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(a) and (b) Tilted-view SEM images of uncoated and MgZnO-coated ZnO NRAs; the scale bars are 2 μm. (c) Z-contrast TEM image of a single MgZnO-coated ZnO nanorod. (d) Line-scan composition profiles of Mg and Zn elements along the radial direction of the core/shell nanorod. (e) I-V curves of the uncoated (red dashed line) and coated (blue solid line) LEDs; the near-linear I-V characteristic in the inset verifies an ohmic contact between Ni/Au electrode and p-GaN. (f) Schematic diagram of a MgZnO-coated ZnO NRA/p-GaN heterojunction LED.
(a) RT PL spectra of MgZnO-coated/uncoated ZnO NRAs and GaN film. (b) RT EL spectra and Gaussian deconvolution analysis of uncoated and coated devices measured at an injection current of 3.5 mA.
(a) RT EL spectra of uncoated (left) and coated (right) devices obtained at different air-exposure periods, the injection current is fixed at 5 mA. (b) and (c) The variations of ηrr, ηnr, and RNBE/DL of both LEDs with air-exposure time; for clarity, the inset in (c) exhibits a magnified image of the last four data points.
(a) RT EL spectra of the long-term air-exposed, uncoated device before (red solid line) and after (blue dashed line) vacuum desorption; the injection current is 3 mA. (b) O 1 s core-level XPS spectra of the fresh, exposed, and desorbed ZnO NRAs. (c) Schematic diagram showing the surface-mediated carrier tunneling, trapping, and recombination processes in the uncoated ZnO NRA.
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