Resonant Raman scattering study of V, Cr and Co ions implanted into GaN

Abstract

200 keV ions of V, Cr and Co were implanted into wurtzite GaN/sapphire thin films at fluences of 5 × 10¹⁴ cm⁻², 5 × 10¹⁵ cm⁻² and 5 × 10¹⁶ cm⁻². The modifications in the structural and lattice vibrational properties were studied using X-ray diffraction and UV Raman spectroscopy techniques. First principles calculations were also carried out to explore the dopant related electronic states and recombination centers in the implanted materials. The results revealed lattice expansion in the implanted regions and implantation induced modifications in the phonon structure of the materials. The strong photoluminescence emission observed for as-grown sample was suppressed and completely disappeared at an implantation fluence of 5 × 10¹⁵ cm⁻² due to the increase in concentration of non-radiative recombination centers. An outgoing resonance showing multiple phonon scattering related to longitudinal optical (LO) phonons was observed for all implanted samples. In the case of the highest fluence sample, a broad phonon band comprising of optical overtones was observed in the Raman shift region of 1100 to 1700 cm⁻¹.