We have considered the processes determining the steady-state population of
longitudinal optical (LO) phonons being intensively produced in GaAs by el
ectrons optically excited or accelerated in strong external electric field.
The emitted LO phonons pass their energy to acoustic phonon systems throug
h anharmonic decay into longitudinal acoustic (LA) phonons. The latter emer
ge as almost monoenergetic and concentrated in a narrow layer in the recipr
ocal space. Had the occupation numbers of k states within this layer grown
to unity, the decay process would have become stimulated, effectively desol
ating the built-in LO states and giving rise to various nonlinear phenomena
. We show that this is actually the case by tracing LA phonon kinetics and
calculating the number of phonons in each k state available for feedback. T
he results obtained substantially clarify the physical picture of energy tr
ansfer processes mediating heat removal in GaAs. [S0163-1829(99)02131-1].