PHOTOCONDUCTION AND STRUCTURAL-PROPERTIES OF AMORPHOUS SELENIUM SULFUR SEMICONDUCTORS

The effect of sulphur addition on some structural properties of a-Se was studied for compositions up to about 30 at.% S. The sulphur in the binary amorphous semiconductor system Se-S was found to affect the density (d), microhardness (VH), dielectric constant (epsilon) and tendency to crystallization (T(c) - T(g)), as well as the spectral response and the temperature dependence of the photocurrent in different ways. The compositional dependence of d, VH, epsilon and T(c) - T(g) showed an irregular behaviour up to about 5 at.% S, with the highest (or lowest) value at the composition 0.2 at.% S, after which the character of the compositional dependence is almost monotonic. The photoconductivity results are discussed on the basis of these results, showing that the recombination processes in pure selenium and in sulphur-contaminated selenium differ from each other.