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  • 1
    Digitale Medien
    Digitale Medien
    Nearly 100% internal phosphorescence efficiency in an organic light-emitting device (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5048-5051 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We demonstrate very high efficiency electrophosphorescence in organic light-emitting devices employing a phosphorescent molecule doped into a wide energy gap host. Using bis(2-phenylpyridine)iridium(III) acetylacetonate [(ppy)2Ir(acac)] doped into 3-phenyl-4(1′-naphthyl)-5-phenyl-1,2,4-triazole, a maximum external quantum efficiency of (19.0±1.0)% and luminous power efficiency of (60±5) lm/W are achieved. The calculated internal quantum efficiency of (87±7)% is supported by the observed absence of thermally activated nonradiative loss in the photoluminescent efficiency of (ppy)2Ir(acac). Thus, very high external quantum efficiencies are due to the nearly 100% internal phosphorescence efficiency of (ppy)2Ir(acac) coupled with balanced hole and electron injection, and triplet exciton confinement within the light-emitting layer. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1409582
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  • 2
    Digitale Medien
    Digitale Medien
    Electroluminescence mechanisms in organic light emitting devices employing a europium chelate doped in a wide energy gap bipolar conducting host (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8049-8055 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The mechanism for energy transfer leading to electroluminescence (EL) of a lanthanide complex, Eu(TTA)3phen (TTA=thenoyltrifluoroacetone,phen=1,10-phenanthroline), doped into 4,4′-N,N′-dicarbazole-biphenyl (CBP) host is investigated. With the device structure of anode/hole transport layer/Eu(TTA)3phen(1%):CPB/electron transport layer/cathode, we achieve a maximum external EL quantum efficiency (η) of 1.4% at a current density of 0.4 mA/cm2. Saturated red Eu3+ emission based on 5Dx–7Fx transitions is centered at a wavelength of 612 nm with a full width at half maximum of 3 nm. From analysis of the electroluminescent and photoluminescent spectra, and the current density–voltage characteristics, we conclude that direct trapping of holes and electrons and subsequent formation of the excitons occurs on the dopant, leading to high quantum efficiencies at low current densities. With increasing current between 1 and 100 mA/cm2, however, a significant decrease of η along with an increase in CBP host emission is observed. We demonstrate that the decrease in η at high current densities can be explained by triplet–triplet annihilation. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.373496
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  • 3
    Digitale Medien
    Digitale Medien
    Growth of abrupt InGaAs(P)/In(GaAs)P heterointerfaces by gas source molecular beam epitaxy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 201-209 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We demonstrate a novel method for the growth of abrupt InGaAs(P)/In(GaAs)P heterojunctions by gas source molecular beam epitaxy. We find that exposure of freshly grown InP to an As flux during growth interruption between layers of different compositions results in the substitution of surface P atoms and As atoms, thereby generating a strained transition layer at each interface. By assuring a group-III stabilized surface during interruption required to grow InGaAs(P)/In(GaAs)P heterointerfaces, As/P substitution can be avoided, thereby resulting in improved interface quality. Heterointerface abruptness was examined by double-crystal x-ray diffraction and low temperature photoluminescence. The results show that the interfaces grown with the modified switching sequence are considerably more abrupt than those obtained using conventional sequences where As/P interdiffusion extends over several monolayers. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.359370
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  • 4
    Digitale Medien
    Digitale Medien
    Study of InxGa1−xAs/InAsyP1−y structures lattice mismatched to InP substrates (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6229-6234 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Material properties of several lattice-mismatched InxGa1−xAs/InAsyP1−y (0.66〈x〈0.84, 0.29〈y〈0.66) alloys grown on InP substrates are investigated. The lattice constants and compositions were measured using x-ray diffraction and electron probe microanalysis. Photoluminescence, white light transmission, and detector cutoff wavelengths were used to determine the band gap of InxGa1−xAs as a function of In concentration x. The three methods agree to within 3%. The quality of the grown layers was also investigated using these techniques, in addition to cross-section transmission electron microscopy and Nomarsky optical microscopy. The dependence of the experimental measurements of band gap and lattice constant on material composition, measured by electron probe microanalysis, was compared against theoretical values. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.363699
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  • 5
    Digitale Medien
    Digitale Medien
