Defect structure of Ge/epi-Gd2O3/Si heterostructures grown by Molecular beam epitaxy

A systematic investigationof defect structure of Ge(111)/epi-Gd2O3 (111)/Si (111) heterostructuresby X-rays diffraction (XRD) and Transmission electron microscopy (TEM) methods.The hetero-structures were grown by molecular beam epitaxy (MBE). Ge growth begins in the Volmer-Weber growth mode, the resultant islands coalesce within the first ∼10 nm of growth, beyond which a smooth two-dimensional surface evolves. Coalescence of the initially formed islands results in the formation of rotation and reflection microtwins, which constitute a volume fraction of less than 1% of the epilayers. It is also observed that while the stacking sequence of the (111) planes in the Ge epilayer is similar to that of the Si substrate, the (111) planes of the Gd2O3 epilayer are rotated by 180° about the [111] direction.