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2 Feb 1998

Volume 72, Issue 5, pp. 513-622

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Effect of column III vacancy on arsenic precipitation in low-temperature grown III–V arsenides

M. N. Chang, J.-W. Pan, J.-I. Chyi, K. C. Hsieh, and T.-E. Nee

Appl. Phys. Lett. 72, 587 (1998); http://dx.doi.org/10.1063/1.120814 (3 pages) | Cited 9 times

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Separately grown p-type, intrinsic, and n-type GaAs at low temperatures as well as a combined p-i-n structure have been used to study the formation of As precipitates upon annealing at 800 °C. For the separate structures, least precipitates have been noticed in the n-type material. In contrast, the highest density of precipitates appears in the n region for the p-i-n structure. In addition, an obvious band depleted of precipitates, exists in the intrinsic region near the n-i interface. A general vacancy model, including Fermi level effect and crystal bonding strength (thermodynamic factor), has been developed to explain the current results as well as to predict As precipitation in various low temperature grown III–V heterostructures. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
64.75.-g Phase equilibria
61.72.J- Point defects and defect clusters
81.05.Ea III-V semiconductors
81.30.Mh Solid-phase precipitation
61.72.Cc Kinetics of defect formation and annealing
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Annealing effect on concentration of EL6-like deep-level state in low-temperature-grown molecular beam epitaxial GaAs

J. Darmo, F. Dubecký, P. Kordoš, and A. Förster

Appl. Phys. Lett. 72, 590 (1998); http://dx.doi.org/10.1063/1.120815 (3 pages) | Cited 2 times

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A deep-level donor state with signatures similar to the EL6 level observed in low-temperature-grown molecular beam epitaxial (MBE) GaAs grown at 250 °C and annealed in the temperature range 310–370 °C was studied. The annealing kinetics of this level suggest a confined pair recombination, likely VGa and Asi. A correlation between the deep level observed and recently published photoluminescence data of low-temperature-grown MBE GaAs is found. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.72.Cc Kinetics of defect formation and annealing
73.20.Hb Impurity and defect levels; energy states of adsorbed species
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Charge release of lanthanum-doped lead zirconate titanate stannate antiferroelectric thin films

Baomin Xu, Paul Moses, Neelesh G. Pai, and L. Eric Cross

Appl. Phys. Lett. 72, 593 (1998); http://dx.doi.org/10.1063/1.120817 (3 pages) | Cited 38 times

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The charge release speed and backward phase switching time of lanthanum-doped lead zirconate titanate stannate antiferroelectric thin films were investigated by directly measuring the switching current upon removal of the applied electric field. The backward switching time is about 6 ns. The maximum switching current density can reach 9400 A/cm2, and more than half of the stored charge can be released in 10 ns. These results show that the obtained antiferroelectric thin films are very promising for decoupling capacitor applications in high speed multichip modules. © 1998 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
77.22.Ch Permittivity (dielectric function)
77.80.-e Ferroelectricity and antiferroelectricity

Solid-state metathesis reactions under pressure: A rapid route to crystalline gallium nitride

Charles H. Wallace, Sang-Ho Kim, Garry A. Rose, Lin Rao, James R. Heath, Malcolm Nicol, and Richard B. Kaner

Appl. Phys. Lett. 72, 596 (1998); http://dx.doi.org/10.1063/1.120818 (3 pages) | Cited 13 times

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High pressure chemistry has traditionally involved applying pressure and increasing temperature until conditions become thermodynamically favorable for phase transitions or reactions to occur. Here, high pressure alone is used as a starting point for carrying out rapid, self-propagating metathesis reactions. By initiating chemical reactions under pressure, crystalline phases, such as gallium nitride, can be synthesized which are inaccessible when initiated from ambient conditions. The single-phase gallium nitride made by metathesis reactions under pressure displays significant photoluminescence intensity in the blue/ultraviolet region. The absence of size or surface-state effects in the photoluminescence spectra show that the crystallites are of micron dimensions. The narrow lines of the x-ray diffraction patterns and scanning electron microscopy confirm this conclusion. Brightly luminescent thin films can be readily grown using pulsed laser deposition. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)
62.50.-p High-pressure effects in solids and liquids

