Effect of the thermal annealing and the nominal composition in the elemental distribution of InxAl1-xAsySb1-y for triple junction solar cells

In this work, the effect of thermal annealing under As overpressure in the composition distribution of In8Al42As34.5Sb15.5 layers, lattice matched to InP for triple junction solar cells, is analysed by APT. We have found that in the as-grown sample there is a statistically significant number of In-rich regions with size similar to 10 angstrom. Upon annealing, the composition gradient from the centre of the In-rich regions towards the homogeneous region is reduced, and the size of the enriched regions increases up to similar to 35 angstrom. This points to In out-diffusion as an initial step of the material homogenization, which would explain previous results of PL emission. Additionally, the comparison of the obtained results with previous analysis by the authors has shown that the increase in the In content of InAlAsSb epitaxial layers has a strong effect on the composition distribution of the material, stimulating deviations from the random alloy in both the group III and the group V sub-lattices. (C) 2019 Elsevier B.V. All rights reserved.