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Abstract: As next-generation displays, micron-sized light-emitting diode (µLED) displays have been researched intensively with advantages of higher wall-plug efficiency and wider color gamut compared to conventional liquid crystal displays (LCDs) and organic LED (OLED) displays. Currently, mini LED displays with a chip size of more than 100 µm are commercially available in spite of the huge costs caused by a large chip size. For blue and green LEDs, InGaN-based LEDs are used, while for red, AlInGaP-based LEDs are currently used. In order to reduce the cost of µLED displays and to open a market for the application of small displays such as smartphones and AR/VR displays, each chip size has to be reduced to a micron size. When the size of µLEDs becomes small (especially smaller than 40 µm), the EQE decreases dramatically. This decrease is due to surface recombination and the sidewall damage of the mesa from the plasma-assisted dry etching, which contribute to increased Shockley-Read-Hall non-radiative recombination at small dimensions. Potassium hydroxide (KOH) has been used to improve the electrical performance of GaN-based devices by removing the plasma-damaged material on the device's side walls. However, there are several issues with the conventional µLEDs, such as color mixing, color purity, emission directionality, and thermal and color stability. Those problems of µLEDs could be addressed by using single-mode emission InGaN-based blue, green, and red microcavity light-emitting diodes (MC-LEDs). These MC-LEDs have the advantages of thermal stability and spectral purity since the spectral width and shape are determined by the overlap of the InGaN quantum well (QW) emission and the cavity mode. In addition, the emission of MC-LEDs is more directional than conventional LEDs. These advantages suggest MC-LEDs could be the best fit for display applications.

Author's bio:
Nobel Prize in Physics, NAE, NAI, NIHF
Royal Academy of Engineering
CREE Distinguished Professor, Materials

Honors:
Global Energy Prize
Zayed Future Energy Prize Lifetime Achievement
Harvey Prize for advancements in Science and Technology
Benjamin Franklin Medal in Engineering
Millennium Technology Prize

Research Description:
Widely recognized as a pioneer in light emitters based on wide-bandgap semiconductors, Nakamura continues to focus on the development of GaN thin film technology for the development of highly efficient Nitride-based LEDs and laser diodes.

Education:
Doctor of Engineering, University of Tokushima
Master of Electronic Engineering, University of Tokushima
Bachelor of Electronic Engineering, University of Tokushima

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