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30 Dec 2002

Volume 81, Issue 27, pp. 5099-5257

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Wafer-scale integration of GaAs optoelectronic devices with standard Si integrated circuits using a low-temperature bonding procedure

A. Georgakilas, G. Deligeorgis, E. Aperathitis, D. Cengher, Z. Hatzopoulos, M. Alexe, V. Dragoi, U. Gösele, E. D. Kyriakis-Bitzaros, K. Minoglou, and G. Halkias

Appl. Phys. Lett. 81, 5099 (2002); http://dx.doi.org/10.1063/1.1531221 (3 pages) | Cited 9 times

Online Publication Date: 19 December 2002

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A methodology for the heterogeneous integration of epitaxial GaAs wafers with fully processed standard bipolar complementary metal-oxide-semiconductor Si wafers is presented. The complete low-temperature wafer bonding process flow, including procedures for the Si wafer planarization and GaAs substrate removal, has been developed and evaluated. The implementation of an in-plane optical link, consisting of an edge-emitting laser diode, a waveguide and a photodiode, is demonstrated. © 2002 American Institute of Physics.
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85.60.-q Optoelectronic devices
85.40.Ls Metallization, contacts, interconnects; device isolation
81.65.Cf Surface cleaning, etching, patterning

InP-based two-dimensional photonic crystal on silicon: In-plane Bloch mode laser

C. Monat, C. Seassal, X. Letartre, P. Regreny, P. Rojo-Romeo, P. Viktorovitch, M. Le Vassor d’Yerville, D. Cassagne, J. P. Albert, E. Jalaguier, S. Pocas, and B. Aspar

Appl. Phys. Lett. 81, 5102 (2002); http://dx.doi.org/10.1063/1.1532554 (3 pages) | Cited 54 times

Online Publication Date: 19 December 2002

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Defectless two-dimensional photonic crystal structures have been fabricated by drilling holes in a thin multi-quantum-well InP-based heterostructure transferred onto a silicon host wafer. Extremely low group velocity modes, which correspond to the predicted photonic valence band edge, have been observed for different filling factors. Under pulsed optical pumping, room temperature laser operation around 1.5 μm has been achieved on these structures with a threshold in the milliwatt range. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.70.Qs Photonic bandgap materials
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Periodic entrainment of power dropouts in mutually coupled semiconductor lasers

J. M. Buldú, Raúl Vicente, Toni Pérez, Claudio R. Mirasso, M. C. Torrent, and J. García-Ojalvo

Appl. Phys. Lett. 81, 5105 (2002); http://dx.doi.org/10.1063/1.1533837 (3 pages) | Cited 14 times

Online Publication Date: 19 December 2002

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We examine the effect of current modulation in the irregular dropout dynamics exhibited by two mutually coupled semiconductor lasers. Our experimental results show that a weak periodic modulation in the injection current of one of the lasers entrains the power dropouts in a very efficient way. It is also observed that the laser with the highest frequency leads the dynamics independent of which laser is modulated. As a result, the entrainment is anticipative when modulation is applied to the laser with lowest frequency. Numerical simulations of a model based on delay-coupled rate equations successfully reproduce the behavior observed. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
85.30.De Semiconductor-device characterization, design, and modeling
42.60.By Design of specific laser systems

Edge-coupled membrane terahertz photonic transmitters based on metal–semiconductor–metal traveling-wave photodetectors

Jin-Wei Shi, Shi-Wei Chu, Ming-Chun Tien, Chi-Kuang Sun, Yi-Jen Chiu, and John E. Bowers

Appl. Phys. Lett. 81, 5108 (2002); http://dx.doi.org/10.1063/1.1533846 (3 pages) | Cited 10 times

Online Publication Date: 19 December 2002

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Ultra-high-speed photodetectors and printed-circuit antennas construct photonic transmitters. In this letter, we demonstrate a terahertz (THz) photonic transmitter: edge-coupled membrane photonic transmitters based on metal–semiconductor–metal traveling-wave photodetectors, which are fabricated with low-temperature-grown GaAs photoabsorption layers. With a membrane-based and edge-coupled structure, the demonstrated photonic transmitters can eliminate the requirement of Si lenses and attain an over 20 times higher optical-to-THz power conversion efficiency 2×10−4 than vertical illuminated photonic transmitters with Si lenses at the same operation frequency. © 2002 American Institute of Physics.
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07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
85.60.Gz Photodetectors (including infrared and CCD detectors)
84.40.Ba Antennas: theory, components and accessories
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Speckle suppression of laser light using liquid crystals aligned by photoisomerization of dye molecules

