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17 Dec 2001

Volume 79, Issue 25, pp. 4073-4251

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Systematic measurement of AlxGa1−xN refractive indices

Ümit Özgür, Grady Webb-Wood, Henry O. Everitt, Feng Yun, and Hadis Morkoç

Appl. Phys. Lett. 79, 4103 (2001); http://dx.doi.org/10.1063/1.1426270 (3 pages) | Cited 33 times

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Dispersion of the ordinary and extraordinary indices of refraction have been measured systematically for wurtzitic AlxGa1−xN epitaxial layers with 0.0 ⩽ x ⩽ 1.0 throughout the visible wavelength region. The dispersion, measured by a prism coupling waveguide technique, is found to be well described by a Sellmeier relation. Discrepancies among previous measurements of refractive index dispersion, as a consequence of different growth conditions and corresponding band gap bowing parameter, are reconciled when the Sellmeier relation is parameterized not by x but by band gap energy. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Evaluation of the precipitate contribution to the infrared absorption in interstitial oxygen measurements in silicon

A. Sassella, A. Borghesi, B. Pivac, and M. Porrini

Appl. Phys. Lett. 79, 4106 (2001); http://dx.doi.org/10.1063/1.1425457 (3 pages) | Cited 1 time

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The spurious contribution of oxide precipitates to the infrared absorption of interstitial oxygen in silicon is determined from spectra collected at 7 K for samples with different initial interstitial oxygen Oi concentration subjected to a three-step thermal treatment. These data can be used to correct the residual Oi values determined at room temperature following the standard procedure from the intensity of the 1107 cm−1 absorption band. The error in residual Oi is found to reach values on the order of 2×1017 atoms/cm3 for samples with initial Oi content higher than 6.5×1017 atoms/cm3. © 2001 American Institute of Physics.
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61.72.J- Point defects and defect clusters
78.30.Am Elemental semiconductors and insulators
64.75.-g Phase equilibria

Optical investigation of shallow acceptor states in GaN grown by hydride vapor-phase epitaxy

V. Kirilyuk, P. R. Hageman, P. C. M. Christianen, P. K. Larsen, and M. Zielinski

Appl. Phys. Lett. 79, 4109 (2001); http://dx.doi.org/10.1063/1.1427151 (3 pages) | Cited 6 times

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The evolution of low-temperature photoluminescence (PL) spectra with the thickness of the layer (3–400 μm) is investigated on high-quality GaN grown by hydride vapor-phase epitaxy. With increasing layer thickness, three acceptor bound exciton peaks are found to reduce in intensity, although the impurity concentrations, measured by secondary ion mass spectrometry, do not depend on the sample thickness. The observed acceptor transitions are attributed to intrinsic defects, originating from the substrate/layer interface and decreasing in density with the thickness of the layer. The optical properties, studied by reflectance, temperature and excitation power dependent PL, are compared to those of homoepitaxial GaN films grown by metalorganic chemical vapor deposition. © 2001 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.35.-y Excitons and related phenomena

Determination of residual stresses in Pb(Zr0.53Ti0.47)O3 thin films with Raman spectroscopy

Wei-Hua Xu, Dexin Lu, and Tong-Yi Zhang

Appl. Phys. Lett. 79, 4112 (2001); http://dx.doi.org/10.1063/1.1426271 (3 pages) | Cited 31 times

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The present work uses Raman spectra to measure residual stresses in Pb(Zr0.53Ti0.47)O3 thin films. Based on thermodynamic analysis, a linear relationship is found between the stress and the square of the Raman frequency in the A1 [transverse optical3 (TO3)] and E [longitudinal optical3 (LO3)] modes. We calibrate the linear relationship by measuring the Raman spectra of stressed bulk Pb(Zr0.53Ti0.47)O3 samples. Then, we assess residual stresses in the lead zirconate titanate thin films at different thicknesses and different annealing temperatures. The residual stresses extracted from the A1(TO3) mode are consistent with those from the E(LO3) mode, which are more or less the same as those measured by the x-ray diffraction sin2 ψ method. © 2001 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.60.Bs Mechanical and acoustical properties
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators

