InGaN micro-pixellated light-emitting diodes with nano-textured surfaces and modified emission profiles

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

Towards 10 Gb/s orthogonal frequency division multiplexing-based visible light communication using a GaN violet micro-LED

“…These include much superior color rendering indices [9,10] and the absence of a direct blue component, which has proven to be disruptive to the human circadian rhythm [11]. The micro-LED die shapes employed in this work are also expected to be advantageous for efficient light extraction, by analogy with previous designs employing non-circular emitting areas [12].…”

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“…[ 50 ] For a micro‐LED array [ 51 ] R th was found to decrease with pixel size: from 72 K W −1 for a broad‐area LED to 36 K W −1 for a pixel size of 20 µm. Device geometry is a potential design parameter: rhomboidal‐shaped micro‐LEDs (with interdigitated contacts) sustained much higher maximum currents than square LEDs [ 52 ] because of i) reduced series resistance, ii) suppressed current crowding, and iii) improved heat dissipation. Simulations showed the relative increase in the junction temperature for broad‐area power chips dropping by over 60% by adopting an interdigitated multipixel array.…”

III‐Nitride Micro‐LEDs for Efficient Emissive Displays

“…[]. There are both industrial efforts and academic research on micro‐LEDs and micro‐LED displays . In principle, the pixels in an inorganic LED emissive display are direct‐emitting blue, green, and red LEDs, just as for OLED displays.…”