Carrier dynamics in modulation-doped InAs GaAs quantum dots

Journal article, 2005

Photoexcited carrier dynamics was studied in n and p modulation-doped self-assembled InAs GaAs quantum dots by means of time-resolved photoluminescence with excitation and detection energies varied through barrier, wetting layer, and quantum dot states. Carrier transfer to the ground state of the dots was found to occur within 5 to 6 and 12 ps for the doped and undoped samples, respectively. The experiments suggest that in all samples the carrier capture into the highest quantum dot levels proceeds by phonon emission. The significant difference in the transfer times is attributed to different relaxation mechanisms for the subsequent process of intradot carrier relaxation. For the doped samples, the presence of built-in carriers in the dots leads to efficient electron-hole scattering, while in the undoped structure scattering by phonons is identified as the main relaxation channel. Additionally, experimental results show decreased carrier lifetimes in the doped structures, which is attributed to nonradiative recombination at doping-induced recombination centers in the vicinity of the quantum dot layers.