Supersaturated substitutional alloys formed by ion implantation and pulsed laser annealing of group-III and group-V dopants in silicon

The formation of supersaturated substitutional alloys by ion implantation and rapid liquid-phase-epitaxial regrowth induced by pulsed laser annealing has been studied using Rutherford backscattering, ion channeling analysis. Group-III (Ga, In) and group-V (As, Sb, Bi) dopants have been implanted into single-crystal silicon at doses ranging from 1×1015 to 1×1017/cm2. The samples were annealed with a Q-switched ruby laser (energy density ∼1.5 J/cm2, pulse duration ∼15×10−9 sec). Ion channeling analysis shows that laser annealing incorporates these dopants into substitutional lattice sites at concentrations far in excess of the equilibrium solid solubility. Channeling measurements indicate the silicon crystal is essentially defect free after laser annealing. Also values for the maximum dopant concentration (Cmaxs) that can be incorporated into substitutional lattice sites are determined for our annealing conditions. Dopant profiles determined by Rutherford backscattering are compared to model calculations which incorporate both dopant diffusion in liquid silicon and a distribution coefficient from the liquid. It is necessary to assume an interfacial distribution coefficient (k′) far greater than the equilibrium value k0 to fit the experimental data. The relationship of Cmaxs and k′ to the formation of these supersaturated alloys is discussed.