Ultrafast carrier dynamics and intervalley scattering in ZnSe

Intraband carrier dynamics were measured in ZnSe films by a two-wavelength pump probe technique with 180 fs resolution. A below-band pump pulse was used to heat carrier distributions in N-type samples by free carrier absorption. The electron cooling time constant was observed to be 500 fs. Intervalley scattering was seen to play a significant role in the electron dynamics and the scattering time from the L back to the Γ valley was measured to be 1.8 ps. By examining the ratio of the intervalley component to the total response as a function of pump photon energy, the bottom of the L valley was determined to lie 1.30 eV above the Γ-valley minimum.