A low-temperature cleaning technique incorporating an ultraviolet Light-ozone treatment with conventional hydrogen-passivation techniques is shown to yield a low concentration of surface contaminants: 0.01 monolayer. An additional advantage is that no ultrahigh vacuum prebaking treatments are required for substrates receiving this treatment prior to epitaxy. Epitaxial silicon layers deposited onto substrates receiving the present technique are characterized by a threading dislocation density on the order of 10(4)/cm(2) which is considerably lower than the 10(5)/cm(2)-10(6)/cm(2) order measured for films receiving more conventional preparation techniques. The results of this study suggest that aqueous solutions are a significant source of surface carbon and that residual carbon on the silicon surface before epitaxy contributes to the generation of threading dislocations in Si homoepitaxial films.