Comparison of Surface-Excited and Volume-Excited Photoconduction in Cadmium Sulfide Crystals

Abstract

Surface-excited photoconduction is compared with volume-excited photoconduction in cadmium sulfide crystals with a wide range of sensitivities. Measurements are presented as a function of exciting wavelength for (1) spectral response, (2) photocurrent as a function of light intensity, (3) photocurrent decay time, (4) infrared quenching, and (5) thermally stimulated current. The results supply additional evidence that the free electron lifetime for surface excitation is smaller than the lifetime for volume excitation because of a higher rate of recombination at the surface, associated with the adsorption of moist air on the crystal surface.