Hot electrons and phonons excited in GaAs by subpicosecond laser pulses have been studied by inelastic light scattering for photoexcited electron densities varying between ${10}^{17}$ and ${10}^{19}$ ${\mathrm{cm}}^{\mathrm{-}3}$. Transient overshoot of longitudinal-optical (LO) phonon temperature above the electron temperature has been observed. This is explained by the fast production of zone-center LO phonons by hot electrons combined with slower reabsorption of the emitted phonons due to rapid cooling of Γ valley electrons by intervalley scattering.

• Received 27 March 1989

DOI:https://doi.org/10.1103/PhysRevLett.64.946