Evaluation of Anisotropic Three-Dimensional Strain Relaxation in Stripe-Shaped Ge_1-xSn_x Mesa Structure

We evaluated the anisotropic three-dimensional strain relaxation in the patterned Ge_1-xSn_x mesa structure by Raman spectroscopy and X-ray diffraction(XRD). The strain states in the channel region change complicatedly depending on the channel shape. Therefore, accurate strain evaluation technique is strongly desired. In this study, measurements were carried out using a thin Ge_1-xSn_x film grown epitaxially on a Ge substrate by metal organic chemical vapor deposition (MOCVD). After growing the epitaxial film, a stripe-shaped mesa structures simulating the channel shape were fabricated. From the results of Raman spectroscopy and XRD, strain relaxation was confirmed at pattern width W = 0.2 μm or less in the in-plane minor axis and the out-of-plane direction.