  We present a theory for the intersubband absorption including electronic
ground state correlations in a doped GaAs/Al_{35}Ga_{65}As quantum well system.
Focusing on the influence of the Coulomb interaction among the carriers at low
temperatures, we find that the ground state correlations lead to an increased
renormalization and spectral broadening of the absorption spectrum. At T = 1 K,
its full width at half maximum is increased by up to a factor 3. The inclusion
of electron-phonon scattering strongly reduces the relative impact of the
electronic correlations.
