Lattice Constant Effect on Diffracted Transmission of ITO Periodic Nanostructures and Improvement of the Light Extraction Efficiency of Light-Emitting Diodes.

Zhanxu Chen,Feng Wu,Runhong Ding,Wei Wan

doi:10.3390/mi12060693

Zhanxu Chen, Feng Wu + Show 2 more

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Journal: Micromachines	Publication Date: Jun 14, 2021
Citations: 2	License type: CC BY 4.0

Affiliation: Guangdong Polytechnic Normal University

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We studied the effects of the lattice pitch of indium-doped tin oxide (ITO) periodic nanostructures on the diffracted transmission to improve the light extraction efficiency of light-emitting diodes (LEDs). Periodic hexagonal ITO nanopillars with lattice constants of 600, 800, 1050, 1200, and 1600 nm were fabricated on ITO electrodes. We found that the light extraction efficiency strongly depended on the lattice constant. The LEDs with a lattice constant of 800 nm ITO nanopillars showed an increase in light extraction of 83%. In addition, their electrical properties were not degraded compared to conventional LEDs. The dependence of the extraction efficiency on the lattice constant was also calculated using a 3D finite-difference time-domain (FDTD) method, and this dependence was in good agreement with the experimental measurements. The transmission of each diffraction order and with the total transmission of ITO nanopillars with different lattice constants were calculated using the FDTD method to investigate the enhancement effect.

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To date, light emitting diodes (LEDs) have been widely utilized as energy-saving and environment-friendly light sources [1,2,3,4,5]
The entire LED epitaxial wafer consists of a 2-inch sapphire (Al2 O3 ) substrate, a 2-μm undoped GaN (u-GaN) buffer layer, a 3-μm n-GaN layer, an active layer of five-period
A 2-inch LED wafer was divided into six parts to prepare the samples

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Introduction

Light emitting diodes (LEDs) have been widely utilized as energy-saving and environment-friendly light sources [1,2,3,4,5]. Research is ongoing to improve LED performance through more efficient light-generating and light-extracting structures [6,7]. Researchers have incorporated PhCs into LEDs and greatly improved the light extraction efficiency [6,7,8,11,18,19,20,21,22]. The light extraction enhancement factor is affected by the structural parameters, such as the lattice constant, filling factor, and etch depth. Kim et al made the air-hole array patterns with a period that varied from 300 to 700 nm to investigate PhC GaN-based LEDs with peak wavelength of λ = 400 nm and found the best enhancement factor was 2.1 when the lattice constant was 500 nm [22]

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