Recombination dynamics in a variety of InGaN/GaN quantum systems has been studied by time resolved photoluminescence (PL). We have discovered that the time-decay of PL exhibits a scaling law: the nonexponential shape of this decay is preserved for quantum wells and quantum boxes of various sizes while their decay time varies over several orders of magnitude. To explain these results, we propose an original model for electron-hole pair recombination in these systems, combining the effects of internal electric fields and of carrier localization on a nanometer-scale. These two intricate effects imply a separate localization of electrons and holes. Such a microscopic description accounts very well for both the decays shape and the scaling law.

Time-resolved photoluminescence (PL), at T=8 K, is used to study a graded-width InGaN/GaN quantum well. Across the sample, the well width continuously varies from ∼5.5 to 2.0 nm corresponding to PL peak energies varying between 2.0 and 2.9 eV and to PL decay rates covering four orders of magnitude. The plot of decay times versus PL energies is very well fitted by a calculation of the electron–hole recombination probability versus well width. The only fitting parameter is the electric field in the well, which we find equal to 2.45±0.25 MV/cm, in excellent agreement with experimental Stokes shifts for this type of samples.

We report the observation of confined modes in the mixed photon/exciton-like branches of exciton–polaritons propagating along the growth axis of a 700 nm-thick GaN film, deposited by Molecular Beam Epitaxy on bulk GaN substrates. The energies of the confined modes are in agreement with a simple modelling of quantized wavevectors in the thin layer, including the proper four-branch dispersion relation of polaritons in the wurtzite GaN. Such an observation results from the large coherence length of the exciton–polariton in the epilayer, testifying to the very good crystalline quality of the material.

We propose an overview of specific optical properties of quantum-size artificial structures made of group-III nitride semiconductors with natural wurtzite symmetry. We consider the cases of quantum wells and of quantum boxes obtained by the Stranski-Krastanov growth mode. We comment on results of continuous-wave and time-resolved optical spectroscopy, in comparison with our envelope-function calculations of excitonic energies and oscillator strengths. The influence on recombination dynamics of internal electric fields and carrier localization is discussed in detail.