Substrate orientation-dependence of electron mobility in strained SiGe layers

The behavior of the low field electron mobility in strained active SiGe layers on SiGe substrates with arbitrary orientation and Ge mole fraction is investigated using Monte Carlo simulation. Euler´s angles are introduced to determine the substrate orientation and direction for the in-plane component of the mobility. The strain tensor is transformed to a general form and the splitting of X and L valleys is then calculated using linear deformation potential theory. Additionally the hydrostatic shift is taken into account. For doped materials, the ionized impurity scattering rate is modified to take into consideration all valleys and orientations. The Pauli exclusion principle is considered for high doping level and its interplay with the strain effects is discussed.