of Ge in InP by altering the local stoichiometry of the InP substrate. By co-implanting P with Ge to create a group V-rich environment, we directly observed an enhancement of the Ge substituting the In sublattice. A corresponding increase in the n-type conductivity by as much as three times was also observed in the Ge and P co-implanted sample. However, due to the altered local stoichiometry, the Ge solubility in InP was reduced by a factor of 2. The residual crystalline damage in the P co-implanted InP after annealing was also decreased due to the compensation of the nonstoichiometry related damage by the excess P in the middle of the implanted region. © 1997 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
61.66.Bi Elemental solids
61.66.Dk Alloys
78.70.Dm X-ray absorption spectra
81.05.Ea III-V semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
72.20.My Galvanomagnetic and other magnetotransport effects

Pt/p-strained-Si Schottky diode characteristics at low temperature

S. Chattopadhyay, L. K. Bera, S. K. Ray, and C. K. Maiti

Appl. Phys. Lett. 71, 942 (1997); http://dx.doi.org/10.1063/1.119696 (3 pages) | Cited 4 times

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The Schottky barrier height and ideality factor of Pt on p-type strained Si (grown on a graded relaxed Si0.82Ge0.18 buffer layer) have been investigated in the temperature range (90–150 K) using the current-voltage characteristics and are found to be temperature dependent. While the ideality factor decreases with an increase in temperature, the barrier height increases. Simulation based on a drift-diffusion emission model has been used to explain the experimental results. © 1997 American Institute of Physics.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices
73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.De Semiconductor-device characterization, design, and modeling
73.40.Ns Metal-nonmetal contacts

n-type high-conductive epitaxial diamond film prepared by gas source molecular beam epitaxy with methane and tri-n-butylphosphine

Toshihiko Nishimori, Koji Nakano, Hitoshi Sakamoto, Yuji Takakuwa, and Shozo Kono

Appl. Phys. Lett. 71, 945 (1997); http://dx.doi.org/10.1063/1.119922 (3 pages) | Cited 12 times

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An n-type phosphorous (P) doped epitaxial diamond film with high conductivity was grown on a C(001) substrate by gas source molecular beam epitaxy using methane and tri-n-butylphosphine. The electrical conductivity of the diamond film was measured to be 0.33 (Ω cm)−1 at 23 °C with its activation energy to be 0.12 eV. The Hall measurements showed n-type conduction and a carrier concentration of 1.6×1018 cm−3 at 400 °C, which is comparable to the P concentration determined by secondary-ion-mass spectroscopy. These indicate the formation of shallow P donors with high electrical activation efficiency. A p-n junction diode was fabricated by growing a P-doped epitaxial film on a boron-doped C(001) substrate, which showed for the first time a rectification ratio of ∼ 103 at 10 V. © 1997 American Institute of Physics.
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73.61.Cw Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Cy Elemental semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.05.ub Fullerenes and related materials
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Free excitons with n = 2 in bulk GaN

M. Steube, K. Reimann, D. Fröhlich, and S. J. Clarke

Appl. Phys. Lett. 71, 948 (1997); http://dx.doi.org/10.1063/1.119697 (2 pages) | Cited 19 times

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The direct observation of free A, B, and C excitons with n = 2 in hexagonal bulk gallium nitride (GaN) by two-photon spectroscopy is reported. From these data, the band gaps, exciton binding energies, and hole masses for the three uppermost valence bands are calculated. © 1997 American Institute of Physics.
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71.35.Cc Intrinsic properties of excitons; optical absorption spectra
71.20.Nr Semiconductor compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

The composition and structure of InGaAs/InAlAs interfaces at the monatomic scale

G. Mountjoy, P. A. Crozier, P. L. Fejes, R. K. Tsui, and G. D. Kramer

Appl. Phys. Lett. 71, 950 (1997); http://dx.doi.org/10.1063/1.119698 (3 pages) | Cited 3 times

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We have applied high-resolution chemical imaging in a transmission electron microscope to study compositional variations across an InGaAs/InAlAs double quantum well structure in the (100) orientation. The structures of interest are grown on an InP support and consist of two 40 Å layers of InGaAs separated by 20 Å of InAlAs. For this (InGa)x(InAl)1−xAs system, we have obtained compositional information with an accuracy of about 20% and a maximum spatial resolution of 1/4 unit cell. The results clearly show compositional irregularities on a monatomic scale. © 1997 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.35.Ct Interface structure and roughness
68.55.-a Thin film structure and morphology

