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  • 1
    Electronic Resource
    Electronic Resource
    An investigation of the diffusion of silicon in delta-doped gallium arsenide, as determined using high-resolution secondary ion mass spectrometry (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 821-826 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon delta-doped samples of various densities were grown by molecular-beam epitaxy and analyzed using high-resolution secondary ion mass spectrometry. A marked difference was observed between profiles produced from samples doped below a surface density of 1.3×1013 cm−2, where all the silicon was incorporated on gallium sites, and highly doped samples, where autocompensation had occurred. All samples were grown at nominally 580 °C and all the doped planes showed some degree of broadening. A computer model of a two-step diffusion process was developed which produced a set of diffusion coefficients for the lower-doped samples. The diffusion coefficient associated with the post deposition growth for these low-doped samples was approximately 4.2×10−17 cm2 s−1. The more highly doped samples, because of their complicated profiles, were modeled using a graphical technique. This technique revealed the presence of a much larger diffusion coefficient, which is tentatively assigned to silicon diffusing as nearest-neighbor pairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349640
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  • 2
    Electronic Resource
    Electronic Resource
    The temperature dependence of threshold current of chemical beam epitaxy grown InGaAs–InP lasers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1804-1807 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of threshold current between 130 and 310 K of 1.65 μm In0.53Ga0.47As–InP bulk lasers grown by chemical beam epitaxy has been measured. Comparison with a calculation of the spontaneous recombination current at threshold allows one to determine the proportion of current loss over this temperature range. It is found that the loss can be described using an Auger recombination component of the form Rauger=C'n3 exp(−Ea/kBT) where n is the carrier population density in the undoped active region. The activation energy Ea is found to be 39±5 meV which is in excellent agreement with the theoretical value for the conduction to heavy hole band/split-off to heavy hole band Auger process. The values obtained for the Auger coefficient C over the temperature range are in close agreement with published values obtained by time resolved photoluminescence. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360212
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  • 3
    Electronic Resource
    Electronic Resource
    Gain-current characteristics of strained AlGaInP quantum well lasers (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2792-2794 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single quantum well AlGaInP lasers, each having a 65 A(ring) width well have been fabricated with GaxIn1−xP well compositions from x=0.43 to 0.54 grown on substrates orientated 10° off the (100) axis. The threshold currents have been measured from 120 K to room temperature and the samples show a systematic variation with x. At low temperature the results are in good agreement with our calculated gain-current curves and we show that at room temperature the rapid increase in threshold current density with decreasing length is due to a thermally activated leakage current rather than gain saturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110336
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  • 4
    Electronic Resource
    Electronic Resource
    Gain-current calculations for bulk GaInP lasers including many-body effects (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3521-3523 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The gain-current characteristics of undoped GaInP (660-nm) bulk lasers have been calculated over a range of temperatures. The calculations use parabolic bands with strict k selection and include band-gap narrowing and lifetime broadening due to carrier-carrier interactions at high densities. The broadening lifetime τ has been implemented as a constant value of 10−13 s and as a carrier-dependent value proportional to n−1/3. Using τ=10−13 s, our calculations for GaInP at room temperature give a value for the differential gain β of 0.026 cm−1 (A cm−2 μm−1)−1 and a value for the transparency current J0 of 4.4 kA cm−2 μm−1. These are in close agreement with experimental results. Results for GaAs at room temperature are also given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105669
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  • 5
    Electronic Resource
    Electronic Resource
    Calculation of gain-current characteristics in ZnCdSe-ZnSe quantum well structures including many body effects (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3780-3782 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The gain-spontaneous recombination characteristics have been calculated for a 40 A(ring) Zn0.8Cd0.2Se-ZnSe quantum well including many body effects. We examine the effect of the inclusion of the Coulomb enhancement on the gain spectra and the gain-current relationship. We show that, in the absence of the Coulomb enhancement, the threshold current density of a 340 μm 40 A(ring) Zn0.8Cd0.2Se-ZnSe quantum well laser is underestimated by approximately 40% and the lasing wavelength overestimated by 4 nm. Our calculation of the scattering lifetime for the first electron-heavy hole transition gives a lifetime varying between 29 and 37 fs, and shows that the carrier-phonon scattering mechanism in II-VI quantum wells is more dominant than in III-V materials. We also comment on the effect the neglect of Coulomb enhancement has on the calculation of leakage currents in a laser at threshold. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115381
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  • 6
    Electronic Resource
    Electronic Resource
