Exchange effects in the screening of a phonon mode in a semiconductor quantum well

We study the screening of the first two polar optical phonon modes in a QW using the rigid wall case. The screened potential was calculated by employing nonlocal dielectric functions obtained in multisubband extensions of (a) the RPA and (b) the Hubbard (H) approximations. The purpose of the calculations is to study the influence of the design parameters, such as the well width and the change in carrier population, in the above mentioned different approximations. The QW is modelled by an infinite potential well and also by the selfconsistent Hartree approximation to consider the modulation doped QW. The main design parameter is found to be the carrier population. Furthermore, it is found that the selfconsistent re-shaping of the electronic potential well—and hence the carrier distribution—affects the resulting screened potential significantly.