Using a model cubic anharmonic crystal potential and Fermi’s golden rule, an expression for the anharmonic relaxation time for a nonequilibrium long-wavelength LO phonon is rigorously derived. Decay times for various bulk, alloy, and quantum-well semiconductor systems are calculated. Comparison with time-resolved Raman measurements indicates that a relatively high value of the Grüneisen constant (1.8 for GaAs) gives the best agreement between experiment and theory.

• Received 11 July 1994

DOI:https://doi.org/10.1103/PhysRevB.50.14179