Critical thickness of strained Si1-xGex on Ge(111) and Ge-on-Si(111)

Abstract

Critical thicknesses (tc) of Ge-rich strained Si1-xGex layers grown on various Ge substrates are precisely determined experimentally, and tc is revealed to strongly depend on the substrate conditions. We find that tc of Si1-xGex on Ge-on-Si(111) is much lower than that on the Ge(111) substrate for x > 0.75 while, for x < 0.75, tc 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.