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24 Jan 2000

Volume 76, Issue 4, pp. 397-519

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Near-field optical spectroscopy using an incoherent light source

L. Aigouy, F. X. Andréani, A. C. Boccara, J. C. Rivoal, J. A. Porto, R. Carminati, J.-J. Greffet, and R. Mégy

Appl. Phys. Lett. 76, 397 (2000); http://dx.doi.org/10.1063/1.125766 (3 pages) | Cited 25 times

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We present a method to perform near-field optical spectroscopy. It consists of an apertureless near-field optical microscope combined with an incoherent light source and a monochromator. We show that the optical response of the tip depends both on the wavelength and the tip apex shape. The experimental optical response of the tips is in good agreement with the predicted theoretical one. The near-field optical spectrum obtained on a gold island in the visible spectrum range (λ = 400–600 nm) is presented and shows that the method is reliable to perform spectroscopic measurements on submicrometer-sized objects. © 2000 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
07.60.Rd Visible and ultraviolet spectrometers

Investigation of polarization-pinning mechanism in deep-line-etched vertical-cavity surface-emitting lasers

L. J. Sargent, J. M. Rorison, M. Kuball, R. V. Penty, I. H. White, S. W. Corzine, M. R. T. Tan, S. Y. Wang, and P. J. Heard

Appl. Phys. Lett. 76, 400 (2000); http://dx.doi.org/10.1063/1.125767 (3 pages) | Cited 7 times

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Recently, it has been shown that the etching of deep trenches in close proximity to GaAs vertical-cavity surface-emitting laser (VCSEL) apertures causes the linearly polarized TE emission to be pinned in a direction parallel to the line etch. In this letter, we show that etching introduces compressive strain or relaxes tensile strain through the creation of free interfaces. An anisotropic variation of strain is the origin of the polarization pinning effect. We report on the enhancement of polarization pinning by postannealing after etching. Photoluminescence and Raman measurements of the VCSEL wafer were taken before and after etching and annealing. The observed shift in the Fabry–Perot mode was used to model the strain, giving 4×108 dyn/cm2, or 0.05%, compressive strain perpendicular to the etch. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems
81.05.Ea III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
81.40.Tv Optical and dielectric properties related to treatment conditions

Solar-blind AlGaN photodiodes with very low cutoff wavelength

D. Walker, V. Kumar, K. Mi, P. Sandvik, P. Kung, X. H. Zhang, and M. Razeghi

Appl. Phys. Lett. 76, 403 (2000); http://dx.doi.org/10.1063/1.125768 (3 pages) | Cited 55 times

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We report the fabrication and characterization of AlxGa1−xN photodiodes (x ∼ 0.70) grown on sapphire by low-pressure metalorganic chemical vapor deposition. The peak responsivity for −5 V bias is 0.11 A/W at 232 nm, corresponding to an internal quantum efficiency greater than 90%. The device response drops four orders of magnitude by 275 nm and remains at low response for the entire near-ultraviolet and visible spectrum. Improvements were made to the device design including a semitransparent Ni/Au contact layer and a GaN:Mg cap layer, which dramatically increased device response by enhancing the carrier collection efficiency. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
85.60.Dw Photodiodes; phototransistors; photoresistors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Doubling the frequency of depleted fundamental waves in periodically poled KTiOPO4

D. Eger, M. B. Oron, A. Bruner, M. Katz, Y. Tzuk, and A. Englander

Appl. Phys. Lett. 76, 406 (2000); http://dx.doi.org/10.1063/1.125769 (3 pages) | Cited 1 time

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Frequency doubling of a diode-pumped Nd:YAG laser in 1 and 2 cm long periodically poled KTiOPO4 wafers has been investigated. Up to 60% doubling efficiency has been achieved. The good agreement obtained between measured results and those calculated by numerical integration of the coupled wave equations demonstrate that the efficiency is limited by the basic process of backconversion and dephasing rather than by thermal effects. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization

Absorbance spectroscopy and identification of valence subband transitions in type-II InAs/GaSb superlattices

Ron Kaspi, Charles Moeller, Andrew Ongstad, Michael L. Tilton, Donald Gianardi, Gregory Dente, and Prabhakara Gopaladasu

Appl. Phys. Lett. 76, 409 (2000); http://dx.doi.org/10.1063/1.125770 (3 pages) | Cited 23 times

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We describe the molecular-beam epitaxy growth, as well as both the structural and optical characterization of a set of InAs/GaSb type-II strained-layer superlattice samples, in which the GaSb layer thickness is systematically increased. Absorbance spectroscopy measurements show well-defined features associated with transitions from the various valence subbands to the lowest conduction subband, and also a significant blueshift of the band edge when the GaSb layers thickness is increased. Empirical pseudopotential method calculations are shown to successfully predict the blueshift and help identify the higher-energy transitions. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
78.30.Fs III-V and II-VI semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Surface treatment of indium tin oxide by SF6 plasma for organic light-emitting diodes

Beomrak Choi, Hyunsik Yoon, and Hong H. Lee

Appl. Phys. Lett. 76, 412 (2000); http://dx.doi.org/10.1063/1.125771 (3 pages) | Cited 35 times

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SF6 plasma treatment of indium tin oxide highly improves the power efficiency and the stability of the organic light-emitting diode based on poly[2-methoxy-5-(2-ethylhexyloxy)-1,4phenylenevinylene]. The treatment leads to a slight reduction in the surface roughness and a decrease in the surface content of Sn. The major effect, however, has to do with the surface incorporation of fluorine. This fluorinated surface improves the hole injection and thus the device performance. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
72.30.+q High-frequency effects; plasma effects
73.50.Mx High-frequency effects; plasma effects
68.35.B- Structure of clean surfaces (and surface reconstruction)

p-GaN surface treatments for metal contacts

Jingxi Sun, K. A. Rickert, J. M. Redwing, A. B. Ellis, F. J. Himpsel, and T. F. Kuech

Appl. Phys. Lett. 76, 415 (2000); http://dx.doi.org/10.1063/1.125772 (3 pages) | Cited 86 times

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The chemical bonding and electronic properties of wet, chemically treated p-GaN surfaces were studied using synchrotron radiation photoemission spectroscopy. Chlorine-based chemical bonding was identified on the conventional HCl-treated p-GaN surface, which is associated with a shift of the surface Fermi level toward the conduction band edge by ∼0.9 eV with respect to the thermally cleaned surface. Compared to the HCl-treated surface, the surface Fermi level on the KOH-treated surface lies about ∼1.0 eV closer to the valence band edge, resulting in a much smaller surface barrier height to p-type materials than the HCl-treated surface. The smaller surface barrier height to p-GaN after KOH treatment can lead to a lower contact resistivity and can play an important role in lowering the metal contact resistivity to p-GaN. © 2000 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors
73.40.Ns Metal-nonmetal contacts
68.35.Dv Composition, segregation; defects and impurities
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
73.40.Cg Contact resistance, contact potential
73.20.At Surface states, band structure, electron density of states
79.60.Dp Adsorbed layers and thin films
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