Role of N clusters in InxGa1-xAs1-yNy band-gap reduction

We study the origin of the giant band-gap bowing observed in InxGa1-xAs1-yNy alloys upon nitrogen incorporation by exploiting the capability of atomic hydrogen to form bonds with nitrogen atoms. The formation of these bonds pushes the band gap of InxGa1-xAs1-yNy alloys toward that of InxGa1-xAs, while subsequent thermal annealing restores the band gap of the untreated InxGa1-xAs1-yNy. The activation energy for thermal dissociation, ED, of the N-H complexes follows a Gaussian distribution with a mean value increasing with y. Values of ED similar to those found in the alloy limit are found in the case of very dilute N concentrations (impurity limit), where different N-H complexes are singled out. These results show that the giant band-gap bowing should be accounted for by different N complexes rather than by a single N complex.