GaN optical degradation during high energy Sn⁵⁺ ion irradiation

GaN(0001) epilayers grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD) have been irradiated with 75 MeV Sn⁵⁺ ions at the fluences of 10¹¹, 10¹², and 10¹³ ions/cm². Structural and optical studies reveal that GaN epilayer withstands 75 MeV Sn⁵⁺ ion irradiations up to 10¹¹ ions/cm² ion fluences. High resolution X-ray diffraction results showed that the FWHM corresponding to (0002) plane increased from 227 to 279 arc-seconds after Sn-ions irradiation. Red shift was observed in the yellow luminescence (YL) emission by photoluminescence (PL), corresponds to the concentration of ion fluences. Donor-bound exciton (DBE) and free exciton (FE^A, FE^B and FE^C) emissions were observed for as-grown and irradiated GaN samples up to 10¹² ions/cm² at 2K PL measurements. Free excitons are dominated by low-temperature PL measurements for as-grown and irradiated GaN samples at 10¹¹ and 10¹² ion fluences. Atomic force microscopy images show the RMS roughness increases with increasing Sn-ion fluences by removing as-grown GaN surface defects.