Article

Defect-reduced green GaInN/GaN light-emitting diode on nanopatterned sapphire

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: 3.52). 01/2011; 98. DOI: 10.1063/1.3579255
Source: IEEE Xplore

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]

0 Bookmarks
 · 
105 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Indirect illumination with light-emitting diodes (LEDs) and diffusers is widely applied in various fields that require uniform illumination. In this paper, a design of diffuse reflection freeform surface is proposed. Based on the Lambertian characteristic of LEDs and ideal diffuse surface, a mathematical model is developed. Nonlinear algebraic equations are established by redistributing the energy emitted from LEDs to the illuminated scene for uniform illumination. Solving these equations numerically, the outline of the diffuse surface is obtained. Finally, by using ray tracing software TracePro, the simulation result shows that the irradiance uniformity of the detection plane is above 95% with high accepted tolerance.
    Journal of Display Technology 01/2014; 10(1). · 1.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: GaN-based light-emitting diodes (LEDs) on patterned sapphire substrate (PSS) with patterned composite SiO2/Al2O3 passivation layers and TiO2/Al2O3 distributed Bragg reflector (DBR) backside reflector have been proposed and fabricated. Highly passivated Al2O3 layer deposited on indium tin oxide (ITO) layer with excellent uniformity and quality has been achieved with atomic layer deposition (ALD) technology. With a 60 mA current injection, an enhancement of 21.6%, 59.7%, and 63.4% in the light output power (LOP) at 460 nm wavelength was realized for the LED with the patterned composite SiO2/Al2O3 passivation layers, the LED with the patterned composite SiO2/Al2O3 passivation layers and Ag mirror + 3-pair TiO2/SiO2 DBR backside reflector, and the LED with the patterned composite SiO2/Al2O3 passivation layer and Ag mirror + 3-pair ALD-grown TiO2/Al2O3 DBR backside reflector as compared with the conventional LED only with a single SiO2 passivation layer, respectively.
    Optics Express 09/2013; 21(18). · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Step graded-refractive index (SGRI) (ZnO)x(SiO2)1-x micropillar multilayers have been introduced and demonstrated on GaN-based LEDs combined with the mesh ITO. The SGRI (ZnO)x(SiO2)1-x micropillars were produced by controlling the Zn/Zn+Si ratio of co-sputtered ZnO and SiO2. The introduced three-layered SGRI (ZnO)x(SiO2)1-x micropillars improved both critical angle inside GaN LEDs and Fresnel transmittance coefficient (ηFr) as well as had better light coupling into the micropillars. Moreover, a high number of layers of the SGRI micropillars would aid the light coupled in the pillars to escape from the side wall of the pillar. LEDs with three-layered SGRI (ZnO)x(SiO2)1-x micropillars exhibited output power enhancements of 12.2% with a 20 mA Vf of 3.19 V. The output power of the mesh ITO LEDs with SGRI (ZnO)x(SiO2)1-x micropillars was further enhanced to 15.3% by improving the current spreading.
    Journal of Display Technology 05/2013; 9(5). · 1.69 Impact Factor

Full-text (2 Sources)

Download
42 Downloads
Available from
May 21, 2014