Size-dependence of the Linear and Nonlinear Optical Properties of GaN Nanoclusters

In this paper, we present the results of our first-principles quantum mechanical studies of the electronic structure, geometry, and linear and nonlinear optical (NLO) properties of tetrahedral Ga m N m ( m = 1, 4, 7, 17) atomic clusters. Our calculated results suggest that the linear and NLO properties both exhibit a strong dependence upon cluster size and shape (geometry). However, the size- and the geometry-dependences are more pronounced for the NLO properties than for the linear optical properties. For clusters containing equal numbers of Ga and N atoms, an open-structure with no network-forming ring has a much larger second-order NLO coefficient than a cluster with a closed ring structure.