Photochemical vapor deposition of hydrogenated amorphous silicon films from disilane and trisilane using a low pressure mercury lamp

Abstract

The photolysis of disilane (Si₂H₆) and trisilane (Si₃H₈) under direct excitation by light from a low pressure mercury lamp was carried out to prepare hydrogenated amorphous silicon films (a‐Si:H). The electronic and optical properties of the films were investigated as functions of preparation conditions such as partial pressure and substrate temperature. The conductivity of the films prepared from Si₃H₈ at 300 °C was 10⁻¹⁰ S cm⁻¹ in the dark and 10⁻⁵ S cm⁻¹ under the illumination of a He‐Ne laser with a photon flux of 10¹⁵ cm⁻² s⁻¹. The high photoconductivity was attained when the silane gas was blown over the substrate from a slit‐type nozzle placed beside the substrate plate at a pressure of less than 20 Torr.