Kinetic roughening and smoothing of the crystalline-amorphous interface during solid phase epitaxial crystallization of GeSi alloy layers

The morphology of the crystalline-amorphous interface is studied during solid-phase epitaxial crystallization of amorphous GeSi alloy layers with depth-dependent Ge distributions. The interface is shown to undergo an initial strain-induced roughening transition when the Ge concentration exceeds 6.6 at. %. As crystallization continues in strain-relaxed material the interface is shown to further roughen or smooth in response to changes in the Ge distribution. This evolution of the interface morphology is shown to be a consequence of kinetic effects whereby the differential velocity between the leading and trailing edges of the rough interface increases in regions of increasing Ge concentration and decreases in regions of decreasing Ge concentration.