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  • 1985-1989  (18)
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  • 1
    Electronic Resource
    Electronic Resource
    Gain-switched semiconductor laser amplifier as an ultrafast dynamical optical gate (1988)
    Springer
    Applied physics 46 (1988), S. 69-77 
    Details
    ISSN: 1432-0649
    Keywords: 42.55.Px ; 42.60.Da ; 85.60.Jb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A gain-switched semiconductor laser is shown to act as an optical gate with picosecond resolution and amplification for light pulses from another laser source. The amplification mechanism and the gate width change qualitatively when the gate laser undergoes a transition from a pumping rate slightly below the dynamic laser threshold to slightly above the dynamic threshold. If the gate laser is pumped below but close to its dynamical threshold, unsaturated amplification of an external signal pulse occurs over a delay time range between the external optical pulse and the electrical driving pulse of about 100–200 ps which is equivalent to the optical gate width. The signal amplification is observed to increase by two orders of magnitude and the gate width decreases by one order of magnitude if the gate laser is pumped slightly above the dynamical threshold. Amplification then occurs for input signals injected much earlier. A detailed theory of coherent, time-dependent amplification including the nonlinear dynamics of the semiconductor laser is shown to account for the observations. Both amplification regimes, below and above threshold, are reproduced in the numerical simulations. The extremely short and highly sensitive gate range above threshold is identified as being due to the gain maximum related with the first relaxation oscillation of the laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00698655
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  • 2
    Electronic Resource
    Electronic Resource
    Optical and electrical characterization of high-resistivity liquid-phase-epitaxial In0.53Ga0.47AsB: Fe (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4574-4579 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Semi-insulating In0.53Ga0.47As with carrier concentration n=1.2×1012 cm−3, resistivity up to 1090 Ω cm, and mobility up to 9500 cm2/V s at 300 K is grown by liquid-phase epitaxy and doping with Fe. The influence of Fe doping on the photoluminescence of In0.53Ga0.47As is systematically investigated. An acceptor level at Ev+150 meV, tentatively assigned to Fe by some of us earlier, is definitively identified as an Fe-related complex. This acceptor level, however, is not responsible for the semi-insulating behavior of In0.53Ga0.47As as shown by statistical calculations. High-resolution deep-level transient spectroscopy experiments show two deep acceptors at EC−ET=0.44 and 0.30 eV, respectively. The first one, which dominates, is identified as being caused by the Fe3+/Fe2+ acceptor level. The second, somewhat weaker one, might be caused by the O-related trap recently discovered by Loualiche et al. [Appl. Phys. Lett. 51, 1361 (1987).] Combining the Fe acceptor energy position in In0.53Ga0.47As with its known value in InP and the known conduction-band discontinuity of the InP/In0.53Ga0.47As heterointerface we find that the vacuum referred binding energy model is approximately but not strictly valid. In this model the transition-metal impurity levels are aligned with respect to the vacuum level across interfaces regardless of the surrounding host crystal environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341260
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  • 3
    Electronic Resource
    Electronic Resource
    Carrier injection in semiconductors with position-dependent band structure: Electron-beam-induced current at heterojunctions (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2505-2514 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present simulations of external carrier injection in semiconductors with position-dependent band structure by numerical solution of the current transport equations across the device. As a model case, we examine electron-beam-induced current at heterojunctions. Our treatment is applicable to an arbitrary position-dependent band structure, and any form of external generation, and allows for an external bias applied to the device. The quality of ohmic contacts is taken account of by realistic boundary conditions. For excitation by an electron beam at a GaAs/AlGaAs n-N isotype heterojunction, we present band profiles, as well as linescans, of electron-beam-induced current and voltage. The influence of external generation rate, interface grading, and contact quality is investigated. The latter is shown to be important in epitaxial layers which are only a few minority-carrier diffusion lengths thick. The saturation behavior of the signal with increasing injection level is studied as a function of device parameters, and the applicability of such measurements to the determination of band offsets is critically discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341633
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Calorimetric absorption and transmission spectroscopy for determination of quantum efficiencies and characterization of ultrathin layers and nonradiative centers (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 303-309 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel absorption technique, calorimetric absorption spectroscopy (CAS), is described and modeled in detail. The technique is more sensitive than any other low-temperature absorption technique reported hitherto and it is quantitative. Quantum efficiencies can be determined by combining CAS with calorimetric transmission spectroscopy. The method is based on integral detection of phonons emitted during nonradiative recombination processes. A low-temperature carbon resistor acts as phonon detector. The sensitivity of CAS is so large that a simple combination of a tungsten lamp and a spectrometer can be used as the illumination source. Depending on the excitation density, αd products down to 10−8 can be detected. These features make it possible to apply CAS for the characterization of the interface structure of single quantum wells with thicknesses of less than 1 nm as well as for the study of the fine structure of deep traps in semiconductors. Examples for all these applications are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341427
