New approach to the high quality epitaxial growth of lattice-mismatched materials

Publisher Website
Google Scholar
Abstract
We have reconsidered the problem of the critical layer thickness h c for growth of strained heterolayers on lattice‐mismatched substrates, using a new approach which allows us to determine the spatial distribution of stresses in a bi‐material assembly and include the effects of a finite size of the sample. The possibility of dislocation‐free growth of lattice‐mismatched materials on porous silicon substrates is discussed as an example of a more general problem of heteroepitaxialgrowth on small seed pads of lateral dimension l, having a uniform crystal orientation over the entire substrate wafer. It turns out that for a given mismatch f, the critical film thickness h l c strongly depends on l, rising sharply when the latter is sufficiently small, l≲l min. The characteristic size l min( f ) below which, effectively, h l c ( f )→∞, is determined in terms of the experimentally known (or calculated for growth on a monolithic substrate) function h ∞ c ( f )≡h c ( f ). When l≲l min, then the entire elastic stress in the epitaxialfilm will be accommodated without dislocations.