Electron and hole spin relaxation in InP-based self-assembled quantum dots emitting at telecom wavelengths

We investigate the electron and hole spin relaxation in an ensemble of self-assembled InAs/${\mathrm{In}}_0.53{\mathrm{Al}}_0.24{\mathrm{Ga}}_0.23\mathrm{As}$/InP quantum dots with emission wavelengths around 1.5 $\ensuremath{\mu}\mathrm{m}$ by using pump-probe Faraday rotation spectroscopy. Electron-spin dephasing due to the randomly oriented nuclear Overhauser fields is observed. At low temperatures we find a submicrosecond longitudinal electron-spin relaxation time ${T}₁$ which depends unexpectedly strongly on temperature. At high temperatures the electron-spin relaxation time is limited by optical phonon scattering through spin-orbit interaction decreasing down to 0.1 ns at 260 K. We show that the hole spin relaxation is activated much more effectively by a temperature increase compared with the electrons.