Interdiffusion in a symmetrically strained Ge/Si superlattice

The x-ray diffraction technique is used to measure the interdiffusion coefficients of a symmetrically strained Ge/Si superlattice consisting of alternating Ge and Si layers grown on a Ge0.4Si0.6 buffer layer. The buffer layer was 200 nm thick and was grown on a Si (100) substrate in order to symmetrize the strain, and thus maintain pseudomorphic growth of the superlattice. After the sample was annealed at different temperatures with various times, the interdiffusion coefficient Dλ was determined by monitoring the intensity decay of the low-angle x-ray diffraction peak resulting from the superlattice structure. The activation energy is calculated to be 3.1±0.2 eV in the annealing temperature range of 640–780 °C.