Identification of the local vibrational modes of small nitrogen clusters in dilute GaAsN

Ultra-high-resolution infra-red local vibrational mode (IR LVM) spectroscopy measurements together with density-functional calculations have been used to identify the signatures of close substitutional nitrogen ( N As ) pairs in GaAs 1 - x N x alloys with concentrations of x < 0.025 . We show that the presence of sub-peaks close to the N As absorption band can be attributed to nitrogen pairs up to fourth neighbor position. Additionally, we suggest that the nitrogen pairs which give rise to the deepest levels below the conduction band edge are the first to be removed upon annealing.