Photoexcited hot electrons and excitons in CdSe at 2 °K

A study of the radiative recombination from the free carriers and the free excitons in CdSe reveals that the free carriers as well as the free excitons are "hot." When the lattice is at ≅2 °K, the exciton and the free-carrier temperatures are, respectively, ∼ 25 °K and ∼ 140 °K at the highest intensity used in these experiments, ∼ 4×${10}^6$ W/${\mathrm{cm}}^2$. The results on electron heating can be quantitatively explained by a theory based on polar-optical scattering as the dominant energy-loss mechanism for the electrons. Thus the dynamics of the electron heating is well understood but that of excitons is not.