${\mathit{L}}_6$-${\mathit{X}}_6$ intervalley scattering time and deformation potential for ${\mathrm{Al}}_{0.6}$${\mathrm{Ga}}_{0.4}$As determined by femtosecond time-resolved infrared absorption spectroscopy

Hot electrons in ${\mathrm{Al}}_{0.6}$ ${\mathrm{Ga}}_{0.4}$As were produced in the ${\mathit{X}}_6$ valley from a photoexcited indirect transition by a 585-nm femtosecond pump pulse. The time evolution of the population of electrons in the bottom of the ${\mathit{X}}_6$ alley was monitored by a femtosecond infrared probe pulse. The ${\mathit{L}}_6$→${\mathit{X}}_6$ intervalley scattering time of ∼200 fs and the ${\mathit{L}}_6$ ${\mathit{X}}_6$ intervalley deformation potential of ∼2.7×${10}^8$ eV/cm were determined from the measured kinetic data.