The formation of crystal defects in a Ge-on-insulator layer, fabricated by oxidizing a SiGe-on-insulator layer (Ge-condensation technique), was studied systematically. It was found that the crystal defects in the Ge-on-insulator layer were threading dislocations and micro-twins that were formed mainly for Ge fraction ranges above ~0.5. When the Ge fraction reached ~1 and the Ge-on-insulator layer was formed, the density of micro-twins significantly decreased and their width considerably increased. The relaxation of compressive strain, observed in SiGe-on-insulator and Ge-on-insulator layers, could not be attributed to the formation of the micro-twins, but to perfect dislocations that could not be detected as defects in lattice images.

The Generation of Crystal Defects in Ge-on-Insulator (GOI) Layers in the Ge-Condensation Process. S.Nakaharai, T.Tezuka, N.Hirashita, E.Toyoda, Y.Moriyama, N.Sugiyama, S.Takagi: Semiconductor Science and Technology, 2007, 22, S103-6