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17 Feb 2003

Volume 82, Issue 7, pp. 1003-1136

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 1069 (2003); http://dx.doi.org/10.1063/1.1544428 (3 pages)

M. L. Povinelli, Steven G. Johnson, J. D. Joannopoulos, and J. B. Pendry
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InAs/AlSb quantum cascade lasers operating at 10 μm

K. Ohtani and H. Ohno

Appl. Phys. Lett. 82, 1003 (2003); http://dx.doi.org/10.1063/1.1545151 (3 pages) | Cited 19 times

Online Publication Date: 10 February 2003

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InAs/AlSb intersubband quantum cascade lasers based on bound-to-continuum transitions are fabricated and operation at 10 μm is demonstrated. A spatially indirect intersubband transition together with a double plasmon waveguide structure is employed. Threshold current density is 4.9 kA/cm2 at 4 K. Temperature dependence of the threshold current density is also presented. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Fd III-V semiconductors

Triplet exciton confinement in phosphorescent polymer light-emitting diodes

Fang-Chung Chen, Gufeng He, and Yang Yang

Appl. Phys. Lett. 82, 1006 (2003); http://dx.doi.org/10.1063/1.1544658 (3 pages) | Cited 54 times

Online Publication Date: 10 February 2003

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A series of iridium complexes, with triplet energy levels above or below the triplet level of host polymer, were used to study the flow of excitons between the host and the dopants. The performance of phosphorescent polymer light-emitting diodes has been shown to be sensitive to the triplet energy of the dopant. When the dopant exciton level was higher than that of the host polymer, a “backward excitation energy transfer” occurred; hence, the photoluminescence is quenched and the device performance is poor. When the triplet energy level of the dopant was lower than that of the host polymer, the exciton is confined to the dopant site, and the device shows better performance due to this confinement. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.70.Jk Polymers and organics
71.35.-y Excitons and related phenomena

Hole depth- and shape-induced radiation losses in two-dimensional photonic crystals

R. Ferrini, B. Lombardet, B. Wild, R. Houdré, and G.-H. Duan

Appl. Phys. Lett. 82, 1009 (2003); http://dx.doi.org/10.1063/1.1545167 (3 pages) | Cited 20 times

Online Publication Date: 10 February 2003

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A phenomenological model is adopted to study three-dimensional radiation losses in two-dimensional (2D) photonic crystals (PhC) deeply etched in a step-index waveguide. In the case of low vertical refractive index contrast, losses are modeled in a 2D approach and out-of-plane scattering is translated into an effective imaginary index in the air holes. The case of truncated-cone holes is analytically solved. Depth and shape contributions to losses are extracted showing that the verticality of the hole sidewalls is a fundamental parameter. In order to validate the model, the case of a 2D triangular lattice etched through an InP/GaInAsP slab waveguide is studied both theoretically and experimentally. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.65.Cf Surface cleaning, etching, patterning
78.66.Fd III-V semiconductors

Reflectivity of planar metallic fractal patterns

Lei Zhou, Weijia Wen, C. T. Chan, and Ping Sheng

Appl. Phys. Lett. 82, 1012 (2003); http://dx.doi.org/10.1063/1.1553993 (3 pages) | Cited 21 times

Online Publication Date: 10 February 2003

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We studied the reflective properties of a small dielectric plate covered with a fractal-like metallic pattern generated by a particular type of space-filling curves. We found, both experimentally and theoretically, that the plate can reflect electromagnetic waves in a multitude of frequencies, generated from a near-field monopole antenna. Some of the reflected waves have wavelengths much larger than the lateral dimension of the plate. In comparison, a metal plate of the same size failed to reflect when its lateral size was smaller than half of the corresponding wavelength. © 2003 American Institute of Physics.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
84.40.Ba Antennas: theory, components and accessories
05.45.Df Fractals
78.70.Gq Microwave and radio-frequency interactions

3.4-THz quantum cascade laser based on longitudinal-optical-phonon scattering for depopulation

Benjamin S. Williams, Hans Callebaut, Sushil Kumar, Qing Hu, and John L. Reno

Appl. Phys. Lett. 82, 1015 (2003); http://dx.doi.org/10.1063/1.1554479 (3 pages) | Cited 148 times

