Transport in the surface channel of strained Si on a relaxed Si_{1 - x}Ge_x substrate

A real time Green's functions formalism is used to study the electron transport in a uniformly-doped strained-Si surface channel on a relaxed Si_1-xGe_x buffer. Our theoretical mobility results, for N_s = 10¹² cm^-2 and for several Ge concentrations in the substrate, are in good agreement with the available experimental data. We find that the low-field electron mobility is affected strongly by rather high fixed-oxide charge, interface-trap and surface-roughness scattering, in addition to non-polar optical phonon scattering. Significant mobility enhancement with increasing Ge fraction in the substrate is observed only for low values of N_s. The weighting coefficients a and b for the inversion and depletion charge densities in the definition of the effective transverse electric field E_eff are not found to be considerably affected by the strain. Strain induced increase of the population of the higher lying sub-bands from the Δ₂-band leads to a reduction of the inversion layer capacitance C_inv.