Strain conservation in implantation-doped GeSi layers on Si(100)

Abstract

Metastable pseudomorphic GeSi layers grown by chemical vapor deposition or by molecular beam epitaxy on Si(100) substrates were implanted at room temperature. The implantations were performed with 90 keV As ions to a dose of 1 x 1013 cm-2 for Ge0.08Si0.92 layers and 70 keV BF2 ions to a dose of 3x 1013 cm-2 for Ge0.06Si0.94 layers. The samples were subsequently annealed for short 10–40 s durations in a lamp furnace with a nitrogen ambient, or for a long 30 min period in a vacuum tube furnace. For Ge0.08Si0.92 samples annealed for a 30 min-long duration at 700°C, the dopant activation can only reach 50% without introducing significant strain relaxation, whereas samples annealed for short 40 s periods (at 850°C) can achieve more than 90% activation without a loss of strain. For Ge0.06Si0.94 samples annealed for either 40 s or 30 min at 800°C, full electrical activation of the boron is exhibited in the GeSi epilayer without losing their strain. However, when annealed at 900°C, the strain in both implanted and unimplanted layers is partly relaxed after 30 min, whereas it is not visibly relaxed after 40 s.