Online Publication Date: 10 February 2003

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We report the development of a quantum cascade laser, at λ = 87.2 μm, corresponding to 3.44 THz or 14.2 meV photon energy. The GaAs/Al0.15Ga0.85As laser structure utilizes longitudinal-optical (LO) phonon scattering for electron depopulation. Laser action is obtained in pulsed mode at temperatures up to 65 K, and at 50% duty cycle up to 29 K. Operating at 5 K in pulsed mode, the threshold current density is 840 A/cm2, and the peak power is approximately 2.5 mW. Based on the relatively high operating temperatures and duty cycles, we propose that direct LO-phonon-based depopulation is a robust method for achieving quantum cascade lasers at long-wavelength THz frequencies. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
63.20.K- Phonon interactions
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.67.De Quantum wells

A way to obtain visible blue light emission in porous silicon

Q. W. Chen, D. L. Zhu, C. Zhu, J. Wang, and Y. G. Zhang

Appl. Phys. Lett. 82, 1018 (2003); http://dx.doi.org/10.1063/1.1554774 (3 pages) | Cited 29 times

Online Publication Date: 10 February 2003

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Strong blue emission around 435 nm from porous silicon (PS) embedded in Pb(Zrx,Ti1−x)O3 (PZT) is realized, which is stable and clearly visible to the naked eye even after exposure in an ambient atmosphere for a year. The sample is obtained by hydrothermal etching of (100)-oriented single crystal silicon wafers in an HF aqueous solution, followed by pulsed laser ablation deposition of a PZT thin layer on the surface of the PS. The electrons and holes excited from silicon nanocrystallites could be separated by the PZT-induced electrostatic field and migrate to the boundaries of PS/PZT along opposite directions, respectively. Therefore, the blue emission is interpreted in terms of the recombination of excited carriers from the silicon nanocrystallites in the interfacial region of PS/PZT. © 2003 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.60.Fi Electroluminescence
78.55.Ap Elemental semiconductors
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Ga vacancies and grain boundaries in GaN

J. Oila, K. Saarinen, A. E. Wickenden, D. D. Koleske, R. L. Henry, and M. E. Twigg

Appl. Phys. Lett. 82, 1021 (2003); http://dx.doi.org/10.1063/1.1542946 (3 pages) | Cited 12 times

Online Publication Date: 10 February 2003

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We have applied a low-energy positron beam to study epitaxial Si-doped GaN layers, where the grain size varies from 0.2 to 2–5 μm. Negatively charged Ga vacancies are found in n-type samples. Their concentration is independent of the grain size, suggesting that Ga vacancies exist in the grain interior. Positrons are observed to get trapped also at other negatively charged centers. The positron trapping rate at these defects correlates with the grain-boundary density. We attribute the observed shallow positron traps, which do not contain open volume, to negatively charged edge-type dislocations which define the grain boundaries. © 2003 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Eq III-V semiconductors
61.72.J- Point defects and defect clusters
61.72.Mm Grain and twin boundaries
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
78.70.Bj Positron annihilation

Localized epitaxial growth of α-Al2O3 thin films on Cr2O3 template by sputter deposition at low substrate temperature

P. Jin, S. Nakao, S. X. Wang, and L. M. Wang

Appl. Phys. Lett. 82, 1024 (2003); http://dx.doi.org/10.1063/1.1544442 (3 pages) | Cited 23 times

Online Publication Date: 10 February 2003

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Low-temperature growth of α-Al2O3 films by sputtering was studied with x-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Pure α-Al2O3 film was formed at 400 °C using Cr2O3 as template, whereas amorphous or θ-Al2O3 was formed without Cr2O3. HRTEM revealed localized epitaxial growth of α-Al2O3 on Cr2O3 with the relationship [011]Al2O3/[011]Cr2O3, suggesting the importance of Cr2O3 as a structural template for the growth of α-Al2O3, in addition to other contributions such as good stoichiometry, low sputter pressure, and low deposition rate under optimized deposition conditions. Successful growth of α-Al2O3 by sputtering at 400 °C or below makes the film widely applicable to even glass substrates. © 2003 American Institute of Physics.
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81.15.Cd Deposition by sputtering
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
68.37.Lp Transmission electron microscopy (TEM)

