REAL-TIME STRESS EVOLUTION DURING SI1-XGEX HETEROEPITAXY - DISLOCATIONS, ISLANDING, AND SEGREGATION

We have used sensitive real-time measurements of film stress during Si 1-xGex molecular beam epitaxy to examine strain relaxation due to cohe rent island formation, and to probe the kinetics of Ge surface segrega tion. We first describe our novel curvature-measurement technique for real-time stress determination. Measurements of the relaxation kinetic s during high temperature Si79Ge21 growth on Si (001) are reported in which formation of highly regular arrays of [501]-faceted islands prod uce 20% stress relaxation. An island shape transition is also observed that reduces the effective stress by up to 50% without dislocations. Nonuniform composition profiles due to Ge surface segregation during g rowth of planar alloy films are determined with submonolayer thickness resolution from the real-time stress evolution. Up to two monolayers of Ge can segregate to the growth surface.