Critical thickness for strain relaxation of Ge1−xSnx (x ≤ 0.17) grown by molecular beam epitaxy on Ge(001)

Abstract

We investigated the critical thickness (hc) for plastic relaxation of Ge1−xSnx grown by molecular beam epitaxy. Ge1−xSnx films with various Sn mole fraction x (x ≤ 0.17) and different thicknesses were grown on Ge(001). The strain relaxation of Ge1−xSnx films and the hc were investigated by high-resolution x-ray diffraction and reciprocal space mapping. It demonstrates that the measured hc values of Ge1−xSnx layers are as much as an order of magnitude larger than that predicted by the Matthews and Blakeslee (M-B) model. The People and Bean (P-B) model was also used to predict the hc values in Ge1−xSnx/Ge system. The measured hc values for various Sn content follow the trend, but slightly larger than that predicted by the P-B model.