Effects of thermal annealing on the optical properties of inganas/gaas multiple quantum wells

We present an optical characterization of as-grown and thermally annealed InGaNAs/GaAs multiple quantum well samples. In both samples, from the analysis of the photoluminescence spectra we can infer that the low-temperature photoluminescence emission is related to carriers localized in the alloy potential fluctuations; with increasing temperature, we observe their gradual delocalization and then the transition towards a completely different type of lineshape, typical of free carrier recombinations. The comparison between the photoluminescence spectra of the as-grown and the annealed samples shows that a remarkable improvement of the optical properties occurs after the thermal annealing. This improvement is related to an important reduction in the density of the defects and in the depth of the alloy potential fluctuations.