Tensile-strained Ge1−x Sn x layers on Si(001) substrate by solid phase epitaxy featuring seed layer introduction

Herein, we examined the seed layer-induced solid-phase epitaxy (SPE) of Ge 1− x Sn x layers on Si(001) substrate toward their in-plane strain control. We sequentially deposited crystallized Ge 1− x Sn x seed layers at 360 °C with thicknesses of 2 and 4 nm and amorphous Ge 1− x Sn x layers at 80 °C. First, it was found that the thicker Ge 1− x Sn x seed layer effectively promotes the Ge 1− x Sn x epitaxial growth, whereas polycrystalline Ge 1− x Sn x is likely to be formed for the no seed layer case. Then, we discussed the possible role of the seed layer in SPE promotion of the Ge 1− x Sn x layer on Si(001). Finally, we demonstrated that the in-plane strain ε in the SPE-Ge 1− x Sn x layer can be controlled by the annealing temperature according to the thermal expansion coefficient difference between the SPE-Ge 1− x Sn x layer and Si substrate. In this study, we succeeded in forming tensile-strained Ge and Ge 1− x Sn x layers on Si(001) substrate by 500 °C annealing; the ε values were 0.20% and 0.16%, respectively.