J. Semicond. > Volume 37 > Issue 10 > Article Number: 104003

Increased effective reflection and transmission at the GaN-sapphire interface of LEDs grown on patterned sapphire substrates

Dongxue Wu 1, 2, 3, , Ping Ma 1, 2, 3, , , Boting Liu 1, 2, 3, , Shuo Zhang 1, 2, 3, , Junxi Wang 1, 2, 3, and Jinmin Li 1, 2, 3,

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Abstract: The effect of patterned sapphire substrate (PSS) on the top-surface (P-GaN-surface) and the bottom-surface (sapphire-surface) of the light output power (LOP) of GaN-based LEDs was investigated, in order to study the changes in reflection and transmission of the GaN-sapphire interface. Experimental research and computer simulations were combined to reveal a great enhancement in LOP from either the top or bottom surface of GaN-based LEDs, which are prepared on patterned sapphire substrates (PSS-LEDs). Furthermore, the results were compared to those of the conventional LEDs prepared on the planar sapphire substrates (CSS-LEDs). A detailed theoretical analysis was also presented to further support the explanation for the increase in both the effective reflection and transmission of PSS-GaN interface layers and to explain the causes of increased LOP values. Moreover, the bottom-surface of the PSS-LED chip shows slightly increased light output performance when compared to that of the top-surface. Therefore, the light extraction efficiency (LEE) can be further enhanced by integrating the method of PSS and flip-chip structure design.

Key words: light output powertransmissioneffective reflectionpatterned sapphire substratelight-emitting diodes

Abstract: The effect of patterned sapphire substrate (PSS) on the top-surface (P-GaN-surface) and the bottom-surface (sapphire-surface) of the light output power (LOP) of GaN-based LEDs was investigated, in order to study the changes in reflection and transmission of the GaN-sapphire interface. Experimental research and computer simulations were combined to reveal a great enhancement in LOP from either the top or bottom surface of GaN-based LEDs, which are prepared on patterned sapphire substrates (PSS-LEDs). Furthermore, the results were compared to those of the conventional LEDs prepared on the planar sapphire substrates (CSS-LEDs). A detailed theoretical analysis was also presented to further support the explanation for the increase in both the effective reflection and transmission of PSS-GaN interface layers and to explain the causes of increased LOP values. Moreover, the bottom-surface of the PSS-LED chip shows slightly increased light output performance when compared to that of the top-surface. Therefore, the light extraction efficiency (LEE) can be further enhanced by integrating the method of PSS and flip-chip structure design.

Key words: light output powertransmissioneffective reflectionpatterned sapphire substratelight-emitting diodes



References:

[1]

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[2]

Zhang Y, Wei T, Wang J. The improvement of GaN-based light-emitting diodes using nanopatterned sapphire substrate with small pattern spacing[J]. AIP Advances, 2014, 4(2): 027123. doi: 10.1063/1.4867091

[3]

Kim H G, Na M G, Kim H K. Effect of periodic deflector embedded in InGaN/GaN light emitting diode[J]. Appl Phys Lett, 2007, 90(26): 261117. doi: 10.1063/1.2752777

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Lee Y J, Hsu T C, Kuo H C. Improvement in light-output efficiency of near-ultraviolet InGaN-GaN LEDs fabricated on stripe patterned sapphire substrates[J]. Mater Sci Eng B, 2005, 122(3): 184. doi: 10.1016/j.mseb.2005.05.019

[5]

Wu D S, Wang W K, Wen K S. Defect reduction and efficiency improvement of near-ultraviolet emitters via laterally overgrown GaN on a GaN/patterned sapphire template[J]. Appl Phys Lett, 2006, 89(16): 161105. doi: 10.1063/1.2363148

[6]

Cui H, Park S H. Numerical simulations of light-extraction efficiencies of light-emitting diodes on micro and nanopatterned sapphire substrates[J]. Micro Nano Lett, 2014, 9(12): 841. doi: 10.1049/mnl.2014.0373

[7]

Du C, Wei T, Zheng H. Size-controllable nanopyramids photonic crystal selectively grown on p-GaN for enhanced light-extraction of light-emitting diodes[J]. Opt Express, 2013, 21(21): 25373. doi: 10.1364/OE.21.025373

[8]

Yamada M, Mitani T, Narukawa Y. InGaN-based near-ultraviolet and blue-light-emitting diodes with high external quantum efficiency using a patterned sapphire substrate and a mesh electrode[J]. Jpn J Appl Phys, 2002, 41(12B): L1431.

