Time-resolved non-contact THz diagnostics of impurity state in different sulfur-implanted/laser-annealed silicon samples

An optical pump/terahertz probe method was utilized to evaluate the active impurity concentration and structural state in the sulfur-implanted (1018-1021 cm-3) surface layers of the crystalline silicon wafer, both in the as-implanted and nanosecond-laser annealed states. This method enabled, for the first time, non-contact electrical measurements of carrier scattering and recombination rates even in the implantation-disordered, poorly conducting hyperdoped Si samples. These measurements enabled the direct comparison of their active impurity content vs the concentration of implanted sulfur and its laser-annealing activation from the cluster form, indicating sulfur precipitation down to the equilibrium solubility limit in the as-implanted samples at the high impurity concentrations of 1020-1021 cm-3. These studies revealed the advanced potential modalities of the versatile optical pump/terahertz probe method for the unbiased non-contact acquisition of key electrical parameters in poorly conducting materials.