Monte Carlo modeling of the electron mobility in strained Si_(1-x)Ge_x layers on arbitrarily oriented Si_(1-y), Ge_y substrates

摘要

Under strain the electronic properties of Si and SiGe significantly change. For the semiconductor industry the improvement of the kinetic properties is most interesting. In this work we present Monte Carlo modeling of the low field electron mobility in strained Si_(1-x)Ge_x layers grown on relaxed Si_(1-y)Ge_y substrates of arbitrary orientation. An analytical conduction band model is used. The valley splitting is calculated using linear deformation-potential theory. The dependence on the substrate orientation is taken into consideration by transforming the strain tensor. Hooke's law is then used to determine the elements of the strain tensor in the principle coordinate system. The phonon and ionized impurity scattering rates are modified to account for the change of the conduction band. A zero field Monte Carlo method used to calculate the low field mobility tensor in the strained material is described and the influence of the Pauli exclusion principle is discussed. Simulation results are given for both undoped and doped layers for different compositions x and y as well as for several substrate orientations. The anisotropic behavior of the mobility as a function of the in-plane angle is demonstrated and the interplay between the strain effects and effects due to Fermi-Dirac statistics is shown.