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 $\mu \mathrm{m}$ 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.

• Received 26 June 2018
• Revised 1 November 2018

DOI:https://doi.org/10.1103/PhysRevB.98.205306