Defect-reduced green GaInN/GaN light-emitting diode on nanopatterned sapphire
ABSTRACT Green GaInN/GaN quantum well light-emitting diode (LED) wafers were grown on nanopatterned c-plane sapphire substrate by metal-organic vapor phase epitaxy. Without roughening the chip surface, such LEDs show triple the light output over structures on planar sapphire. By quantitative analysis the enhancement was attributed to both, enhanced generation efficiency and extraction. The spectral interference and emission patterns reveal a 58% enhanced light extraction while photoluminescence reveals a doubling of the internal quantum efficiency. The latter was attributed to a 44% lower threading dislocation density as observed in transmission electron microscopy. The partial light output power measured from the sapphire side of the unencapsulated nanopatterned substrate LED die reaches 5.2 mW at 525 nm at 100 mA compared to 1.8 mW in the reference LED. (C) 2011 American Institute of Physics. [doi:10.1063/1.3579255]
Full-textDOI: · Available from: Christian Wetzel, Jul 25, 2015
- SourceAvailable from: Nelson Tansu
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- "Recent works have shown the importance of growing GaN-based LEDs on nanopatterned substrates   , and the two related works were reported in this special issue "
ABSTRACT: In order to achieve the advanced lighting with the energy-saving and environmental-protecting capabilities, the tech-nologies of solid-state lighting have been developed rapidly. In all solid-state lighting applications, light-emitting diode (LED) is the most popular technique due to its advantages of small volume, long lifetime, high reliability, low power consumption, and nonpollution. The progress in solid-state lighting has been driven by innovations in wide range of technologies in materials, devices, and novel concepts [1–5]. In addition to the progress in visible InGaN-based light-emitting diodes (LEDs) based on III-nitride based semiconductor, the improved under-standing in the AlGaN-based LEDs [6, 7] has also resulted in new understanding on the device physics of III-nitride semiconductor physics which in turn results in new concept and approaches to handle the limitation in the fields of nitride-based LEDs. Several of these concepts have resulted in new approaches to suppress the charge separation effect [8, 9], carrier leakage process [10–14], light extraction issue [15–17], and Auger processes [18–21] in the InGaN-based LEDs. The improved understanding on the fundamental properties of InGaN as active regions has resulted in the ability to advance this field into practical technologies being implemented in the daily technologies used in our society. In this special issue, the editors attempt to bring some of the recent advances in the field of device engineering and applications of III-nitride based LEDs with the goals of achieving high brightness and low-cost approaches. Up to now, the nitride-based materials are maturely devel-oped to apply for LED applications. However, to obtain the LED devices with high brightness, high efficiency, and low cost, there are still some techniques to be improved, especially for the nitride-epilayer growth with low defect density and device fabrication with high heat dissipation. In this special issue, there are seven contributed papers to discuss these issues from the LED epilayer quality to the high efficiency package. The implementation and test of LED-based lamp for lighthouse application were discussed at the system level ("Implementation and test of a LED-based lamp for a lighthouse" by L. Mercatelli et al.). Such applications of LED in lighthouse have different requirement from those used in general illumination. The important new application from LED will broaden the new potential inno-vations required in enabling this technology to be suitable for implementation. The investigation of novel phosphor material for con-verting blue/UV LEDs into white LEDs was also discussed specifically for investigating the color rendering index and its thermal stability ("Color rendering index thermal sta-bility improvement of glass-based phosphor-converted white light-emitting diodes for solid-state lighting" by C.-C. Tsai).International Journal of Photoenergy 09/2014; DOI:10.1155/2014/278263 · 2.66 Impact Factor
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- "The vast advances of high efficiency InGaN based LEDs had been achieved by addressing the fundamental limitation in the III-Nitride based technology. Specifically, these approaches include the methods to suppress charge separation in active regions –, the use of nano-patterned sapphires for reducing dislocation density in GaN –, and various microphotonics methods to improve light extraction in LEDs –. So far, sapphire has been the most commonly used substrate for the LED fabrication. "
ABSTRACT: An auto-split laser lift-off (LLO) method for fabrication of vertical-injection GaN-based green light-emitting diodes (ASV-LEDs) is demonstrated. The ASV-LEDs exhibited a significant improvement in the light output and thermal dissipation, as compared with that of conventional LEDs on sapphire. The intrinsic physical mechanism of the auto-split LLO technique is studied by a Frank-Read dislocation clustering model. The laser energy density and mesa spacing are shown to be key factors in the auto-split LLO method. It is believed that this method offers an alternative way to fabricate high-performance GaN-based thin-film LEDs.IEEE Photonics Journal 08/2013; 5(4):8400407-8400407. DOI:10.1109/JPHOT.2013.2274768 · 2.33 Impact Factor
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- "This is because extending wavelength from blue to green and yellow normally requires higher indium composition with lower InGaN growth temperature, which tends to worsen the crystalline quality of the InGaN. Also, it has been reported that green and yellow LEDs are more sensitive to threading dislocations (TDs) . For GaN-based LEDs grown on Si substrates, due to the existence of a large amount of TDs in the GaN buffer, the longest wavelength of fabricated InGaN/GaN multiquantum well (MQW) LEDs on Si was 518 nm measured at 0.5-mA current injection, reported by Egawa et al. . "
ABSTRACT: High-performance GaN-based green and yellow light-emitting diodes (LEDs) are grown on SiO2 nanorod patterned GaN/Si templates by metalorganic chemical vapor deposition. The high-density SiO2 nanorods are prepared by nonlithographic HCl-treated indium tin oxide and dry etching. The dislocation density of GaN is significantly reduced by nanoscale epitaxial lateral overgrowth. In addition to the much improved green LED (505 and 530 nm) results, the fabricated yellow (565 nm) InGaN/GaN-based multiquantum well (MQW) LEDs on Si substrates are demonstrated for the first time. High-quality GaN buffer and localized states in MQWs are correlated to obtaining high-efficiency long-wavelength emission in our devices.IEEE Electron Device Letters 07/2013; 34(7):903-905. DOI:10.1109/LED.2013.2260126 · 3.02 Impact Factor