Keiichi Sueda, Kouji Tsubakimoto, Noriaki Miyanaga, and Masahiro Nakatsuka

Appl. Phys. Lett. 81, 5111 (2002); http://dx.doi.org/10.1063/1.1533123 (3 pages) | Cited 3 times

Online Publication Date: 19 December 2002

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For energy applications of high-power laser systems, uniform patterns are especially important in inertial confinement fusion research. We have demonstrated alignment control of liquid crystals using photoisomerization induced by polarized ultraviolet light to fabricate a polarization control plate. A glass substrate of a liquid-crystal cell, coated with polyvinyl alcohol doped with azo dye, was illuminated with a linearly polarized third harmonic of a Nd:YAG laser light. We confirmed the alignment of liquid crystals within the illuminated region dependent on the polarization direction of the ultraviolet light through the photoisomerization of azo dye molecules. Reduction of laser speckle pattern contrast by a polarization control plate was discussed. © 2002 American Institute of Physics.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.30.Ms Speckle and moiré patterns
61.30.-v Liquid crystals
82.30.Qt Isomerization and rearrangement
42.25.Ja Polarization
82.50.-m Photochemistry
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Resonance-enhanced laser-induced plasma spectroscopy for sensitive elemental analysis: Elucidation of enhancement mechanisms

S. L. Lui and N. H. Cheung

Appl. Phys. Lett. 81, 5114 (2002); http://dx.doi.org/10.1063/1.1532774 (3 pages) | Cited 9 times

Online Publication Date: 19 December 2002

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When performing laser-induced plasma spectroscopy for elemental analysis, the analyte signal-to-noise ratio increased from four to over fifty if the plume was reheated by a dye laser pulse tuned to resonant absorption. Time-resolved studies showed that the enhancement was not due to resonance photoionization. Rather, efficient and controlled rekindling of a larger plume volume was the key mechanism. The signal-to-noise ratio further increased to over a hundred if the atmosphere was replaced by a low-pressure heavy inert gas. The ambient gas helped confine and thermally insulate the expanding vapor. © 2002 American Institute of Physics.
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82.80.Dx Analytical methods involving electronic spectroscopy
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
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Control of the morphology transition for the growth of cubic GaN/AlN nanostructures

E. Martinez-Guerrero, F. Chabuel, B. Daudin, J. L. Rouvière, and H. Mariette

Appl. Phys. Lett. 81, 5117 (2002); http://dx.doi.org/10.1063/1.1527975 (3 pages) | Cited 12 times

Online Publication Date: 19 December 2002

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The Stransky–Krastanow growth mode of strained layers which gives rise to a morphology transition from two-dimensional layer to three-dimensional islands is studied in details for the cubic gallium nitride on cubic aluminum nitride (GaN/AlN) system grown by molecular beam epitaxy. Besides the lattice parameter mismatch which governs this transition, we evidence the importance of two other parameters, namely the substrate temperature and the III/V flux ratio. Tuning each of these two parameters enables to control the strain relaxation mechanism of a GaN deposited onto AlN, leading to the growth of either quantum wells or quantum dots. © 2002 American Institute of Physics.
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81.07.St Quantum wells
81.07.Ta Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Determination of absolute indium content in InGaN/GaN multiple quantum wells using anomalous x-ray scattering

H. H. Lee, M. S. Yi, H. W. Jang, Y.-T. Moon, S.-J. Park, D. Y. Noh, M. Tang, and K. S. Liang

Appl. Phys. Lett. 81, 5120 (2002); http://dx.doi.org/10.1063/1.1530376 (3 pages) | Cited 9 times

