The effects of substrate temperature and hydrogen dilution on mobilitylifetime product and hydrogen bonding are reported for amorphous silicongermanium films with bandgaps from 1.1 to 1.74 eV deposited by Hg-sensitized photo-CVD. The ratio of dihydride to monohydride bonding and preferential H attachment to silicon both decreased with hydrogen dilution. The best films were deposited with hydrogen dilution at substrate temperatures between 230 and 250 ° C. Model equations used to calculate radical fluxes to the substrate are described.