Dependence of Hole Mobilities on the Growth Direction and Strain Condition in $Si_{1-x}Ge_x$ Layers Grown on $Si_{1-y}Ge_y$ Substrate

$Si_{1-y}Ge_y$ 위에 성장시킨 $Si_{1-x}Ge_x$ 에서 성장방향과 응력변형 조건에 따른 정공의 이동도 연구

The band structures of $Si_{1-x}Ge_x$ layers grown on $Si_{1-y}Ge_y$ substrate are calculated using k$\cdot$p and strain Hamiltonians. The hole drift mobilities in the plane direction are then calculated by taking into account the screening effect and the density-of-states of the impurity band. When $Si_{1-x}Ge_x$ is grown on Si substrate, the mobilities of (110) and (111) $Si_{1-x}Ge_x$ layers are larger than that of (001) $Si_{1-x}Ge_x$. However, due to the large defect and surface scattering, (110) and (111) $Si_{1-x}Ge_x$ layers may not be useful for the development of the fast device. Meanwhile, when Si is grown on $Si_{1-y}Ge_y$ substrate, the mobilities of (001) and (110) Si layers are greatly enhanced. Based on the amount of defect and the surface scattering, it is expected that Si grown on (001) $Si_{1-y}Ge_y$ substrate, where the Ge contents is larger than 10%(y>0.1), has the highest mobility.