In-plane strain fluctuation in strained-Si/SiGe heterostructures

Abstract

In-plane strain fluctuation in the strained-Si/relaxed-SiGe heterostructure was studied by micro-Raman spectroscopy. It was found that misfit dislocation, which is necessarily induced by strain relaxation of SiGe buffer layers, caused micrometer-scale inhomogeneous strain field in the strained-Si layer as well as SiGe buffer, which may degrade device performance. After annealing, the fluctuation was found to be enhanced due to partial strain relaxation of strained Si, particularly in the region where tensile strain was relatively high before annealing. From homoepitaxial growth of SiGe on planarized SiGe buffer layers, it was confirmed that the growth rate also fluctuated laterally, in correspondence with the in-plane strain variation.