Chem. Mater. 2010, 22, 3779–3789 3779 DOI:10.1021/cm100915q
Synthesis, Stability Range, and Fundamental Properties of Si-Ge-Sn Semiconductors Grown Directly on Si(100) and Ge(100) Platforms Junqi Xie,† Andrew V. G. Chizmeshya,† John Tolle,† Vijay R. D’Costa,‡ Jose Menendez,‡ and John Kouvetakis*,† †
Department of Chemistry and Biochemistry and ‡Department of Physics, Arizona State University, Tempe, Arizona 85287 Received March 31, 2010. Revised Manuscript Received April 27, 2010
This paper reports a comprehensive experimental and theoretical account of synthesis, optical response, transport properties, and thermodynamic stability for a new family of Ge1-x-ySixSny semiconductor alloys based entirely on group IV elements. Device quality layers are grown directly on both Ge(100) and Si(100) wafers using low-temperature chemical vapor deposition (CVD) of commercially available sources such as trisilane, digermane, and stannane, thereby making the process suitable for direct industrial scale up and applications. This soft chemistry process is extended to demonstrate fabrication of p- and n-type layers on Si and determine their transport properties by both contactless optical methods and conventional Hall experiments. Spectroscopic analyses by UV-IR ellipsometry and Raman scattering show that the alloys possess fundamental optical and bonding properties identical to those of the materials previously grown on Ge-Sn buffers. Transmission electron microscopy (XTEM), Rutherford backscattering (RBS), and high resolution X-ray diffraction (HRXRD) characterizations demonstrated that precise tuning of the composition to achieve a Si/Sn ratio of ∼3.7 yields strain-free films with Ge-like unit cell dimensions. In the case of growth on Ge(100) the films exhibit the expected flawless registry afforded by the perfect chemical and structural matching with the underlying platform. When grown on Si(100) the lattice misfit with the substrate is compensated by periodic edge-type dislocations at the interface. Independent variation of the Si/Sn ratio from ∼1.5-4 produces a range of tetragonally distorted films on Si(100) with significant compressive strains (
