Assessment of nitrogen incorporation in dilute GaAsN films using isotopically enriched molecular beam epitaxy and resonant nuclear reaction analysis

This paper describes the development of a new materials analysis technique enabled by modifying standard crystal growth methods for dilute nitride III-V semiconductors. The key to this method is the use of nitrogen gas enriched with the (15) N isotope during material growth via molecular beam epitaxy, which allows enhanced detection of nitrogen using resonant nuclear reaction analysis (RNRA). Films of GaAs N-15 have been synthesized and examined using x-ray diffraction (XRD) and secondary ion mass spectroscopy. Accelerator-based ion beam analysis techniques, both RNRA and Rutherford backscattering spectrometry (including ion beam channeling configurations), were used to examine the films to obtain depth profiles of nitrogen, to assess their crystallinity, and to determine whether nitrogen is incorporated into substitutional or interstitial lattice sites. This method avoids possible artifacts from surface contamination by N and has confirmed that for the growth parameters investigated, the incorporation of N-15 into the material corresponds with the expected enrichment of the feed gas, that the films have excellent crystallinity and uniform composition throughout their thickness, and that the nitrogen in GaAsN is predominantly incorporated substitutionally, in agreement with the lattice distortion observed by XRD.