We report an experimental study of the photoluminescence (PL) properties, after both picosecond and continuous-wave excitation, of GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum-well structures. The comparison between the PL decay time and the PL integrated intensity allows us to determine the temperature dependence of both the radiative and the nonradiative time constants. We find that the nonradiative processes play an important role and become dominant for T≥100 K. The radiative time constant turns out to be definitely higher than the measured PL decay time and increases by several orders of magnitude as the temperature is raised from T=4 K to room temperature. The experimental results are finally compared with the theories existing in the literature.

We report on continuous-wave and time-resolved measurements of the photoluminescence of good-quality single quantum wells at low temperatures (4–30 K). Luminescence arising from both free and localized excitons is observed and the influence of excitation localization on the photoluminescence decay time is investigated. Resonant pumping at the light-hole exciton transition is found to greatly increase the generation of free heavy-hole excitons. In this case, the free-exciton lifetime increases linearly with temperature (10–30 K) and the dependence of the slope on the well thickness is found to be in good quantitative agreement with the theoretical model of Andreani et al. [Solid State Commun. 77, 641 (1991)].

We report polarization-resolved high spectral resolution photoluminescence measurements in self-assembled strain-free $\text{GaAs}/{\text{Al}}_{0.3}{\text{Ga}}_{0.7}\text{As}$ quantum dots designed and realized in order to reduce as much as possible strain and segregation, which affected previous fine-structure splitting (FSS) experiments. Photoluminescence from isolated quantum dots exhibits a linearly polarized FSS. FSS clearly shows a quantum size effect monotonically decreasing from 90 to $20\mu \text{eV}$ by decreasing the quantum dot size (increasing emission energy). While this finding is similar to that observed in strained In(Ga)As/GaAs quantum dots, clearly it requires a different explanation, being our quantum dots not affected by strain-induced piezoelectricity. We ascribed the observed FSS to a size dependent reduction in dot shape anisotropy as evidenced by structural data analysis. Moreover the linear polarization in dots with shape close to cylindrical symmetry is not along the [110] crystallographic axis but it turns out randomly distributed, highlighting the role of extrinsic effects.