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Microcalorimetric measurements of small absorption coefficients have been performed on thin GaN–AlGaN quantum wells grown by Reactive Molecular Beam Epitaxy on Al 2 O 3 substrates. In addition to strong absorption at the energy of the GaN buffer and at the energy of the thick AlGaN barrier layers, we could also readily detect transitions associated to the quantum well. These measurements which pave the way to a precise determination of the gap mismatch between the well and the barrier layers are combined with self consistent excitonic and envelope function calculations in the context of a model for the band line-ups which includes the piezoelectric effect.

We report here on the study of the theoretical optical properties of Ga based nitrides systems. The dipolar matrix elements and hole effective masses are presented as a function of the reciprocal wavevector for strained bulk GaN. We compute then the A, B and C exciton binding energies for strained GaN/Al0.2Ga0.8N quantum structures and present the calculated optical density for a 50 A wide well.

International audience; We report here on the study of the optical properties of ZnCdSe-ZnSe quantum structures elaborated by metal-organic chemical vapour deposition on GaAs substrates. The band structure of these samples is experimentally investigated by means of photoluminescence and photoreflectance spectroscopy. This makes clear the relationship between strain, carrier confinement and excitonic effects. We have computed for the first time heavy- and light-hole excitons associated with ground and excited states sub-bands, in the context of a self-consistent two-parameter trial function.

Theoretical studies of the excitonic properties for different designs of MgS-ZnSe structures are presented. Excitonic binding energies are calculated for single quantum wells. For MgS-ZnSe superlattices, the energy of electron-hole transitions are evaluated and compared with the experimental photoluminescence spectra.

We have investigated theoretically the optical properties of strained (001) ZnSe-(Zn, Cd)Se single quantum wells with a low cadmium content (~10%). Due to the band offset and strain energy, the electron-to-light-hole transitions are marginally type I. We compute the dispersion relations and joint density of states for a typical structure away from Λ and show that the degeneracy can occur between lh 1 and hh 3 sub-bands in a large area of the Brillouin zone. This can cancel the selection rules for interband processes.

Exciton properties have been calculated for polarized GaN/AlGaN quantum well (QW) as a function of the injection intensity for various temperatures. A self-consistent process is performed to solve Schrodinger and Poisson equations, and a trial function that takes into account quantum exclusion principle in the filling of the reciprocal space is chosen for the exciton. When carriers are injected in the quantum structure, three different regimes are evidenced before the complete bleaching of the electron–hole interaction at large excitation intensities. We show that, for a given structure, the critical injection intensity of carriers at which this exciton starts to dissociate due to kinetic effects increases with the temperature of the lattice.