Online Publication Date: 19 December 2002

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We have determined the absolute indium content incorporated in the crystalline lattice of InGaN films and InGaN/GaN multiple quantum wells using anomalous x-ray scattering (AXS). AXS spectra were obtained near the In K absorption edge at the InGaN (0006) Bragg peak where the InGaN Bragg reflection is well-resolved from the GaN reflections. By comparing the indium composition obtained by AXS to regular x-ray scattering results, which are also sensitive to the lattice strain, we determine the Poisson ratio of InGaN to be ν ≈ 0.23. The AXS method can be effective in determining absolute chemical composition of InGaN independent of the lattice strain, which is especially valuable for InGaN multiple quantum wells. © 2002 American Institute of Physics.
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68.65.Fg Quantum wells
78.70.Ck X-ray scattering

Morphological and mechanical properties of carbon-nanotube-reinforced semicrystalline and amorphous polymer composites

M. Cadek, J. N. Coleman, V. Barron, K. Hedicke, and W. J. Blau

Appl. Phys. Lett. 81, 5123 (2002); http://dx.doi.org/10.1063/1.1533118 (3 pages) | Cited 203 times

Online Publication Date: 19 December 2002

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In this work, multiwalled carbon nanotubes were investigated as potential mechanical reinforcement agents in two hosts, polyvinyl alcohol (PVA) and poly(9-vinyl carbazole) (PVK). It was found that, by adding various concentrations of nanotubes, both Young’s modulus and hardness increased by factors of 1.8 and 1.6 at 1 wt % in PVA and 2.8 and 2.0 at 8 wt % in PVK, in reasonable agreement with the Halpin–Tsai theory. Furthermore, the presence of the nanotubes was found to nucleate crystallization of the PVA. This crystal growth is thought to enhance matrix-nanotube stress transfer. In addition, microscopy studies suggest extremely strong interfacial bonding in the PVA-based composite. This is manifested by the fracture of the polymer rather that the polymer-nanotube interface. © 2002 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.25.-g Mechanical properties of nanoscale systems
62.20.D- Elasticity
62.20.Qp Friction, tribology, and hardness
62.20.M- Structural failure of materials

Thermal conductivity of germanium, silicon, and carbon nitrides

D. T. Morelli and J. P. Heremans

Appl. Phys. Lett. 81, 5126 (2002); http://dx.doi.org/10.1063/1.1533840 (3 pages) | Cited 16 times

Online Publication Date: 19 December 2002

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We present a model calculation of the thermal conductivity of germanium nitride, silicon nitride, and carbon nitride in a temperature range in which intrinsic phonon scattering is dominant. We show that, in spite of the rather complex crystal structure of these nitrides, thermal conductivities exceeding 100 W m−1 K−1 can be attained in some of these compounds due to the combination of high Debye temperature and small Grüneisen constant. © 2002 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
63.20.-e Phonons in crystal lattices

Photoluminescence studies on InGaN/GaN multiple quantum wells with different degree of localization

M. Hao, J. Zhang, X. H. Zhang, and S. Chua

Appl. Phys. Lett. 81, 5129 (2002); http://dx.doi.org/10.1063/1.1531837 (3 pages) | Cited 13 times

Online Publication Date: 19 December 2002

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It has been found, by using photoluminescence (PL) studies, that both the localized states and nonradiative recombination centers in In0.06Ga0.94N/GaN multiple quantum wells (MQWs) can be greatly suppressed by inserting a monolayer of AlN before the growth of each well layer. While inserting a monolayer of AlN before each well layer does not have any effect on the growth rate or on the indium content of MQWs, it does improve room-temperature PL intensity of the In0.06Ga0.94N/GaN MQWs. The physics behind the suppression of localized states and nonradiative recombination centers is discussed. © 2002 American Institute of Physics.
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78.67.De Quantum wells
73.21.Fg Quantum wells
68.65.Fg Quantum wells
78.55.Cr III-V semiconductors
68.37.Lp Transmission electron microscopy (TEM)

Observation of orthogonally polarized transverse electric and transverse magnetic oscillation modes in a microcavity excited by localized two-photon absorption

Dru Morrish, Xiaosong Gan, and Min Gu

Appl. Phys. Lett. 81, 5132 (2002); http://dx.doi.org/10.1063/1.1531222 (3 pages) | Cited 6 times

