InGaN micro-pixellated light-emitting diodes with nano-textured surfaces and modified emission profiles |
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Authors: | Z Gong Y F Zhang P Kelm I M Watson E Gu and M D Dawson |
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Institution: | (1) Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore, 117602, Singapore;(2) Singapore-MIT Alliance, National University of Singapore, 4 Engineering Drive 3, Singapore, 117576, Singapore |
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Abstract: | We present the fabrication details and performance characteristics of InGaN light-emitting diodes (LEDs) consisting of arrays
of interconnected micro-pixels where each micro-pixel is nano-textured via nano-imprinting. We have taken the further step
of embodying the pixels in a rhomboidal geometry. It is found that the power output of these nano-textured micro-LEDs with
rhomboidal geometries is 57% higher than that of conventional square-shaped broad-area reference LEDs. The series resistance
of the textured LEDs is reduced, owing to the multi-finger electrodes introduced. Furthermore, these LEDs can sustain higher
operation current of up to 500 mA without encapsulation, suggesting improved thermal dissipation capability. Finally, the
combined effects of surface texturing, micro-LED configuration, and geometric shaping on the light extraction are analyzed.
It is found that the power enhancement by surface texturing, micro-pixellating and the rhomboidal geometry are 32%, 16%, and
9%, respectively, implying that surface texturing is the most effective contribution to increasing the light extraction efficiency
in our design. The angular dependent far-field beam profile is also remarkably changed, compared with the standard Lambertian
emission pattern of the conventional square-shaped LEDs. Substantial increase in the EL intensity is evident from both the
top surface and the sidewall. |
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