On the limits to Ti incorporation into Si using pulsed laser melting

摘要

Fabrication of p-Si(111) layers with Ti levels well above the solid solubility limit was achieved via ion implantation of 15keV ~(48)Ti~+ at doses of 10~(12) to 10~(16)cm~2 followed by pulsed laser melting using a Nd:YAG laser (FWHM = 6 ns) operating at 355 nm. All implanted layers were examined using cross-sectional transmission electron microscopy, and only the 10~16)cm~2 Ti implant dose showed evidence of Ti clustering in a microstructure with a pattern of Ti-rich zones. The liquid phase diffusivity and diffusive velocity of Ti in Si were estimated to be 9 × 10~(-4) cm~2/s and (2 ± 0.5) × 10~4m/s, respectively. Using these results the morphological stability limit for planar resolidification of Si:Ti was evaluated, and the results indicate that attaining sufficient concentrations of Ti in Si to reach the nominal Mott transition in morphologically stable plane-front solidification should occur only for velocities so high as to exceed the speed limits for crystalline regrowth in Si(111).