Electrical and optical properties of amorphous Si:F:H alloys

Abstract

Amorphous alloys based on silicon and containing hydrogen and fluorine have been fabricated using a radio-frequency glow discharge in silicon tetrafluoride and hydrogen. Films have been well characterized using conductivity, photoconductivity, field-effect and infra-red techniques. Amorphous alloys fabricated from a gas ratio of SiF4 : H2=10: 1 are shown to possess a localized density of states with a minimum value of less than 1017 cm−3 eV−1. These films are highly photoconductive, devoid of photostructural changes and are mechanically stable. Because of the low density of localized states, the alloys have been doped with 50 v.p.p.m. of arsine in the premix to attain a room temperature conductivity ≥ 5 Ω−1 cm−1.