Current Optics and Photonics

Optical Society of Korea (한국광학회)
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Reducing Efficiency Droop in (In,Ga)N/GaN Light-emitting Diodes by Improving Current Spreading with Electron-blocking Layers of the Same Size as the n-pad

  • Pham, Quoc-Hung (Department of Mechanical Engineering, National Central University) ;
  • Chen, Jyh-Chen (Department of Mechanical Engineering, National Central University) ;
  • Nguyen, Huy-Bich (Department of Mechanical Engineering, Nong Lam University)
  • Received : 2020.02.21
  • Accepted : 2020.06.25
  • Published : 2020.08.25
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Abstract

In this study, the traditional electron-blocking layer (EBL) in (In,Ga)N/GaN light-emitting diodes is replaced by a circular EBL that is the same size as the n-pad. The three-dimensional (3D) nonlinear Poisson, drift-diffusion, and continuity equations are adopted to simulate current transport in the LED and its characteristics. The results indicate that the local carrier-density distribution obtained for the circular EBL design is more uniform than that for the traditional EBL design. This improves the uniformity of local radiative recombination and local internal quantum efficiency (IQE) at high injection levels, which leads to a higher lumped IQE and lower efficiency droop. With the circular EBL, the lumped IQE is higher in the outer active region and lower in the active region under the n-pad. Since most emissions from the active region under the n-pad are absorbed by the n-pad, obviously, an LED with a circular EBL will have a higher external quantum efficiency (EQE). The results also show that this LED works at lower applied voltages.

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References

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