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Single-phase SixSnyGe1−x−y alloys (x⩽0.25,y⩽0.11) were grown on Si using chemical vapor deposition. First principles simulations predict that these materials are thermodynamically accessible and yield lattice constants as a function of Si/Sn concentrations in good agreement with experiment. An empirical model derived from experimental SixGe1−x and SnyGe1−y binary data also provides a quantitative description of the composition dependence of the lattice parameters. Spectroscopic ellipsometry of selected samples yields dielectric functions indicating a band structure consistent with highly crystalline semiconductor materials of diamond symmetry. Incorporation of Si into SnyGe1−y leads to an additional reduction of the E2 critical point, as expected based on the E2 values of Si and Ge.

We describe methodologies for integration of compound semiconductors with Si via buffer layers and templates based on the GeSn system. These layers exhibit atomically flat surface morphologies, low defect densities, tunable thermal expansion coefficients, and unique ductile properties, which enable them to readily absorb differential stresses produced by mismatched overlayers. They also provide a continuous selection of lattice parameters higher than that of Ge, which allows lattice matching with technologically useful III-V compounds. Using this approach we have demonstrated growth of GaAs, GeSiSn, and pure Ge layers at low temperatures on Si(100). These materials display extremely high-quality structural, morphological, and optical properties opening the possibility of versatile integration schemes directly on silicon.

We introduce a new chemical approach to the incorporation of high concentrations of active n-dopant atoms into group-IV semiconductors via low temperature, low cost, high efficiency routes involving carbon-free single-source inorganic hydrides. Controlled substitution of As into Ge-based semiconductors is made possible by the use of As(GeH3)3, which furnishes structurally and chemically compatible AsGe3 molecular cores. As(GeH3)3 is synthesized in high purity yields (∼75%) via a new single-step method based on reactions of GeH3Br and As[Si(CH3)3]3, circumventing the need for toxic and unstable starting materials as used in earlier approaches. We demonstrate the development of a viable route to the entire family of compounds M(GeH3)3 {M = P, As, Sb}, suitable for doping or superdoping applications of a wide range of functional materials. The structural, vibrational, and thermochemical properties of M(GeH3)3 are simulated for the first time via density functional theory calculations using both all-electron and effective core potentials. The vibrational calculations are in excellent agreement with the observed infrared spectra and the thermochemical stability is predicted to decrease with increasing molecular mass, in accord with experimental observations. The simulated structures show that the Ge−M−Ge angles decrease with increasing M size and further resolve inconsistencies with earlier gas electron diffraction measurements of P(GeH3)3. Bulk supercell calculations are then used to study the formation free energy of P, As, and Sb incorporation in bulk Ge, as well as the bond and lattice strains induced by the dopant atoms in the host diamond-structure lattice. As a first example of the usability of the M(GeH3)3 family, we demonstrate the successful doping of metastable Ge1- y Sn y alloys. This represents a crucial step toward the goal of developing photonic devices, such as photodetectors and photovoltaic cells, based on Ge1- y Sn y . Infrared ellipsometry experiments demonstrate high carrier concentrations and excellent resistivities in As(GeH3)3-doped Ge1- y Sn y . The latter are only moderately higher than those measured in pure Ge for the same dopant levels.