Zinc oxide is a wide gap semiconductor (≈ 3.4 eV) which one of the main advantages is a large exciton binding energy (60 meV). This thesis is dedicated to the study of excitonic properties of ZnO/(Zn,Mg)O single quantum wells (QW). The existence of an internal electric field in polar QW grown along the main axis c is well established for a few years. The effects of this electric field on emission and absorption properties of polar QW grown by molecular beam epitaxy (MBE) on sapphire substrate are discussed. We also demonstrate the direct formation of excitons-phonons complexes in the case of narrow wells by an experience of photoluminescence excitation. Moreover, the presence of this internal electric field combined with the high density of non-radiative defects due to hetero-epitaxial growth leads to a low radiative efficiency. Reflectivity, continuous-wave and time-resolved photoluminescence experiments have been performed on homo-epitaxial QW grown by MBE on non-polar M-plane. First we demonstrate the absence of internal electric field in these QW. We also report the formation of excitons-donors and excitons-excitons complexes. The most important observation is the drastic improvement of radiative efficiency: excitons recombination is essentially radiative up to 325 K. The exciton lifetime increases linearly with temperature, which indicates that excitonic properties are preserved up to room temperature. This outcome is essential for the exploitation of QW based on ZnO in optoelectronics or as a model system.
