Low-temperature growth of silicon and silicon-germanium alloy by ultrahigh vacuum ion-beam sputter deposition
The use of energetic (average energy $\simeq$ 18 eV), rather than thermal, Si beams increased Si(001) epitaxial thicknesses t$\rm\sb{e}$ by up to an order of magnitude over the growth temperature range $\rm T\sb{s}=80{-}300\sp\circ$C yielding t$\rm\sb{e}$ = 10 nm-1.2 $\mu$m at a growth rate R = 0.1 nm-s$\sp{-1}$. The overall increase in t$\rm\sb{e}$ is attributed primarily to more effective filling of interisland trenches which form during growth in the low adatom mobility two-dimensional multilayer mode and which provide preferential sites for the nucleation of the terminal amorphous phase. The evolution of surface roughness was found to be inconsistent with conventional scaling and hyperscaling laws and led to the formation of mounds separated by a well-defined length scale. In addition, Sb doping $\rm(\langle E\sb{Sb}\rangle\simeq14$ eV), corresponding to a steady-state surface coverage of only ${\simeq}4\times10\sp{-5}$ ML leading to bulk concentration of ${\simeq}2\times10\sp{18}$ cm$\sp{-3}$, at $\rm T\sb{s}=250{-}300\sp\circ$C increased the rate of surface roughening and decreased epitaxial thickness t$\rm\sb{e}$ by a factor of $\sbsp{>}{\sim}$2.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign