Improvement of structural properties of Si/Ge superlattices

Abstract

Short-period Si/Ge strained-layer superlattices are grown by molecular beam epitaxy (MBE) on Si(100) and Ge(100) substrates. Low-energy electron diffraction and Auger electron spectroscopy are performed between growth intervals, to obtain structural and compositional information. Raman spectroscopy and transmission electron microscopy are used for ex-situ characterization. Different buffer layers, varying in thickness and composition, are investigated to minimize the defect density in a symmetrically strained Si/Ge superlattice and to optimize the superlattice quality for various strain adjustments. The maximum thickness for two-dimensional and lattice-matched growth of the individual silicon and germanium layers on a strain-symmetrizing buffer are discussed. In addition, the thermal stability of short-period Si/Ge superlattices is studied as a function of strain distribution.