Ductility of ultrafine grained copper

Hyoung Seop Kim and Yuri Estrin

Appl. Phys. Lett. 79, 4115 (2001); http://dx.doi.org/10.1063/1.1426697 (3 pages) | Cited 32 times

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In this letter, we address the effect of grain refinement on room-temperature ductility of copper. Recent experimental results have shown that this material, as well as a number of other single-phase metals that are ductile when coarse grained, lose their ductility with decreasing grain size in the submicrometer range. A recently developed model in which such materials are considered as effectively two-phase ones (with the grain boundaries treated as a linearly viscous second phase) was applied to analyze the stability of Cu against ductile necking. As a basis, Hart’s stability analysis that accounts for strain-rate-sensitivity effects was used [E. W. Hart, Acta Metall. 15, 351 (1967)]. The results confirm the observed trend for reduction of room-temperature ductility with decreasing grain size. The model can be applied to predicting the grain-size dependence of ductility of other metallic materials as well. © 2001 American Institute of Physics.
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62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
61.72.Mm Grain and twin boundaries

Lateral composition modulation in short period superlattices: The role of growth mode

C. Dorin, J. Mirecki Millunchick, Y. Chen, B. G. Orr, and C. A. Pearson

Appl. Phys. Lett. 79, 4118 (2001); http://dx.doi.org/10.1063/1.1425452 (3 pages) | Cited 5 times

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The role of the growth mode on lateral composition modulation is studied in short period superlattices of AlAs/InAs and GaAs/InAs. Reflection high energy electron diffraction and scanning tunneling microscopy are used to monitor the growth mode and the quality of the interfaces. Cross-sectional transmission electron microscopy indicates that samples that grow via the layer-by-layer growth mode do not exhibit lateral composition modulation and the superlattice structure is well defined. Lateral composition modulation forms when roughening occurs during growth. However, too much roughening, i.e., three-dimensional island nucleation destroys the regularity of the composition modulation in both the lateral and vertical directions. These results are in general agreement with theoretical predictions. © 2001 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.65.Cd Superlattices
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Dv Composition, segregation; defects and impurities

Thermal conductivity and interfacial thermal resistance of polymeric low k films

Chuan Hu, Michael Kiene, and Paul S. Ho

Appl. Phys. Lett. 79, 4121 (2001); http://dx.doi.org/10.1063/1.1419239 (3 pages) | Cited 7 times

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The effective thermal conductivity of four polymeric thin films with distinct molecular morphologies has been measured as a function of film thickness down to 70 Å using a 3ω technique. Comparing to SiO2, the intrinsic thermal conductivity of polymers is about 5–10 times smaller while the interfacial thermal resistance is about 2–10 times larger. The interfacial thermal resistances are explained in terms of the mismatches of acoustic and mechanical properties between polymers and crystalline materials. Both elastic and inelastic scatterings at the interface are examined. © 2001 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
68.35.Ja Surface and interface dynamics and vibrations
77.84.Jd Polymers; organic compounds
61.41.+e Polymers, elastomers, and plastics
77.55.-g Dielectric thin films
68.35.Iv Acoustical properties
63.50.-x Vibrational states in disordered systems

Energy level alignment driven by electron affinity difference at 3,4,9,10-perylenetetracarboxylic dianhydride/n-GaAs(100) interfaces

Sunggook Park, Thorsten U. Kampen, Dietrich R. T. Zahn, and Walter Braun

Appl. Phys. Lett. 79, 4124 (2001); http://dx.doi.org/10.1063/1.1426253 (3 pages) | Cited 14 times

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Ultraviolet photoemission spectroscopy (UPS) was employed to investigate the electronic structure upon deposition of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on differently treated n-GaAs(100) surfaces. Interface dipoles are found to form according to the electron affinities (EA) of the substrates and PTCDA films at the interfaces and, consequently, the vacuum level alignment rule does not hold. The results demonstrate that the energy offset between the conduction band minimum of n-doped inorganic semiconductors and the lowest unoccupied molecular orbital of organic molecular films at the interfaces can be obtained using UPS by systematically varying the EA of substrates with a known band gap. © 2001 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.20.Rv Polymers and organic compounds
79.60.Jv Interfaces; heterostructures; nanostructures

