Tensile-strained Ge_1−x Sn _x layers on Si(001) substrate by solid-phase epitaxy featuring seed layer introduction

Abstract

Herein, we examined the seed layer induced solid-phase epitaxy (SPE) of Ge1−x Sn x layers on Si(001) substrate toward their in-plane strain control. We sequentially deposited the crystallized Ge1−x Sn x seed layers at 360 °C with thicknesses of 2 and 4 nm and amorphous Ge1−x Sn x layers at 80 °C. First, it was found that the polycrystalline Ge1−x Sn x is likely formed for no seed layer case whereas the thicker Ge1−x Sn x seed layer effectively promotes the Ge1−x Sn x epitaxial growth. Then, we discussed a possible role of the seed layer on the SPE promotion on Si(001). Finally, we demonstrated that the in-plane strain ε in the SPE-Ge1−x Sn x layer can be controlled by the annealing temperature according to the thermal expansion coefficient difference between SPE-Ge1−x Sn x layer and Si substrate. In this study, we succeed to form tensile-strained Ge and Ge1−x Sn x layers on Si(001) substrate by 500 °C annealing; ε values were 0.28% and 0.18% respectively.