Effect of N + ion implantation on n-GaN

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We analysed the effect of 70 keV nitrogen ion implantation in n-GaN to 10 14–10 16 cm −2 dose by optical absorption, Raman spectroscopy and photoluminescence. Optical absorption spectra of unimplanted samples gave a band gap of 3.4 eV. On implantation with N +, the optical absorption was noticeable at energy below the band gap, also presumably, arising out of defects and disorder produced by ion implantation. E 2 (high) and A 1 (LO) Raman modes of GaN layer have been observed and analysed. The behavior of Raman shift and FWHM of GaN modes with N + dose are explained on the basis of implantation-induced lattice damage. The PL spectra of unimplanted samples showed a peak at 3.4 eV corresponding to the band gap of GaN and an emission at 2.3 eV which is normally attributed to N Ga antisite defects. On irradiation with N + ion there was a drastic increase in the intensity of emission at 2.3 eV. This suggests that the defect responsible for the emission of 2.3 eV increases on N + implantation. At higher doses, additional emission bands at 2.2 and 2.45 eV were observed in the PL spectra, which might be due to the defect complexes.