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  • 1
    Electronic Resource
    Electronic Resource
    Fourier transform infrared study of tricarbon hydride radicals trapped in Ar at 10 K (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1583-1596 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational spectra of tricarbon hydride radicals formed by trapping the products of the vacuum ultraviolet photolysis of methylacetylene and various deuterated isotopomers in argon at 10 K have been investigated by Fourier transform spectroscopy in the range 200–3400 cm−1. Supplementary studies have examined the photolysis products of allene as well as C3H6 and C3D6, cyclopropane. The results reveal new information on the vibrations of C3H; five C3H2 isomers, cyclopropenylidene, vinylidenecarbene, triplet propargylene, trans- and cis-propenediylidene; two C3H3 isomers, propargyl and cyclopropenyl; and C3H5, allyl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459137
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of temperature and oxygen concentration on the photoluminescence of epitaxial metalorganic vapor-phase epitaxy GaAs:O (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1175-1179 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Semi-insulating epitaxial GaAs:O prepared in a metalorganic vapor-phase epitaxy growth process using DEALO [(C2H5)2AlOC2H5] as the oxygen source has been characterized by temperature-dependent (12–300 K) photoluminescence. Oxygen-related deep level photoluminescence bands were detected at ∼0.8 and ∼1.1 eV. The relative intensities of the two bands were sensitive to both oxygen concentration and temperature. At a given temperature, an increase in oxygen concentration led to an increase in the intensity of the lower energy band relative to the higher energy band. A similar effect occurred at a given oxygen concentration as the temperature was raised. Band edge luminescence was also measured and was observed to quench when the oxygen concentration exceeded ∼1018 cm−3. The results indicate that oxygen is incorporated differently in epitaxial GaAs than in bulk GaAs. We propose that the difference is due to the incorporation of Al when DEALO is used in the growth of epitaxial GaAs:O. We suggest equally plausible microscopic models, based on the number of nearest-neighbor Al associated with O and multiple charge states, to explain the properties of the oxygen-related photoluminescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357842
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  • 3
    Electronic Resource
    Electronic Resource
    Acceptor diffusion and segregation in (AlxGa1−x)0.5In0.5P heterostructures (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4891-4899 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Acceptor segregation is investigated as a function of compositional difference, Δx, between adjacent layers in (AlxGa1−x)0.5In0.5P heterostructures. Magnesium, Zn, Be, and Mn acceptor species are all shown to segregate out of the high band gap Al-rich (AlxGa1−x)0.5In0.5P layers and into the low band gap Al-poor (AlxGa1−x)0.5In0.5P layers during high temperature epitaxial growth of such heterostructures. The observed acceptor segregation appears to be independent of growth method or dopant incorporation method (metalorganic chemical vapor deposition, gas source molecular-beam epitaxy, or ion implantation), and increases with increasing compositional difference between adjacent (AlxGa1−x)0.5In0.5P layers. A theoretical model is developed to describe acceptor segregation based on charge separation and the resulting electric field across the heterointerface, and the resulting acceptor segregation is shown to vary as (mh AL*/mh CL*)3/2 exp(ΔEV/kT) where mh AL* and mh CL* are the hole effective masses in the active layer and confining layer, and ΔEV is the valence band offset. Comparison between experimentally measured and theoretically predicted acceptor segregation ratios gives excellent agreement for (AlxGa1−x)0.5In0.5P heterostructures over the range of compositional differences from Δx=0.12 to Δx=0.93. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1461060
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  • 4
    Electronic Resource
    Electronic Resource
    1.4× efficiency improvement in transparent-substrate (AlxGa1−x)0.5In0.5P light-emitting diodes with thin (≤2000 Å) active regions (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2230-2232 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Improvement of 1.4× in the external quantum efficiency and luminous efficiency (lm/W) of transparent-substrate (AlxGa1−x)0.5In0.5P/GaP light-emitting diodes is demonstrated. The improvement is accomplished by reducing the thickness of the active layer to ≤2000 Å and increasing the internal quantum efficiency by using multiple thin (≤500 Å) active layers. The maximum luminous efficiency achieved is 73.7 lm/W at λp∼615 nm and the maximum external quantum efficiency is 32.0% at λp∼632 nm. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123810
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  • 5
    Electronic Resource
    Electronic Resource
    High-power truncated-inverted-pyramid (AlxGa1−x)0.5In0.5P/GaP light-emitting diodes exhibiting 〉50% external quantum efficiency (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2365-2367 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A truncated-inverted-pyramid (TIP) chip geometry provides substantial improvement in light extraction efficiency over conventional AlGaInP/GaP chips of the same active junction area (∼0.25 mm2). The TIP geometry decreases the mean photon path-length within the crystal, and thus reduces the effects of internal loss mechanisms. By combining this improved device geometry with high-efficiency multiwell active layers, record-level performance for visible-spectrum light-emitting diodes is achieved. Peak efficiencies exceeding 100 lm/W are demonstrated (100 mA dc, 300 K) for orange-emitting (λp∼610 nm) devices, with a peak luminous flux of 60 lumens (350 mA dc, 300 K). In the red wavelength regime (λp∼650 nm), peak external quantum efficiencies of 55% and 60.9% are measured under direct current and pulsed operation, respectively (100 mA, 300 K). © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125016
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  • 6
    Electronic Resource
    Electronic Resource
