Strain control of Si and Si_1-xGe_x layers in the Si/Si_1-xGe_x/Si heterostructures by stripe-shape patterning for future Si-based devices

By stripe-shape patterning of the Si/strained Si_1-xGe _x/Si(100) heterostructures, the strained Si_1-xGe _x layer is relaxed and the relaxation induces tensile strain in the capping Si layer. The degree of the relaxation becomes larger for a narrower stripe, higher Ge fraction, and thinner capping Si layer. It is found that the relaxation in Si_1-xGe_x layer proceeds in the region from the stripe edge to the inner position of 0.4 μm away from the edge. The strain degree in the capping Si layer becomes smaller towards depth direction for the thicker capping Si layer than 5-10 nm. The resistivity measurements of the in-situ doped capping Si and Si_1-xGe_x layers in the stripe-shape patterned heterostructure show that the tensile strain induces mobility enhancement for both electron and hole, and the relaxation of strain induces mobility reduction for hole in Si_1-xGe_x layer.