    Evolution of quasi-epitaxial growth of a crystalline organic semiconductor on graphite (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 3223-3225 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have studied the evolution of the growth of a crystalline organic semiconductor thin film using reflection high energy electron diffraction (RHEED). Our results indicate that highly ordered crystalline films of an organic compound; namely 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA), can be grown on graphite by the ultrahigh vacuum process of organic molecular beam deposition even though the crystal structures of the two materials are highly mismatched. The RHEED patterns show the evolution of planar crystal growth from 2 monolayer (∼6 A(ring)) coverage until at least 50 A(ring) as the films are deposited onto substrates cooled to 100 K. At larger film thicknesses, somewhat nonplanar but still crystalline growth occurs. Furthermore, crystalline thin films were obtained independent of growth rate, which was as high as 3.0 A(ring)/s. To our knowledge, this is the first direct experimental evidence of the evolution of growth from monolayer to bulk film coverage into an ordered, quasi-epitaxial structure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.106700
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  • 6
    Digitale Medien
    Digitale Medien
    Low-threshold 1.3-μm wavelength, InGaAsP strained-layer multiple quantum well lasers grown by gas source molecular beam epitaxy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 892-894 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report the growth, by gas source molecular beam epitaxy (GSMBE) of low-threshold 1.3-μm wavelength strained-layer In0.86Ga0.14As0.52P0.48/In0.86Ga0.14 As0.3P0.7 separate confinement heterostructure multiple quantum well lasers. Threshold currents as low as 16 mA were measured for a 390×5-μm ridge laser, and a threshold current density of Jth=490 A/cm2 was achieved for a 1200×5-μm device. Apparently, this is the lowest value of Jth reported to date for 1.3-μm lasers grown by GSMBE, and is comparable to the best devices grown by other techniques such as chemical beam epitaxy and metalorganic vapor phase epitaxy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.112192
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  • 7
    Digitale Medien
    Digitale Medien
    Strain compensated In1−xGaxAs(x〈0.47) quantum well photodiodes for extended wavelength operation (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2263-2265 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The use of highly strained (−2.0%) In0.83Ga0.17As quantum wells for the detection of light to a wavelength of λ∼2.0 μm is reported. Crystal quality for a 50 period multiple quantum well (MQW) detector grown on InP substrates is maintained through strain compensation using tensile strained In0.83Ga0.17P barriers. Transmission electron microscopy and double crystal x-ray diffraction reveal smooth interfaces and no observable defects for In0.83Ga0.17As layers with widths less than 80 Å. Single-pass quantum efficiencies of 30% have been achieved at λ=1.95 μm, using a 75 μm diam MQW, strain-compensated, top illuminated, low dark current (∼250 pA at 20 V) p-i-n detector. The theoretical cutoff wavelength limit for diodes fabricated using this technique is calculated to be λ=2.15 μm. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.121696
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  • 8
    Digitale Medien
    Digitale Medien
    A 2.0 μm cutoff wavelength separate absorption, charge, and multiplication layer avalanche photodiode using strain-compensated InGaAs quantum wells (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2581-2583 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report an avalanche photodiode structure for use at wavelengths as long as 2.1 μm. Light is absorbed in a 100 period structure consisting of In0.83Ga0.17As quantum wells strain compensated by In0.83Ga0.17P barrier layers. Photogenerated electrons are injected into a high field In0.52Al0.48As (ionization rate ratio=0.2) gain region initiating low noise avalanche multiplication. Primary dark currents of ∼5 nA and responsivities of 45 A/W at a wavelength of 1.9 μm are observed. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.123904
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  • 9
    Digitale Medien
    Digitale Medien
    Growth and characterization of small band gap (∼0.6 eV) InGaAsN layers on InP (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1287-1289 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We demonstrate the growth of small band gap (Eg∼0.6 eV) strained and lattice matched single crystal InGaAsN alloys on InP substrates. InGaAsN layers with N concentrations varying from 0.6% to 3.25% were grown by gas source molecular beam epitaxy using a radio frequency plasma nitrogen source. Lattice-matched, 0.5-μm-thick InGaAsN layers with smooth surface morphologies and abrupt interfaces were achieved. Low temperature photoluminescence measurements reveal a band gap emission wavelength of 1.9 μm (at 20 K) for lattice matched InGaAsN (N∼2%). Tensile strained In0.53Ga0.47As/In0.53Ga0.47As0.994N0.006 multiple quantum wells emitting at 1.75 μm at 20 K are also reported. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.123526
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  • 10
    Digitale Medien
    Digitale Medien
    Helium ion-implanted InGaAsP tunnel junction current blocking layers (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 984-986 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We experimentally investigate and model He+-implanted InGaAsP tunnel junctions used for lateral current confinement in vertical-cavity surface-emitting lasers (VCSELs). Prior to implantation, a 56-μm-diameter tunnel junction exhibits a peak-to-valley ratio of 2.2 and a differential resistance of 27 Ω at −2 V. After implantation at a dose of 3.3×1013 cm−2, the current under reverse bias reduces by a factor of 〉107. Placing tunnel junctions close to the laser active region does not degrade the gain in the quantum wells. With He+-implanted tunnel junctions, mirrorless test VCSEL structures up to 50 μm diameter have uniform current distribution across the entire light-emitting apertures. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1498145
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