Fig. 1. Schematic diagrams of the DUV LEDs nanorod structure fabrication process. (a) SiO2 nanospheres deposited on the wafer. (b) CF4-based ICP etching shrinks the nanospheres. (c) Cl-based ICP etches down wafer to n-AlGaN layer. (d) SiO2 nanospheres are removed by the buffer oxide etchant.

Fig. 2. (a) Top-view and (b) cross-sectional SEM images of nanorod array structure.

Fig. 3. TDPL band peak positions for (a) nanorod and (b) planar DUV LEDs and (c) their Arrhenius plots of the normalized PL intensities as a function of temperature.

Fig. 4. Dependence of the (a) integrated PL intensity, (b) PL relative efficiency, and (c) peak photon energy on excitation-energy density at room temperature for two samples.

Fig. 5. (a) TRPL spectra of the planar and nanorod DUV LEDs at room temperature. Time-dependent carrier density extracted for (a) and scaled to (b) 1/[I(t)]1/2 for the bimolecular recombination model and (c) (1/2)ln[I(t)] for the monomolecular recombination model.

Fig. 6. Fabrication process of nanorod DUV LED devices. (a) Depositing SiO2 as insulating layer to passivate the surface of nanorod LEDs. (b) Partial SiO2 is removed to expose n-AlGaN and p-GaN. (c) Ti/Al/Ti/Au and Ni/Au metal stacks are deposited on the n-AlGaN and p-GaN as the n-type contact and the p-type contact, respectively. (d) Al/Ti/Au stack metal layers are deposited on the p-contact of nanorods to connect p-contact together. (e)–(h) Corresponding SEM diagrams of (a), (b), (c), and (d), respectively.

Fig. 7. (a) EL spectra of the nanorod AlGaN DUV LED at different injection current densities (from 10  A/cm2 to 120  A/cm2) under CW biasing condition. (b) Current-voltage characteristics of both kinds of LEDs, and the inset is the current-voltage curve on a semi-log scale. (c) LOPs and EQEs under different current densities. (d) Normalized angle-resolved EL spectra of nanorod and planar DUV LEDs measured at 20  A/cm2.

Fig. 8. Schematic diagrams of the (a) planar and (b) nanorod DUV LEDs for FDTD computation with boundary conditions.

Fig. 9. Cross-sectional near-field electric field intensity of the investigated (a), (c) planar and (b), (d) nanorod DUV LEDs for (a), (b) TE and (c), (d) TM polarizations at x–z plane, respectively.