Polaron relaxation channel in InAs/GaAs self-assembled quantum dots

Polaron relaxation in n-type InAs quantum dots has been studied by picosecond time-resolved pump-probe spectroscopy. Due to inhomogeneous broadening of the absorption features associated with transitions between s-like ground state and p-like first excited state, the energy dependence of the polaron decay time has been measured over a wide spectral region from 40 to 60 meV. The polaron lifetime increases continuously from 20 ps at 40 meV to 65 ps at 54 meV. By analysing the temperature dependence of the polaron lifetime the main polaron decay channel has been identified as the cubic overtone (2LA) decay channel. By fitting the experimental data we extract the LO-phonon lifetime of 10 +/- 2 ps (at 33 meV) for InAs quantum dots and electron-phonon coupling strength of 6.2 +/- 0.5 meV.