Dynamic response of 1.3-mu m-wavelength InGaAs/GaAs quantum dots

The temperature-dependent dynamic response of 1.3-mu m-InGaAs/GaAs quantum dots is investigated using time-resolved photoluminescence upconversion wit h subpicosecond temporal resolution for excitation in either the GaAs bulk region surrounding the dots or within the wetting layer. Relaxation to the quantum-dot ground state occurs on a time scale as short as 1 ps, while rad iative lifetimes as short as 400 ps are measured. The influence of nonradia tive recombination is observed only for temperatures above 250 K. At temper atures below 77 K, an increase in the relaxation time and lifetime is obser ved when carriers are injected into the bulk GaAs region versus excitation into the wetting layer, which suggests that diffusion in the bulk GaAs regi on influences both the relaxation rate and the recombination rate. (C) 2000 American Institute of Physics. [S0003-6951(00)01010-X].