Decay of polar-optical phonons in semiconductors

In electrical transport in compound semiconductors, the polar optical phonons can be driven from equilibrium by energetic phonon emission from the electrons. These phonons decay via bulk interactions with the acoustic modes through anharmonic terms of the crystal potential and through the second-order electric moment, or second-order piezoelectric, of the lattice. The relaxation rates for these processes are calculated and applied to InSb. It is found that the second-order electric moment dominates the decay of the polar modes although the two processes are comparable in magnitude.