Short and long annealing of high-dose arsenic-implanted pseudomorphic Ge_xSi_1-x on Si(100)

Metastable pseudomorphic epi-Ge_xSi_1-x (x=8%, 16%) films of a common thickness of 145±10 nm were deposited on Si(100) substrates by chemical vapor deposition and then implanted at room temperature with 90 keV arsenic ions to a dose of 1.5×10¹⁵/cm². This implantation amorphizes the top ∼125 nm of the epi-GeSi layers. Implanted as well as nonimplanted GeSi samples were subsequently annealed by (1): short (10-40 s) lamp annealing in nitrogen ambient at 600-800 °C; or (2): long (30 min) furnace annealing in vacuum (∼5×10^-7 Torr) at 500-800 °C. Silicon samples were also implanted and annealed as references. The amorphized ep-GeSi recrystallizes via solid-phase epitaxy when annealed at or above 500 °C. The initial pseudomorphic strain of the epi-GeSi is thereby lost for both short and long annealing. High densities of dislocations (10¹⁰-10¹¹/cm²) are typically present in the regrown GeSi layers, but not in the regrown Si samples. Just after the completion of solid-phase epitaxial regrowth, ∼80%-100% of the implanted arsenic ions become electrically active; further annealing decreases the activation. We conclude and generalize that metastably strained GeSi layers amorphized by a high dose of implanted dopants will not recover their original crystallinity and strain after solid-phase epitaxial regrowth, regardless of annealing procedure, although the implanted dopants are electrically activated in the process.