Tensile-strained Ge_1-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 Ge1-xSnx layers on Si(001) substrate toward their in-plane strain control. We sequentially deposited crystallized Ge1-xSnx seed layers at 360 degrees C with thicknesses of 2 and 4 nm and amorphous Ge1-xSnx layers at 80 degrees C. First, it was found that the thicker Ge1-xSnx seed layer effectively promotes the Ge1-xSnx epitaxial growth, whereas polycrystalline Ge1-xSnx 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 Ge1-xSnx layer on Si(001). Finally, we demonstrated that the in-plane strain epsilon in the SPE-Ge1-xSnx layer can be controlled by the annealing temperature according to the thermal expansion coefficient difference between the SPE-Ge1-xSnx layer and Si substrate. In this study, we succeeded in forming tensile-strained Ge and Ge1-x Sn x layers on Si(001) substrate by 500 degrees C annealing; the epsilon values were 0.20% and 0.16%, respectively.