Strain relief in epitaxial fluoride buffer layers for semiconductor heteroepitaxy

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Abstract
Strain in epitaxial BaF2 layers grown by molecular beam epitaxy on CaF2 covered Si is found to be completely relieved at room temperature in films thicker than ∼250 nm, despite a large lattice and thermal expansion mismatch. In thinner films, planar tensile strain up to 5×10−3 is observed. Partial or complete strain relief occurs during temperature cycling near room temperature, and even if further layers are grown on top of the BaF2 film. This suggests that such films may be of use as buffers to relieve stresses in heteroepitaxial semiconductor-on-semiconductor structures.