Online Publication Date: 19 December 2002

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We report on the observation of orthogonally polarized transverse electric (TE) and transverse magnetic (TM) oscillation modes in a microcavity excited by localized two-photon absorption. The polarization-dependent features of morphology-dependent resonance (MDR) effects in a microsphere under two-photon fluorescence excitation are quantitatively investigated. In addition to a clear separation of excitation and resonance wavelengths under two-photon excitation, the fluorescence emission can be tightly controlled in three-dimensional space within a microsphere. The experimental results demonstrate not only the orthogonal polarization nature of TE and TM oscillation modes but also the dependence of the strength and the polarization properties of MDR peaks on excitation locations in a microsphere. © 2002 American Institute of Physics.
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42.25.Ja Polarization

Breakdown of the approximations of small perturbations in continuum modeling of amorphous thin film growth

C. Streng, K. Samwer, and S. G. Mayr

Appl. Phys. Lett. 81, 5135 (2002); http://dx.doi.org/10.1063/1.1532551 (3 pages) | Cited 4 times

Online Publication Date: 19 December 2002

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Morphology evolution of thin film growth can be quantitatively modeled by employing rate equations for two-dimensional, single-valued functions within a treatment of small perturbations. This description can be expected to be valid in an intermediate film thickness regime, where substrate influences and three-dimensional effects are minor. The breakdown of the mathematical description in its upper film thickness limit is systematically investigated by a detailed comparison of experiments and simulation. Possible reasons for the failure are discussed and improvements are suggested. © 2002 American Institute of Physics.
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68.55.A- Nucleation and growth
61.43.-j Disordered solids
68.35.B- Structure of clean surfaces (and surface reconstruction)

F-enhanced morphological and thermal stability of NiSi films on BF2+-implanted Si(001)

A. S. W. Wong, D. Z. Chi, M. Loomans, D. Ma, M. Y. Lai, W. C. Tjiu, S. J. Chua, C. W. Lim, and J. E. Greene

Appl. Phys. Lett. 81, 5138 (2002); http://dx.doi.org/10.1063/1.1533856 (3 pages) | Cited 20 times

Online Publication Date: 19 December 2002

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The morphological and thermal stability of conducting NiSi films formed on Si(001) are significantly enhanced by pre-implantation of the Si wafer with BF2+. In the absence of F, the maximum silicidation temperature Tmax is 650 °C; higher temperatures lead to the formation of the competing high-resistivity NiSi2 phase. Tmax, however, is increased to ⩾750 °C during NiSi formation on Si(001) implanted with 20 keV BF2+ at a dose of 5×1015 cm−2. The observed enhancement in NiSi thermal stability is due to F segregation to the silicide/Si(001) interface and silicide grain boundaries, which retards NiSi grain growth, leading to much smoother layers, and inhibits NiSi2 nucleation. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.60.Dv Thermal stability; thermal effects
68.35.Dv Composition, segregation; defects and impurities
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.72.Mm Grain and twin boundaries
61.72.Cc Kinetics of defect formation and annealing

Effects of 6H-SiC surface reconstruction on lattice relaxation of AlN buffer layers in molecular-beam epitaxial growth of GaN

Jun Suda, Kouhei Miura, Misako Honaga, Yusuke Nishi, Norio Onojima, and Hiroyuki Matsunami

Appl. Phys. Lett. 81, 5141 (2002); http://dx.doi.org/10.1063/1.1533855 (3 pages) | Cited 2 times

Online Publication Date: 19 December 2002

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Growth of GaN on on-axis 6H-SiC (0001)Si substrates with an AlN buffer layer was performed by molecular-beam epitaxy. The effects of SiC surface reconstruction on the lattice relaxation of AlN buffer layers and the crystalline quality of GaN layers were studied. High-temperature HCl-gas etching followed by HF chemical treatment resulted in an atomically flat SiC surface with a 1×1 structure. The AlN layer grown on the surface showed slow lattice relaxation. GaN grown on the AlN buffer layer exhibited the narrowest (0002) x-ray rocking curve of 70 arcsec and 107 cm−2 screw-type dislocation density, which was two orders of magnitude smaller than that of GaN grown on as-received substrates. © 2002 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Lk Linear defects: dislocations, disclinations

