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24 Nov 2003

Volume 83, Issue 21, pp. 4279-4450

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 4294 (2003); http://dx.doi.org/10.1063/1.1629140 (3 pages)

Han-Youl Ryu, Masaya Notomi, and Yong-Hee Lee
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Visible and near-infrared alternating-current electroluminescence from sputter-grown GaN thin films doped with Er

Joo Han Kim, N. Shepherd, M. R. Davidson, and Paul H. Holloway

Appl. Phys. Lett. 83, 4279 (2003); http://dx.doi.org/10.1063/1.1622106 (3 pages) | Cited 11 times

Online Publication Date: 18 November 2003

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A demonstration of visible and near-infrared (NIR) alternating-current electroluminescence from sputter-grown GaN thin films doped with Er is reported. The alternating-current thin-film electroluminescent (ACTFEL) devices were constructed using a standard single-insulating structure, Al/GaN:Er/aluminum–titanium–oxide/indium–tin–oxide/Corning 7059 glass. Visible emissions peaked at 550 and 665 nm as well as NIR emissions centered at 1000 and 1550 nm were observed from the fabricated ACTFEL devices operating at room temperature. The visible and NIR emissions at 550, 665, 1000, and 1550 nm were attributed to the Er3+ 4f–4f intrashell transitions from the 4S3/2, 4F9/2, 4I11/2, and 4I13/2 excited-state levels to the 4I15/2 ground state, respectively. The green 550 nm emission had a larger dI/dV and a higher threshold voltage, Vth than the NIR 1550 nm emission, which could result from the need for higher electron impact energy to impact-excite the Er ion into the higher-energy excited-states for emission of green light. © 2003 American Institute of Physics.
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78.60.Fi Electroluminescence
78.66.Fd III-V semiconductors
81.15.Cd Deposition by sputtering

Direct measurement of the refractive index profile of phase gratings, recorded in silver halide holographic materials by phase-contrast microscopy

I. Bányász

Appl. Phys. Lett. 83, 4282 (2003); http://dx.doi.org/10.1063/1.1629794 (3 pages) | Cited 5 times

Online Publication Date: 18 November 2003

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Plane-wave phase holograms recorded in Agfa-Gevaert 8E75HD emulsions and processed by the combination of AAC developer and the R-9 bleaching agent were studied by phase-contrast microscopy, using high-power immersion (100×) objective. Thus the modulation of the refractive index as a function of the bias exposure and the visibility of the recording interference pattern can also be determined. Measured diffraction efficiencies were compared to those predicted by coupled wave theory, using the measured refractive index modulations. Direct measurement of the phase profile of the gratings can be used for optimizing processing. © 2003 American Institute of Physics.
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42.40.Eq Holographic optical elements; holographic gratings
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Electrically switchable and thermally erasable biphotonic holographic gratings in dye-doped liquid crystal films

C.-R. Lee, T.-S. Mo, K.-T. Cheng, T.-L. Fu, and A. Y.-G. Fuh

Appl. Phys. Lett. 83, 4285 (2003); http://dx.doi.org/10.1063/1.1629374 (3 pages) | Cited 24 times

Online Publication Date: 18 November 2003

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This study investigates high-resolution photoinduced biphotonic holographic gratings in azo-dye-doped liquid crystal films. A biphotonic grating (BG) is formed under the illumination of one linearly polarized green light with the simultaneous irradiation of an interference pattern created by two linearly polarized red lights. This study ascribes the formation of this grating to two mechanisms. One mechanism is the green-light-inducing strong dye absorption followed by adsorption through the trans–cis isomerization; the other mechanism is the inhibition effect of adsorption induced by the red light through the cis–trans inverse isomerization. These produce a twisted nematic structure-modulated pattern, which, in turn, causes the BG. Additional experiments demonstrate that the formed BGs are electrically switchable and thermally erasable. © 2003 American Institute of Physics.
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42.40.Eq Holographic optical elements; holographic gratings
82.30.Qt Isomerization and rearrangement
42.70.Df Liquid crystals

Ultraviolet amplified spontaneous emission from zinc oxide ridge waveguides on silicon substrate