    All-optical synchronization of self-pulsating laser diodes (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3534-3536 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We examine the behavior of self-pulsating laser diodes when injected with periodic optical signals. We experimentally and theoretically investigate the phase difference between the injected optical signal and the synchronized self-pulsating laser diode emission. We explore the phase difference dependence on detuning between the laser free-running self-pulsation frequency and the applied signal frequency, and on the injected signal power. The determined sensitive dependence of the phase difference on these factors has important consequences when self-pulsating lasers are used as optical signal processing elements in all-optical communication networks, where such sensitivity may lead to timing problems. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116521
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  • 7
    Electronic Resource
    Electronic Resource
    Experimental investigation of the differential gain in semiconductor lasers and its influence on Q-switching performance (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2009-2011 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The gain spectra of AlGaInP, single quantum well, laser diodes were obtained by measurement of their spontaneous emission spectra and subsequent conversion according to the Einstein relations. From these spectra the ratio of differential absorption to differential gain, γ was calculated. At energies greater than the lasing transition a threefold increase in the differential absorption may be achieved in compressively strained devices, giving a value of γ=14.4. These results indicate that by detuning the saturable absorber energy within a Q-switched device by 20 meV a doubling of the inversion factor may be obtained. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116862
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  • 8
    Electronic Resource
    Electronic Resource
    Photoluminescence studies of free-standing quantum boxes (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3472-3480 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report photoluminescence measurements made on free-standing, lattice-matched GaAs/AlGaAs and pseudomorphic InGaAs/GaAs quantum boxes fabricated by laterally patterning quantum wells using electron-beam lithography and either reactive ion etching or ion beam milling. At temperatures below 10–20 K the luminescence efficiency of most of the GaAs quantum-box arrays tends to scale with the volume of quantum-well material remaining after processing even for the smallest boxes which have lateral dimensions of only 40–50 nm. These observations indicate that the surface recombination rate in GaAs submicron structures can be small relative to the radiative recombination rate at low temperatures. In contrast, radiative recombination in the InGaAs/GaAs quantum boxes is strongly quenched for lateral dimensions less than 500 nm. We suggest that this is because photoexcited carriers are laterally localized in the GaAs boxes by potentials of the order of a few meV, possibly associated with interface disorder or strain relaxation, and that such localization effects are smaller in the InGaAs boxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345337
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  • 9
    Electronic Resource
    Electronic Resource
    Optical measurement of the ambipolar diffusion length in a ZnCdSe–ZnSe single quantum well (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 536-538 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a straightforward technique for the measurement of carrier diffusion in semiconductors. Using an optical microscope we can spatially image luminescence with a resolution of ∼500 nm. We measured the ambipolar diffusion length in a Zn0.75Cd0.25Se–ZnSe single quantum well by fitting the spatially resolved luminescence profile with the solution of the two-dimensional diffusion equation. The ambipolar diffusion length was found to be 498 nm at a carrier density of ∼1×1018 cm−3 and we deduce an ambipolar diffusion constant of 1.7 cm2 s−1. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364094
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  • 10
    Electronic Resource
    Electronic Resource
    Inhibition profiles of sodium cromoglycate and nedocromil sodium on mediator release from mast cells of human skin, lung, tonsil, adenoid and intestine (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical & experimental allergy 22 (1992), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We have studied an aspect of the functional heterogeneity of human mast cells, namely responsiveness to the inhibitory effects of sodium cromoglycate and nedocromil sodium. The effects of these drugs were examined on the release of histamine and PGD2 from mast cells of human skin, lung, tonsils, adenoids and intestine. A high concentration, 1000 μM, of sodium cromoglycate was required to significantly inhibit histamine release from lung and tonsillar mast cells. Nedocromil sodium, 1000 μM, was more effective than sodium cromoglycate against histamine release from lung, tonsillar and adenoidal cells. Both compounds showed tachyphylaxis in lung and tonsillar mast cells but not in adenoidal and intestinal mast cells. In contrast, in intestinal mast cells, the effect of nedocromil sodium was weaker and more variable than sodium cromoglycate. Skin mast cells differed from mast cells of the other anatomical sites in being unresponsive to sodium cromoglycate and nedocromil sodium. Our results confirm that high concentrations of sodium cromoglycate and nedocromil sodium are required to achieve even modest inhibition of mediator release from human mast cells under in vitro conditions. Notwithstanding this, the results also indicate that differences exist among skin, lung, tonsillar, adenoidal and intestinal mast cells with respect to their sensitivity to sodium cromoglycate and nedocromil sodium, thus extending our knowledge of functional heterogeneity within the human mast cell populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2222.1992.tb03102.x
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