High Ge content SGOI substrates obtained by the Ge condensation technique: A template for growth of strained epitaxial Ge

In the first part of this work, the fabrication of silicon germanium-on-insulator substrates (SGOI) by the Ge condensation technique was studied. Ge atomic fractions as high as 93% have been obtained while maintaining nice structural properties of the films. We show that these layers exhibit a large compressive strain and that the strain can be lowered by introducing some annealing steps in argon ambient during the condensation. SGOI substrates with a Ge atomic fraction of 75% were subsequently used as template for the growth of strained epitaxial Ge layers. Because of the important strain in the SGOI, the temperature for the in-situ bake prior to the growth has to be carefully selected in order to avoid relaxation. Ge layers with compressive strain up to −1% and thicknesses up to 40 nm have been obtained. The crystal quality, roughness and thermal stability of the strained Ge layers were finally evaluated.