Stimulated transparency of a superconducting plate caused by nonlinear interaction of electromagnetic waves

S. A. Derev’anko, I. O. Lyubimova, V. A. Yampol’skii, and F. Pérez-Rodríguez

Appl. Phys. Lett. 71, 953 (1997); http://dx.doi.org/10.1063/1.119699 (3 pages) | Cited 2 times

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A nonlinear effect in the electrodynamics of hard superconductors is predicted and theoretically studied. It is shown, that a low-frequency (LF) electromagnetic wave can pass through a superconducting plate, due to its interaction with another wave propagating in the opposite direction, even at small amplitudes of the LF wave when it cannot reach the opposite boundary of the sample without assistance. The dependence of the LF surface impedance on the amplitude of the high-frequency (hf) wave is studied within the framework of the critical state model. The LF surface impedance is found to be drastically increased by the overlapping of the regions of wave penetration. © 1997 American Institute of Physics.  
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74.25.N- Response to electromagnetic fields
74.20.-z Theories and models of superconducting state
73.25.+i Surface conductivity and carrier phenomena

Measurement of the dynamic input impedance of a dc superconducting quantum interference device at audio frequencies

Paolo Falferi, Renato Mezzena, Stefano Vitale, and Massimo Cerdonio

Appl. Phys. Lett. 71, 956 (1997); http://dx.doi.org/10.1063/1.119700 (3 pages) | Cited 13 times

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The coupling effects of a commercial dc superconducting quantum interference device (SQUID) to an electrical LC resonator which operates at audio frequencies ( ≈ 1 kHz) with quality factors Q ≈ 106 are presented. The variations of the resonance frequency of the resonator as functions of the flux applied to the SQUID are due to the SQUID dynamic inductance in good agreement with the predictions of a model. The variations of the quality factor point to a feedback mechanism between the output of the SQUID and the input circuit. © 1997 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.30.Le Amplifiers

Electrical transport properties of artificially layered films of [BaCuO2]2/[(Sr,Ca)CuO2]n

F. Arciprete, G. Balestrino, S. Martellucci, P. G. Medaglia, A. Paoletti, and G. Petrocelli

Appl. Phys. Lett. 71, 959 (1997); http://dx.doi.org/10.1063/1.119923 (3 pages) | Cited 15 times

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In this letter we show that SrCuO2/BaCuO2 and CaCuO2/BaCuO2 based artificial structures of very good crystallographic quality can be grown by pulsed laser deposition. We demonstrate that the most important parameters which determine the superconductive properties are the chemical composition, the oxygen growth pressure, and the CO2 contamination. A major difference is found in the behavior of resistivity between films containing Sr and Ca, respectively. Namely [BaCuO2]2/[SrCuO2]n films never show any trace of superconductivity, while [BaCuO2]2/[CaCuO2]n films result in having, for growth oxygen pressures PO2 ≥ 0.2 mbar, a full transition with Tc (zero resistance) up to 46 K. Furthermore we demonstrate that even a tiny amount of CO2 in the oxygen growth atmosphere can suppress completely the superconducting properties of these artificial structures. © 1997 American Institute of Physics.
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74.78.Fk Multilayers, superlattices, heterostructures
81.15.Fg Pulsed laser ablation deposition
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.62.Fj Effects of pressure
74.78.-w Superconducting films and low-dimensional structures

Preparation of regular arrays of antidots in YBa2Cu3O7 thin films and observation of vortex lattice matching effects

A. Castellanos, R. Wördenweber, G. Ockenfuss, A. v.d. Hart, and K. Keck

Appl. Phys. Lett. 71, 962 (1997); http://dx.doi.org/10.1063/1.119701 (3 pages) | Cited 85 times

