Effects of BF2 and B Implantation-Doping on Crystalline Degradation of Pseudomorphic Metastable Ge0.06Si0.94

Abstract

Pseudomorphic metastable Ge0.06Si0.94 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 Ge0.06Si0.94 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.