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9 Aug 1999

Volume 75, Issue 6, pp. 745-878

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Photoconductive detection of millimeter waves using proton implanted GaAs

C. S. Wong, J. M. Dai, and H. K. Tsang

Appl. Phys. Lett. 75, 745 (1999); http://dx.doi.org/10.1063/1.124499 (3 pages) | Cited 1 time

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We show that ion-damaged GaAs may be used to detect millimeter electromagnetic waves in photoconductive sampling gates. The semi-insulating GaAs material which was implanted with a dose of 1014 cm−2 protons at an energy of 200 keV gave a signal to noise improvement of about 11.4 dB when compared with as-grown semi-insulating GaAs. The improvement is in spite of a reduced carrier mobility in the ion-implanted material and is due to the shorter carrier lifetime and formation of ohmic contacts with the ion-damaged semi-insulating GaAs. © 1999 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
61.72.uj III-V and II-VI semiconductors
61.82.Fk Semiconductors
84.40.Ba Antennas: theory, components and accessories
61.80.Jh Ion radiation effects
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.40.Ns Metal-nonmetal contacts

Temperature dependence of the stimulated emission in a conjugated polymer

Ch. Spiegelberg, N. Peyghambarian, and B. Kippelen

Appl. Phys. Lett. 75, 748 (1999); http://dx.doi.org/10.1063/1.124500 (3 pages) | Cited 12 times

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We report measurements of photoluminescence and stimulated emission of poly(2,5bis(2′-ethylhexyloxy)-1,4-phenylenevinylene for temperatures between 15 and 300 K. We show that the threshold for spectral line narrowing depends only slightly on the temperature. The observed decrease of the threshold intensity at lower temperatures can be mainly attributed to an increase of the quantum efficiency. We assign this deviation from the expected behavior for a four-level system to the dominant inhomogeneous broadening. © 1999 American Institute of Physics.
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78.45.+h Stimulated emission
78.66.Qn Polymers; organic compounds
42.70.Hj Laser materials
42.70.Jk Polymers and organics
78.55.Kz Solid organic materials

Influence of electric field on the behavior of Si nanoparticles generated by laser ablation

Junichi Muramoto, Ippei Sakamoto, Yoshiki Nakata, Tatsuo Okada, and Mitsuo Maeda

Appl. Phys. Lett. 75, 751 (1999); http://dx.doi.org/10.1063/1.124501 (3 pages) | Cited 9 times

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The influence of an electric field on particle behavior was investigated to control the transport of Si nanoparticles in a laser ablation plume by an ultraviolet Rayleigh scattering (UV-RS) technique. The majority of the nanoparticles, which could be observed by the UV-RS technique, were transported to the negatively biased electrode, indicating that they were positively charged. The deposition efficiency of nanoparticles onto a substrate was also improved by applying an electric field. © 1999 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.15.Fg Pulsed laser ablation deposition
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Vs Fine-particle systems
61.46.-w Structure of nanoscale materials
78.66.Db Elemental semiconductors and insulators
81.05.Cy Elemental semiconductors

Diffraction from oxide confinement apertures in vertical-cavity lasers

P. A. Roos, J. L. Carlsten, D. C. Kilper, and K. L. Lear

Appl. Phys. Lett. 75, 754 (1999); http://dx.doi.org/10.1063/1.124502 (3 pages) | Cited 3 times

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Direct measurement of scattered fields from oxide confinement apertures in vertical-cavity lasers is presented. Diffraction fringes associated with each transverse lasing mode are detected in the far field from devices with varying oxide aperture dimensions and with quantum efficiencies as high as 48%. The diffracted pattern symmetries match the rectangular symmetry of the oxide apertures present in the devices and fringe locations are compared to Fraunhofer theory. The fraction of power diffracted from the lasing mode remains roughly constant as a function of relative pump rate, but is shown to depend on both transverse mode order and oxide aperture size. © 1999 American Institute of Physics.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.25.Fx Diffraction and scattering

Widely tunable continuous-wave THz laser

Yu. P. Gousev, I. V. Altukhov, K. A. Korolev, V. P. Sinis, M. S. Kagan, E. E. Haller, M. A. Odnoblyudov, I. N. Yassievich, and K.-A. Chao

Appl. Phys. Lett. 75, 757 (1999); http://dx.doi.org/10.1063/1.124503 (3 pages) | Cited 46 times

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We present experimental results on continuous-wave generation of THz radiation by strained Ge and a theoretical model for population inversion of carriers giving rise to the stimulated THz emission. Resonant acceptor states induced by strain and resonance hole scattering under applied electric field are necessary for the inversion. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.05.Cy Elemental semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
71.20.Mq Elemental semiconductors
71.55.Cn Elemental semiconductors
42.50.-p Quantum optics
62.20.F- Deformation and plasticity
72.20.Ht High-field and nonlinear effects
42.60.Fc Modulation, tuning, and mode locking

