Local structure analysis of Ga1-xInxN alloy using extended X-ray absorption fine structure measurements

We investigated the local atomic structure around In atoms of MOCVD-grown Ga1-x,InxN alloy (0.01 ≤ x ≤ 0.21) using extended X-ray absorption fine structure (EXAFS) measurements of the In K-edge. For x ≤ 0.16, the In-Ga and In-In atomic distances were constant at 3.22-3.30 Å and 3.25-3.30 Å, respectively, and close to the Ga-Ga atomic distance in the ideal wurtzite GaN. On the other hand, the In-N bond length was constant at 1.85-2.21 Å, which is close to that in the ideal wurtzite InN. These results suggest that the internal strain of the Ga1-xInxN alloy is relaxed by the bond angle changing of In-N-Ga or In-N-In. The coordination numbers of the second-nearest neighbor In of In were higher than that estimated from random GaInN alloy, in which In atoms randomly occupy the cation sublattice of GaInN alloy. This behavior can be explained by the segregation of In atoms starting even at x = 0.01. For x = 0.21, the interatomic distance and the coordination number could not be accurately estimated using our simple model, in which single interatomic distances of In-Ga and In-In were assumed.