Simulation of Raman scattering from nonequilibrium phonons in InP and InAs

Excitation of semiconductors by intense sub-picosecond laser beams has been a major method of studying the dynamics of far-from-equilibrium electron and hole systems. The thermalization of the initial distributions of these carriers probes the details of the band structure and the dynamics of electron-phonon interactions. We have used 0.6 ps laser pulses at 1.952 eV to study the generation of nonequilibrium LO phonons in both InP and InAs. These two materials provide a contrast in that the thermalization (relaxation) of the Raman signal probes different decay mechanisms. In InP, for example, we find that the decay of the Raman signal is dominated by the lifetime of the LO phonons. To the contrary, in InAs, our studies show that the decay of the Raman signal is dominated by the time required for particles to return to the Γ valley from the L valleys of the conduction band. This time is much larger than the LO phonon lifetime