Mid-infrared intraband transitions in self-organized InAs/GaAs quantum dots

We have investigated the mid-infrared absorption between confined levels of undoped and n-doped InAs/GaAs quantum dots obtained by self-organized growth. We show that the quantum jots exhibit, in the 90-500 meV spectral range, intraband absorption between confined levels which is polarized along the growth axis of the dots. The infrared resonances are attributed to intraband transitions between confined holes and to bound-to-continuum transitions of electrons. The intraband absorption in the conduction band is broader (approximate to 120 meV) than the absorption in the valence band (approximate to 15 meV). The absorption cross-section of the conduction intraband absorption is measured as 3.2 x 10(-15) cm(2) for a one dot layer plane. Photo-induced intraband absorption is observed for both resonant and non-resonant excitation of the dots.