Micro Raman analysis on the impact of light ion irradiation of hydride vapor-phase epitaxy grown gallium nitride epilayers

Abstract

Gallium Nitride (GaN) epilayer grown by Hydride Vapor-Phase Epitaxy was irradiated with 100 MeV O7+ light ions for different fluences. The X-ray diffraction results confirmed that all the grown epilayers have wurtzite structure. The thickness of the pristine GaN is measured by cross-section scanning electron microscopy. From atomic force microscopy, the irradiated sample's surface morphology and root mean square values were analyzed. The stopping range of ions in the materials calculation provided the projected range for the irradiation ions. From Raman spectroscopy, Raman active mode of EH2 and A1(LO) vibration was observed. These Raman modes were fitted by the Lorentz fitting method for line-shape model identification to calculate the area under the curve, full-width half maximum, and peak shift position. The biaxial stress, carrier concentration, and phonon lifetime for both pristine and irradiated GaN epilayers were obtained from the Raman active mode. The results indicated that the carrier concentration increases for higher fluences due to the defect formations. The photoluminescence spectrum was measured for all the epilayers and defect-induced photoluminescence emission was obtained for these irradiation epilayers.