Solid phase epitaxial re-growth of Sn ion implanted germanium thin films

Doping of Ge with Sn atoms by ion implantation and annealing by solid phase epitaxial re-growth process was investigated as a possible way to create Ge_1-xSn_x layers. Ion implantation was carried out at liquid nitrogen to avoid nano-void formation and three implant doses were tested: 5×10¹⁵, 1×10¹⁵ and 5×10 ¹⁴ at/cm², respectively. Implant energy was set to 45 keV and implants were carried out through an 11 nm SiN_xO_y film to prevent Sn out-diffusion upon annealing. This was only partially effective. Samples were then annealed in inert atmosphere either at 350°C varying anneal time or for 100 s varying temperature from 300 to 500°C. SPER was effective to anneal damage without Sn diffusion at 350° for samples implanted at medium and low fluences whereas the 5×10¹⁵ at/cm² samples remained with a ∼15 nm amorphous layer even when applying the highest thermal budget.