Ultrafast dynamics in phosphorus-implanted silicon wafers: The effects of annealing

Abstract

Carrier relaxation in phosphorus-implanted silicon wafers (10(16) P+/cm(2)) annealed at different temperatures ranging from 350 to 1100 degreesC is investigated by near-infrared ultrafast time-resolved reflectivity measurements. A kinetic model based on four couple differential equations describing the carrier density, electron, hole, and lattice temperatures is used to evaluate the expected changes in the time-resolved reflectivity. This model was used to fit the experimental data having the trap recombination time constant and the optical absorption coefficient as fitting parameters. Our measurements reveal a complicated recovery of the ion-implanted silicon samples to crystallinity following annealing with carrier lifetimes ranging from <1 psec for the nonimplanted sample and reaching similar to95 psec for the highest-annealed sample. Although this recovery directly effects the lifetime of the carriers, there are nontrivial mechanisms that activate recombination centers and traps throughout the annealing process, resulting in carrier lifetimes that are shorter than expected at higher annealing temperatures. Raman scattering data demonstrate the disorder and the recovery of ion-implanted silicon to its crystalline form, offering a direct comparison to the time resolved reflectivity data.