[9]

Tadatomo K, Okagawa H, Ohuchi Y, et al. High output power near-ultraviolet and violet light-emitting diodes fabricated on patterned sapphire substrates using metalorganic vapor phase epitaxy. Third International Conference on Solid State Lighting, 2004: 243

[10]

Wang C C, Ku H, Liu C C. Enhancement of the light output performance for GaN-based light-emitting diodes by bottom pillar structure[J]. Appl Phys Lett, 2007, 91(12): 121109. doi: 10.1063/1.2786015

[11]

Gao H, Yan F, Zhang Y. Enhancement of the light output power of InGaN/GaN light-emitting diodes grown on pyramidal patterned sapphire substrates in the micro-and nanoscale[J]. J Appl Phys, 2008, 103(1): 014314. doi: 10.1063/1.2830981

[12]

Cuong T V, Cheong H S, Kim H G. Enhanced light output from aligned micropit InGaN-based light emitting diodes using wet-etch sapphire patterning[J]. Appl Phys Lett, 2007, 90(13): 131107. doi: 10.1063/1.2714203

[13]

An Tielei, Sun Bo, Wei Tongbo. Light-extraction enhancement of freestanding GaN-based flip-chip light-emitting diodes using two-step roughening methods[J]. Journal of Semiconductors, 2013, 34(11): 114006. doi: 10.1088/1674-4926/34/11/114006

[14]

Pan J W, Tsai P J, Chang K D. Light extraction efficiency analysis of GaN-based light-emitting diodes with nanopatterned sapphire substrates[J]. Appl Opt, 2013, 52(7): 1358. doi: 10.1364/AO.52.001358

[15]

Lee J H, Oh J T, Kim Y C. Stress reduction and enhanced extraction efficiency of GaN-based LED grown on cone-shape-patterned sapphire[J]. IEEE Photon Technol Lett, 2008, 20(17-20): 1563.

[16]

Skaar J. Fresnel equations and the refractive index of active media[J]. Phys Rev E, 2006, 73(2): 026605. doi: 10.1103/PhysRevE.73.026605

[17]

Ding Q A, Li K, Kong F. Improving the vertical light extraction efficiency of GaN-based thin-film flip-chip LED with double embedded photonic crystals[J]. IEEE J Quantum Electron, 2015, 51(2): 1.

[18]

Lee Y J, Kuo H C, Lu T C. Fabrication and characterization of GaN-based LEDs grown on chemical wet-etched patterned sapphire substrates[J]. J Electrochem Soc, 2006, 153(12): G1106. doi: 10.1149/1.2359701

[19]

Lee T X, Lin C Y, Ma S H. Analysis of position-dependent light extraction of GaN-based LEDs[J]. Opt Express, 2005, 13(11): 4175. doi: 10.1364/OPEX.13.004175

[20]

Chen Maoxing, Xu Chen, Xu Kun. Thermal simulation and analysis of flat surface flip-chip high power light-emitting diodes[J]. Journal of Semiconductors, 2013, 34(12): 124005. doi: 10.1088/1674-4926/34/12/124005

[1]

Wang L, Zhang Y, Li X. Partially sandwiched graphene as transparent conductive layer for InGaN-based vertical light emitting diodes[J]. Appl Phys Lett, 2012, 101(6): 061102. doi: 10.1063/1.4742892

[2]

Zhang Y, Wei T, Wang J. The improvement of GaN-based light-emitting diodes using nanopatterned sapphire substrate with small pattern spacing[J]. AIP Advances, 2014, 4(2): 027123. doi: 10.1063/1.4867091

[3]

Kim H G, Na M G, Kim H K. Effect of periodic deflector embedded in InGaN/GaN light emitting diode[J]. Appl Phys Lett, 2007, 90(26): 261117. doi: 10.1063/1.2752777

[4]

Lee Y J, Hsu T C, Kuo H C. Improvement in light-output efficiency of near-ultraviolet InGaN-GaN LEDs fabricated on stripe patterned sapphire substrates[J]. Mater Sci Eng B, 2005, 122(3): 184. doi: 10.1016/j.mseb.2005.05.019

[5]

Wu D S, Wang W K, Wen K S. Defect reduction and efficiency improvement of near-ultraviolet emitters via laterally overgrown GaN on a GaN/patterned sapphire template[J]. Appl Phys Lett, 2006, 89(16): 161105. doi: 10.1063/1.2363148

