CL spectra and peak energies. (a) CL spectra of the GaN nanorods (as shown in Figure 1a) taken at temperatures of 20 K to 300 K. (b) Temperature-dependent NBE peak energy and defect-related (Y7) peak energy. The red and blue solid curves are the Varshni-equation-fitted curves of NBE and Y7 states, respectively. (c) The CL spectrum of the GaN nanorods was performed at a temperature of 20 K and at the position of the red-circled region indicated in (a). The CL spectrum was fitted by a three-peak Gaussian model.