High Crystalline Quality of Si0.5 Ge0.5 Layer Grown on a Novel Three-layer Strain Relaxed Buffer

A novel three-layer graded SiGe strain relaxed buffer, whose Ge concentration increased from bottom to top by roughly 10% with an in-situ annealing after each layer grown, is developed to effectively constrain the threading dislocation and attain a high crystalline quality of Si
_0.5
Ge
_0.5
layer. Moreover, a chemical mechanical planarization step can be applied to the strain relaxed buffer to further improve the surface roughness and crystalline quality of Si
_0.5
Ge
_0.5
layer. So, a high crystal quality and atomically smooth surface Si
_0.5
Ge
_0.5
layer can be successfully realized. Meanwhile, this novel three-layer graded SiGe strain relaxed buffer also can increase the critical thickness of Si
_0.5
Ge
_0.5
from less than 20nm to at least 50 nm and attain 0.6% compressive strain for Si
_0.5
Ge
_0.5
layer by utilizing the scanning moiré fringe imaging technique.