Investigations on the 100 MeV Au⁷⁺ion irradiation of GaN

Abstract

Metal organic chemical vapour deposition (MOCVD) grown n-type GaN on sapphire substrates was irradiated with 100 MeV Au 7+ ions, varying the fluence as 1 × 10 12 , 1 × 10 13 and 5 × 10 13 ions cm −2 at room temperature. The irradiated samples were characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), Raman scattering, photoluminescence and UV-visible optical absorption spectrum. XRD analysis reveals a huge lattice disorder for fluence beyond 1 × 10 13 ions cm −2 . This is observed from the increase in the FWHM and decrease in the intensity of the GaN (0 0 0 2) peak. The sapphire peak totally vanishes for higher fluence. Raman modes E 2 (high) and A 1 (LO) are observed at 568 cm −1 and 749 cm −1 respectively. For the fluence of 1 × 10 12 ions cm −2 the E 2 (high) shifts to lower frequency and a further increase in fluence results in a broader less intense E 2 mode. Additional modes around 100 cm −1 and 220 cm −1 were observed and the origin of those modes is discussed. We also observed the Boson peak, the intensity of which increases as the fluence increases. AFM images show the roughness of GaN increases with increasing ion fluences. At a fluence of 5 × 10 13 ions cm −2 , a new type of ditch and dike structure was observed. These structures were distributed over the irradiated GaN surface. UV-visible absorption spectrum shows that the band gap energy decreases with increasing ion fluences and also that the band edge is broadened. The results are discussed by the complementary use of these studies.

Response of GaN to energetic ion irradiation: conditions for ion track formation

“…In addition, grazing incidence SHI irradiation [15][16][17] was applied in order to study the response of the GaN surface in particular. Possible compositional changes in this case were investigated by TOF-ERDA which is sensitive to a possible nitrogen loss which has been reported previously for this material [18][19][20]. Our results are interpreted in terms of the material changes predicted by the thermal spike model [21,22].…”

Raman and infrared study of 100MeV swift Ag8+ heavy ion irradiation effects in CaSO4·2H2O single crystals

“…In Fig. 4, the intensity of the different Raman bands after a given dose I(D), normalized to the intensity of this peak for unirradiated sample Io is plotted as log 10 FT-IR studies have been carried out to confirm the surface amorphisation. Fig.…”

“…This shift is an indicative of an evolution towards a highly disordered material. Suresh Kumar et al [10] have studied GaN using 100 MeV Au 7+ ion irradiation by varying the fluences 1 × 10 12 to 5 × 10 13 ions/cm 2 at room temperature. The structural studies were investigated using XRD and Raman scattering measurements.…”

Investigations on 40MeV Li3+ ions irradiated GaN epilayers

“…This shift is associated with the nitrogen loss that occurs upon irradiation [6]. This indicates that the lattice damage is high at LT irradiation as compared to RT irradiation.…”

“…Previous reports [4,5] have indicated that GaN is very resistant to amorphisation and there exist a dose range of disorder saturation during irradiation. Recently our group reported that the lattice disorder has been observed after 100 MeV Au 7+ ions irradiation effects of GaN [6]. Irradiation in GaN at 15 K indicates a pronounced recombination of the defects produced within the primary collision cascades [7].…”