Finite element analysis of epitaxial lateral overgrown GaN: Voids at the coalescence boundary

M. Benyoucef, M. Kuball, G. Hill, M. Wisnom, B. Beaumont, and P. Gibart

Appl. Phys. Lett. 79, 4127 (2001); http://dx.doi.org/10.1063/1.1426276 (3 pages) | Cited 11 times

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We report on the finite element analysis of stress distribution at the coalescence boundary in epitaxial lateral overgrown (ELO) GaN related to voids. Different void geometries were considered in our model to investigate the influence of their size/shape on the stress distribution. Large compressive stress is localized in the vicinity of the voids, also an increased tensile stress is present at the corners of the SiN mask. Confocal micro-Raman mapping experiments confirm the presence of increased stress at the coalescence boundary of ELO GaN. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.60.Bs Mechanical and acoustical properties
61.72.Qq Microscopic defects (voids, inclusions, etc.)
02.70.Dh Finite-element and Galerkin methods
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors

Oxidation kinetics of tunnel barrier and its effect on exchange bias of proximity interface

Seung-Young Bae, Kyung-Ho Shin, Je-Hyung Lee, Keung-Won Rhie, Kyoung-Il Lee, Jae-Geun Ha, and Shan Xiang Wang

Appl. Phys. Lett. 79, 4130 (2001); http://dx.doi.org/10.1063/1.1423772 (3 pages)

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Atomic migration in metallic multilayers of magnetic tunnel junction (MTJ), and consequent compositional modulation at the interface during plasma oxidation of an Al tunnel barrier is reported. Surprising effects of such modulation in our specific MTJ appear as the systematic increase in exchange bias of the NiFe buffer layer beneath an FeMn antiferromagnet. Cation-current-limited oxidation of the Al metal layer drives atomic migration in the underlying multilayers to compensate for the cation vacancies created in the metal side of the metal/oxide interface. The condition of oxide growth which manifests different migration behavior is also discussed. © 2001 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.65.Ac Multilayers
81.65.Mq Oxidation
52.77.-j Plasma applications
75.30.Et Exchange and superexchange interactions

Hexagonal GaN grown on GaAs{11n} substrates by metalorganic vapor-phase epitaxy using AlAs intermediate layers

Mitsuru Funato, Shuichiro Yamamoto, Kiyohiro Kaisei, Koichiro Shimogami, Shizuo Fujita, and Shigeo Fujita

Appl. Phys. Lett. 79, 4133 (2001); http://dx.doi.org/10.1063/1.1426275 (3 pages) | Cited 4 times

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Hexagonal GaN (h-GaN) layers are grown by metalorganic vapor-phase epitaxy on GaAs{11n}A and B (n = 8, 4, 3, 2, 1) substrates using AlAs intermediate layers. The best quality of h-GaN is obtained on (1math4)B, where the crystallographic relationship is found from a pole figure to be h-GaN{0001}‖GaAs(3math5)B and h-GaN{10math2}‖GaAs(001). We propose a simple model that explains why such a crystallographic relationship is easily realized on {114} resulting in the superior structural and optical properties. Furthermore, from a comparison between the growth on the A and B substrates, it is pointed out that the polarity is a key factor in determining the crystallographic properties. © 2001 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.55.A- Nucleation and growth

Diagnostics of surface layer disordering using optical third harmonic generation of a circular polarized light

V. V. Yakovlev and S. V. Govorkov

Appl. Phys. Lett. 79, 4136 (2001); http://dx.doi.org/10.1063/1.1427425 (3 pages) | Cited 5 times

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A nonlinear optical technique based on a third-harmonic generation of a circular polarized light is proposed for the diagnostics of order–disorder transformations in semiconductors. Applications of this technique to study both noncentrosymmetric (GaAs) and centrosymmetric (Si) materials are demonstrated. © 2001 American Institute of Physics.
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68.35.Rh Phase transitions and critical phenomena
78.68.+m Optical properties of surfaces
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
64.70.K- Solid-solid transitions
61.50.Ks Crystallographic aspects of phase transformations; pressure effects