Damage-free separation of GaN thin films from sapphire substrates

W. S. Wong, T. Sands, and N. W. Cheung

Appl. Phys. Lett. 72, 599 (1998); http://dx.doi.org/10.1063/1.120816 (3 pages) | Cited 133 times

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Gallium nitride thin films grown on sapphire substrates were successfully separated and transferred onto Si substrates using single 38 ns KrF excimer laser pulses directed through the transparent substrate at fluences in the range of 400–600 mJ/cm2. The absorption of the 248 nm radiation by the GaN at the interface induces rapid thermal decomposition of the interfacial layer, yielding metallic Ga and N2 gas. The substrate is easily removed by heating above the Ga melting point of 30 °C. Scanning electron microscopy and x-ray diffraction of the GaN films before and after lift-off demonstrate that the structural quality of the GaN films is not altered by the separation and transfer process. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
79.20.Ds Laser-beam impact phenomena
85.40.Sz Deposition technology
81.65.-b Surface treatments
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
68.55.-a Thin film structure and morphology
68.35.Gy Mechanical properties; surface strains
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High-Tc direct current SQUIDs on silicon bicrystal substrates operating at 77 K

F. Schmidl, S. Linzen, S. Wunderlich, and P. Seidel

Appl. Phys. Lett. 72, 602 (1998); http://dx.doi.org/10.1063/1.120819 (3 pages) | Cited 10 times

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We investigated Josephson junctions and dc superconducting quantum interference devices (SQUIDs) on silicon bicrystal substrates with epitaxially grown 24° Y1Ba2Cu3O7−x, (YBCO) grain boundaries. Buffer layers and passivation/contact layers were prepared for the YBCO thin films by laser deposition techniques. The observed current–voltage characteristics of ion-beam etched, as well as direct laser patterned junctions with products of the critical current and the normal resistance up to 150 μV at 77 K, can be described within the resistively shunted junction model. The inductance of dc SQUIDs was varied by additional laser patterning. In this way, dc SQUIDs with transfer functions up to 30 μV/Φ0 and a white noise level of 30 μΦ0/math at 77 K were reached. © 1998 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.50.+r Tunneling phenomena; Josephson effects
85.25.Cp Josephson devices
74.25.Sv Critical currents
61.72.Mm Grain and twin boundaries
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Exchange-biased ferromagnetic tunnel junctions via reactive evaporation of nickel oxide films

Chang He Shang, Geetha P. Berera, and Jagadeesh S. Moodera

Appl. Phys. Lett. 72, 605 (1998); http://dx.doi.org/10.1063/1.120825 (3 pages) | Cited 15 times

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Nickel oxide films, prepared by reactive evaporation at room temperature, have shown good properties to be used as an exchange biasing antiferromagnet on ferromagnetic tunnel junctions. For instance, in the case of Co/Al2O3/Co/NiO junction, NiO shows an exchange field of 17 Oe at 295 K, increasing to 174 Oe at 77 K, and the junction magnetoresistances are 17% at 295 K and 22% at 77 K. The temperature dependence of the exchange field and junction magnetoresistance are also investigated between 77 K and 400 K. © 1998 American Institute of Physics.
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75.30.Et Exchange and superexchange interactions
73.40.Gk Tunneling
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
71.70.Gm Exchange interactions
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics

Effect of external stress on polarization in ferroelectric thin films

Tetsuo Kumazawa, Yukihiro Kumagai, Hideo Miura, Makoto Kitano, and Keiko Kushida

Appl. Phys. Lett. 72, 608 (1998); http://dx.doi.org/10.1063/1.120820 (3 pages) | Cited 74 times

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The polarization changes caused by applying mechanical stresses to a lead zirconate titanate (PZT) thin film were investigated. Both the remnant and spontaneous polarizations decreased when the PZT film was loaded with tensile stress. For compressive stresses, the remnant polarization increased, but spontaneous polarization did not change. In fatigue with tensile stress state, the polarization decreased earlier than when there was no stress, which depend on whether or not the initial polarization value was high. Conversely, in fatigue with compressive stress, the initial higher remnant polarization value was maintained compared with the polarization in the unstress condition. © 1998 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
77.22.Ej Polarization and depolarization
77.65.Bn Piezoelectric and electrostrictive constants
77.80.-e Ferroelectricity and antiferroelectricity

