INTRABAND ABSORPTION IN N-DOPED INAS GAAS QUANTUM DOTS/

We have investigated the intraband absorption within the conduction ba nd of InAs/GaAs quantum dots. The islands obtained by self-organized e pitaxy are modulation doped with a silicon planar doping 2 nm below th e dot layer plane. The dots exhibit infrared absorption polarized alon g the growth axis in the midinfrared spectral range. The absorption is maximum around 150 meV with a large broadening around 130 meV. This b roadening is attributed to size fluctuations within the one dot layer plane and the consequent variation of the electron confinement energy with the dot size. The magnitude of the absorption along the growth ax is for the one dot layer plane is approximate to 2.5 X 10(-2)% which c orresponds to an equivalent absorption cross section sigma(z) approxim ate to 3.1 X 10(-15) cm(2). We show that the intraband absorption can also be clearly observed using a photoinduced infrared absorption tech nique with the doped quantum dots. (C) 1997 American Institute of Phys ics. [S0003-6951(97)01645-8].