Ultrathin amorphous Si layer for the growth of strain relaxed Si_(0.75)Ge_(0.25) alloy layer

摘要

We propose a method for the growth of strain relaxed and smooth Si_(0.75)Ge_(0.25) alloy layers on a Si(001) substrate. In this method, we have used an ultrathin amorphous Si (UTA-Si) layer as a buffer layer and implemented a two-step process to grow the top alloy layer. High-resolution x-ray diffraction studies show that the alloy layers are highly relaxed. Topographic studies by contact mode atomic force microscopy show that the surfaces are very smooth. UTA-Si works as a strain adjuster and helps to reduce residual strain introducing dislocation in the buffer and substrate regions. However, it was observed that the residual strain and the surface morphology depend on the thickness of the UTA-Si buffer layers and also on the growth mode of the alloy layer.