Behavior of monocrystalline silicon under cyclic microindentations with a spherical indenter

I. Zarudi, L. C. Zhang, and M. V. Swain

Appl. Phys. Lett. 82, 1027 (2003); http://dx.doi.org/10.1063/1.1541110 (3 pages) | Cited 28 times

Online Publication Date: 10 February 2003

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This study discusses the behavior of high-pressure phases of monocrystalline silicon when subjected to cyclic indentations with a spherical indenter. It was found that specific phases form in the second and subsequent indentation cycles under low maximum loads. An increase of the maximum indentation load causes changes of subsequent indentation cycles of the phase transformation events to occur earlier on both loading and unloading. The repeated indentations result in the formation of a multiphase structure in the deformed zone, featuring a nonhysteresis behavior. After a critical stage, the properties of the transformed material are stabilized and further indentations can no longer alter the load–displacement curve. It was also found that the greater the maximum load, the faster the occurence of property stabilization. © 2003 American Institute of Physics.
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62.20.Qp Friction, tribology, and hardness
62.20.D- Elasticity
64.70.K- Solid-solid transitions
64.75.-g Phase equilibria

Ni-based bulk metallic glass formation in the Ni–Nb–Sn and Ni–Nb–Sn–X (X = B,Fe,Cu) alloy systems

Haein Choi-Yim, Donghua Xu, and William L. Johnson

Appl. Phys. Lett. 82, 1030 (2003); http://dx.doi.org/10.1063/1.1544434 (3 pages) | Cited 109 times

Online Publication Date: 10 February 2003

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Refractory Ni-based bulk metallic glasses are formed in the three-component Ni–Nb–Sn system near a ternary eutectic composition located within the three-phase field bounded by the three intermetallics Ni3Nb, Ni6Nb7 (μ-phase), and Ni2NbSn (BiF3-type). Bulk amorphous alloys of composition Ni60Nb40−xSnx with 3<x<9 were prepared by injection-casting the molten alloys into copper models. X-ray diffraction and differential scanning calorimetry studies show the cast strips to be fully amorphous up to thicknesses from 0.5 to 3 mm as x is varied. Maximum glass-forming ability (GFA) observed when x is between 6 and 7. These refractory bulk amorphous alloys exhibit high glass transition temperatures 881<Tg<895 K, a large, stable, undercooled liquid region with ΔT = Tx−Tg, at ∼40–60 K, very high Vickers hardness (VH ∼ 1000–1280 Kg/mm2), and estimated yield strengths in the range of 3 to 3.8 GPa. The effects of small quaternary additions of B and Fe on the GFA of the ternary alloys are also reported. © 2003 American Institute of Physics.
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64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
81.05.Kf Glasses (including metallic glasses)
62.20.F- Deformation and plasticity
62.20.Qp Friction, tribology, and hardness
81.40.Lm Deformation, plasticity, and creep
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Evidence for a Type-II band alignment between cubic and hexagonal phases of GaN

X. H. Lu, P. Y. Yu, L. X. Zheng, S. J. Xu, M. H. Xie, and S. Y. Tong

Appl. Phys. Lett. 82, 1033 (2003); http://dx.doi.org/10.1063/1.1541113 (3 pages) | Cited 12 times

Online Publication Date: 10 February 2003

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The photoluminescence spectra of a series of thin, undoped, hexagonal GaN films containing cubic GaN inclusions grown by molecular-beam epitaxy on 6H-SiC have been studied as a function of temperature and excitation power. The dependence of the line shape and peak position of a peak at ∼3.17 eV on laser power suggests that it is associated with a spatially indirect Type-II transition between hexagonal and cubic GaN. The values of the band offsets extracted from our data are in good agreement with theoretical predictions. © 2003 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.55.-a Thin film structure and morphology

Experimental demonstration of photonic crystal waveplates

D. R. Solli, C. F. McCormick, R. Y. Chiao, and J. M. Hickmann

Appl. Phys. Lett. 82, 1036 (2003); http://dx.doi.org/10.1063/1.1541938 (3 pages) | Cited 23 times

