Microstructural response of InGaN to swift heavy ion irradiation

A monocrystalline In_0.18Ga_0.82N film of ∼275 nm in thickness grown on a GaN/Al₂O₃ substrate was irradiated with 290 MeV ²³⁸U³²⁺ ions to a fluence of 1.2 × 10¹² cm⁻² at room temperature. The irradiated sample was characterized using helium ion microscopy (HIM), Rutherford backscattering spectrometry under ion-channeling conditions (RBS/C), and high-resolution X-ray diffraction (HRXRD). The irradiation leads to formation of ion tracks throughout the thin In_0.18Ga_0.82N film and the 3.0 μm thick GaN buffer layer. The mean diameter of the tracks in In_0.18Ga_0.82N is ∼9 nm, as determined by HIM examination. Combination of the HIM and RBS/C data suggests that the In_0.18Ga_0.82N material in the track is likely to be highly disordered or fully amorphized. The irradiation induced lattice relaxation in In_0.18Ga_0.82N and a distribution of d-spacing of the (0 0 0 2) planes in GaN with lattice expansion are observed by HRXRD.