Characterisation of nitrogen-related defects in compound semiconductors by near-edge x-ray absorption fine structure

We have studied the formation of nitrogen-related defects created in compound semiconductors by low-energy ion bombardment (0.3-5 keV N₂ ⁺ or Ar⁺) using near-edge x-ray absorption fine structure (NEXAFS) around the N K-edge. Nitrogen interstitials and antisites have been identified in NEXAFS spectra of InN and GaN in full agreement with theoretical calculations. Several defect levels within the band gap and the conduction band of GaN and InN were clearly resolved in NEXAFS spectra. We attribute these levels to interstitial and antisite nitrogen in good agreement with theoretical calculations. Interstitial molecular nitrogen, N₂, has been observed in all samples under consideration. The presence of N₂ produces a sharp resonance in low-resolution NEXAFS spectra, showing the characteristic vibrational fine structure in high-resolution measurements.