Raman study of ge/si strained layer superlattices grown on different substrate orientations

We present the growth and characterization of Ge/Si strained layer superlattices grown on different substrate orientations. Prior to the growth of the superlattices, a relaxed thick GexSi1-x buffer layer is grown on Si substrate to symmetrize the strain distribution and thus maintain pseudomorphic growth of the superlattices. The effective Ge fraction x is used to define the degree of interface mixing of these superlattices. It is found that for samples grown on the same orientaion, the degree of interface mixing is higher for samples with smaller period lengths. The samples grown on (110) and (111) substrates also have a higher degree of interface mixing than those grown on (100) substrates. The thermal stability of these Ge/Si strained layer superlattice samples is also studied.