    Oxygen-based deep levels in metalorganic vapor phase epitaxy indium gallium arsenide (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1116-1118 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the defect engineering in metalorganic vapor phase epitaxy InxGa1−x As by controlled oxygen doping. Diethylaluminum ethoxide (DEALO) was used as an oxygen precursor to provide the intentional deep level incorporation. DEALO doping in InxGa1−xAs:Si with x≤0.25 resulted in the reduction in carrier concentrations. The Al and O incorporation with a DEALO mole fraction was weakly dependent on alloy composition for x≤0.25. The degree of electrical compensation, however, decreased as the In content increased at the same oxygen content. Deep level transient spectroscopy investigations on a series of InxGa1−xAs:Si:O samples with x ranging from 0 to 0.18 reveal a set of oxygen-derived deep levels, similar to those found in DEALO-doped GaAs. These characteristic deep levels appear to remain at a relatively constant energy with respect to the valence band, as compared to the rapid decrease in the conduction band of InxGa1−xAs with x. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114979
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  • 7
    Electronic Resource
    Electronic Resource
    Compensation of shallow impurities in oxygen-doped metalorganic vapor phase epitaxy grown GaAs (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6819-6826 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intentional oxygen incorporation, using diethyl aluminum ethoxide [(C2H5)2AlOC2H5] during metalorganic vapor phase epitaxy GaAs was found to compensate C and Zn shallow acceptors as well as Si and Se shallow donors, due to the oxygen-related multiple deep levels within the GaAs band gap. Deep level transient spectroscopy (DLTS) was used to characterize the energy levels associated with these oxygen deep centers. The total measured trap concentration from DLTS can account for the observed compensation in n-type GaAs:O. The total trap concentration in p-type GaAs:O, however, was found to be lower than the observed compensation by a factor of ∼100. These oxygen deep centers exhibit multiple electronic states which have been associated with the local number of Al nearest neighbors and the microscopic structure of the defect. The concentration and nature of these deep levels were not influenced by the chemical identity of the shallow dopants. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363811
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrafast photodetector materials based on oxygen-doped metalorganic vapor phase epitaxy GaAs (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 634-636 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Controlled incorporation of deep level states into III/V materials tailor their electrical and optical characteristics for ultrafast optoelectronics. We investigate the photoinjected carrier dynamics in GaAs grown by metalorganic vapor phase epitaxy (MOVPE) with (C2H5)2AlOC2H5 as an oxygen precursor providing the deep level state control. Photoconductor switching was used to determine the free-carrier trapping times, and femtosecond photoreflectance at 2 eV was used to measure the trapped charge recombination time as a function of oxygen concentration. We also use electro-optic sampling to demonstrate a photodetector with 650-fs measured response time and to show the material applicability to ultrafast optoelectronics. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114143
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  • 9
    Electronic Resource
    Electronic Resource
    PdAl Schottky contact to In0.52Al0.48As grown by metalorganic chemical vapor deposition (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3587-3589 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: β-PdAl was studied as a Schottky contact to metalorganic chemical vapor deposition grown In0.52Al0.48As. Intermetallic alloy β-PdAl was chosen in order to utilize the Al–In exchange reaction which may occur between PdAl and In0.52Al0.48As, which would result in an enhanced Schottky barrier height. I–V, C–V, and deep level transient spectroscopy (DLTS) were used to determine the contact characteristics. The contact barrier height (φb) was measured by I–V and C–V methods after different annealing conditions, and good agreement between I–V and C–V results were obtained. The largest φb value is 0.67 eV from I–V measurement (0.69 eV from C–V) after the diode was annealed at 450 °C for 1 min. DLTS measurements were carried out to examine the effect of deep traps in the In0.52Al0.48As layer. Two deep levels were found, but the concentrations are lower than the intrinsic donor concentration obtained from the Hall method. The activation energies for these two deep levels obtained from an Arrhenius plot are 0.38 and 0.65 eV, respectively. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115326
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  • 10
    Electronic Resource
    Electronic Resource
    Multiple deep levels in metalorganic vapor phase epitaxy GaAs grown by controlled oxygen incorporation (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 604-606 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Oxygen intentionally introduced into GaAs, grown through the metalorganic vapor phase epitaxy process, is shown to introduce a controlled series of deep levels. A novel, commercially available, oxygen precursor, (C2H5)2AlOC2H5, was used as the oxygen source. Capacitance measurements have revealed compensation of both donors and acceptors in these materials when using this source. The determination of the deep level structure of these films has been carried out through the use of deep level transient spectroscopy (DLTS). The DLTS investigation, carried out on GaAs p+-n homojunctions, indicates that unlike the case of bulk oxygen-doped GaAs (GaAs:O), several deep levels are introduced and directly associated with the intentional oxygen introduction. Two principal traps are found to be located at 0.95 and 0.75 eV below the conduction-band edge, with several other minor traps being observed. These intentionally introduced deep levels have been used to form highly resistive GaAs, providing an analog to the currently employed low-temperature semi-insulating nonstoichiometric GaAs grown by molecular beam epitaxy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112270
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