First order Raman scattering analysis of transition metal ions implanted GaN

Neutron irradiation-induced modification of electrical and structural properties of GaN epifilms grown on Al2O3 (0001) substrate

“…Note that the bands at 210, 300 and 670 cm −1 have not been reported earlier for neutron irradiated GaN. However, similar bands often arise upon ion implantation as published by many authors [33][34][35][36][37]. We can conclude that the presence of these modes in the Raman spectra of both neutron irradiated and ion implanted GaN confirms that their origin is linked to intrinsic lattice defects but not to local vibrations of the implanted atoms.…”

“…The peaks in the range 320-530 cm −1 cannot be explained by DARS because of the gap between the acoustic and the optical phonon branches in the vibrational spectrum of GaN. The peak at 360-365 cm −1 has been observed previously in ion implanted GaN and attributed to local vibrational modes of vacancy-related defects [33,35,38]. A characteristic feature of the ∼360 cm −1 mode, as reported in the literature, is a pronounced increase in its intensity during annealing [33,38], so this mode was attributed to vacancy complexes or dislocations [33] due to the fact that dislocations can grow and exist up to very high temperatures.…”

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

“…The mode observed at around 1413 cm À1 , 1371 cm À1 and 1402 cm À1 for V, Cr and Co implanted samples respectively is likely to be an optical overtone of nitrogen vacancy related mode observed at 665 cm À1 in rst order spectra of GaN implanted with same uence of Cr ions. 17 The mode at around 1506 cm À1 , 1466 cm À1 and 1457 cm À1 for V, Cr and Co implanted samples respectively is assigned as an optical overtone of 2A 1 (LO) character. This assignment seems to be justied when (i) LO phonon frequency for GaN is taken into account and (ii) comparison is made with frequency position of 2A 1 (LO) phonons observed for samples implanted at previous uences of 5 Â 10 14 cm À2 and 5 Â 10 15 cm À2 .…”

“…The analysis of rst order Raman spectra (RS) of these materials indicates the appearance of new vibrational modes related to implantation induced disorder. 17 The implanted foreign atoms are expected to produce extra periodicity in the thin lms 19 due to which reduction in intensity and appearance of new peaks in diffraction pattern of the samples is likely. In order to check the effects of the ions implantation on the structural aspects of the materials, (u-2q) X-ray diffraction patterns of the samples were recorded in (0002) symmetry.…”

“…A thin lm wafer was scribed and one piece was kept as reference sample whereas rest of the pieces were implanted with 200 keV ions of V, Cr, and Co at uences 5 Â 10 14 cm À2 , 5 Â 10 15 cm À2 and 5 Â 10 16 cm À2 using LC-4 high energy ion implanter as per details given elsewhere. 17 In order to recover the lattice from implantation induced damages, the implanted samples were thermally annealed in nitrogen ambient at 900 C for duration of 30 s using a rapid thermal annealing (RTA) furnace. The samples were placed inverted onto a different wafer of GaN for saving them from thermal decomposition during high temperature annealing.…”