S. F. Yu, Clement Yuen, S. P. Lau, Y. G. Wang, H. W. Lee, and B. K. Tay

Appl. Phys. Lett. 83, 4288 (2003); http://dx.doi.org/10.1063/1.1629784 (3 pages) | Cited 23 times

Online Publication Date: 18 November 2003

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Zinc oxide (ZnO) thin-film waveguides with ridge structures have been fabricated on n-type (100) silicon substrates. The deposition of high-crystal-quality ZnO thin films on the lattice-mismatched silicon substrate was achieved by using the filtered cathodic vacuum arc technique. A ridge structure is defined on the ZnO thin film by plasma etching. Room temperature amplified spontaneous emission with peak wavelength at 385 nm is observed under 355 nm optical excitation. The pump threshold is found to be around 0.45 MW/cm2. The maximum net optical gain of the ZnO waveguide is larger than 120 cm−1 at a pump intensity of 1.9 MW/cm2. © 2003 American Institute of Physics.
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78.66.Hf II-VI semiconductors
42.82.Et Waveguides, couplers, and arrays
78.55.Et II-VI semiconductors
78.45.+h Stimulated emission
42.79.Gn Optical waveguides and couplers
81.65.Cf Surface cleaning, etching, patterning
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
42.55.Px Semiconductor lasers; laser diodes

Truly bistable twisted nematic liquid crystal display using photoalignment technology

Fion S. Y. Yeung and H. S. Kwok

Appl. Phys. Lett. 83, 4291 (2003); http://dx.doi.org/10.1063/1.1630159 (3 pages) | Cited 9 times

Online Publication Date: 18 November 2003

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Truly bistable twisted nematic liquid crystal display has been fabricated using photoalignment. This display can be switched between the −22.5° and 157.5° twist states by breaking the anchoring condition on one of the substrates. The application of a photoalignable polymer SDA-1 was able to achieve the weak anchoring energy necessary for switching. Both theoretical and experimental results show that this mode has excellent contrast ratio and wide viewing angles. © 2003 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
42.65.Pc Optical bistability, multistability, and switching, including local field effects
61.30.Vx Polymer liquid crystals
42.70.Df Liquid crystals

High-quality-factor and small-mode-volume hexapole modes in photonic-crystal-slab nanocavities

Han-Youl Ryu, Masaya Notomi, and Yong-Hee Lee

Appl. Phys. Lett. 83, 4294 (2003); http://dx.doi.org/10.1063/1.1629140 (3 pages) | Cited 62 times

Online Publication Date: 18 November 2003

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Using finite-difference time-domain calculations, we investigate the hexapole mode of photonic-crystal-slab modified triangular single-defect cavity structures as a good candidate for a high-quality factor (Q) and small-mode volume (V) resonant mode. Structural parameters are optimized to obtain very large Q of even higher than 2×106 with small effective V of the order of cubic wavelength in material, the record value of theoretical Q/V. It is found, by the Fourier-space investigation of resonant modes, that such a high Q from the hexapole mode is achieved due both to the cancellation mechanism related to hexagonally symmetric whispering-gallery-mode distribution and to the mode delocalization mechanism. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
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Comparison between the ultraviolet emission from pulsed microhollow cathode discharges in xenon and argon

Isfried Petzenhauser, Leopold D. Biborosch, Uwe Ernst, Klaus Frank, and Karl H. Schoenbach

Appl. Phys. Lett. 83, 4297 (2003); http://dx.doi.org/10.1063/1.1626020 (3 pages) | Cited 9 times

Online Publication Date: 18 November 2003

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We measured the dynamic I–V characteristics and vacuum ultraviolet (VUV) emission lines of the second continuum in xenon (170 nm) and argon (130.5 nm) from pulsed microhollow cathode discharges (MHCD). For pulse lengths between 1 and 100 μs the dynamic I–V characteristics are similar in both inert gases. Only the time variation of the VUV emission line at 170 nm for xenon can be related to the dimer excited states. In argon the energy transfer between the Ar2∗ dimers and the oxygen impurity atoms is responsible for a qualitatively different time behavior of the resonance line at 130.5 nm. Consequently, the relative VUV efficiency reveals an inverse dependence on the electrical pulse lengths for the MHCD in xenon and argon, respectively. © 2003 American Institute of Physics.
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52.80.Hc Glow; corona
52.80.Yr Discharges for spectral sources (including inductively coupled plasma)
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Enhancement of room-temperature photoluminescence in InAs quantum dots

