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  • 1
    Electronic Resource
    Electronic Resource
    Compensation of charge fluctuations in quantum wells with dual tunneling and photon-assisted escape paths (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4429-4437 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In our previous article [D. H. Huang, A. Singh, and D. A. Cardimona, J. Appl. Phys. 87, 2427 (2000)], we explained the experimentally observed zero-bias residual tunneling current [A. Singh and D. A. Cardimona, Opt. Eng. 38, 1424 (1999)] in quantum-well photodetectors biased by an ac voltage. In this article, we extend our theory to include the photoemission current and reproduce our recent findings on the dynamical drop of photoresponsivity Rph(t) from its static value Rph0 in quantum-well photodetectors as a function of the chopping frequency of the incident optical flux. In this theory, we derive a dynamical equation for a nonadiabatic space-charge field Ena(t) in the presence of an applied electric field Eb(t) and an incident optical flux Φop(t). From it, a compensation of the charge fluctuations in quantum wells is predicted as a result of dual tunneling and photon-assisted escaping paths. We also find a suppression of the nonadiabatic deviation of Rph(t) from Rph0 due to a charge-depletion effect in the quantum wells. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1351867
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal hysteresis loop, dynamical breakdown, and emission-current spike in quantum-well photodetectors (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6032-6043 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A nonadiabatic sequential-tunneling model is developed and applied to explore the common origin of the transient behavior of electrons in quantum-well photodetectors in the presence of different time-dependent external sources, including device temperature, electric field, and incident optical flux. For the time-dependent temperature, a counterclockwise hysteresis loop in the tunneling current as a function of the swept temperature is predicted and attributed to a blockade or an enhancement of the sequential tunneling of electrons between quantum wells by the space-charge-field effect when the device temperature is swept up and then down. When a time-dependent electric field is applied, a dynamical breakdown of the photodetectors is predicted, where the peak of total current linearly increases with the frequency of an ac electric field from its static value under a dc field. This is due to the presence of an additional dielectric current, which is proportional to the oscillation frequency of the ac electric field and whose peak value becomes larger than the value of the saturated tunneling-current peak in the high-frequency domain. Under the dynamical-breakdown condition, the quantum-well photodetectors behave just like a uniform dielectric medium. In the presence of a time-dependent optical flux, an emission-current spike is predicted as a result of the dominant enhancement of the escape probability of electrons from quantum wells over the loss of electron density when an applied dc electric field is small. The experimental observations of the transient behavior of electrons in quantum-well photodetectors are successfully reproduced by our numerical calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415760
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  • 3
    Electronic Resource
    Electronic Resource
    Change of microscopic tunneling on a macroscopic time scale: Current surge model (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2427-2430 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The current surge model is proposed to calculate the tunneling current in multiple quantum well structures in the presence of a slow time-dependent electric field. The microscopic origin of a zero-bias residual current observed and reported previously [A. Singh and D. A. Cardimona, Opt. Eng. (Bellingham) 38, 1424 (1999)] is explored. The mystery of the observation of a microscopic tunneling change on a macroscopic time scale is uncovered, and an involvement of a very slow physical process is shown. Some new features, such as a current "ripple," a current instability, a current hysteresis, and a current "arch," are predicted and confirmed experimentally. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372196
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  • 4
    Electronic Resource
    Electronic Resource
    Diffractive imaging in three-wave interactions (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2640-2645 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The coupled signal and idler diffractive differential equations are solved for the parametric processes of upconversion and down conversion. The complex transfer functions are found in terms of spatial frequency, propagation vectors, gain, and media length. Also, we derive the signal to the idler imaging equation by employing the transfer functions for both upconversion and down conversion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339440
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  • 5
    Electronic Resource
    Electronic Resource
    Multibeam energy transfer in a Kerr medium (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1450-1455 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multibeam coupling in a Kerr medium with a finite response time is studied theoretically. Two different frequency spectra are considered. In the first case the modes are equally spaced and in the second the frequency separations are all unequal. In either case, as the beams propagate, both spectra eventually reach a saturation characterized by a cascading of energy into the lowest frequency if the Kerr constant is positive. The direction of energy transfer is reversed if the Kerr constant is negative. Representative examples are given for a multimode, equally spaced, laser source and for an unequally spaced source. For the former case, we give the optimum medium response time for conversion of a Gaussian spectra. If the frequencies are unequally spaced we present general conditions which have to be satisfied and give two examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346672
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