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9 Jun 2003

Volume 82, Issue 23, pp. 4011-4195

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Appl. Phys. Lett. 82, 4160 (2003); http://dx.doi.org/10.1063/1.1580641 (3 pages)

Eva M. Höhberger, Tomas Krämer, Werner Wegscheider, and Robert H. Blick
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AlGaInP/mirror/Si light-emitting diodes with vertical electrodes by wafer bonding

R. H. Horng, S. H. Huang, D. S. Wuu, and C. Y. Chiu

Appl. Phys. Lett. 82, 4011 (2003); http://dx.doi.org/10.1063/1.1579132 (3 pages) | Cited 4 times

Online Publication Date: 2 June 2003

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In a previous study, we reported a highly efficient AlGaInP light-emitting diode (LED) with a Au/AuBe/SiO2/Si mirror substrate (MS) fabricated by wafer bonding, where a planar electrode structure is used. In view of the more efficient epilayer area utilized, AlGaInP/mirror/barrier/Si LEDs with vertical electrodes are proposed in this work. A variety of barrier layers (Pt/Ti, TaN/Ta, and TiN/Ti) have been incorporated into the mirror structure. The mirror quality after bonding is a confirmed key issue in obtaining vertical MS–LEDs with high brightness. It is found that AuBe thickness has a large effect on the final MS–LED performance due to the difference in the interdiffusion of Be atoms in each mirror structure. The diffusion of excess Be atoms diffusing to the mirror side results in a rougher surface and inferior reflectivity. The luminance intensity of an AlGaInP LED chip (626 nm) with an optimum AuBe thickness can reach a maximum of ∼ 165 mcd at 20 mA with a forward voltage of 2.1 V. After encapsulation into lamps, the peak power efficiency can reach 21.7%, which corresponds to a 9 mW output at 20 mA. Therefore, the MS structure can be extended to fabricate high-brightness AlGaInP LEDs on Si with conventional vertical electrodes. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
68.35.Fx Diffusion; interface formation
78.66.Fd III-V semiconductors
78.66.Db Elemental semiconductors and insulators

Ultrafast sampling measurements using the photomodulated kinetic inductance in high-Tc superconductors

C. J. Stevens, G. Bianchi, and J. F. Ryan

Appl. Phys. Lett. 82, 4014 (2003); http://dx.doi.org/10.1063/1.1576905 (3 pages) | Cited 2 times

Online Publication Date: 2 June 2003

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We provide a demonstration of ultrafast sampling measurements using the photokinetic effect in high-Tc superconductors to observe fast electrical signals in and rf resonator structure. We observe direct mixing of an applied optical sampling pulse with an ultrafast electrical signal capacitatively coupled to the sampling microbridge. The structures used here are 10 μm wide bridges lithographically defined in thin Tl2Ba2CaCu2O10 films. The time resolution and sensitivity of the technique are evaluated and the effects of bias currents on signal strengths are explored. © 2003 American Institute of Physics.
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06.60.Jn High-speed techniques (microsecond to femtosecond)
42.79.-e Optical elements, devices, and systems
74.78.-w Superconducting films and low-dimensional structures
85.25.-j Superconducting devices
74.72.-h Cuprate superconductors

Room-temperature low-voltage electroluminescence in amorphous carbon nitride thin films

R. Reyes, C. Legnani, P. M. Ribeiro Pinto, M. Cremona, P. J. G. de Araújo, and C. A. Achete

Appl. Phys. Lett. 82, 4017 (2003); http://dx.doi.org/10.1063/1.1581000 (3 pages) | Cited 17 times

Online Publication Date: 2 June 2003

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White-blue electroluminescent emission with a voltage bias less than 10 V was achieved in rf sputter-deposited amorphous carbon nitride (a-CN) and amorphous silicon carbon nitride (a-SiCN) thin-film-based devices. The heterojunction structures of these devices consist of: Indium tin oxide (ITO), used as a transparent anode; amorphous carbon film as an emission layer, and aluminum as a cathode. The thickness of the carbon films was about 250 Å. In all of the produced diodes, a stable visible emission peaked around 475 nm is observed at room temperature and the emission intensity increases with the current density. For an applied voltage of 14 V, the luminance was about 3 mCd/m2. The electroluminescent properties of the two devices are discussed and compared. © 2003 American Institute of Physics.
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78.66.Nk Insulators
78.60.Fi Electroluminescence
61.43.Er Other amorphous solids

Temperature transients and thermal properties of GaAs/AlGaAs quantum-cascade lasers

A. J. Borak, C. C. Phillips, and C. Sirtori

Appl. Phys. Lett. 82, 4020 (2003); http://dx.doi.org/10.1063/1.1582374 (3 pages) | Cited 9 times

Online Publication Date: 2 June 2003

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The use of a gated interband photoluminescence technique has allowed the study of the temperature transients in the active volume of a quantum-cascade laser during pulsed operation. The active region was found to rise by ∼40 K during a 150 ns current pulse, returning to the heat-sink temperature in ∼500 ns. The measured temperature transients were fitted, using a one-dimensional heat diffusion model, giving a value of kAR = 1.36±0.2 W cm−1 K−1 for the active region thermal conductivity, at 30 K. This is approximately ten times lower than literature values for bulk AlGaAs alloys of equivalent composition and has significant implications on the prospects for high-power continuous-wave device operation. © 2003 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
78.55.Cr III-V semiconductors

Polymer laser fabricated by a simple micromolding process

Justin R. Lawrence, Graham A. Turnbull, and Ifor D. W. Samuel

Appl. Phys. Lett. 82, 4023 (2003); http://dx.doi.org/10.1063/1.1579858 (3 pages) | Cited 41 times