W. Lu, Y. L. Ji, G. B. Chen, N. Y. Tang, X. S. Chen, S. C. Shen, Q. X. Zhao, and M. Willander

Appl. Phys. Lett. 83, 4300 (2003); http://dx.doi.org/10.1063/1.1623324 (3 pages) | Cited 14 times

Online Publication Date: 18 November 2003

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We report pronounced enhancement of room-temperature photoluminescence up to 80-fold induced by proton implantation and the rapid thermal annealing process in a multilayer InAs/GaAs quantum-dot structure. This effect is studied by a combination of material methods and resulted from both proton passivation and carrier capture enhancement effects. The maximum photoluminescence peak shift is about 23 meV, resulting from the intermixing of quantum dots. Linear dependence behavior as observed for both the nonradiative recombination time and carrier relaxation time on the ion-implantation dose. Maximum enhancement of the photoluminescence is observed for a proton implantation dose of 1.0×1014 cm−2 followed by rapid thermal annealing at 700 °C. These effects will be useful for quantum dot optoelectronic devices. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors

Observation of a pseudogap at terahertz frequencies in the ferromagnetic metallic phase of La2−2xSr1+2xMn2O7 (x = 0.3)

Kouhei Takahashi, Noriaki Kida, and Masayoshi Tonouchi

Appl. Phys. Lett. 83, 4303 (2003); http://dx.doi.org/10.1063/1.1630152 (3 pages) | Cited 2 times

Online Publication Date: 18 November 2003

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We have directly measured the low-energy (0.5–3 meV) complex optical spectra of magnetoresistive La2−2xSr1+2xMn2O7 (x = 0.3) thin films by using THz time-domain spectroscopy. a-axis oriented thin films of La2−2xSr1+2xMn2O7 (x = 0.3) were epitaxially grown on MgO(100) substrates by pulsed laser deposition technique. The films showed paramagnetic insulator to ferromagnetic metal transition at 240 K. In the ferromagnetic metallic phase, we found that the real part of the optical conductivity spectrum exhibits a clear gap signature around 2 meV, which infringes the Drude-like behavior as expected from the electronic and magnetic properties. This provides an optical identification of a pseudogap in La2−2xSr1+2xMn2O7 (x = 0.3). © 2003 American Institute of Physics.
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75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
72.60.+g Mixed conductivity and conductivity transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Coordination and interface analysis of atomic-layer-deposition Al2O3 on Si(001) using energy-loss near-edge structures

K. Kimoto, Y. Matsui, T. Nabatame, T. Yasuda, T. Mizoguchi, I. Tanaka, and A. Toriumi

Appl. Phys. Lett. 83, 4306 (2003); http://dx.doi.org/10.1063/1.1629397 (3 pages) | Cited 25 times

Online Publication Date: 18 November 2003

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The coordination and interface of Al2O3 formed on Si(001) by atomic layer deposition (ALD) were studied using electron energy-loss spectroscopy in a transmission electron microscope. Al energy-loss near-edge structures (ELNESs) were interpreted using first-principles calculations. The Al L23 ELNESs show two peaks at 78.2 and 79.7 eV, which originate from tetrahedrally and octahedrally coordinated aluminum, respectively. The depth profile of coordination in ALD Al2O3/Si was investigated. While both tetrahedrally and octahedrally coordinated Al atoms exist in the ALD Al2O3, the former is dominant near the interface. Aluminum silicate was detected near the interface, and it may cause the difference in aluminum coordination. © 2003 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
79.20.Uv Electron energy loss spectroscopy
68.37.Lp Transmission electron microscopy (TEM)
68.55.-a Thin film structure and morphology