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxy of GaAs/AlGaAs quantum wells on channeled substrates (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 433-435 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs/AlGaAs quantum wells (QWs) were grown by molecular beam epitaxy on GaAs (100) substrates patterned with ridges and grooves in the [011¯] direction. Low-temperature cathodoluminescence was used to measure the Al fraction and QW thickness on top of the ridges and grooves as a function of ridge and groove width. Surface diffusion during growth depletes Ga from the side facets while increasing the incorporation of Ga on the (100) sections of ridges and grooves. The QW thickness on top of a ridge grown at 710 °C increases from 72 to 95 A(ring), and the Al fraction x decreases from x=0.33 to x=0.29 as the ridge width is narrowed from 30 to 4 μm. Graded refractive index separate confinement heterostructure lasers with nominally 70 A(ring) QWs and Al0.2Ga0.8As barriers were grown on patterned substrates at 695 and 725 °C. Lasers fabricated on the overgrown 4-μm-wide ridges have a 20 meV decrease in emission energy compared to laser diodes on 30 μm ridges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100943
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    High-precision band-gap determination of Al0.48In0.52As with optical and structural methods (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 140-141 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The band gap of Al0.48In0.52As lattice matched to InP is determined with high precision at 1.5 and 300 K as 1.511 and 1.439 eV, respectively. This determination, which resolves a long lasting dispute on the most fundamental material parameter of this semiconductor, is based on a comparative study of temperature-dependent photoluminescence, wavelength-dispersive x-ray analysis, and triple-crystal x-ray diffractometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102125
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  • 7
    Electronic Resource
    Electronic Resource
    Detection of pulse to pulse timing jitter in periodically gain-switched semiconductor lasers (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1971-1973 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Methods to assess pulse to pulse timing jitter in periodicallly gain-switched semiconductor lasers are investigated. The power spectrum of the optical pulse train for mutually incoherent fluctuations of the turn-on delay time and the pulse amplitude is calculated. The result shows that a measurement of the power spectrum alone is not sufficient for the characterization of the inherent timing jitter. Additional knowledge of the optical waveform and the transfer characteristics of the detection system is necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101370
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  • 8
    Electronic Resource
    Electronic Resource
    Anisotropic and inhomogeneous strain relaxation in pseudomorphic In0.23Ga0.77As/GaAs quantum wells (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1765-1767 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural properties of pseudomorphic In0.23Ga0.77As/GaAs single quantum wells are investigated with x-ray double-crystal diffractometry. Anisotropic tilting of lattice planes along dislocations and anisotropic reflectivity of fully relaxed domains coexisting with strained domains are reported for the first time. Due to the anisotropic strain relaxation the crystal symmetry changes from tetragonal in the fully strained case to monoclinic in a partially relaxed quantum well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102212
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  • 9
    Electronic Resource
    Electronic Resource
    Substructure in short optical pulses from gain-switched semiconductor lasers (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1600-1602 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spike-like substructure in picosecond optical pulses from gain-switched multimode injection lasers is analyzed. A theoretical description based on the interference of the randomly phased longitudinal laser modes and the transient shift of the envelope of the mode spectrum under gain-switched operation is presented. Single shot, streak camera records and autocorrelation traces are simulated, describing all essential experimental features of the substructure like its random variation from pulse to pulse and inherent periodicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102249
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  • 10
    Electronic Resource
    Electronic Resource
    Reduction of trap concentration and interface roughness of GaAs/AlGaAs quantum wells by low growth rates in molecular beam epitaxy (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 50-52 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simultaneous reduction of interface roughness and of impurity and trap incorporation in GaAs/AlGaAs quantum wells is observed for a decrease of the molecular beam epitaxy growth rate below its standard value 1 μm/h, down to 0.1 μm/h, at a substrate temperature of 620 °C. Thus, layer quality is drastically improved at low, nonstandard growth rates. Incorporation of impurities from the background is observed to induce a transition from two- to three-dimensional growth. The conclusions are based on a detailed study and line shape analysis of quantum well luminescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101751
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