Carrier recombination dynamics in electronically coupled multi-layer InAs/GaAs quantum dots

Optical properties of multi-layer InAs/GaAs quantum dots (QDs) with different GaAs spacer layer thicknesses (dGaAs) of 20, 15 and 10 nm are investigated by time-integrated and time-resolved photoluminescence (PL) spectroscopy. The energy spacing between ground and excited state is observed to be decreased with decrease in dGaAs and increased with increase in excitation intensity. The rate of carrier capture and energy relaxation in QDs is found to be slower at excitation energy of 3.06 eV than that at 1.53 eV which is attributed to intervalley scattering in GaAs. The effect of intervalley scattering process in GaAs on decay time is negligible for dGaAs of 20 nm and is prominent for dGaAs ≤ 15 nm.