Abstract

When electrons and holes are optically injected into GaAs by a short pulse laser with photon energy well above the direct gap, the initial monoenergetic carrier distribution is rapidly changed by both carrier-carrier scattering and electron-LO phonon scattering. The effect of each mechanism on the carrier distributions is very different. Electron-LO phonon scattering causes the carriers to lose energy to the lattice. On the other hand, carrier-carrier scattering efficiently redistributes energy within the carriers and produces a carrier distribution that can be characterized by a well-defined temperature common to both electrons and holes, but different than the lattice temperature. In addition ^1,2τ_e–LO ≃ 165 fsec and is independent of carrier concentration for n < 10¹⁸cm⁻³, while τ_c–c depends¹ on concentration n roughly as τ_c–c ≃ 2 × 10⁴ sec /n cm³. Thus, the relative importance of each mechanism depends upon the carrier concentrations. The initial relaxation of the optically injected carriers is dominated by τ_e–LO at low n, and by τ_c–c at high n. The two rates are equal at n ≃ 1.25 × 10¹⁷cm⁻³.

© 1986 Optical Society of America