We have studied the temperature dependence of the intersublevel absorption in n
-doped InAs/GaAs self-assembled quantum dots. The investigated intersublevel transition corresponds to the optical transition between the s
-type conduction ground state to the p
-type first excited states. These transitions, resonant between 20 and 22 μm, are in-plane polarized along the  and the 
directions. A redshift lower than 3 meV is observed for the transition resonance from low temperature to room temperature. While the effective barrier height from the ground state is around 150 meV, the integrated absorption amplitude decreases by a factor of 4 from low temperature to room temperature. This decrease is modeled by the thermionic emission of the carriers, taking into account the density of states of the two-dimensional wetting layer, the density of states of the three-dimensional bulk layer surrounding the dots and the existence of polaron states associated with the strong electron-phonon coupling in the dots. © 2002 American Institute of Physics.