Epitaxial growth of non-cubic silicon

We report about the formation of a Si twinning-superlattice (TSL). Si layers containing 180° rotation twin boundaries arranged periodical along the [111] direction and only separated by 2.5 nm (corresponding to TSL) have been prepared by molecular beam epitaxy. The method consists of repeating of several growth and annealing circles on boron(B)-predeposited undoped Si substrates. It is shown that the amount of subsurface B on the surface and the growth mode influence the formation of twin boundaries. Only the nucleation of Si on the (3×3)R30°-Si(111) surface covered by atleast 1/3 ML B resulted in the formation of a 180° rotation twin. The presented technology should also be suitable to prepare a new type of semiconductor heterostructures based on Si polytypes.