Epitaxial growth of GexSi

Abstract

Epitaxial growth of ${\mathrm{Ge}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}$ alloy films on a Si substrate is simulated employing a direct Monte Carlo technique. In addition to various interlayer and intralayer diffusion processes of Si and Ge atoms, we include a model strain-driven mechanism that gives rise to defects (local out-of-registry regions) in the overgrowth. Our simulation indicates that (i) the overgrowth is defect-free for $x\ensuremath{\le}0.2$, (ii) defect formation is inevitable for $x\ensuremath{\ge}0.5$, and (iii) the transition between the two cases occurs smoothly within $0.2lxl0.5$. On the basis of our simulation, we predict that for a very low Ge fraction $xl0.1$, the critical temperature for the onset of good epitaxial growth will be substantially above the 400\ifmmode^\circ\else\textdegree\fi{}C found for higher $x$ values.