Aluminium has been introduced into a-Sic: H by co-sputtering of silicon-aluminium in a gas mixture of methane-argon and its effect on the optical, electrical and opto-electronic properties of the films investigated. In the range of fractional aluminium content z up 10−2, the photoconductivity was maintained without a significant change in the optical band gap. A high value of photosensitivity (> 106) was obtained in the range of z between 10−4and 10−3. On increasing z above 10−2, the photoconductivity is quenched, being accompanied by a decrease in the optical band gap as well as by an increase in the dark d.c. conductivity.