MANY-BODY ANALYSIS OF THE EFFECTS OF ELECTRON-DENSITY AND TEMPERATUREON THE INTERSUBBAND TRANSITION IN GAAS ALXGA1-XAS MULTIPLE-QUANTUM WELLS/

Infrared absorption spectroscopy is used to study conduction electron intersubband transitions between the ground and first excited states i n a Si-doped Al0.3Ga0.7As/GaAs quantum well. A line-shape calculation is presented for the absorption coefficient as a function of the incid ent photon energy for different values of T and n(2D) (where 2D is two dimensional). Good agreement between the numerical results and the ex perimental data is achieved. The measured blueshift or redshift of the peak position is quantitatively reproduced as T or n(2D) is reduced, respectively. In the theory the quasi-particle eigenstates are obtaine d using a self-consistent Hartree potential and a z-dependent effectiv e mass and nonparabolic energy dispersion. The screened exchange inter action is calculated based on the Hartree self-consistent wave functio ns and the Thomas-Fermi screening model, and is found to play a crucia l role in the T- and n(2D)-dependence. The many-body theory includes t he depolarization shift from a collective dipole moment and the excito nic shift from the vertex correction.