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The chemical state of N in N-doped amorphous Ge 2 Sb 2 Te 5 (a-GST) samples with 0–14.3 N at.% doping concentrations was investigated by high-resolution x-ray photoelectron spectroscopy (HRXPS) and Ge K-edge x-ray absorption spectroscopy (XAS). HRXPS showed negligible change in the Te 4 d and Sb 4 d core-level spectra. In the Ge 3 d core-level spectra, a Ge nitride (Ge N x) peak developed at the binding energy of 30.2 eV and increased in intensity as the N-doping concentration increased. Generation of Ge N x was confirmed by the Ge K-edge absorption spectra. These results indicate that the N atoms bonded with the Ge atoms to form Ge N x⁠, rather than bonding with the Te or Sb atoms. It has been suggested that the formation of Ge nitride results in increased resistance and phase-change temperature.