Growth of GeSnSiC layers for photonic applications

This work presents epitaxial growth of intrinsic and doped GeSnSiC layers using Ge2H6, SnCl4, CH3SiH3, B2H6, PH3 and Si2H6 deposited at 290–380 °C on strain relaxed Ge buffer layer or Si substrate by using reduced pressure chemical vapor deposition (RPCVD) technique. The GeSnSi layers were compressively strained on Ge buffer layer and strain relaxed on Si substrate. It was demonstrated that the quality of epitaxial layers is dependent on the growth parameters and that the Sn content in epi-layers could be tailored by growth temperature. The Sn segregation caused surface roughness which was decreased by introducing Si and Si-C into Ge layer. content in GeSn was carefully determined from the mismatch, both parallel and perpendicular, to the growth direction when the Poisson ratio was calculated for a certain Ge-Sn composition. The X-ray results were excellently consistent with Rutherford Backscattered Spectroscopy (RBS). Strain relaxed GeSn layers were also used as virtual substrate to grow tensile-strained Ge layers. The Ge cap layer had low defect density and smooth surface which makes it a viable candidate material for future photonic applications.