Online Publication Date: 10 February 2003

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We have constructed and experimentally tested a microwave half-waveplate using the dispersive birefringent properties of a bulk, two-dimensional, photonic crystal away from its band gap. Our waveplate device exhibited a 200:1 polarization contrast, limited by our experimental resolution. We anticipate that photonic crystal waveplates will have important practical applications in several areas, including integrated photonic circuits. © 2003 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
42.70.Qs Photonic bandgap materials
42.82.Gw Other integrated-optical elements and systems
42.25.Lc Birefringence
84.40.-x Radiowave and microwave (including millimeter wave) technology

High-temperature elastic properties of in situ-reinforced Si3N4

Geoffrey A. Swift, Ersan Üstündag, Bjørn Clausen, Mark A. M. Bourke, and Hua-Tay Lin

Appl. Phys. Lett. 82, 1039 (2003); http://dx.doi.org/10.1063/1.1554478 (3 pages) | Cited 5 times

Online Publication Date: 10 February 2003

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A high-temperature tensile stress study of a monolithic silicon nitride (Si3N4) was performed with time-of-flight neutron diffraction. A dedicated engineering diffractometer was employed at temperatures reaching 1375 °C. Rietveld refinements of diffraction spectra allowed the determination of (1) the coefficient of thermal expansion tensor during heating and (2) lattice strains during loading. The stress–strain response of individual lattice reflections was used to calculate the single-crystal elastic stiffness tensor of Si3N4 at 1375 °C via a self-consistent model. © 2003 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
65.40.De Thermal expansion; thermomechanical effects
62.20.D- Elasticity
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
62.20.F- Deformation and plasticity

Electronic structure and energetics of RCo5H4 and RCo5 (R = La,Pr)

L. G. Hector and J. F. Herbst

Appl. Phys. Lett. 82, 1042 (2003); http://dx.doi.org/10.1063/1.1553999 (3 pages) | Cited 4 times

Online Publication Date: 10 February 2003

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Calculations of the spin-dependent electronic structure and enthalpies of formation, ΔH, of the ternary hydrides LaCo5H4, PrCo5H4, and their parent intermetallics are reported. All four compounds are found to be metallic and ferromagnetic. We obtain ΔH(LaCo5H4) = −45.6 kJ/mole H2, ΔH(PrCo5H4) = −39.8 kJ/mole H2, and ΔH(LaCo5) = −12.6 kJ/LaCo5, values which compare very favorably with experiment. With the assumption of the free-ion 4f moment for Pr, the calculated magnetic moments agree well with available measurements. © 2003 American Institute of Physics.
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71.20.Eh Rare earth metals and alloys
75.50.Cc Other ferromagnetic metals and alloys
65.40.G- Other thermodynamical quantities
75.30.Cr Saturation moments and magnetic susceptibilities
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)

Thermomigration in Pb–Sn solder joints under joule heating during electric current stressing

Hua Ye, Cemal Basaran, and Douglas Hopkins

Appl. Phys. Lett. 82, 1045 (2003); http://dx.doi.org/10.1063/1.1554775 (3 pages) | Cited 75 times

Online Publication Date: 10 February 2003

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Electromigration of solder joint under high dc current density is known as a reliability concern for the future high-density flip chip packaging and power packaging. Biased mass diffusion within solder joint from cathode to anode under high dc current density is observed in these experiments. In this letter, the experiments on flip chip solder joints under dc current stressing are conducted and thermomigration due to the thermal gradient in the solder joint caused by joule heating is reported. A three-dimensional coupled electric thermal finite-element (FE) simulation of a realistic flip chip module shows the existence of thermal gradient in the solder joint which is high enough to trigger thermomigration. © 2003 American Institute of Physics.
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81.20.Vj Joining; welding
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
02.70.Dh Finite-element and Galerkin methods
66.30.Qa Electromigration
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Degenerate p-type conductivity in wide-gap LaCuOS1−xSex (x = 0–1) epitaxial films

Hidenori Hiramatsu, Kazushige Ueda, Hiromichi Ohta, Masahiro Hirano, Toshio Kamiya, and Hideo Hosono

Appl. Phys. Lett. 82, 1048 (2003); http://dx.doi.org/10.1063/1.1544643 (3 pages) | Cited 44 times