Low-density polymer thin film formation in supercritical carbon dioxide

Tadanori Koga, Y.-S. Seo, J. L. Jerome, S. Ge, M. H. Rafailovich, J. C. Sokolov, B. Chu, O. H. Seeck, M. Tolan, and R. Kolb

Appl. Phys. Lett. 83, 4309 (2003); http://dx.doi.org/10.1063/1.1629799 (3 pages) | Cited 9 times

Online Publication Date: 18 November 2003

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We report a method for producing stable low-density polymer films by using supercritical carbon dioxide (scCO2). Two different molecular weight polystyrene films with various thicknesses were exposed to scCO2 along the density fluctuation ridge in P–T phase diagram. The swollen structures could be then frozen by flash evaporation of CO2 without forming additional voids. X-ray reflectivity data clearly showed that exposure to scCO2 could be used to produce uniform low-density films of about 2Rg thick or less, where Rg is radius of polymer gyration. © 2003 American Institute of Physics.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.55.-a Thin film structure and morphology
61.41.+e Polymers, elastomers, and plastics

Coordination of boron and phosphorous in borophosphosilicate glasses

R. Carboni, G. Pacchioni, M. Fanciulli, A. Giglia, N. Mahne, M. Pedio, S. Nannarone, and F. Boscherini

Appl. Phys. Lett. 83, 4312 (2003); http://dx.doi.org/10.1063/1.1629147 (3 pages) | Cited 9 times

Online Publication Date: 18 November 2003

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We report boron K-edge x-ray absorption near-edge structure measurements on borophosphosilicate glasses and density functional theory calculations aimed at determining the most stable local geometries for boron and phosphorous. We demonstrate that phosphorous induces a modification in the local structure of boron, from a trigonal to a tetrahedral geometry. The microscopic mechanisms involved are discussed. © 2003 American Institute of Physics.
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61.43.Fs Glasses
78.70.Dm X-ray absorption spectra
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.23.Cq Amorphous semiconductors, metallic glasses, glasses

Ion beam-induced anisotropic plastic deformation at 300 keV

T. van Dillen, A. Polman, C. M. van Kats, and A. van Blaaderen

Appl. Phys. Lett. 83, 4315 (2003); http://dx.doi.org/10.1063/1.1629793 (3 pages) | Cited 34 times

Online Publication Date: 18 November 2003

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Contrary to earlier predictions, ion irradiation at energies as low as 300 keV causes dramatic anisotropic plastic deformation of silica glass. Spherical colloidal silica particles with diameters of 125, 305, and 1030 nm were irradiated with Xe ions at energies in the range 0.3–4.0 MeV at temperatures between 85 and 380 K. Irradiation-induced anisotropic plastic deformation changes the colloid shape from spherical into oblate ellipsoidal at a rate that strongly increases with ion energy. At a fixed fluence, the transverse diameter increases with electronic energy loss. Even at an energy as low as 300 keV large particle anisotropy was found (size aspect ratio of 1.43 at 1×1015 cm−2). The transverse plastic strain gradually decreases with increasing irradiation temperature: it decreases by a factor 4.5 between 85 and 380 K. The data are in agreement with a viscoelastic thermal spike model for anisotropic deformation. © 2003 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.82.Ms Insulators
81.05.Kf Glasses (including metallic glasses)
62.20.F- Deformation and plasticity
61.43.Fs Glasses
81.40.Lm Deformation, plasticity, and creep
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.40.Jj Elasticity and anelasticity, stress-strain relations

Doped thin films of two organic molecules for light-emitting diodes

Umberto Giovanella, Chiara Botta, Mariacecilia Pasini, William Porzio, and Silvia Destri

Appl. Phys. Lett. 83, 4318 (2003); http://dx.doi.org/10.1063/1.1630156 (3 pages)

Online Publication Date: 18 November 2003

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The photoluminescence and electroluminescence of doped organic materials are reported for thin films prepared by ultrahigh-vacuum coevaporation and by spin coating from solution of two emitting molecules. For both films, efficient energy transfer from the donor to the acceptor molecules is observed without relevant dopant segregation for molar concentrations up to 10%. In spin-coated films the energy transfer from the matrix to the dopant is due to purely resonant energy transfer processes while the cosublimated films show the presence of additional thermally activated hopping processes. Light-emitting diodes fabricated with coevaporated films yield electroluminescence with higher efficiency and stability. © 2003 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
78.55.Kz Solid organic materials
78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices

