Epitaxial Ge layer growth of low threading dislocation density and low surface roughness on Si(100) surface was investigated using a single wafer reduced pressure chemical vapour deposition system. Thin seed Ge layer was deposited at 300C at first to form two-dimensional Ge surface followed by thick Ge growth at 550C. A root mean square roughness of about 0.45nm was achieved. As-deposited Ge layers showed a high threading dislocation density of e.g. about 4 x 108/cm2 for a 4.7μm-thick Ge layer thickness. The threading dislocation density was decreasing with increasing Ge thickness. By applying a post-annealing process at 800C, the threading dislocation density was decreased by one order of magnitude. By introducing several cycle of annealing during the Ge growth interrupting the Ge deposition, threading dislocation densities as low as about 7 x 105/cm2 was achieved for 4.7μm Ge thick layer. Surface roughness of the Ge sample with the cyclic annealing process was in the same level as without annealing process (root mean square of about 0.44nm). The Ge layers were tensile strained as a result of a higher thermal expansion coefficient of Ge compared to Si in the cooling process down to room temperature. Enhanced Si diffusion was observed for annealed Ge samples. Direct band-to-band luminescence of the Ge layer grown on Si was demonstrated.

Low Threading Dislocation Density Ge Deposited on Si (100) using RPCVD. Y.Yamamoto, P.Zaumseil, T.Arguirov, M.Kittler, B.Tillack: Solid-State Electronics, 2011, 60[1], 2-6