Improved hole mobilities and thermal stability in a strained-Si/ strained-Si_(1-y)Ge_y/strained-Si heterostructure grown on a relaxed Si_(1-x)Ge_x buffer

摘要

A dual channel heterostructure consisting of strained-Si/strained-Si_(1-y)Ge_y on a relaxed Si_(1-x)Ge_x buffer (y > x), provides a platform for fabricating metal-oxide-semiconductor field-effect transistors with high hole mobilities. Ge outdiffusion during high temperature processing steps from the strained-Si_(1-y)Ge_y layer into the relaxed Si_(1-x)Ge_x buffer reduces the hole mobilities in these heterostructures. We present a strained-Si/strained-Si_(1-y)Ge_y/strained-Si heterostructure on relaxed Si_(1-x)Ge_x, in which the strained-Si layer between the strained-Si_(1-y)Ge_y and relaxed Si_(1-x)Ge_x reduces Ge outdiffusion. Improved hole mobilities in this heterostructure are also observed over similar dual channel heterostructures which could be a result of better hole confinement in the strained-Si_(1-y)Ge_y layer of the proposed heterostructure.