Smooth relaxed Si0.75Ge0.25 layers on Si(001) via in situ rapid thermal annealing

S. Hong, Y. L. Foo, K. A. Bratland, T. Spila, K. Ohmori, M. R. Sardela, J. E. Greene, and E. Yoon

Appl. Phys. Lett. 83, 4321 (2003); http://dx.doi.org/10.1063/1.1629792 (3 pages) | Cited 6 times

Online Publication Date: 18 November 2003

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Atomically flat, fully strained Si1−xGex layers with thicknesses ranging from 8 to 180 nm were grown on Si(001) at 450 °C by gas-source molecular beam epitaxy from Ge2H6/Si2H6 mixtures. We show that smooth, relaxed alloy layers are obtained, without the necessity of using several-microns-thick compositionally graded layers, via in situ rapid thermal annealing of fully strained Si1−xGex(001) layers at 1000 °C for 10 s. Relaxed Si0.75Ge0.25(001) layers with thicknesses of 100–180 nm were found to have surface widths of ≃5 nm, comparable to the best results obtained using thick graded buffer layers. © 2003 American Institute of Physics.
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81.05.Hd Other semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Cc Kinetics of defect formation and annealing
68.55.-a Thin film structure and morphology

Thermal stability of internal gettering of iron in silicon and its impact on optimization of gettering

Peng Zhang, Hele Väinölä, Andrei A. Istratov, and Eicke R. Weber

Appl. Phys. Lett. 83, 4324 (2003); http://dx.doi.org/10.1063/1.1630158 (3 pages) | Cited 7 times

Online Publication Date: 18 November 2003

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The redissolution behavior of gettered iron was studied in p-type Czochralski-grown silicon with a doping level of 2.5×1014 cm−3 and an oxide precipitate density of 5×109 cm−3. The concentrations of interstitial iron and iron–boron pairs were measured by deep level transient spectroscopy. It was found that the dependence of redissolved iron concentration on annealing time can be fitted by the function C(t) = C0[1−exp(−t/τdiss)], and the dissolution rate τdiss−1 has an Arrhenius-type temperature dependence of τdiss−1 = 4.01×104×exp[−(1.47±0.10) eV/kBT] s−1. Based on this empirical equation, we predict how stable the gettered iron is during different annealing sequences and discuss implications for optimization of internal gettering. © 2003 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
81.05.Cy Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
81.10.Fq Growth from melts; zone melting and refining

In-plane polarization anisotropy and polarization rotation for M-plane GaN films on LiAlO2

Pranob Misra, Yue Jun Sun, Oliver Brandt, and Holger T. Grahn

Appl. Phys. Lett. 83, 4327 (2003); http://dx.doi.org/10.1063/1.1630168 (3 pages) | Cited 11 times

Online Publication Date: 18 November 2003

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We investigate the dependence of the transmittance spectra of strained M-plane GaN films on the angle of the linear in-plane polarization, with the c axis of the underlying wurtzite crystal structure in the film plane. Because of the reduced in-plane symmetry and the large in-plane anisotropic strain, the transmission spectra for an arbitrary in-plane polarization angle can be directly derived from two transitions with polarizations parallel and perpendicular to the c axis. Since the energy gap for these two polarizations is shifted by more than 50 meV, the M-plane GaN film becomes dichroic, resulting in a polarization rotation after transmission for energies between the two gaps for an initial angle of 45° by as much as 40° towards the c axis. © 2003 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.Ek Optical activity
78.40.Fy Semiconductors
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
71.20.Nr Semiconductor compounds

Patterning-based investigation of the length-scale dependence of the surface evolution during multilayer epitaxial growth

S. Shah, T. J. Garrett, K. Limpaphayom, T. Tadayyon-Eslami, H. C. Kan, and R. J. Phaneuf

Appl. Phys. Lett. 83, 4330 (2003); http://dx.doi.org/10.1063/1.1630170 (3 pages) | Cited 4 times

