Effects of BF₂ and B implantation-doping on crystalline degradation of pseudomorphic metastable Ge_0.06Si_0.94

Pseudomorphic metastabile Ge_0.06Si_0.94 layers grown by molecular beam epitaxy (MBE) on Si (100) substrates were implanted at room temperature by 70 keV BF₂ ions with two different doses of 3 × 10¹³ and 2.5 × 10¹⁴ cm^-2, or by 16 keV B ions with a dose of 4 × 10¹⁴ cm^-2. The implanted samples were subsequently annealed at 800 and 900°C for 30 min in a vacuum tube furnace. Observed by 2 MeV ⁴He channeling spectrometry before annealing, only the sample implanted at a dose of 2.5 × 10¹⁴ BF₂ cm^-2 is amorphized from surface to a depth of about 90 nm. Crystalline degradation of post-annealed Ge_0.06Si_0.94 samples becomes pronounced as the dose increases. Even though the both samples implanted with 3 × 10¹³ BF₂ cm^-2 and 4 × 10¹⁴ B cm^-2 initially show almost the same levels of radiation damage in the channeling spectra, the sample implanted at 3 × 10¹³ BF₂ cm^-2 only conserves the same crystalline quality as the as-grown GeSi after being annealed. It is concluded that such a low dose of 3 × 10¹³ BF₂ cm^-2 can be doped by implantation without causing radiation or strain-induced defects in the pseudomorphic GeSi.