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-xGe x 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 Si 1-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.