Growth and analysis of SnGe/Ge superlattice structures

Theoretical calculations show that superlattice structures strongly influence the band gap, in addition to the composition and strain. This paper investigates the growth of such structures. For this purpose, one monolayer (ML) of Sn and x ML of Ge (0 ≤ x ≤ 10) were stacked for ten times using molecular beam epitaxy. This corresponds to an average Sn content between 9% and 33%. These layer systems are analyzed using high-resolution X-ray diffractometry. The typical interference patterns due to the superlattice structure are observed. For Ge barriers with a thickness of up to five ML, a pseudomorphic growth could be observed. With thinner barriers, the upper regions begin to partially relax, and with the thinnest barrier of two Ge ML, partial demixing of the semiconductor crystal was observed. Temperature-dependent sheet conductivity and Hall measurements between 10 K and 300 K show an unintentional p-type conductivity of the reference sample which masks partly the superlattice effect.