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Optimized sputtered YBa2Cu3O7 (YBCO) thin films on CeO2-buffered sapphire substrates are patterned into square lattices of submicrometer holes (antidots) with diameters of 250–450 nm and lattice parameters of d = 500–1000 nm without deterioration of superconducting properties. In the mixed state, matching effects between the Abrikosov vortex lattice and the artificial antidot lattice are observed. These effects are in the form of peaks or cusps in the critical current density recorded as a function of magnetic induction at integers n and specific rationals k/l of the matching field Bm = (Φ0/d2). The experimental results are discussed in the context of existing theories. The existence of multiquanta vortices confined by the holes in YBCO films are considered. © 1997 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.25.Op Mixed states, critical fields, and surface sheaths

Generalized magneto-optical ellipsometry

A. Berger and M. R. Pufall

Appl. Phys. Lett. 71, 965 (1997); http://dx.doi.org/10.1063/1.119669 (3 pages) | Cited 31 times

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A complete magneto-optical characterization of any material requires the measurement of both, the magneto-optical and the conventional optical constants. We have developed the method of generalized magneto-optical ellipsometry (GME), which enables us to determine these material constants simultaneously in a single setup. In addition, GME even allows the determination of the magnetization orientation. The experimental setup is very simple, using only two rotatable polarizers as polarization sensitive elements. Our experimental results for permalloy demonstrate the validity of our approach and the feasibility of GME as a practical measurement technique. © 1997 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
07.60.Fs Polarimeters and ellipsometers
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
75.50.Bb Fe and its alloys

Influence of a 36.8° grain boundary on the magnetoresistance of La0.8Sr0.2MnO3−δ single crystal films

K. Steenbeck, T. Eick, K. Kirsch, K. O’Donnell, and E. Steinbeiß

Appl. Phys. Lett. 71, 968 (1997); http://dx.doi.org/10.1063/1.119702 (3 pages) | Cited 107 times

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Epitaxial ferromagnetic manganite films have been sputtered on bicrystal substrates. Their magnetoresistance was measured as a function of magnetic field and temperature. The grain boundary magnetoresistance at low temperature is separated from the intrinsic magnetoresistance near the Curie temperature. The grain boundary magnetoresistance peaks at about 100 Oe and saturates at about 2 kOe. For a La0.8Sr0.2MnO3 film with a grain boundary angle θ = 36.8° a field independent component r0 = 4.1×10−6 Ω cm2 was separated from a field-dependent component which has its maximum rH = 2.3×10−6 Ω cm2 for H of order the coercive field. © 1997 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
75.47.De Giant magnetoresistance
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
61.72.Mm Grain and twin boundaries

Correlation between the signs of the magnetoresistance and of the interlayer coupling in MnGa/(Mn,Ga,As)/MnGa trilayers

W. Van Roy, H. Akinaga, S. Miyanishi, and A. Asamitsu

Appl. Phys. Lett. 71, 971 (1997); http://dx.doi.org/10.1063/1.119703 (3 pages) | Cited 6 times

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A correlation is found between the sign of the magnetoresistance ΔR = (RP−RAP) and the sign of the interlayer coupling in MnGa/(Mn,Ga,As)/MnGa trilayers (subscript P, AP=parallel, antiparallel magnetic alignment of both MnGa layers). Ferromagnetic coupling results in ΔR<0, antiferromagnetic coupling results in ΔR>0. This correlation has not been observed before and can not be explained by the usual model for giant magnetoresistance in magnetic multilayers. © 1997 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.De Giant magnetoresistance
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Et Exchange and superexchange interactions

Hybrid Hall effect device

Mark Johnson, Brian R. Bennett, M. J. Yang, M. M. Miller, and B. V. Shanabrook

Appl. Phys. Lett. 71, 974 (1997); http://dx.doi.org/10.1063/1.119704 (3 pages) | Cited 93 times

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A novel magnetoelectronic device incorporating a single microstructured ferromagnetic film and a micron scale Hall cross was fabricated and characterized at room temperature. Magnetic fringe fields from the edge of the ferromagnet generate a Hall voltage in a thin film semiconducting Hall bar. The sign of the fringe field, as well as the sign of the output Hall voltage, is switched by reversing the magnetization of the ferromagnet. This new device has excellent output characteristics and scaling properties, and may find application as a magnetic field sensor, nonvolatile storage cell, or logic gate. © 1997 American Institute of Physics.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.80.+q Magnetomechanical effects, magnetostriction
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
85.70.-w Magnetic devices

