Non-equilibrium longitudinal optical phonons and their lifetimes

Abstract

Non-equilibrium phonons have been discussed for almost six decades. Here, the nature of the longitudinal optical mode, particularly in polar materials, is discussed along with its lifetime and bottleneck occurrences. The history of non-equilibrium phonons is discussed along with their generation by the relaxation of hot carriers. The role of inter-valley scattering and phonon lifetime is introduced along with the concept of a phonon bottleneck. Various methods of lifetime measurement are introduced. Measurements of the lifetime in a variety of semiconductor materials is reviewed and a possible scaling behavior discussed.

The role of nonequilibrium LO phonons, Pauli exclusion, and intervalley pathways on the relaxation of hot carriers in InGaAs/InGaAsP multi-quantum-wells

“…The decay of LO phonons into acoustic phonons is modeled by the rate equation at each timestep as 29 where is the equilibrium LO phonon population, is the LO phonon population before the decay, is the timestep, is the LO phonon lifetime, and is the change in LO population due to the decay. This form is identical to the decay observed in transient Raman studies measuring the LO phonon lifetime 42 – 46 .…”

“…The main energy loss mechanism for carriers in III–V materials is the emission of LO phonons 42 . Due to their low group velocity, the emitted LO phonons are assumed to remain within the excitation volume, where they are either re-absorbed by the carriers, or undergo anharmonic decay into acoustic phonons, which are assumed to rapidly propagate out of the system.…”