Determination of Electron Trapping Parameters

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Abstract
A detailed investigation of different methods for determining electron trap parameters has been made on crystals of CdS‐CdSe. The principal techniques involved are decay of photoconductivity and thermally stimulated conductivity (TSC). Direct evidence of a quasicontinuous trap distribution with total density of 5×1015 cm−3, trap depth range of 0.1–0.7 eV, and capture cross sections of the order of 10−16 cm2 is obtained, for which correct values of the parameters can be calculated from Fermi‐level analysis of either decay or TSC data. In the same crystals a discrete trap level with density of 2×1014 cm−3, depth of 0.73 eV, and apparent cross section of 10−14 cm2 is also found. In spite of the large value of cross section derived from the freeing of trapped electrons, these traps exactly obey monomolecular kinetics. A temperature threshold at 180°K is found, below which it is not possible to fill these traps. Examination of a number of possibilities favors the proposal that these traps are characterized by a Coulomb‐repulsive barrier.