In-plane polarized intraband absorption in InAs/GaAs self-assembled quantum dots

Abstract

In-plane polarized photoinduced intraband absorption is reported in InAs/GaAs self-assembled quantum dots in the 90--600-meV energy range. This in-plane absorption mainly originates from bound-to-continuum transitions in the conduction and valence bands and lies in the 4--8-\ensuremath{\mu}m spectral range. The continuum is constituted either by the dot quasibound states hybridized with the wetting layer subbands or by the delocalized states of the barriers. A weak in-plane polarized bound-to-bound hole transition is also observed at 11 \ensuremath{\mu}m. Its in-plane absorption cross section is estimated to be around $1.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{\mathrm{cm}}^{2}.$ The energy position of the p-polarized and in-plane polarized intraband transitions is analyzed as a function of the average quantum dot size. An experimental energy diagram of the quantum dots is presented, as deduced from the interband and intraband measurements. The existence, directions, and lengths of the intraband transition dipoles are compared to the ones deduced from the numerical resolution of the three-dimensional effective mass Schr\"odinger equation taking into account the flat lens-shape geometry of the dots.