Impact of the growth parameters on the structural properties of Si_(0.8)Ge_(0.2) virtual substrates

摘要

We have focused in this paper on the impact of the growth rate and of the grading rate on the structural properties of Si_(0.8)Ge_(0.2) virtual substrates grown at 900°C in a commercial reduced pressure chemical vapour deposition reactor. Adopting a grading rate of 4% Ge / μm together with a growth rate around 140 nm min.~(-1) yields very high quality Si_(0.8)Ge_(0.2) virtual substrates. Their macroscopic degree of strain relaxation is indeed very close to 100%, their surface root mean square roughness is around 2.3 nm and most importantly their field threading dislocation density is of the order of 6x10~4 cm~(-2) only, with almost no pile-ups.