Fig. 1. (a) Simulated NW DUV-LED structure. (b) 3D schematic of the NW array composed of a hexagonal periodic structure of 121 NWs. (c) RI of GaN, AlGaN, and silicon substrate. (d) Cross-sectional scanning electron microscope image of MBE-grown NWs [22].

Fig. 2. Comparison of the band structures of NW arrays with θ=0° and 5.25°. Horizontal red lines indicate the frequency of concern.

Fig. 3. LEE versus tapering angle θ for (a) TE polarized emission and (b) TM polarized emission.

Fig. 4. Electric field intensity distribution for (a) cross-sectional view and (b) top view for TE and TM modes in a conventional cylindrical structure (θ=0°) and a structure with tapering angle (θ=5.25°).

Fig. 5. Far-field intensity distribution of (a) TE polarization mode and (b) TM polarization mode for θ=0°, 2.5°, and 5.25°.

Fig. 6. Comparison of Bloch mode profiles of NW array with the tapering angles of 0° and 5.25°.

Fig. 7. Influence of the positional error on the LEE of (a) 5.25° tapering angle TE polarized emission, (b) 5.25° tapering angle TM polarized emission, (c) 0° tapering angle TE polarized emission, and (d) 0° tapering angle TM polarized emission.