Films of the sulfide were grown onto Si substrates by sputtering in Ar and in S-enriched or S-deficient gaseous environments. It was found that the density of electron traps at the ZnS/Si heterojunction was independent of the nature of the ambient gas. However, the photoluminescence intensity increased for films that had been grown in Ar which was enriched with H2S, as compared with those which were grown in Ar. The density of S vacancies was reduced by the presence of H2S; especially when compared with films which had been grown in a mixture of Ar and H. In the latter films, S vacancies increased the electrical conductivity by some 3 orders of magnitude. It was therefore expected that the high-field condition which was essential for hot-electron production in thin-film electroluminescent devices was optimized in films with a reduced S vacancy content.

C.Tsakonas, C.B.Thomas: Journal of Applied Physics, 1995, 78[10], 6098-103