Interactions between gallium and nitrogen dopants in ZnO films grown by radical-source molecular-beam epitaxy

K. Nakahara, H. Takasu, P. Fons, A. Yamada, K. Iwata, K. Matsubara, R. Hunger, and S. Niki

Appl. Phys. Lett. 79, 4139 (2001); http://dx.doi.org/10.1063/1.1424066 (3 pages) | Cited 56 times

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It has been recently predicted that the co-doping of an acceptor (nitrogen) and a donor (aluminum, gallium, indium) in a 2:1 ratio will dope ZnO p-type due to a reduction in the Madelung energy making the nitrogen acceptor energy level more shallow. We have been growing gallium and nitrogen co-doped ZnO films by radical-source molecular-beam epitaxy by use of oxygen and nitrogen radicals supplied via rf radical source cells. Diode-like current–voltage characteristics and donor acceptor pair-like photoluminescence emission were observed for a Ga and N doped ZnO film grown on an undoped ZnO buffer layer. However, Hall measurements revealed that the conductivity was n-type. Formation of a non-ZnO phase in the sample was confirmed by secondary ion mass spectroscopy and x-ray diffraction measurements. Zn and Zn+O secondary ion intensities fell sharply by two orders of magnitude in going from the undoped ZnO layer to the highly co-doped ZnO. X-ray diffraction measurements indicated the formation of ZnGa2O4. © 2001 American Institute of Physics.
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71.55.Gs II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Et II-VI semiconductors
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.Nq Composition and phase identification

Electrical and optical characterization of conducting poly-3-methylthiophene film by THz time-domain spectroscopy

Tae-In Jeon, D. Grischkowsky, A. K. Mukherjee, and Reghu Menon

Appl. Phys. Lett. 79, 4142 (2001); http://dx.doi.org/10.1063/1.1427754 (3 pages) | Cited 16 times

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Using THz time-domain spectroscopy (THz-TDS), we have measured the absorption and dispersion of 7.5/(Ω cm) conducting poly-3-methylthiophene film from low frequencies up to 4 THz. From these measurements the complex conductance that increases with increasing frequency was obtained over this frequency range. The results do not follow simple Drude theory and are not comparable with normal metal and semiconductors; the results were well fit by the localization-modified Drude theory. © 2001 American Institute of Physics.
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72.15.Nj Collective modes (e.g., in one-dimensional conductors)
73.61.Ph Polymers; organic compounds
78.66.Qn Polymers; organic compounds
78.70.Gq Microwave and radio-frequency interactions

Complete suppression of the transient enhanced diffusion of B implanted in preamorphized Si by interstitial trapping in a spatially separated C-rich layer

E. Napolitani, A. Coati, D. De Salvador, A. Carnera, S. Mirabella, S. Scalese, and F. Priolo

Appl. Phys. Lett. 79, 4145 (2001); http://dx.doi.org/10.1063/1.1425458 (3 pages) | Cited 27 times

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A method for completely suppressing the transient enhanced diffusion (TED) of boron implanted in preamorphized silicon is demonstrated. Boron is implanted in a molecular beam epitaxy (MBE) grown silicon sample that has been previously amorphized by silicon implantation. The sample is then annealed in order to epitaxially regrow the amorphous layer and electrically activate the dopant. The backflow of silicon interstitials released by the preamorphization end-of-range (EOR) damage is completely trapped by a carbon-rich silicon layer interposed by MBE between the damage and the implanted boron. No appreciable TED is observed in the samples up to complete dissolution of the EOR damage, and complete electrical activation is obtained. The method might be considered for the realization of ultrashallow junctions for the far future complementary metal–oxide–semiconductor technology nodes. © 2001 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.Nq Composition and phase identification
61.72.uf Ge and Si
66.30.J- Diffusion of impurities
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.J- Point defects and defect clusters
81.05.Gc Amorphous semiconductors
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