COLLECTIVE INTERSUBBAND EXCITATIONS IN QUANTUM-WELLS - COULOMB INTERACTION VERSUS SUBBAND DISPERSION

The dependence of the intersubband absorption line shape on the subban d dispersion and the Coulomb interaction between electrons is studied using the Hartree-Fock semiconductor Bloch equations. For subbands wit h the same effective masses, we show that the absorption/emission line shape is solely determined by the single-electron properties. For ver y different effective masses, the Coulomb interaction results in a str ong redistribution of the oscillator strength. The line shape in this limit is determined by a Fermi-edge collective mode induced by a repel ling electron-hole pair.