MECHANISMS OF ELECTRONIC CONDUCTION THROUGH THIN-FILM ZNS-MN

Gold deposited by d.c. sputtering is found to form an ohmic contact to thin-film manganese-doped zinc sulphide (ZnS:Mn). This has facilitated the investigation of electron transport mechanisms in the bulk of thin-film ZnS:Mn, deposited by r.f. sputtering on to silicon substrates. Analysis of current density versus voltage characteristics as a function of temperature reveals the existence of ohmic and trap-limited space-charge currents. From analysis of these characteristics, the Fermi level in the ZnS:Mn is calculated to be 0.30+/-0.01 eV below the conduction band edge, and a discrete trap is identified at 0.25+/-0.01 eV with a density of approximately 2 x 10(17) cm-3. Evidence suggests that the origin of this trap may be linked to sulphur vacancies.