Pulse Excitation Studies of Gain and Trapping in Photoconductors

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Abstract
Excitation of photoconductors by single pulses of monoenergetic photons shows that the integrated gain over one pulse event is approximately equal to the steady-state gain, except in materials for which the steady-state gain itself is a function of photon flux. Measurement of the peak pulse current as a function of pulse length permits the determination of trap density in a simple manner, which agrees well with values measured independently by thermally stimulated conductivity. A model based on a quasiuniform trap distribution is shown to be capable of predicting the observed dependence of peak pulse current on pulse length without the use of any adjustable parameters. Changes in trap density by several orders of magnitude with variations in ambient atmosphere are demonstrated for certain cadmium sulfide crystals.