Facet growth under stress: the limits of strained-layer stability

A crystal facet is metastable under stress, but the process of growth or sublimation roughens the facet and is expected to render it unstable. This poses a fundamental limit for heteroepitaxial growth of planar layers, e.g., in semiconductor devices. An analysis shows that this facet-growth instability can be suppressed to an arbitrary degree by growing slowly. Moreover, the local stress ("force dipole") inherent in atomic steps introduces a new, purely kinetic effect that dominates at low strain and can render planar growth dynamically stable.