The nonlinear optical transmission of ZnSe epilayers grown by molecular beam epitaxy (MBE) is studied in the near-band-edge region. In single-beam transmission as well as in pump-and-probe experiments at 1.8 K, induced absorption is observed in the excitonic regime for increasing (pump) laser intensity. The diminishing of the excitonic absorption features, the failure to observe specific pump-laser resonances of the induced absorption in pump-and-probe experiments, and the fact that the 'efficiency edge' of the pump process is shifted to lower energies for increasing excitation intensity show that electron-hole plasma is created in the thin layer which prevents longitudinal carrier diffusion. However, at 77 K, induced transmission is observed in the excitonic regime indicating exciton bleaching, most probably caused by exciton screening and collision broadening for excitation densities not yielding excess of the Mott density of the created carriers.
ASJC Scopus subject areas