Efficiency improvement of GaN-based LEDs with ITO texturing window layers using natural lithography

Ray-Hua Horng; Shao Hua Huang; Chiao Chih Yang; Dong Sing Wuu

doi:10.1109/JSTQE.2006.884060

Efficiency improvement of GaN-based LEDs with ITO texturing window layers using natural lithography

Ray-Hua Horng^*, Shao Hua Huang, Chiao Chih Yang, Dong Sing Wuu

^*Corresponding author for this work

Institute of Electronics

Research output: Contribution to journal › Article › peer-review

37 Scopus citations

Abstract

In conventional GaN light-emitting diodes (LEDs), a significant gap exists between the internal and external efficiencies owing to the narrow escape cone for light in high refractive index semiconductors. In this paper, p-side-up GaN/sapphire LEDs with surface-textured indium-tin-oxide (ITO) window layers were investigated using natural lithography with polystyrene spheres as the etching mask. Under optimum etching conditions, the surface roughness of the ITO film can reach 140 nm, while the polystyrene sphere on the textured ITO surface is maintained at about 250-300 nm in diameter. The LEDs fabricated using the surface-textured ITO provided an output power that exceeded that of the planar-surface LED by about 30% and 40% at 20 and 400 mA current injection, respectively. After calculating, the extraction quantum efficiency of ITO/GaN LEDs with and without textured surface is 22.6% and 17.4%, respectively. There is about 5.3% improvement in the extraction quantum efficiency.

Original language	English
Pages (from-to)	1196-1200
Number of pages	5
Journal	IEEE Journal on Selected Topics in Quantum Electronics
Volume	12
Issue number	6
DOIs	https://doi.org/10.1109/JSTQE.2006.884060
State	Published - 1 Nov 2006

Keywords

GaN
Indium-tin oxide (ITO)
Light-emitting diode (LED)
Natural lithography
Surface texturing

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title = "Efficiency improvement of GaN-based LEDs with ITO texturing window layers using natural lithography",

abstract = "In conventional GaN light-emitting diodes (LEDs), a significant gap exists between the internal and external efficiencies owing to the narrow escape cone for light in high refractive index semiconductors. In this paper, p-side-up GaN/sapphire LEDs with surface-textured indium-tin-oxide (ITO) window layers were investigated using natural lithography with polystyrene spheres as the etching mask. Under optimum etching conditions, the surface roughness of the ITO film can reach 140 nm, while the polystyrene sphere on the textured ITO surface is maintained at about 250-300 nm in diameter. The LEDs fabricated using the surface-textured ITO provided an output power that exceeded that of the planar-surface LED by about 30% and 40% at 20 and 400 mA current injection, respectively. After calculating, the extraction quantum efficiency of ITO/GaN LEDs with and without textured surface is 22.6% and 17.4%, respectively. There is about 5.3% improvement in the extraction quantum efficiency.",

keywords = "GaN, Indium-tin oxide (ITO), Light-emitting diode (LED), Natural lithography, Surface texturing",

author = "Ray-Hua Horng and Huang, {Shao Hua} and Yang, {Chiao Chih} and Wuu, {Dong Sing}",

year = "2006",

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AU - Horng, Ray-Hua

AU - Huang, Shao Hua

AU - Yang, Chiao Chih

AU - Wuu, Dong Sing

PY - 2006/11/1

Y1 - 2006/11/1

N2 - In conventional GaN light-emitting diodes (LEDs), a significant gap exists between the internal and external efficiencies owing to the narrow escape cone for light in high refractive index semiconductors. In this paper, p-side-up GaN/sapphire LEDs with surface-textured indium-tin-oxide (ITO) window layers were investigated using natural lithography with polystyrene spheres as the etching mask. Under optimum etching conditions, the surface roughness of the ITO film can reach 140 nm, while the polystyrene sphere on the textured ITO surface is maintained at about 250-300 nm in diameter. The LEDs fabricated using the surface-textured ITO provided an output power that exceeded that of the planar-surface LED by about 30% and 40% at 20 and 400 mA current injection, respectively. After calculating, the extraction quantum efficiency of ITO/GaN LEDs with and without textured surface is 22.6% and 17.4%, respectively. There is about 5.3% improvement in the extraction quantum efficiency.

AB - In conventional GaN light-emitting diodes (LEDs), a significant gap exists between the internal and external efficiencies owing to the narrow escape cone for light in high refractive index semiconductors. In this paper, p-side-up GaN/sapphire LEDs with surface-textured indium-tin-oxide (ITO) window layers were investigated using natural lithography with polystyrene spheres as the etching mask. Under optimum etching conditions, the surface roughness of the ITO film can reach 140 nm, while the polystyrene sphere on the textured ITO surface is maintained at about 250-300 nm in diameter. The LEDs fabricated using the surface-textured ITO provided an output power that exceeded that of the planar-surface LED by about 30% and 40% at 20 and 400 mA current injection, respectively. After calculating, the extraction quantum efficiency of ITO/GaN LEDs with and without textured surface is 22.6% and 17.4%, respectively. There is about 5.3% improvement in the extraction quantum efficiency.

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KW - Indium-tin oxide (ITO)

KW - Light-emitting diode (LED)

KW - Natural lithography

KW - Surface texturing

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