Efficient design of optoelectronic devices based on electron intersubband transitions depends critically on the knowledge of the
intersubband relaxation times which in turn, depends on electron scattering with LO and acoustic phonons. In this article the
intersubband scattering time associated with electron–acoustic-phonon interaction has been discussed in terms of phonon mode
quantization and phonon confinement with describing the acoustic phonon dispersion relation in detail by introducing the cut-off
frequency for each mode. It has been shown that the quantization of acoustic phonon modes lead to an enhancement in electron–
phonon scattering time in AlGaAs quantum well structures. Based on the presented model, a new tailoring method has presented to
adjust the electron–phonon scattering time in intersubband-transition-based structures while keeping the electronic properties
unaltered. Also, we illustrated that for a quantum well with subband energy separation of 30 meV, the intersubband scattering time
with acoustic-phonon-assisted transitions could be tailored from 120 ps to increased value of 400 ps or reduced value of 45 ps
by inserting a 1 nm-thickacoustically soft or hard layers, respectively, while keeping the same the initial energy separation.