Online Publication Date: 10 February 2003

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Epitaxial films of LaCuOS1−xSex (x = 0–1) solid solution were grown on MgO (001) substrates and their electrical and optical properties were examined. Sharp emission due to room-temperature exciton with binding energy of ∼ 50 meV is observed for all x values. Hall mobility becomes large with an increase in the Se content and it reaches 8.0 cm2V−1s−1 in LaCuOSe, a comparable value to that of p-type GaN:Mg. Doping of Mg2+ ions at La3+ sites enhances a hole concentration up to 2.2×1020 cm−3, while maintaining the Hall mobility as large as 4.0 cm2V−1s−1. Consequently, a degenerate p-type electrical conduction with a conductivity of 140 S cm−1 was achieved. © 2003 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
78.55.Hx Other solid inorganic materials
73.50.Lw Thermoelectric effects
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
81.05.Hd Other semiconductors
68.55.-a Thin film structure and morphology

Molecular modification of an ionic semiconductor–metal interface: ZnO/molecule/Au diodes

Adi Salomon, Dvora Berkovich, and David Cahen

Appl. Phys. Lett. 82, 1051 (2003); http://dx.doi.org/10.1063/1.1543638 (3 pages) | Cited 24 times

Online Publication Date: 10 February 2003

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Differences between junctions of metals on ionic or covalent semiconductors persist for junctions, prepared by wet solution methods with a molecular layer at the junctions’ interface. A series of molecules that controls the junction of Au with n-GaAs, does so even stronger with ZnO (300 instead of ∼ 100 mV barrier height change). With ZnO the interface behavior index is found to be 0.55, five times that with GaAs. This agrees remarkably well with results for junctions of these materials with different metals, prepared in ultrahigh vacuum. Thus, the free semiconductor surface, e.g., surface state density, rather than direct metal–semiconductor interactions, appears to dominate junction behavior. © 2003 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.20.At Surface states, band structure, electron density of states
73.40.Cg Contact resistance, contact potential

Electronic properties of the metastable defect in boron-doped Czochralski silicon: Unambiguous determination by advanced lifetime spectroscopy

S. Rein and S. W. Glunz

Appl. Phys. Lett. 82, 1054 (2003); http://dx.doi.org/10.1063/1.1544431 (3 pages) | Cited 13 times

Online Publication Date: 10 February 2003

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By combining data from temperature- and injection-dependent lifetime spectroscopy (TDLS and IDLS) measured by means of the microwave-detected photoconductance decay technique and the quasi-steady state photoconductance technique, respectively, the exact electronic structure of the metastable defect in standard boron-doped Czochralski (Cz) silicon has been determined. A detailed Shockley–Read–Hall analysis of the entire TDLS curve reveals that the Cz-specific defect acts as an attractive Coulomb center [σn(T) = σn0T−2] which is localized in the upper band-gap half at EC−Et = 0.41 eV and has an electron/hole capture cross section ratio k = σn/σp = 9.3. The accuracy of this determination manifests itself by the fact that the corresponding IDLS curve can be simulated with the same parameter set. © 2003 American Institute of Physics.
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71.55.Cn Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.40.+w Photoconduction and photovoltaic effects

Structural, mechanical, and vibrational properties of Ga1−xInxAs alloys: A molecular dynamics study

Paulo S. Branicio, Rajiv K. Kalia, Aiichiro Nakano, Jose P. Rino, Fuyuki Shimojo, and Priya Vashishta

Appl. Phys. Lett. 82, 1057 (2003); http://dx.doi.org/10.1063/1.1542681 (3 pages) | Cited 14 times

Online Publication Date: 10 February 2003

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Structural, mechanical, and vibrational properties of Ga1−xInxAs (0 ⩽ x ⩽ 1) random solid solutions are investigated with classical and ab initio molecular-dynamics simulations. We find that the Ga–As and In–As bond lengths change only slightly as a function of x, despite the large lattice mismatch ( ∼ 7%) between GaAs and InAs crystals. The nearest cation–cation distance has a broad distribution, whereas the nearest neighbor anion–anion distance distribution has two distinct peaks. The elastic constants exhibit a significant nonlinear dependence on x. The phonon density-of-states exhibits two high-frequency optical modes. These results are in excellent agreement with experiments. © 2003 American Institute of Physics.
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71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
61.50.Lt Crystal binding; cohesive energy
78.30.Fs III-V and II-VI semiconductors
71.15.-m Methods of electronic structure calculations
62.20.D- Elasticity

