Deep impurity-center ionization by far-infrared radiation |
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Authors: | S D Ganichev W Prettl I N Yassievich |
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Institution: | 1. Institut für Angewandte Physik, Universit?t Regensburg, D-93040, Regensburg, Germany 2. A. F. Ioffe Physicotechnical Institute, Russian Academy of Sciences, 194021, St. Petersburg, Russia
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Abstract: | An analysis is made of the ionization of deep impurity centers by high-intensity far-infrared and submillimeter-wavelength
radiation, with photon energies tens of times lower than the impurity ionization energy. Within a broad range of intensities
and wavelengths, terahertz electric fields of the exciting radiation act as a dc field. Under these conditions, deep-center
ionization can be described as multiphonon-assisted tunneling, in which carrier emission is accompanied by defect tunneling
in configuration space and electron tunneling in the electric field. The field dependence of the ionization probability permits
one to determine the defect tunneling times and the character of the defect adiabatic potentials. The ionization probability
deviates from the field dependence e(E) ∝ exp(E
2/E
c
2
) (where E is the wave field, and E
c is a characteristic field) corresponding to multiphonon-assisted tunneling ionization in relatively low fields, where the
defects are ionized through the Poole-Frenkel effect, and in very strong fields, where the ionization is produced by direct
tunneling without thermal activation. The effects resulting from the high radiation frequency are considered and it is shown
that, at low temperatures, they become dominant.
Fiz. Tverd. Tela (St. Petersburg) 39, 1905–1932 (November 1997) |
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Keywords: | |
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