Impact of hydrogen surfactant on crystallinity of Ge1−xSnxepitaxial layers

The effect of a hydrogen surfactant on the crystallinity of a Ge 1− x Sn x epitaxial layer was investigated. The improvement of crystallinity on the in-plane uniformity of Ge 1− x Sn x epitaxial layer was observed by X-ray diffuse scattering and transmission electron microscopy. We also observed the decrease in the surface roughness of the Ge 1− x Sn x epitaxial layer. This indicates the suppression of the three-dimensional growth mode of Ge 1− x Sn x epitaxial layer due to a compressive strain. In addition, we observed the reduction in acceptor-like defect density in an undoped-Ge 1− x Sn x epitaxial layer from the capacitance–voltage characteristics of a metal–oxide–semiconductor capacitor. Consequently, introducing hydrogen during the growth leads to the improvement of the crystalline quality of the Ge 1− x Sn x epitaxial layer.