A study of the effect of misfit-induced strain on the kinetics of solid phase epitaxy in the Si1−xGex on 〈001〉 Si system

Abstract

In this paper we present the results of an experimental determination of the rate of solid phase epitaxical regrowth of amorphous Si1−xGex on 〈001〉 Si as a function of temperature and Ge concentration. Layers of chemical vapor deposited Si1−xGex roughly 200-nm thick containing 5.4, 11.6, and 17.0 at. % Ge were amorphized with a two-step process of 100 keV, followed by 200 keV, 29Si ion implantation. This procedure left the near surface region of the substrate, including the entire Si1−xGex film, amorphous to a depth of 380 nm. The epitaxical recrystallization of the alloy portion (5.4, 11.6, or 17 at. % Ge) of the amorphous layer results in the development of large lattice mismatch stresses (0.5–2 GPa). The rate of epitaxical regrowth of the amorphous material was studied with isothermal heating and in situ transmission electron microscopy observations. Isothermal annealing at temperatures between 476 and 602 °C show that, compared to pure unstrained Si, the rate of regrowth is decreased in strained alloys of Si1−xGex. Furthermore, we report that the activation energy for strained-layer regrowth of Si1−xGex is not a strong function of composition and, for all three compositions, was in the range 3.2±0.2 eV. This is significantly larger than the activation energy for the homoepitaxical regrowth of unstrained pure Si. Stress related origins of these observations are discussed.