Photoluminescence of Ge nanoparticles embedded in SiO2 glasses fabricated by a sol–gel method

Heqing Yang, Xingjun Wang, Huazhong Shi, Songhai Xie, Fujian Wang, Xiaoxiao Gu, and Xi Yao

Appl. Phys. Lett. 81, 5144 (2002); http://dx.doi.org/10.1063/1.1506943 (3 pages) | Cited 16 times

Online Publication Date: 19 December 2002

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Ge nanoparticles with different sizes in silica glasses were prepared by a sol–gel method using Cl3–Ge–C2H4–COOH as a Ge source. The size of the Ge nanoparticles decreases with a reduction in the content of Ge in the starting materials, and thus the optical absorption edge shifts to a higher energy. Silica gel glasses doped with Ge nanoparticles showed a strong room-temperature photoluminescence with peaks at 568, 607, 672, 722, and 775 nm. The peak position of photoluminescence spectrum scarcely depends on the Ge/Si ratio. However, the photoluminescence intensity increases sharply as the Ge/Si ratio is reduced. The photoluminescence arises from the Ge clusters of diameter of <1–2 nm with a molecular character instead of nanocrystalline Ge with the diamond structure. © 2002 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.67.Hc Quantum dots
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.46.-w Structure of nanoscale materials

Fabrication of single- or double-row aligned self-assembled quantum dots by utilizing SiO2-patterned vicinal (001) GaAs substrates

Hyo Jin Kim, Junichi Motohisa, and Takashi Fukui

Appl. Phys. Lett. 81, 5147 (2002); http://dx.doi.org/10.1063/1.1534385 (3 pages) | Cited 2 times

Online Publication Date: 19 December 2002

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We investigated the formation of In0.8Ga0.2As self-assembled quantum dots (SAQDs) grown on SiO2-patterned 1°, 2°, and 5°-off (001) GaAs substrates by selective area metalorganic vapor phase epitaxy technique. The SiO2 patterns were filled with various stripe opening windows along the misorientation direction of the substrates. During the growth of the GaAs buffer layer on the opening regions, the steps on the (001) top facet was affected by the widths of the (001) top facet and the misorientation angles of the substrates. Single- or double-row aligned In0.8Ga0.2As SAQDs having definite interval were successfully fabricated on the (001) top facet with optimized top width and periodicity of step bunching. These results indicate that the selective growth technique of SAQDs by utilizing SiO2-patterned vicinal substrates is promising for nanoelectronic device applications such as single-electron memory devices. © 2002 American Institute of Physics.
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81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.16.Dn Self-assembly
85.35.-p Nanoelectronic devices

Reversed truncated cone composition distribution of In0.8Ga0.2As quantum dots overgrown by an In0.1Ga0.9As layer in a GaAs matrix

A. Lenz, R. Timm, H. Eisele, Ch. Hennig, S. K. Becker, R. L. Sellin, U. W. Pohl, D. Bimberg, and M. Dähne

Appl. Phys. Lett. 81, 5150 (2002); http://dx.doi.org/10.1063/1.1533109 (3 pages) | Cited 39 times

Online Publication Date: 19 December 2002

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We present cross-sectional scanning tunneling microscopy results of self-organized In0.8Ga0.2As quantum dots covered by an In0.1Ga0.9As film inside a GaAs matrix prepared by metalorganic chemical vapor deposition. From images of quantum dots with atomic resolution, we determine a spatial distribution of the In composition within the dots with a shape of a reversed truncated cone. The wetting layer and the overgrown In0.1Ga0.9As layer show vertical intermixing. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.08.Bc Wetting
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

Correlation of resistivity with zinc content in a vapor grown (Cd,Zn)Te:Se

V. Corregidor, E. Diéguez, J. L. Castaño, M. Fiederle, V. Babentsov, A. Fauler, and K. Benz

Appl. Phys. Lett. 81, 5153 (2002); http://dx.doi.org/10.1063/1.1533124 (3 pages) | Cited 4 times

