MANY-BODY ANALYSIS OF THE EFFECTS OF ELECTRON-DENSITY AND TEMPERATURE ON 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 in a Si-doped Al0.3Ga0.7As/GaAs quantum well. A line-shape calculation is presented for the absorption coefficient as a function of the incident photon energy for different values of T and n(2D) (where 2D is two dimensional). Good agreement between the numerical results and the experimental 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 obtained using a self-consistent Hartree potential and a z-dependent effective mass and nonparabolic energy dispersion. The screened exchange interaction is calculated based on the Hartree self-consistent wave functions and the Thomas-Fermi screening model, and is found to play a crucial role in the T- and n(2D)-dependence. The many-body theory includes the depolarization shift from a collective dipole moment and the excitonic shift from the vertex correction.