Online Publication Date: 2 June 2003

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We report polymer distributed feedback lasers fabricated using solvent-assisted microcontact molding. The poly[2-methoxy-5-(3,7-dimethyloctyloxy) paraphenylenevinylene] film is patterned by placing it in conformal contact with an elastomeric mould inked with a suitable solvent. When the resulting microstructured film is pumped with the 532 nm pulsed output of a microchip laser, we observe lasing above a threshold pump energy of 225 nJ. Above threshold the emission narrows to a linewidth of less than 0.6 nm at a wavelength of 638 nm. This micromolding technique may find application to a wide range of wavelength-scale microstructured organic photonic devices. © 2003 American Institute of Physics.
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42.70.Hj Laser materials
42.55.Px Semiconductor lasers; laser diodes
81.10.Fq Growth from melts; zone melting and refining
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.86.+b Optical workshop techniques
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
42.70.Jk Polymers and organics
42.60.By Design of specific laser systems

Electrically tunable waveguide laser based on ferroelectric liquid crystal

Masahiro Kasano, Masanori Ozaki, Katsumi Yoshino, Dirk Ganzke, and Wolfgang Haase

Appl. Phys. Lett. 82, 4026 (2003); http://dx.doi.org/10.1063/1.1580992 (3 pages) | Cited 18 times

Online Publication Date: 2 June 2003

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Laser action in a waveguide configuration has been demonstrated in a planar alignment cell of dye-doped chiral smectic liquid-crystal mixtures with a short pitch helical structure. In this configuration, doped dye can effectively be excited by a pump beam illuminating perpendicularly the helical axis and the laser light emitted along the helical axis propagates in the waveguide. Lasing wavelength can be tuned by adjusting the periodicity of the helical pitch upon applying the electric field. © 2003 American Institute of Physics.
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42.55.Mv Dye lasers
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
61.30.-v Liquid crystals

Monte Carlo simulation of tunable mid-infrared emission from coupled Wannier–Stark ladders in semiconductor superlattices

M. Manenti, F. Compagnone, A. Di Carlo, P. Lugli, G. Scamarcio, and F. Rizzi

Appl. Phys. Lett. 82, 4029 (2003); http://dx.doi.org/10.1063/1.1581382 (3 pages) | Cited 7 times

Online Publication Date: 2 June 2003

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We present a theoretical and experimental study on the mid-infrared electroluminescence associated with transitions between electric-field-induced conduction states, forming the Wannier–Stark ladder, in strongly coupled GaAs/AlAs superlattices. The interwell and intrawell radiative transitions in the whole range of electric fields from the moderate localization to the resonance-induced delocalization regimes have been experimentally investigated. Monte Carlo simulations show a very good agreement between experimental and theoretical electroluminescence spectra. Results show that the application of an electric field in the range from 100 to 250 kV/cm shifts the emission peak, related with interwell diagonal transitions between Stark-localized ground states of two adjacent wells, up to the limit corresponding to the merging of this electroluminescence peak with the intersubband emission between excited and ground state of the same well. The theoretical investigation indicates that interwell scattering via LO phonons is responsible for the population of the excited state of the ladder. © 2003 American Institute of Physics.
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78.60.Fi Electroluminescence
02.70.Uu Applications of Monte Carlo methods
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Photoluminescence enhancement of colloidal quantum dots embedded in a monolithic microcavity

Carl B. Poitras, Michal Lipson, Hui Du, Megan A. Hahn, and Todd D. Krauss

Appl. Phys. Lett. 82, 4032 (2003); http://dx.doi.org/10.1063/1.1581007 (3 pages) | Cited 28 times

Online Publication Date: 2 June 2003

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We demonstrate an enhancement of the spontaneous emission from colloidal CdSe quantum dots embedded in a half-wavelength one-dimensional cavity. When embedded in the cavity, the emission of the quantum dots is enhanced by a factor of 2.7. We also show a strong amplification by one order of magnitude in the absorption of the CdSe quantum dots due to the cavity effect. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors

Enhanced room-temperature emission in Cr4+ ions containing alumino-silicate glasses

C. Batchelor, W. J. Chung, S. Shen, and A. Jha

Appl. Phys. Lett. 82, 4035 (2003); http://dx.doi.org/10.1063/1.1581374 (3 pages) | Cited 19 times

Online Publication Date: 2 June 2003

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The Bi2O3 modified alumino-silicate glasses, when excited at 800 nm exhibited a broadband emission of Cr4+ in the range of 1.2 to ∼1.6 μm at room temperature. The mean lifetime of (1E−3A2)→3T1 transition in Cr4+-doped glass at RT was as long as ∼426 μs, enabling the realization of both tunable lasers and broadband fiber amplifiers. The Cr4+ emission at RT also showed the dependency on the excitation wavelength and site distribution within the chosen glass host. A photoinduced charge transfer process from the Cr3+ ion into Cr4+ ion appears to be responsible for the excitation of Cr4+. © 2003 American Institute of Physics.
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78.55.Qr Amorphous materials; glasses and other disordered solids
42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Hj Laser materials
42.70.Ce Glasses, quartz

Extremely low threshold-current-density InGaAs quantum-well lasers with emission wavelength of 1215–1233 nm

Nelson Tansu, Jeng-Ya Yeh, and Luke J. Mawst

Appl. Phys. Lett. 82, 4038 (2003); http://dx.doi.org/10.1063/1.1581978 (3 pages) | Cited 31 times

Online Publication Date: 2 June 2003

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Extremely low threshold-current-density In0.4Ga0.6As quantum-well (QW) lasers have been realized in the 1215–1233 nm wavelength regime. The measured room-temperature threshold current density of the InGaAs QW lasers with a cavity length of 1000 μm is only 90 A/cm2 at an emission wavelength of 1233 nm. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
73.63.Hs Quantum wells
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