Improvement of amorphous-carbon active-layer thin-film light-emitting diodes using room-temperature ultrasound treatment

Woo Yeong Cho, Koeng Su Lim, and S. Ostapenko

Appl. Phys. Lett. 75, 760 (1999); http://dx.doi.org/10.1063/1.124504 (3 pages) | Cited 1 time

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Ultrasound treatment (UST) applied at room temperature enhances electroluminescent intensity (maximum at 600 nm) and optical output in thin-film light-emitting diodes with hydrogenated amorphous-carbon as an active layer. This positive UST effect is attributed to a reduction of the diode series resistance caused by a change of the interface and contact resistances. The UST effect is saturated with increase of the ultrasound amplitude. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Db Elemental semiconductors and insulators
78.66.Jg Amorphous semiconductors; glasses
43.35.Ty Other physical effects of sound
81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
73.40.Cg Contact resistance, contact potential
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
62.65.+k Acoustical properties of solids
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants

Optical resonance modes in GaN pyramid microcavities

H. X. Jiang, J. Y. Lin, K. C. Zeng, and W. Yang

Appl. Phys. Lett. 75, 763 (1999); http://dx.doi.org/10.1063/1.124505 (3 pages) | Cited 25 times

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An array of GaN hexagonal pyramids with a side length of 8.0 μm was fabricated by selective epitaxial overgrowth. These microsized pyramids are highly efficient microcavities. Three types of optical resonance modes with mode spacings of 10, 5.0, and 6.0 Å were observed when a single pyramid was pumped optically by an intense ultraviolet laser beam. An optical ray tracing method has been developed for calculating the optical resonance modes inside the pyramid microcavities. It was shown that a single pyramidal cavity can support several different types of optical resonance modes. The calculated mode spacing agrees very well with the observations. The uniqueness and advantages of this class of hexagonal pyramidal microcavities over the other microcavities are discussed. The implications of our finding on the future GaN microcavity light emitters including micro-light-emitting diodes, microcavity lasers, and vertical-cavity-surface emitting lasers are also discussed. © 1999 American Institute of Physics.
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42.55.Sa Microcavity and microdisk lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.15.Dp Wave fronts and ray tracing
42.55.Px Semiconductor lasers; laser diodes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Significant improvement of device durability in organic light-emitting diodes by doping both hole transport and emitter layers with rubrene molecules

Gosuke Sakamoto, Chihaya Adachi, Toshiki Koyama, Yoshio Taniguchi, Charles D. Merritt, Hideyuki Murata, and Zakya H. Kafafi

Appl. Phys. Lett. 75, 766 (1999); http://dx.doi.org/10.1063/1.124506 (3 pages) | Cited 42 times

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We have developed highly durable organic light-emitting diodes. The basic structure of the diodes is anode/hole injection layer/hole transport layer+dopant/emitter layer+dopant/cathode. Both the hole transport and the emitter layers were doped with the highly fluorescent rubrene molecules. With the doping of both layers, 85% of the initial luminance was successively maintained even after 1000 h of continuous operation under constant current driving. Doping of only one of these layers, either the hole transport layer or emitter layer, on the other hand, resulted in shorter lifetime. We mention the possible mechanisms of the doping that enhance the device duration. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds

A photoconductive model for superior GaAs THz photomixers

E. R. Brown

Appl. Phys. Lett. 75, 769 (1999); http://dx.doi.org/10.1063/1.124507 (3 pages) | Cited 33 times

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Theoretical methods are used to evaluate the THz output from photomixer structures consisting of interdigitated electrodes and planar antennas on top of a low-temperature-grown GaAs layer. Consistent with experiment, the THz power from a standard photomixer is found to be limited by low external quantum efficiency (∼1%). This arises primarily from low photoconductive gain, which is attributed to a long transit time (between electrodes) for the majority of photocarriers generated in the structure. The modeling is then applied to an improved structure containing a thinner absorbing layer (≈0.34 μm for λ = 0.85 μmpump) with a dielectric mirror below it to induce resonant-cavity absorption near the surface where the gain is higher. Through increased gain and absorptivity, the model predicts ≈7× greater THz output for the same optical pump power. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
85.30.De Semiconductor-device characterization, design, and modeling
85.60.Bt Optoelectronic device characterization, design, and modeling
72.40.+w Photoconduction and photovoltaic effects
73.50.Pz Photoconduction and photovoltaic effects
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