Ultrasmall and ultradense InGaN-based RGB monochromatic micro-light-emitting diode arrays by pixilation of conductive p-GaN
Zhe Zhuang, Daisuke Iida, Kazuhiro Ohkawa
Abstract
We describe 5 μm squircle InGaN-based red, green, and blue (RGB) monochromatic micro-light-emitting diodes (μLEDs) with an interpitch of 4 μm by pixilation of conductive p-GaN using a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">H</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> -plasma treatment. The p-GaN was passivated by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">H</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> plasma and prevented the current’s injection into the InGaN quantum wells below. We observed that InGaN-based red μLEDs exhibited a broader full width at half-maximum and larger peak wavelength blueshift at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:mn>11.5</mml:mn> <mml:mi>–</mml:mi> <mml:mn>115</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">A</mml:mi> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> than the green/blue μLEDs. The on-wafer light output power density of the red μLEDs at a wavelength of 632 nm at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m4"> <mml:mrow> <mml:mn>115</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">A</mml:mi> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> was approximately <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m5"> <mml:mrow> <mml:mn>936</mml:mn> <mml:mtext> </mml:mtext> <mml:msup> <mml:mrow> <mml:mtext>mW/</mml:mtext> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , the highest value reported thus far for InGaN-based red μLEDs. This value was comparable with that of the green/blue μLEDs at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m6"> <mml:mrow> <mml:mn>11.5</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">A</mml:mi> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , indicating that the red μLEDs can satisfy the requirement of high brightness levels for specific displays. The color gamut based on InGaN RGB μLEDs covered 83.7% to 75.9% of the Rec. 2020 color space in the CIE 1931 diagram at 11.5 to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m7"> <mml:mrow> <mml:mn>115</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">A</mml:mi> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> .