Exchange-biased spin valves combining a high magnetoresistance ratio with soft-magnetic behavior

J. C. S. Kools, S. Lardoux, and F. Roozeboom

Appl. Phys. Lett. 72, 611 (1998); http://dx.doi.org/10.1063/1.120821 (3 pages) | Cited 1 time

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We report on the preparation of bottom spin valves combining a high giant magnetoresistance effect (above 10%) with a soft-magnetic behavior (coercivities of a few hundreds of A/m). By optimization of film composition and preparation conditions, it is possible to obtain materials having magnetoresistance values around 16%, which display minor loop coercivities of 0.2 kA/m, and sensitivities of 11%/kA/m. © 1998 American Institute of Physics.
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75.47.De Giant magnetoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Et Exchange and superexchange interactions

Magnetic expansion readout of 0.2 μm packed domains on a magneto-optical disk with an in-plane magnetized readout layer

Xiao Ying, Kastusuke Shimazaki, Hiroyuki Awano, Masahumi Yoshihiro, Hitoshi Watanabe, Norio Ohta, and K. V. Rao

Appl. Phys. Lett. 72, 614 (1998); http://dx.doi.org/10.1063/1.120822 (3 pages) | Cited 2 times

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We have investigated an in-plane magnetized readout-layer-based magnetic domain expansion phenomenon in a magneto-optical (MO) medium. Very high-density 0.2 μm packed domains are expanded up to three times the readout signal level in comparison with the conventional approach of applying alternative external field in the readout process. This result suggests that more than 10 Gbits/in. MO recording density may be achieved by implementing the domain expansion technique, using even the currently available 680 nm laser and numerical aperture of 0.55. © 1998 American Institute of Physics.
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85.70.Sq Magnetooptical devices
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
78.20.Ls Magneto-optical effects

Perpendicular coupling at Fe–FeF2 interfaces

T. J. Moran, J. Nogués, D. Lederman, and Ivan K. Schuller

Appl. Phys. Lett. 72, 617 (1998); http://dx.doi.org/10.1063/1.120823 (3 pages) | Cited 94 times

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We have studied the exchange anisotropy of ferromagnetic Fe films grown on antiferromagnetic FeF2 single crystals. The behavior of the hysteresis loops of the Fe above and below the Néel temperature TN of FeF2 indicates a 90° rotation of the ferromagnetic easy axis due to the antiferromagnetic ordering. By examining the Fe hysteresis loops together with the FeF2 susceptibility behavior we infer that below TN the ferromagnetic and antiferromagnetic spins are coupled perpendicular to each other. This behavior can be explained by recent micromagnetic calculations on exchange bias systems, or by magnetoelastic effects. © 1998 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics
75.30.Et Exchange and superexchange interactions
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Structure and polarization in epitaxial ferroelectric PbZr0.52Ti0.48O3/YBa2Cu3O7−x/Nd:YAlO3 thin films

A. M. Grishin, M. Yamazato, Y. Yamagata, and K. Ebihara

Appl. Phys. Lett. 72, 620 (1998); http://dx.doi.org/10.1063/1.120824 (3 pages) | Cited 14 times

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We fabricate epitaxial PbZr0.52Ti0.48O3/YBa2Cu3O7−x submicron film ferroelectric/superconductor heterostructures on the single-crystal YAlO3+1%Nd2O3 substrate by the pulsed laser deposition technique. Frequency independent low loss tan δ = 0.04 and dielectric constant of 950, high electric resistivity ρ (150 kV/cm)=6×1011Ω cm, remnant polarization of 32 μC/cm2, no visible fatigue after 107 short bipolar pulses switching indicate excellent electrical performance of the new capacitor structure. The slight crystallite polar axis misalignment and depolarizing effect were found to be responsible for the shape of the apparent polarization loop. The only fitting parameter depolarizing coefficient N = 2.37×10−4 gives the best fit between theory and experimental data and corresponds to prolate ellipsoidal shaped crystallites with the length-to-diameter ratio of 140. © 1998 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
77.55.-g Dielectric thin films
81.15.Fg Pulsed laser ablation deposition
77.22.Ej Polarization and depolarization
74.72.-h Cuprate superconductors
77.80.Dj Domain structure; hysteresis
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
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