Effects of electron beam annealing on optical and structural properties of GaN nanorods grown by HVPE

Gallium nitride (GaN) nanorods were grown on Al₂O₃ (0 0 0 1) substrates at 500 °C by hydride vapor phase epitaxy (HVPE) and their structural and optical properties were improved by e-beam annealing. After e-beam annealing for 4 h by applying an acceleration energy of 30 keV, cathodoluminescence peak positions for the single nanorod and the grouped nanorods were shifted toward lower energy region by 46 and 34 meV, respectively. For Raman scattering spectroscopy measurements, it was also observed that E₂ (high) peak positions shifted to the lower frequency region. Using the deviation between E₂ (high) peak positions for before and after e-beam annealing, the relaxation of biaxial compressive stress was calculated to be ∼0.8 Gpa. These results suggest that the optical and structural properties of GaN nanorods could be improved by e-beam annealing.