26 January 2004 High-output power near-ultraviolet and violet light-emitting diodes fabricated on patterned sapphire substrates using metalorganic vapor phase epitaxy
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Abstract
The external quantum efficiency (EQE, ηe) 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 (Po) 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 Po and the EQE were 26.3 mW and 43%, respectively. Furthermore, we obtained the Po 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, Kazuyuki Tadatomo, Hiroaki Okagawa, Hiroaki Okagawa, Youichiro Ohuchi, Youichiro Ohuchi, Takashi Tsunekawa, Takashi Tsunekawa, Hiromitsu Kudo, Hiromitsu Kudo, Yasuhide Sudo, Yasuhide Sudo, Munehiro Kato, Munehiro Kato, Tsunemasa Taguchi, 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); doi: 10.1117/12.513288; https://doi.org/10.1117/12.513288
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