Passivation of defects in nitrogen-doped polycrystalline Cu2O thin films by crown-ether cyanide treatment

Y. Okamoto, S. Ishizuka, S. Kato, T. Sakurai, N. Fujiwara, H. Kobayashi, and K. Akimoto

Appl. Phys. Lett. 82, 1060 (2003); http://dx.doi.org/10.1063/1.1555267 (3 pages) | Cited 12 times

Online Publication Date: 10 February 2003

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Crown-ether cyanide treatment, which simply involves immersion in KCN solutions containing 18-crown-6 followed by rinse, is studied in relation to electrical and optical properties of nitrogen-doped, polycrystalline Cu2O thin films, and its effect is compared with that of hydrogen treatment. By the crown-ether cyanide treatment, the luminescence intensity due to the near-band-edge emission of Cu2O at around 680 nm is enhanced, and the hole density is increased from the order of 1016 to 1017 cm−3, analogous to hydrogen treatment. The effects of the passivation by the hydrogen treatment completely disappear after annealing at 350 °C, while those of the crown-ether cyanide treatment stay unchanged after the same annealing treatment. From these results, the crown-ether cyanide treatment for polycrystalline Cu2O thin films can be concluded to be a more suitable method of passivating defects than the hydrogen treatment. © 2003 American Institute of Physics.
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81.65.Rv Passivation
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Le Other inorganic semiconductors
78.66.Li Other semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
78.55.Hx Other solid inorganic materials
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
61.72.Cc Kinetics of defect formation and annealing
71.55.Ht Other nonmetals

Generation-recombination low-frequency noise signatures in GaAs metal–semiconductor field-effect transistors on laterally oxidized AlAs

S. Y. Tzeng, M. J. Cich, R. Zhao, H. Feick, and E. R. Weber

Appl. Phys. Lett. 82, 1063 (2003); http://dx.doi.org/10.1063/1.1555710 (3 pages) | Cited 1 time

Online Publication Date: 10 February 2003

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Low-frequency noise characteristics of GaAs-on-insulator metal–semiconductor field-effect transistors, for which the insulating buffer layer was produced by lateral wet-oxidation of AlAs, are studied. Devices with different gate widths were fabricated resulting in different overoxidation times for the AlAs layer. Three characteristic generation-recombination noise signatures are observed depending on the measurement temperature and the gate bias. A generation-recombination noise signature with energy level at Ec−0.69 eV is found to increase with the amount of overoxidation time. This near midgap trap shows an increase in concentration towards the oxide interface, and it is tentatively assigned to an arsenic-antisite-related defect known from previous studies as EB4. A possible mechanism for the formation and the microscopic origin of this defect are discussed. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
81.65.Mq Oxidation
72.70.+m Noise processes and phenomena
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Investigation of interface trap states in TiN/Al2O3/p-Si capacitor by deep level transient spectroscopy

In Sang Jeon, Jaehoo Park, Dail Eom, Cheol Seong Hwang, Hyeong Joon Kim, Chan Jin Park, Hoon Young Cho, Jong-Ho Lee, Nae-In Lee, and Ho-Kyu Kang

Appl. Phys. Lett. 82, 1066 (2003); http://dx.doi.org/10.1063/1.1554773 (3 pages) | Cited 12 times

Online Publication Date: 10 February 2003

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The minority carrier (electron) capture process and the interface trap density of a TiN/Al2O3/p-Si metal–oxide–semiconductor capacitor were examined by deep level transient spectroscopy (DLTS). It was found that the activation energies of the large peaks detected at higher temperatures with gate bias voltages of 1.8, 1.5, 1.3, and 1.1 V were 0.19, 0.24, 0.29, and 0.37 eV, respectively. These energies were related to the electron-capture process from the conduction band by interface states in the upper half of the Si band gap. The interface state passivation effect of postannealing in a hydrogen ambient was studied from the minority carrier capture process and the usual DLTS signals. The Dit at an energy of 0.35 eV from the valence bandedge decreased from 1×1012 cm−2 eV−1 at the as-fabricated state to 4×1011 cm−2 eV−1 after H2 annealing at 450 °C. It was also found that the Dit at an energy of 0.3 eV from the conduction bandedge decreased to the same amount by the same annealing process. © 2003 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.65.Rv Passivation
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Toward photonic-crystal metamaterials: Creating magnetic emitters in photonic crystals

