TIME-RESOLVED INVESTIGATION OF COHERENT LO-PHONON RELAXATION IN III-V SEMICONDUCTORS

Relaxation of coherent LO phonons is investigated in InP, GaAs, and GaP by use of an infrared time-resolved coherent anti-Stokes Raman-scattering technique. Measurements were performed as a function of crystal temperature in the range 6-320 K. The measured LO-phonon dephasing times art about four-times longer in InP than in GaAs. This difference is attributed to the closing of the cubic combination relaxation channel which dominates the decay in GaAs but is energetically forbidden in InP. In this compound, as in GaP, both a less efficient combination relaxation channel and the overtone decay route where the initial phonon splits into two isoenergetic longitudinal-acoustic phonons significantly contribute to the LO-phonon decay.