Defect-reduced green GaInN/GaN light-emitting diode on nanopatterned sapphire. Appl Phys Lett 98:151102

Future Chips Constellation, Rensselaer Polytechnic Institute, Troy, New York 12180, USA and Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
Applied Physics Letters (Impact Factor: 3.3). 04/2011; 98. DOI: 10.1063/1.3579255
Source: IEEE Xplore


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]

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    • "Recent works have shown the importance of growing GaN-based LEDs on nanopatterned substrates [22] [23] [24], and the two related works were reported in this special issue "
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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 [5]–[7], the use of nano-patterned sapphires for reducing dislocation density in GaN [8]–[10], and various microphotonics methods to improve light extraction in LEDs [11]–[13]. So far, sapphire has been the most commonly used substrate for the LED fabrication. "
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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) [3]. 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. [4]. "
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