Thermal stability of biatomic Si sheets in Ge

Abstract

Certain short-period Si/Ge superlattices containing biatomic sheets of Si have been proposed as candidates for light-emitting Si-based structures. The thermal stability of biatomic sheets of Si in such structures is thus of interest and has been investigated here using the way in which their distinctive double-peaked lines in the Raman spectrum changes with annealing. The Raman data obtained were correlated with the results of an electron microscopical examination of the annealed samples which further demonstrated that, at 700 degrees C, rather than the layers becoming mixed through a simple interdiffusion process they instead become periodically of varying thickness in a way which would lower their strain energy. It is postulated that the changes in layer thickness arise as a result of interface diffusion. The results provide a useful starting point for understanding how direct-gap Si-based structures can be processed.