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NEXAFS and XPS study of GaN formation on ion-bombarded GaAs surfaces

Interaction of low-energy nitrogen ions (0.3-2 keV N2+) with GaAs (100) surfaces has been studied by x-ray photoemission spectroscopy (XPS) around N 1s and Ga 3d core-levels and near-edge x-ray absorption fine structure (NEXAFS) around the N K-edge, using synchrotron radiation. At the lowest bombardment energy, nitrogen forms bonds with both Ga and As, while Ga-N bonds form preferentially at higher energies. Thermal annealing at temperatures above 350oC promotes formation of GaN on the surface, but it is insufficient to remove disorder introduced by ion implantation. We have identified nitrogen interstitials and antisites in NEXAFS spectra, while interstitial molecular nitrogen provides a clear signature in both XPS and NEXAFS. The close similarity between NEXAFS spectra from thin GaN films and ion-bombarded GaAs samples supports our proposition about formation of thin GaN films on ion-bombarded GaAs.

NEXAFS; XPS; semiconductors; GaN; GaAs; nitrogen defects

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