Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Improving the Light Extraction Efficiency of GRIN Coatings Pillar Light Emitting Diodes

  • Moe, War War (Department of Electronic Engineering, Mandalay Technological University (MTU)) ;
  • Aye, Mg (Department of Electronic Engineering, Mandalay Technological University (MTU)) ;
  • Hla, Tin Tin (Department of Electronic Engineering, Mandalay Technological University (MTU))
  • Received : 2022.05.26
  • Accepted : 2022.06.15
  • Published : 2022.06.27
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Abstract

This study investigated a graded-refractive-index (GRIN) coating pattern capable of improving the light extraction efficiency of GaN light-emitting diodes (LEDs). The planar LEDs had total internal reflection thanks to the large difference in refractive index between the LED semiconductor and the surrounding medium (air). The main goal of this paper was to reduce the trapped light inside the LED by controlling the refractive index using various compositions of (TiO2)x(SiO2)1-x in GRIN LEDs consisting of five dielectric layers. Several types of multilayer LEDs were simulated and it was determined the transmittance value of the LEDs with many layers was greater than the LEDs with less layers. Then, the specific ranges of incident angles of the individual layers which depend on the refractive index were evaluated. According to theoretical calculations, the light extraction efficiency (LEE) of the five-layer GRIN is 25.29 %, 28.54 % and 30.22 %, respectively. Consequently, the five-layer GRIN LEDs patterned enhancement outcome LEE over the reference planar LEDs. The results suggest the increased light extraction efficiency is related to the loss of Fresnel transmission and the release of the light mode trapped inside the LED chip by the graded-refractive-index.

Keywords

Acknowledgement

The author especially thanks to Dr. Tin Tin Hla, Professor and Head of Department of Electronic Engineering at Mandalay Technological University, for her constructive advice and editing this research. The author is deeply thankful to her supervisor Dr. Mg Aye, Associate Professor of the Department of Electronic Engineering at Mandalay Technological University, for his teaching, advice, supervision, and supports during the preparation of this research.

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