Strain Measurements in Si/Si_0.5Ge_0.5 Superlattices by He Ion Channeling

Abstract

He ion channeling experiments have been performed on molecular beam grown Si/SiGe superlattices to determine the strain fields. Angular yield scans provide directly the tetragonal strains in the layers. In Si/Si_0.5Ge_0.5 superlattices grown on (100) Si only the SiGe layers are strained. Almost equal but opposite strains in the Si and SiGe layers have been found in a Si/Si_0.5Ge_0.5 superlattice deposited on a 230 nm thick Si_O.71Ge_0.29 buffer layer. Strain symmetrization yields the minimum elastic energy and thus to the most stable structure.