FESEM images, CL spectra, and peak energy. (a) FESEM images of a single GaN nanorod dispersed on a Si substrate. (b) Temperature-dependent CL spectra of a single GaN nanorod. The near-band-edge peaks were blueshifted as the temperature decreased. (c) Position-dependent CL spectra of the single GaN nanorod at T = 20 K. Each position of the GaN nanorod from top to bottom corresponds to the color box region indicated in (a). (d) The peak energy determined by Gaussian fitting and the peak intensity against the spectrum base line in (c) were plotted versus the GaN nanorod diameter.