Preparation of Highly Photoconductive a-SiGex from Fluorides by Controlling Reactions with Atomic Hydrogen

Highly photoconductive a-SiGe x alloys with an optical gap of 1.2–1.7 eV are prepared by plasma-induced decomposition of fluorides (SiF4 and GeF4) and the introduction of atomic hydrogens (hydrogen radicals). Two new preparing methods are proposed to attain high alloy quality by controlling the reactions for making precursors using hydrogen radicals. Attempts have been made to deposit alloys on a substrate apart from the plasma to avoid damage of the films by bombardment of the particles. By this means, highly photoconductive a-SiGe x :H(F) films with an optical gap of 1.4eV were obtained with high growth rates.