LOW TEMPERATURE INFRARED PHOTOCONDUCTORS.
DAVID SARNOFF RESEARCH CENTER PRINCETON N J
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Oscillations of photocurrent which are periodic in photon energy with a period equal to the longitudinal optical LO phonon energy have been investigated as a function of the percentage absorption of the incident radiation and as a function of electric field. From the result that the oscillation amplitude is independent of fractional absorption, it may be concluded that the oscillatory effect is not due to a periodically varying absorption coefficient. The oscillation amplitude as a function of electric field is such that the amplitude is independent of field at low fields and that the oscillations disappear at fields above about 30 voltscm. The results have been interpreted in terms of a model in which carriers excited to high energies by photon absorption first lose energy very rapidly by emission of LO phonons and then, more slowly, gain or lose energy by interaction with the electric field and with acoustical phonons during the lifetime of the carrier. If the photoconductive gain is a function of carrier energy, the existence of oscillations and the form of the electric field dependence of the oscillation amplitude can be predicted. Author