[6]

Cui H, Park S H. Numerical simulations of light-extraction efficiencies of light-emitting diodes on micro and nanopatterned sapphire substrates[J]. Micro Nano Lett, 2014, 9(12): 841. doi: 10.1049/mnl.2014.0373

[7]

Du C, Wei T, Zheng H. Size-controllable nanopyramids photonic crystal selectively grown on p-GaN for enhanced light-extraction of light-emitting diodes[J]. Opt Express, 2013, 21(21): 25373. doi: 10.1364/OE.21.025373

[8]

Yamada M, Mitani T, Narukawa Y. InGaN-based near-ultraviolet and blue-light-emitting diodes with high external quantum efficiency using a patterned sapphire substrate and a mesh electrode[J]. Jpn J Appl Phys, 2002, 41(12B): L1431.

[9]

Tadatomo K, Okagawa H, Ohuchi Y, et al. High output power near-ultraviolet and violet light-emitting diodes fabricated on patterned sapphire substrates using metalorganic vapor phase epitaxy. Third International Conference on Solid State Lighting, 2004: 243

[10]

Wang C C, Ku H, Liu C C. Enhancement of the light output performance for GaN-based light-emitting diodes by bottom pillar structure[J]. Appl Phys Lett, 2007, 91(12): 121109. doi: 10.1063/1.2786015

[11]

Gao H, Yan F, Zhang Y. Enhancement of the light output power of InGaN/GaN light-emitting diodes grown on pyramidal patterned sapphire substrates in the micro-and nanoscale[J]. J Appl Phys, 2008, 103(1): 014314. doi: 10.1063/1.2830981

[12]

Cuong T V, Cheong H S, Kim H G. Enhanced light output from aligned micropit InGaN-based light emitting diodes using wet-etch sapphire patterning[J]. Appl Phys Lett, 2007, 90(13): 131107. doi: 10.1063/1.2714203

[13]

An Tielei, Sun Bo, Wei Tongbo. Light-extraction enhancement of freestanding GaN-based flip-chip light-emitting diodes using two-step roughening methods[J]. Journal of Semiconductors, 2013, 34(11): 114006. doi: 10.1088/1674-4926/34/11/114006

[14]

Pan J W, Tsai P J, Chang K D. Light extraction efficiency analysis of GaN-based light-emitting diodes with nanopatterned sapphire substrates[J]. Appl Opt, 2013, 52(7): 1358. doi: 10.1364/AO.52.001358

[15]

Lee J H, Oh J T, Kim Y C. Stress reduction and enhanced extraction efficiency of GaN-based LED grown on cone-shape-patterned sapphire[J]. IEEE Photon Technol Lett, 2008, 20(17-20): 1563.

[16]

Skaar J. Fresnel equations and the refractive index of active media[J]. Phys Rev E, 2006, 73(2): 026605. doi: 10.1103/PhysRevE.73.026605

[17]

Ding Q A, Li K, Kong F. Improving the vertical light extraction efficiency of GaN-based thin-film flip-chip LED with double embedded photonic crystals[J]. IEEE J Quantum Electron, 2015, 51(2): 1.

[18]

Lee Y J, Kuo H C, Lu T C. Fabrication and characterization of GaN-based LEDs grown on chemical wet-etched patterned sapphire substrates[J]. J Electrochem Soc, 2006, 153(12): G1106. doi: 10.1149/1.2359701

[19]

Lee T X, Lin C Y, Ma S H. Analysis of position-dependent light extraction of GaN-based LEDs[J]. Opt Express, 2005, 13(11): 4175. doi: 10.1364/OPEX.13.004175

[20]

Chen Maoxing, Xu Chen, Xu Kun. Thermal simulation and analysis of flat surface flip-chip high power light-emitting diodes[J]. Journal of Semiconductors, 2013, 34(12): 124005. doi: 10.1088/1674-4926/34/12/124005

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D X Wu, P Ma, B T Liu, S Zhang, J X Wang, J M Li. Increased effective reflection and transmission at the GaN-sapphire interface of LEDs grown on patterned sapphire substrates[J]. J. Semicond., 2016, 37(10): 104003. doi: 10.1088/1674-4926/37/10/104003.

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Manuscript received: 28 January 2016 Manuscript revised: 15 April 2016 Online: Published: 01 October 2016

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