CHEMICAL-BONDS AND SPIN PROPERTIES OF A-SIXGEY-HZ ALLOYS

Hydrogenated amorphous silicon-germanium alloys are considered important low band gap materials for thin film solar cell technology, but the dangling bond densities increase with the germanium content to prohibitive values. We report on IR and electron spin resonance spectra and show some relationships between the preferential attachment of hydrogen, the dangling bond configurations and the preparation conditions in the plasma. We discuss our g values using the theoretical model proposed by Ishii for such binary alloys. These values and the peak-to-peak linewidth DELTA-H deduced from derivative absorption curves exhibit a strong modification with the germanium content of the local environment of the dangling bond. We confirm that a moderate substrate temperature and a high dilution of the reactant gases in hydrogen lead to better alloys.