Disorder induced in GaN thin films by 200 MeV silver ions

Abstract

GaN is a material of strategic importance due to its versatility in high temperature, radiation prone and chemical environments. The present study explores evolution of defects in GaN thin films in swift heavy ion radiation regime. GaN thin films grown by metal organic chemical vapour deposition techniques were irradiated with 200 MeV Ag ions at various fluences starting from 5 × 1010 to 5 × 1012 ions/cm2. Structural analysis revealed accumulation of lattice damage with increasing fluence. XRD analysis reveals that swift heavy ions of silver (Ag) deposit more energy into the target lattice, inducing localized damage at higher fluences, leading to broader peaks in irradiated samples. Recrystallization becomes evident at fluences of 1 × 1011 ions/cm2 of Ag 200 MeV ion irradiation, as indicated by a decrease in Full Width at Half Maximum (FWHM). The compressive stress identified in Raman analysis is associated with the c-axis and elevates the wavenumber of the E2(H) mode following Ag ion irradiation. Meanwhile, the pristine sample exhibits narrow A1 (LO) phonon mode peaks, indicating good crystallinity. Photoluminescence investigations demonstrate that Ag ions induce point defects in GaN, evident through analysis of YL, GL, and BL defect-related emission peaks following irradiation at various fluences.