Infrared absorption due to local vibrational modes of nitrogen in GaAs : N and GaAs-based dilute nitrides

摘要

This paper reviews recent experimental progress in the investigation of nitrogen in GaAs and GaAs-based dilute nitrides by Fourier transform infrared absorption spectroscopy. Isolated substitutional nitrogen on the anion site gives rise to a local vibrational mode at a wavenumber of 472 cm(-1), which can be detected at low temperatures as a sharp absorption band. Based on a comparison with secondary ion mass spectroscopy and x-ray diffraction analysis, a calibration factor is derived for the integrated absorption of the band. Quantitative determination of substitutional nitrogen is possible in epitaxial layers of only 10 nm thickness. The influence of indium-nitrogen bonding on the local mode frequency is discussed. A mode at 490 cm(-1) is tentatively attributed to the InGa3N configuration. An additional local vibrational mode occurs at 638 cm(-1). A valence-force model is presented, which reproduces quantitatively the experimentally observed host-isotope fine structure. The results are consistent with an assignment to a nitrogen-gallium vacancy complex.