Phonon bottleneck in self-formed ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ quantum dots by electroluminescence and time-resolved photoluminescence

We demonstrate experimentally that a photon bottleneck for carrier relaxation does exist in self-formed ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ quantum dots. With time-resolved photoluminescence, we measured the carrier relaxation lifetime and radiative recombination lifetime in five discrete levels as a function of temperature. We found that the higher the temperature and the level were, the shorter the relaxation lifetime was (1 ns-10 ps). The radiative recombination lifetime measured was about 1 ns and was found to be independent of temperature. We also simulated electroluminescence spectra at 77 and 300 K with the measured lifetimes. We found that the first, second, and third levels could not be fully filled with injected carriers.