A novel method for synthesizing device-quality alloys and ordered phases in a Si—Ge—Sn system uses a UHV-CVD process and reactions of SnD4 with SiH3GeH3. Using the method, single-phase SixSnyGe1-x-y semiconductors (x≦0.25, y≦0.11) are grown on Si via Ge1-xSnx buffer layers The Ge1-xSnx buffer layers facilitate heteroepitaxial growth of the SixSnyGe1-x-y films and act as compliant templates that can conform structurally and absorb the differential strain imposed by the more rigid Si and Si—Ge—Sn materials. The SiH3GeH3 species was prepared using a new and high yield method that provided high purity semiconductor grade material.