Figure 5 | Scientific Reports

Figure 5

From: Study on Light Extraction from GaN-based Green Light-Emitting Diodes Using Anodic Aluminum Oxide Pattern and Nanoimprint Lithography

Figure 5

Top-view photographs of (a) planar LED, (b) PhC_130nm sample and (c) AAO_130nm sample taken in PL microscope. (d) Emission patterns for planar, AAO- and PhC- LEDs; (e) angular resolution PL spectra for AAO-LED (left) and PhC-LED (right). Both of them were measured from positive zenith. The luminescence from the AAO_130 nm and PhC_130 nm sample is much brighter than that from the planar LED. Besides, the pattern of luminescence from the PhC_130 nm sample is a prefect hexagon while the one from the AAO_130 nm sample is a deteriorate hexagon, which is marked by white arrows. All of the AAO-LEDs and PhC-LEDs gain the light extraction enhancements compared with the planar one. Moreover, the angular plots of AAO-LEDs show much smoother than those of PhC-LEDs in the central protrusions and a few sharp lobes are observed when the zenith angle θ is around 60 ~ 70°.

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