Critical thickness of strained Si_1-xGe_x on Ge(111) and Ge-on-Si(111)

Abstract

Abstract Critical thicknesses ( t c ) of Ge-rich strained Si 1-x Ge x layers grown on various Ge substrates are precisely determined experimentally, and t c is revealed to strongly depend on the substrate conditions. We find that t c of Si 1-x Ge x on Ge-on-Si(111) is much lower than that on the Ge(111) substrate for x > 0.75 while, for x < 0.75, t c becomes equivalent between both substrates, origins of which can be discussed in terms of dislocation nucleation and surface ridge formation. This study provides critical design parameters for strained SiGe(111) based devices, such as high-mobility channels and spintronic devices on a Si platform.