Role of dislocations on Sn diffusion during low temperature annealing of GeSn layers

A study of the mechanism of Sn out-diffusion was performed by annealing Ge0.905Sn0.095 layers at 300 C-degrees. The changes in Sn composition and strain state were confirmed by x-ray diffraction and photoluminescence spectroscopy. Surface defects, appearing as Sn particles, with the highest density of 3.5 x 10(8) cm(-2) were detected by atomic force microscopy after annealing for 2 h. The strain in the GeSn layer stabilized for more prolonged annealing, while the density of particles decreased and their size increased. Annealing results are discussed in terms of Sn segregation and subsequent diffusion along dislocation lines, enhanced out-diffusion by dislocations migration, and surface particle coalescence.