Strain-relaxed Si1-xGex and strained Si grown by sputter epitaxy

Strained Si on our previously proposed strain-relief relaxed thin quadruple-Si1-xGex-layer buffer was formed by sputter epitaxy, the buffer relaxation mechanism and controllability of which were basically the same as those of gas-source molecular beam epitaxy (GS-MBE); the strained-Si crystallinity obtained by sputter epitaxy was largely comparable to that obtained by GS-MBE. By using sputter epitaxy, a flatter strained Si surface that exhibits almost no cross-hatch undulation morphology is obtained. The strain rate of the topmost 60-nm-thick strained Si layer grown on the quadruple-Si1-xGex-layer buffer with a total thickness of 240nm and a top Ge content of 0.35 was 0.84% in the lateral direction. The results suggest that our environmentally light-load sputter epitaxy method can be applied to the fabrication of high-density Si/Si1-xGex strained devices.