Phonon temperature overshoot in GaAs excited by subpicosecond laser pulses

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.