Online Publication Date: 18 November 2003

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We describe an investigation of the lateral length scale dependence of the evolution of topographical corrugations during multilayer molecular beam epitaxial growth in the GaAs/AlAs multilayer system. By patterning the substrate at series of well-defined spatial periods, we are able to study selectively the changes which occur as a function of lateral period over a wide range of corrugation amplitudes. A critical pattern period, which increases monotonically with thickness, separates an initial long spatial period regime where roughness is amplified, from a later, short spatial period regime in which the topography of the growing surface smoothes out. © 2003 American Institute of Physics.
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68.65.Ac Multilayers
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.07.-b Nanoscale materials and structures: fabrication and characterization
68.47.Fg Semiconductor surfaces
81.05.Ea III-V semiconductors
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Identification of a Br-correlated bandgap state in GaAs by radiotracer spectroscopy

F. Albrecht, G. Pasold, J. Grillenberger, N. Achtziger, W. Witthuhn, M. Risse, R. Vianden, and M. Dietrich

Appl. Phys. Lett. 83, 4333 (2003); http://dx.doi.org/10.1063/1.1629370 (3 pages)

Online Publication Date: 18 November 2003

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A deep energy level of bromine in the bandgap of GaAs was determined by means of Radiotracer deep-level transient spectroscopy (DLTS) measurements. For this purpose, the radioactive isotope 77Br was implanted in p-type as well as in n-type GaAs. In the course of repeated DLTS measurements at n-type GaAs, the spectra are dominated by the occurrence of one bandgap state with the trap parameters Et = EC−0.45(2) eV and σ = 2×10−14 cm2. This level vanishes on time scales of the nuclear half-life of the elemental transmutation from 77Br to 77Se (T1/2 = 57 h). Thereby, a definite correlation can be drawn between the observed bandgap state and a Br-correlated defect. © 2003 American Institute of Physics.
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71.55.Eq III-V semiconductors
71.20.Nr Semiconductor compounds

Characteristics of SiO2/n-GaN interfaces with β-Ga2O3 interlayers

Yoshitaka Nakano, Tetsu Kachi, and Takashi Jimbo

Appl. Phys. Lett. 83, 4336 (2003); http://dx.doi.org/10.1063/1.1629371 (3 pages) | Cited 15 times

Online Publication Date: 18 November 2003

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We report on the characteristics of SiO2/n-GaN metal-oxide-semiconductor (MOS) structures with β-Ga2O3 interlayers. β-Ga2O3 15 nm thick was grown by dry oxidation at 800 °C for 6 h, and 100-nm-thick SiO2 was then deposited by sputtering. Capacitance–voltage measurements show a low interface trap density of ∼ 3.9×1010 eV−1 cm−2, probably indicating an unpinning of the surface Fermi level. Additionally, current–voltage measurements display a low leakage current of ∼1.2 μA/cm2 at a gate voltage of +20 V, regardless of rough oxide surface, as confirmed by atomic force microscopy observations. Thus, the stacked SiO2/β-Ga2O3 insulator is found to improve both the electrical interface properties and the gate dielectric characteristics of the GaN MOS structures. © 2003 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Mq Oxidation
81.15.Cd Deposition by sputtering

In-plane strain fluctuation in strained-Si/SiGe heterostructures

K. Sawano, S. Koh, Y. Shiraki, N. Usami, and K. Nakagawa

Appl. Phys. Lett. 83, 4339 (2003); http://dx.doi.org/10.1063/1.1629142 (3 pages) | Cited 27 times

Online Publication Date: 18 November 2003

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In-plane strain fluctuation in the strained-Si/relaxed-SiGe heterostructure was studied by micro-Raman spectroscopy. It was found that misfit dislocation, which is necessarily induced by strain relaxation of SiGe buffer layers, caused micrometer-scale inhomogeneous strain field in the strained-Si layer as well as SiGe buffer, which may degrade device performance. After annealing, the fluctuation was found to be enhanced due to partial strain relaxation of strained Si, particularly in the region where tensile strain was relatively high before annealing. From homoepitaxial growth of SiGe on planarized SiGe buffer layers, it was confirmed that the growth rate also fluctuated laterally, in correspondence with the in-plane strain variation. © 2003 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
61.72.Cc Kinetics of defect formation and annealing
68.55.A- Nucleation and growth

