INTERSUBBAND TRANSITIONS IN STRAINED IN0.07GA0.93AS AL0.40GA0.60AS MULTIPLE-QUANTUM WELLS AND THEIR APPLICATION TO A 2-COLORS PHOTODETECTOR/

Infrared absorption spectroscopy is used to study the conduction band intersubband transitions in Si-doped In0.07Ga0.93As/Al0.40Ga0.60As mul tiple quantum-well structures with the doping being restricted to the well region. The chemical potential determined by the electron density is designed to be above the second subband edge for samples with cert ain well widths, so that two absorption peaks with a different wavelen gth would be observed as one of the requirements for a two-colors phot odetector. The optical absorption spectra are calculated from which th e peak position energies are extracted and compared with the experimen tal measurements for different well widths. Good agreement between num erical results and experimental data is achieved. In our theory, self- consistent screened Hartree-Fock calculations were performed, which in cludes the effects of the z-dependent electron effective mass, dielect ric constant, and the nonparabolic dispersion. The strain effect is al so taken into consideration by the deformation theory. In addition, th e calculated optical absorption spectra included the many-body depolar ization and excitonlike shifts.