Online Publication Date: 19 December 2002

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We report the possibility to grow semi-insulating (Cd,Zn)Te:Se crystals by the modified Markov method (MMM) from the vapor phase. When oriented Cd(Te,Se) seed material was used for the growth, lattice matching and doping with Se resulted in an increase of resistivity up to several units of 109 Ω cm. A homogenous Zn distribution was also observed. The content of Se and Zn in the seed and grown crystals was determined by photoluminescence and energy dispersive analysis by x ray measurements. Resistivity and Zn concentration maps show a good spatial correlation in which the highest values of resistivity correspond to the areas of the highest Zn concentration. The main part of the crystals demonstrate a low extinction coefficient in the IR spectral region, except for the Zn inhomogeneity region. © 2002 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.10.Bk Growth from vapor
72.80.Ey III-V and II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
78.55.Et II-VI semiconductors
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Fs III-V and II-VI semiconductors

Dielectric functions and critical points of BexZn1−xTe alloys measured by spectroscopic ellipsometry

M. R. Buckley, F. C. Peiris, O. Maksimov, M. Muñoz, and M. C. Tamargo

Appl. Phys. Lett. 81, 5156 (2002); http://dx.doi.org/10.1063/1.1534387 (3 pages) | Cited 19 times

Online Publication Date: 19 December 2002

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Using a rotating analyzer spectroscopic ellipsometer, we have investigated the complex dielectric function of a series of ternary BexZn1−xTe thin films in the energy range between 0.7 and 6.5 eV for alloy concentrations between x = 0.0 and x = 0.52. After determining the alloy concentrations using x-ray diffraction and photoluminescence techniques, a standard inversion technique was used to obtain the optical constants from the measured ellipsometric spectra. Analyzing the second derivative of both the real and the imaginary parts of the dielectric constant, we have deduced the critical point parameters corresponding to the electronic transitions in the Brillouin zone. We find that the energy of the critical points with respect to Be concentration does not show any bowing effects unlike many other II–VI semiconductor ternary alloys. © 2002 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)
78.66.Hf II-VI semiconductors
71.20.Nr Semiconductor compounds
77.22.Ch Permittivity (dielectric function)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
07.60.Fs Polarimeters and ellipsometers
78.40.Fy Semiconductors
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The Mn3+/2+ acceptor level in group III nitrides

T. Graf, M. Gjukic, M. S. Brandt, M. Stutzmann, and O. Ambacher

Appl. Phys. Lett. 81, 5159 (2002); http://dx.doi.org/10.1063/1.1530374 (3 pages) | Cited 108 times

Online Publication Date: 19 December 2002

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Molecular-beam-epitaxy grown GaN:Mn and AlN:Mn layers with Mn concentrations around 1020 cm−3 were investigated by optical absorption and photoconductivity measurements. From electron spin resonance Mn is known to be mostly present in the neutral acceptor state in GaN without codoping. This leads to a reassignment of the optical absorption features to a charge transfer from the neutral Mn3+ oxidation state, either by direct photoionization at 1.8 eV or through a photothermal ionization process via an excited state at 1.42 eV above the Mn3+ ground state by spin-allowed Mn3+ 5E→5T internal absorption. The position of the Mn3+/2+ acceptor level at 1.8 eV above the valence-band edge of GaN makes the realization of carrier-mediated ferromagnetism rather unlikely in GaN:Mn. © 2002 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
75.50.Pp Magnetic semiconductors
72.40.+w Photoconduction and photovoltaic effects
73.50.Pz Photoconduction and photovoltaic effects
76.30.Fc Iron group (3d) ions and impurities (Ti-Cu)
78.40.Fy Semiconductors

Electrical detection of spin accumulation and spin precession at room temperature in metallic spin valves

F. J. Jedema, M. V. Costache, H. B. Heersche, J. J. A. Baselmans, and B. J. van Wees

Appl. Phys. Lett. 81, 5162 (2002); http://dx.doi.org/10.1063/1.1532753 (3 pages) | Cited 17 times

