Intraband absorption spectroscopy of self-assembled quantum dots

We report on the intraband absorption in InAs/GaAs self-assembled semiconductor quantum dots. The growth of the InAs clusters is achieved by molecular beam epitaxy. The infrared absorption of n-doped, p-doped and undoped quantum dots is investigated by direct or photo-induced spectroscopy. We show that the quantum dots exhibit electron and hole intraband absorptions. The electronic transitions are attributed to the absorption between the ground level to the continuum. The hole intraband transitions are dominated by resonant transitions between bound levels. The intraband transitions are mostly polarized along the growth axis of the clusters. The absorption cross-sections for a one-dot layer plane are in the range 10(-16)-10(-15) cm(2). Finally, we show that the InAs clusters exhibit a weak in-plane polarized absorption. The in-plane polarized absorption is evidenced using an interband optical pumping tuned in resonance with the wetting layer absorption energy.