OPTICAL AND ELECTRICAL-PROPERTIES OF EVAPORATED AMORPHOUS SILICON WITH HYDROGEN

The optical and electrical properties of evaporated amorphous silicon with hydrogen have been studied under various deposition conditions. Infrared measurements indicate that the hydrogen content of the films are comparable to a-Si : H films produced by other techniques. The optical-absorption coefficient below the band gap of ∼1.55 eV was measured to be ∼100 cm-1 for samples made at deposition temperatures of ∼275-325 °C. For these samples the photoresponse at room temperature and the temperature dependence of the conductivities were studied. Dark conductivities were found to be thermally activated for T≳300 K with activation energies of ∼0.75 eV. We found type-1 photoconductivity and investigated its dependence on the light intensity. When samples were heated to ∼175 °C in a vacuum and then exposed to air, they exhibited time-dependent increases in the dark conductivity and photoconductivity. This effect was reversible by a reanneal in a vacuum. High-temperature anneals to ∼450 °C increased the optical absorption below 1.4 eV and decreased the photoresponse significantly.