M. L. Povinelli, Steven G. Johnson, J. D. Joannopoulos, and J. B. Pendry

Appl. Phys. Lett. 82, 1069 (2003); http://dx.doi.org/10.1063/1.1544428 (3 pages) | Cited 25 times

Online Publication Date: 10 February 2003

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In this work, we explore the possibility of designing photonic crystals to act as magnetic metamaterials: structures that exhibit magnetic properties despite the nonmagnetic character of their constituents. The building blocks of a magnetic material are microscopic magnetic dipoles, and to create a synthetic analog we employ point-defect modes in a photonic crystal. We begin by identifying a point defect mode in a three-dimensional crystal whose local field pattern resembles an oscillating magnetic moment. By analyzing the far-field pattern of the field radiated from the defect, we prove quantitatively that such modes can be designed with a primarily magnetic character: over 98% of the emitted power goes into magnetic multipole radiation. Unlike the constituents of natural para- and ferromagnetic materials, these synthetic magnetic emitters can be designed to operate without losses even at optical frequencies. © 2003 American Institute of Physics.
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75.90.+w Other topics in magnetic properties and materials (restricted to new topics in section 75)
42.70.Qs Photonic bandgap materials
61.72.J- Point defects and defect clusters

Magnetism and interface properties of epitaxial Fe films on high-mobility GaAs/Al0.35Ga0.65As(001) two-dimensional electron gas heterostructures

B. Roldan Cuenya, M. Doi, W. Keune, S. Hoch, D. Reuter, A. Wieck, T. Schmitte, and H. Zabel

Appl. Phys. Lett. 82, 1072 (2003); http://dx.doi.org/10.1063/1.1542934 (3 pages) | Cited 12 times

Online Publication Date: 10 February 2003

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An optimized heterostructure design and an optimized surface sputter-cleaning procedure allow the growth of high-quality epitaxial Fe(001) thin films at Ts< ∼ 50 °C on selectively doped GaAs/Al0.35Ga0.65As heterostructures, while retaining the high quality transport property of the two-dimensional electron gas. Magneto-optic Kerr effect measurements and model calculations indicate a dominant uniaxial in-plane anisotropy (easy axis along [110], hard axis along [1−10]) and small coercivity (∼15 Oe). Interface sensitive 57Fe Mössbauer measurements prove the absence of both magnetic “dead layers” and “half-magnetization” phases (compared to pure Fe), and provide evidence for intermixing within a few monolayers, retaining, however, a metallic Fe state and high Fe magnetic moments at the interface. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects
81.65.Cf Surface cleaning, etching, patterning
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
76.80.+y Mössbauer effect; other γ-ray spectroscopy
75.30.Cr Saturation moments and magnetic susceptibilities
78.66.Bz Metals and metallic alloys

Thermal effects and in-plane magnetic anisotropy in thin-film recording media

Antony Ajan, E. N. Abarra, B. R. Acharya, A. Inomata, I. Okamoto, and M. Shinohara

Appl. Phys. Lett. 82, 1075 (2003); http://dx.doi.org/10.1063/1.1541095 (3 pages) | Cited 3 times

Online Publication Date: 10 February 2003

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The effect of thermal activation on the in-plane magnetic anisotropy [measured as orientation ratio (OR)] of granular longitudinal magnetic recording media is investigated. Temperature and time dependent studies were made on media with different magnetic layer thicknesses. We find that OR is independent of temperature for a stable medium but shows a large increase with temperature for thermally unstable media. At low temperatures and high field sweep rates, the OR values are found to be the same, independent of the magnetic layer thickness. The unique value when thermal activation is reduced is consistent with the high population of the cobalt c axes along the texturing direction as the origin of anisotropy. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Ss Magnetic recording materials
75.30.Gw Magnetic anisotropy
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
81.05.Bx Metals, semimetals, and alloys
75.50.Cc Other ferromagnetic metals and alloys
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