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Qian YZ, Yang ZY, Huang YH, Lin KH, Wu ST. Directional high-efficiency nanowire LEDs with reduced angular color shift for AR and VR displays. Opto-Electron Sci 1, 220021 (2022). doi: 10.29026/oes.2022.220021
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Original Article Open Access
Directional high-efficiency nanowire LEDs with reduced angular color shift for AR and VR displays
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Abstract
The emission wavelength of InGaN/GaN dot-in-wire LED can be tuned by modifying the nanowire diameter, but it causes mismatched angular distributions between blue, green, and red nanowires because of the excitation of different waveguide modes. Besides, the far-field radiation patterns and light extraction efficiency are typically calculated by center dipoles, which fails to provide accurate results. To address these issues, we first compare the simulation results between central dipole and dipole cloud with experimental data. Next, we calculate and analyze the display metrics for full-color nanowire LEDs by 3D dipole cloud. Finally, we achieve unnoticeable angular color shift within ±20° viewing cone for augmented reality (AR) and virtual reality (VR) displays with an improved light extraction efficiency.-
Keywords:
- nanowire LED /
- microdisplay /
- AR/VR light engines /
- angular color shift
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References
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Supplementary Information
Supplementary information for Directional high-efficiency nanowire LEDs with reduced angular color shift for AR and VR displays
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Qian YZ, Yang ZY, Huang YH, Lin KH, Wu ST. Directional high-efficiency nanowire LEDs with reduced angular color shift for AR and VR displays. Opto-Electron Sci 1, 220021 (2022). doi: 10.29026/oes.2022.220021
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Figure 1.
(a) 3D-FDTD InP nanowire LED simulation schematic. (b) Simulated far-field radiation patterns of InP nanowire LED. The experimental data (black curve) included for comparison are from ref.31.
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Figure 2.
(a) Schematic of FDTD simulation model in x-z plane. (b) Top view of blue hexagonal nanowire LED. (c) Measured EL spectra of single nanowire LEDs with different diameters from ref.25.
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Figure 3.
(a–c) Normalized 2D angular distribution for (a) blue, (b) green, and (c) red LEDs. (d) Normalized 1D angular distribution when azimuthal angle φ=0°.
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Figure 4.
(a) Simulated color triangle of the GaN/InGaN nanowire LED display and CIE coordinates of 18 reference colors at 0° viewing angle. (b) Simulated color shift of 18 reference colors from 0° to 20° viewing angle. Inset: Simulated average color shift from 0° to 30° viewing angle.
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Figure 5.
(a–c) 2D colormap of angular FWHM as a function of n-GaN thickness and p-GaN capping height: (a) blue, (b) green, and (c) red nanowire LEDs. (d–f) 2D colormap of effective LEE as a function of n-GaN thickness and p-GaN capping height: (d) blue, (e) green, and (f) red nanowire LEDs.
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Figure 6.
(a–c) Normalized 2D angular distribution for optimized (a) blue, (b) green, and (c) red LEDs. (d) Comparison of normalized 1D angular distribution between unoptimized (solid lines) and optimized (dashed lines) nanowire LEDs.
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Figure 7.
Comparison between calculated effective EQE of nanowire LED (horizontal dash lines) with measured EQE of (a) blue InGaN µLEDs from ref.9,43, (b) green InGaN µLEDs from ref.43-47 and (c) red AlGaInP µLEDs from ref.48 as a function of mesa diameter. Vertical dash lines: EQE of µLEDs with 10-µm mesa size.
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Figure 8.
(a) Simulated angular color shift of 18 reference colors from 0° to 20° after optimization. (b) Simulated average color shift from 0° to 30° viewing angle after optimization.
