Time-resolved spectroscopy of MBE-grown InGaN/GaN self-formed quantum dots

GaInN/GaN quantum dots have been grown by molecular beam epitaxy on sapphir e substrates. By changing the size and composition of the dots, the emissio n energy can be tuned over the entire visible spectrum. We present time-res olved photoluminescence obtained on such samples with emission energies ran ging from 2.4 to 3.0 eV. We observe that the radiative recombination rate o f electron-hole pairs varies over several decades, in correlation with the transition energy. When the decay time of the ground-state recombination re aches several microseconds, a much faster (nanoseconds) recombination is ob served at higher energy. This is tentatively explained in terms of the part ial screening of the internal field by a finite number of electron-hole pai rs.