One- and two-photon-excited time-resolved photoluminescence investigations of bulk and surface recombination dynamics in ZnSe

Measurements of femtosecond time-resolved one- and two-photon-excited photoluminescence of bulk ZnSe enable us to distinguish the surface and bulk contributions to recombination dynamics. A photoluminescence lifetime of several nanoseconds or longer is measured for the bulk. A fast relaxation component with a decay time constant τ_T of a few tens of picoseconds observed in one-photon-pumped time-resolved spectra is identified as the result of diffusion and rapid surface recombination. A one-dimensional model taking into account surface nonradiative recombination and carrier diffusion is able to describe the observed behavior. The temperature dependence of τ_T shows good agreement with the theory. At room temperature, a surface recombination velocity S =5.8×10⁵ cm s^-1 and a diffusion constant D=10 cm² s^-1 are found using this model.