MONTE-CARLO SIMULATIONS OF GE SEGREGATION IN STRAINED SI AND SIGE ALLOYS

A simple Monte Carlo simulation model has been developed to study the segregation of Ge in strained Si and Si1-xGex structures. The model is fitted to experimental SIMS data on the low concentration exponential surface segregation and the high concentration self-limited surface s egregation at 450 and 560-degrees-C. The model treats the surface segr egation as due to a thermally activated exchange process either during the adatom diffusion or after the capture of the adatom at a step. Th e simulated build-up of the Ge surface concentration at the growth of Si0.9Ge0.1 agrees well with experimental data. The simulations show th at the surface segregation is negligible at 350-degrees-C and has a ma ximum at approximately 470-degrees-C. Growth simulations of ultrathin superlattices at 450-degrees-C show strongly broadened interfaces in t he Ge bulk concentration profiles.