High-output power near-ultraviolet and violet light-emitting diodes fabricated on patterned sapphire substrates using metalorganic vapor phase epitaxy

Kazuyuki Tadatomo; Hiroaki Okagawa; Youichiro Ohuchi; Takashi Tsunekawa; Hiromitsu Kudo; Yasuhide Sudo; Munehiro Kato; Tsunemasa Taguchi

doi:10.1117/12.513288

26 January 2004 High-output power near-ultraviolet and violet light-emitting diodes fabricated on patterned sapphire substrates using metalorganic vapor phase epitaxy

Kazuyuki Tadatomo, Hiroaki Okagawa, Youichiro Ohuchi, Takashi Tsunekawa, Hiromitsu Kudo, Yasuhide Sudo, Munehiro Kato, Tsunemasa Taguchi

Author Affiliations +

Proceedings Volume 5187, Third International Conference on Solid State Lighting; (2004) https://doi.org/10.1117/12.513288
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

Abstract

The external quantum efficiency (EQE, η_e) of conventional near-ultraviolet (NUV) light-emitting diodes (LEDs) with an InGaN multi-quantum-well (MQW) structure is limited by high dislocation density and by the narrow escape cone due to total internal reflection at the GaN/air or sapphire/air interface. We have fabricated the NUV and violet InGaN-MQW-LEDs with the high EQE on the patterned-sapphire substrate (PSS) using a single growth process by metal-organic vapor phase epitaxy (MOVPE). The PSS with parallel grooves along the <11-20>_GaN direction or the <1-100>_GaN direction was fabricated by a standard photolithography and subsequent reactive ion etching (RIE). In this study, fabricated the LED on the PSS with parallel grooves along the <11-20>_GaN direction. The GaN layer grown by lateral epitaxy on a patterned substrate (LEPS) has dislocation density of 1.5x10⁸ cm^-2. The LEPS-NUV (or violet)-LED chips were mounted on the Si bases in a flip-chip bonding arrangement. When the LEPS-NUV-LED (the emission peak wavelength λp: 382 nm) was operated at a forward-bias current of 20 mA at room temperature (RT), the output power (P_o) and the EQE were 15.6 mW and 24%, respectively. When the LEPS-violet-LED (λp: 405 nm) was operated at a forward-bias current of 20 mA at RT, the P_o and the EQE were 26.3 mW and 43%, respectively. Furthermore, we obtained the P_o of approximately 61 mW at 50 mA and 111 mW at 100 mA, respectively. It was revealed that the PSS is very effective in reducing the dislocation density and for increasing the extraction efficiency due to the multiple scattering of the emission light at the GaN/patterned sapphire interface.

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Kazuyuki Tadatomo, Hiroaki Okagawa, Youichiro Ohuchi, Takashi Tsunekawa, Hiromitsu Kudo, Yasuhide Sudo, Munehiro Kato, and Tsunemasa Taguchi "High-output power near-ultraviolet and violet light-emitting diodes fabricated on patterned sapphire substrates using metalorganic vapor phase epitaxy", Proc. SPIE 5187, Third International Conference on Solid State Lighting, (26 January 2004); https://doi.org/10.1117/12.513288

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