Anisotropic strains and magnetoresistance of La0.7Ca0.3MnO3

T. Y. Koo, S. H. Park, K.-B. Lee, and Y. H. Jeong

Appl. Phys. Lett. 71, 977 (1997); http://dx.doi.org/10.1063/1.119705 (3 pages) | Cited 61 times

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Thin films of perovskite manganite La0.7Ca0.3MnO3 were grown epitaxially on SrTiO3(100), MgO(100) and LaAlO3(100) substrates by the pulsed laser deposition method. Microscopic structures of these thin film samples as well as a bulk sample were fully determined by x-ray diffraction measurements. The unit cells of the three films have different shapes, i.e., contracted tetragonal, cubic, and elongated tetragonal for SrTiO3, MgO, and LaAlO3, respectively, while the unit cell of the bulk is cubic. It is found that the samples with a cubic unit cell show smaller peak magnetoresistance at low fields (≲1 T) than the noncubic ones do. The present result demonstrates that the magnetoresistance of La0.7Ca0.3MnO3 at low fields can be controlled by lattice distortion via externally imposed strains. © 1997 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
72.20.My Galvanomagnetic and other magnetotransport effects
68.55.-a Thin film structure and morphology
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
73.61.Ng Insulators

A source of hyperthermal neutrals for materials processing

M. J. Goeckner, T. K. Bennett, and S. A. Cohen

Appl. Phys. Lett. 71, 980 (1997); http://dx.doi.org/10.1063/1.119706 (3 pages) | Cited 23 times

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In this letter, we describe a unique method of producing hyperthermal neutrals for material processing. The hyperthermal neutrals are produced by accelerating ions across a sheath from a plasma onto a surface. On impact, the ions are neutralized and reflected with ∼ 50% of their incident energy. These neutrals then bounce off of additional surfaces prior to impacting the target. This unique multiple bounce system was developed for the following reasons: to reduce contamination from sputtered surface material, improve beam uniformity, and reduce UV radiation in the beam path. As a test of this method, we built a prototype beam source and used it to ash photoresist at rates up to 0.022 μm/min. These rates are consistent with a predicted neutral beam flux, 2×1014 cm−2 s−1. In addition, a simple model is used to indicate that this method is capable of producing economically acceptable ash rates. Comparisons with other neutral-beam production methods are made. © 1997 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.40.Hf Plasma-material interactions; boundary layer effects

Single-crystal Si field emitter fabricated by anodization

Katsuya Higa, Kiyoaki Nishii, and Tanemasa Asano

Appl. Phys. Lett. 71, 983 (1997); http://dx.doi.org/10.1063/1.119707 (3 pages) | Cited 1 time

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A process for fabrication of field emitter arrays using anodization of single-crystal Si is demonstrated, when anodization is carried out in the dark on Si having n/p junctions, porous Si is preferentially formed in the p-type region. A needlelike tip structure can be formed beneath the unanodized n-type Si layer, since the anodization proceeds almost isotropically. The porous region can be easily oxidized and selectively removed by chemical etching. The shape of emitter can be controlled by changing the dimension of the n/p junction and varying the resistivity of p-type region. Fabrication of an emitter array and its field emission characteristic are reported. © 1997 American Institute of Physics.
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85.45.Db Field emitters and arrays, cold electron emitters
85.45.Bz Vacuum microelectronic device characterization, design, and modeling
81.05.Cy Elemental semiconductors
79.70.+q Field emission, ionization, evaporation, and desorption
82.45.-h Electrochemistry and electrophoresis
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.Mq Oxidation
81.05.Rm Porous materials; granular materials
81.65.Cf Surface cleaning, etching, patterning
FREE

Erratum: “Distributed feedback quantum cascade lasers” [Appl. Phys. Lett. 70, 2670 (1997)]

Jérôme Faist, Claire Gmachl, Federico Capasso, Carlo Sirtori, Deborah L. Sivco, James N. Baillargeon, and Alfred Y. Cho

Appl. Phys. Lett. 71, 986 (1997); http://dx.doi.org/10.1063/1.120561 (1 page) | Cited 1 time

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Abstract Unavailable
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
99.10.Cd Errata
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