BOLTZMANN EQUATION APPROACH TO PHOTOCONDUCTIVITY IN SEMICONDUCTORS WITH OPTICAL PHONONS.
EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZURICH (SWITZERLAND)
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The Boltzmann equation for the distribution function of conduction electrons in an electric field, including generation of electrons due to photon absorption, recombination, elastic scattering, and optical phonon emission, is constructed and solved with the aid of some simple assumptions about the energy dependences of the various transition rates. The photoconductive current, as a function of photon energy, shows oscillations with minima at multiples of the optical phonon energy, in agreement with recent observations in the low temperature photoconductivity of several semiconductors. The oscillations are the result of the strong interaction of electrons with longitudinal optical phonons. An energy variation of either lifetime or elastic scattering is not necessary for the existence of these oscillations, although their exact shape depends on it. The calculated field dependence of the shape of the oscillatory photoconductivity agrees qualitatively with experiments in InSb. Author