Electronic structure of pentacene adsorbates on Au(111) surfaces

Taku Suzuki, Mitsunori Kurahashi, Xin Ju, and Yasushi Yamauchi

Appl. Phys. Lett. 83, 4342 (2003); http://dx.doi.org/10.1063/1.1630161 (3 pages) | Cited 9 times

Online Publication Date: 18 November 2003

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The electronic structure of pentacene deposited on a Au(111) substrate in the initial stage of growth was investigated using metastable deexcitation spectroscopy. The occupation of the pentacene π∗ 4b1u orbital, which corresponds to the lowest unoccupied molecular orbital of the gas phase species, was found at the Fermi level. The donation and backdonation-type interactions between the pentacene adsorbate and the Au surface are discussed. © 2003 American Institute of Physics.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.43.Fg Adsorbate structure (binding sites, geometry)
73.20.At Surface states, band structure, electron density of states

Field-effect transistors on tetracene single crystals

R. W. I. de Boer, T. M. Klapwijk, and A. F. Morpurgo

Appl. Phys. Lett. 83, 4345 (2003); http://dx.doi.org/10.1063/1.1629144 (3 pages) | Cited 138 times

Online Publication Date: 18 November 2003

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We report on the fabrication and electrical characterization of field-effect transistors at the surface of tetracene single crystals. We find that the mobility of these transistors reaches the room-temperature value of 0.4 cm2/V s. The nonmonotonous temperature dependence of the mobility, its weak gate voltage dependence, as well as the sharpness of the subthreshold slope, confirm the high quality of single-crystal devices. This is due to the fabrication process that does not substantially affect the crystal quality. © 2003 American Institute of Physics.
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85.65.+h Molecular electronic devices
85.30.Tv Field effect devices
72.80.Le Polymers; organic compounds (including organic semiconductors)

Real-time observation of the energy band diagram during microcrystalline silicon p–i interface formation

Hiroyuki Fujiwara, Michio Kondo, and Akihisa Matsuda

Appl. Phys. Lett. 83, 4348 (2003); http://dx.doi.org/10.1063/1.1631058 (3 pages) | Cited 3 times

Online Publication Date: 18 November 2003

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We have performed real-time infrared attenuated total reflection spectroscopy to characterize free-carrier absorption during microcrystalline silicon (μc-Si:H) p–i interface formation. In the μc-Si:H i-layer growth on the p layer, a free-carrier concentration in the p layer showed a large variation, in accordance with a built-in potential present at the p/i interface. We demonstrate that real-time observation of the energy band diagram is possible during semiconductor thin-film growth by employing free carriers in a doped layer as a probe. © 2003 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
68.35.Ct Interface structure and roughness
78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators
71.20.Mq Elemental semiconductors
78.47.-p Spectroscopy of solid state dynamics
68.55.-a Thin film structure and morphology

Stress-induced effects on depletion-layer capacitance of metal–oxide–semiconductor capacitors

Kazunori Matsuda and Yozo Kanda

Appl. Phys. Lett. 83, 4351 (2003); http://dx.doi.org/10.1063/1.1630166 (3 pages) | Cited 8 times

Online Publication Date: 18 November 2003

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Depletion-layer capacitance of n-type metal–oxide–semiconductor capacitors is investigated under a uniaxial 〈110〉 stressed condition, by means of a high-frequency sweep measurement at room temperature. Abrupt large shifts of the depletion-layer capacitance by the stress are observed. Gauge factors of the effects are approximately 13–33 at 500 ppm strain, which are almost comparable with the piezoresistance effect, and have an opposite sign in tension and compression. The capacitance shifts could be explained with the intrinsic Fermi level which lifts and drops by a change in the ratio of the density-of-states effective masses of holes to electrons due to the band splitting. © 2003 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
85.30.Tv Field effect devices
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
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