Online Publication Date: 19 December 2002

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We have fabricated a multiterminal lateral mesoscopic metallic spin valve demonstrating spin precession at room temperature (RT), using tunnel barriers in combination with metallic ferromagnetic electrodes as a spin injector and detector. The observed modulation of the output signal due to the spin precession is discussed and explained in terms of a time-of-flight experiment of electrons in a diffusive conductor. The obtained spin relaxation length λsf = 500 nm in an aluminum strip will make detailed studies of spin dependent transport phenomena possible and allow one to explore the possibilities of the electron spin for new electronic applications at RT. © 2002 American Institute of Physics.
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72.25.Ba Spin polarized transport in metals
73.23.-b Electronic transport in mesoscopic systems
73.40.Gk Tunneling

Onset of long-range diffusion and exponent of 1/fα noise in metal films with electromigration damage

Swastik Kar and A. K. Raychaudhuri

Appl. Phys. Lett. 81, 5165 (2002); http://dx.doi.org/10.1063/1.1523155 (3 pages) | Cited 5 times

Online Publication Date: 19 December 2002

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Investigations of low-frequency conductance fluctuations have been done on silver films which have been made to undergo electromigration damage. The system shows a clear increase in noise magnitude after electromigration damage. The noise spectral power shows a distinct presence of 1/f3/2 component arising out of long-range diffusion. The temperature dependence of noise (150 K<T<350 K) shows a marked deviation from the Dutta–Horn type behavior with the 1/f3/2 term showing a strong dominance at higher temperatures. We propose that the increase of noise in metal films after electromigration damage arise predominantly from this spectral component. © 2002 American Institute of Physics.
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73.61.At Metal and metallic alloys
66.30.Qa Electromigration
73.50.Td Noise processes and phenomena

Effect of crystal defects on the electrical properties in epitaxial tin dioxide thin films

J. E. Dominguez, L. Fu, and X. Q. Pan

Appl. Phys. Lett. 81, 5168 (2002); http://dx.doi.org/10.1063/1.1530745 (3 pages) | Cited 19 times

Online Publication Date: 19 December 2002

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Epitaxial (101) tin dioxide thin films with thickness ranging from 6 and 100 nm were deposited on the (10math2) α-Al2O3 substrate by femtosecond pulsed laser ablation. Due to the lattice and thermal expansion mismatch with the substrate, the SnO2 film shows interfacial misfit dislocations, antiphase boundaries (APBs), and partial dislocations. The APBs lie along the (math01) planes with a displacement of 1/2[101]. The densities of APBs and partial dislocations vary with film thickness, whereas the average spacing of misfit dislocations remains constant. Hall effect measurements showed that both electron concentration and mobility decrease with a reduction in the film thickness, which is ascribed to the scattering of electrons by crystal defects and interfaces and the effect of a native space charge region at the near-surface region of the films. The response of the films to reducing gases was found to depend on the electron concentration of the film and the relative fraction, with respect to film thickness, of material that is depleted of electrons. © 2002 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
72.80.Ga Transition-metal compounds
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
72.20.Fr Low-field transport and mobility; piezoresistance
68.55.A- Nucleation and growth
81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
65.40.De Thermal expansion; thermomechanical effects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Ee Mobility edges; hopping transport
73.50.Dn Low-field transport and mobility; piezoresistance
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.-d Chemical analysis and related physical methods of analysis

Interface states at ZnSe/Ge heterojunctions: the role of atomic interdiffusion and disorder

M. Peressi, F. Favot, G. Cangiani, and A. Baldereschi

Appl. Phys. Lett. 81, 5171 (2002); http://dx.doi.org/10.1063/1.1532555 (3 pages) | Cited 4 times

Online Publication Date: 19 December 2002

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The origin of electronic states localized at ZnSe/Ge (110) interface is investigated by means of ab initio pseudopotential calculations. Some selected interface configurations are considered, one corresponding to the abrupt interface and others corresponding to partially disordered interfaces, with Zn-Ge or Se-Ge swaps. Remarkably, the existence of interface electronic states within the heterojunction band gap critically depends on the atomic-scale morphology of the interface: unlike the abrupt case, disordered interfaces exhibit localized states extending over the whole interface Brillouin zone. The presence of interfacial density of states, experimentally detectable, is therefore an indication of disorder and atomic interdiffusion. © 2002 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.20.Fz Weak or Anderson localization
68.35.Ct Interface structure and roughness
68.35.Fx Diffusion; interface formation
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
73.20.Hb Impurity and defect levels; energy states of adsorbed species
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