Effects of BF2+ implantation on the strain-relaxation of pseudomorphic metastable Ge0.06Si0.94 alloy layers

Metastable pseudomorphic Ge_0.06Si_0.94 alloy layers grown by molecular beam epitaxy (MBE) on Si (1 0 0) substrates were implanted at room temperature by 70 keV BF₂⁺ ions with three different doses of 3 × 10¹³, 1 × 10¹⁴, and 2.5 × 10¹⁴ cm^?2. The implanted samples were subsequently annealed at 800°C and 900°C for 30 min in a vacuum tube furnace. Observed by MeV ⁴He channeling spectrometry, the sample implanted at a dose of 2.5 × 10¹⁴ BF₂⁺ cm^?2 is amorphized from surface to a depth of about 90 nm among all as-implanted samples. Crystalline degradation and strain-relaxation of post-annealed Ge_0.06Si_0.94 samples become pronounced as the dose increases. Only the samples implanted at 3 × 10¹³ cm^?2 do not visibly degrade nor relax during anneal at 800°C . In the leakage current measurements, no serious leakage is found in most of the samples except for one which is annealed at 800°C for 30 min after implantation to a dose of 2.5 × 10¹⁴ cm^?2. It is concluded that such a low dose of 3 × 10¹³ BF₂⁺ cm^?2 can be doped by implantation to conserve intrinsic strain of the pseudomorphic GeSi, while for high dose regime to meet the strain-relaxation, annealing at high temperatures over 900°C is necessary to prevent serious leakages from occuring near relaxed GeSi/Si interfaces.