Interdiffusion in group IV semiconductor material systems: applications, research methods and discoveries

Abstract

Group IV semiconductor alloys and heterostructures such as SiGe, GeSn, Ge/Si and SiGe:C have been widely used and under extensive research for applications in major microelectronic and photonic devices. In the growth and processing of these materials, nanometer scale interdiffusion happens that are generally undesirable for device performance. With higher Ge molar fractions and higher compressive strains, Si-Ge interdiffusion can be much faster than dopant diffusion. However, Si-Ge interdiffusion behaviors have not been well understood until recent years. Much less studies are available for GeSn. This review starts with basic properties and the applications of major group IV semiconductors, and then reviews the progress made so far on Si-Ge and Ge-Sn interdiffusion behaviors. Theories, experimental methods, design and practical considerations are discussed together with the key findings in this field.

Oxide-Free Three-Dimensional Germanium/Silicon Core–Shell Metalattice Made by High-Pressure Confined Chemical Vapor Deposition

“…Earlier studies of core–shell Ge–Si nanocrystals have also noted a blue shift in the absorption edge onset due to strain . Ge and Si have a lattice mismatch of ∼4%, and it has been shown that lattice mismatch-induced strain is often compensated by interdiffusion of Ge and Si. ,− The shift in the Ge 3d edge in close proximity to the shell and the presence of a Ge–Si vibrational mode in the Raman spectrum indicate the possibility of interdiffusion leading to a change in the bonding environment of Ge. Since the shift in the Ge 3d edge occurs at sites close to or in the shell, we believe that the Ge–Si region is localized at the interface/shell and not in the Ge core.…”

“…The shell and core interaction serve as a second parameter. The shell thickness and controlled interdiffusion of Ge and Si have been used previously in nanostructures to modify the strain and alloy composition at the interface, providing control of the band offset, band gap and charge carrier distribution in the material. ,,,,− The confinement of both electrons and holes in an oxide free Ge nanostructure can be realized in a core–shell metalattice and in principle can be tuned to affect the charge carrier mobility.…”

A unified theory of free energy functionals and applications to diffusion

“…Finally, we consider interdiffusion in SiGe, a highly studied phenomenon with broad technological importance ( 47 – 52 ). Our choice of this system as an additional case study is motivated by two characteristics.…”

“…First, remarkably and somewhat uniquely, a large body of work ( 48 , 49 , 53 ) has established reasonable estimates for both the equilibrium thermodynamic and diffusion properties relevant to SiGe interdiffusion, enabling quantitative and predictive modeling. Second, we use the very simple phase behavior of the Si-Ge solid solution to demonstrate that gradient energy contributions may be significant in unexpected situations—notably, most diffusion modeling in semiconductor systems assumes Fickian physics in which gradient energy contributions are neglected ( 47 ).…”

“…Literature data ( 47 , 48 ) are used to fully parametrize the GSG model, including the chemical potential function, the self-diffusivity, and the coherency strain contribution ( 21 , 47 ) ( SI Appendix , Supplementary Text B ). The only remaining parameter is the effective interaction range, , which we fix to be twice the lattice parameter, i.e., (see SI Appendix , Supplementary Text C , for additional results with and ).…”