Structural and Optical Properties of Ge1-XSnx Alloys Grown on GaAs (001) by R. F. Magnetron Sputtering

Ge_1-xSn_x alloys were grown on GaAs (001) substrates in a conventional R. F. magnetron sputtering system with two independent plasmas not simultaneous focus to substrate. We determined the in-plane and in-growth lattice parameters for different Sn concentrations by high resolution X-ray diffraction (HRXRD). We observed that Ge_1-xSn_xlayers with low Sn concentrations have pseudomorphic characteristics. But this layers relax at Sn concentrations higher than the ones growth on Ge (001) substrates.

We also determined the band gap transitions and we found that the indirect-direct band gap crossover occurs as is predicted in Ge_1-xSn_x alloys growth on Ge (001). Raman spectroscopy confirms the presence and Sn concentrations of the Ge_1-xSn_x layers.