Improved extraction efficiency of light-emitting diodes by modifying surface roughness with anodic aluminum oxide film

Chien Chun Wang, Hung Chi Lu, Chien Chih Liu, Fenq Lin Jenq, Yeong Her Wang, Mau Phon Houng

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

An anodic alumina oxide (AAO) film with nanoroughening is added on the top window layer of AlGaInP light-emitting diodes (LEDs) to improve the light extraction of the device. The AAO film has a natural porosity to provide light scattering centers at the surface, allowing an increase of light emission intensity with no loss of or damage to the semiconductor material. Further, the fabricated AAO film with a refractive index is about n = 1:7 which is intermediate between those of air and the window layer of GaP. By inserting this layer between the ambient and GaP, it broadens the critical angle for light emission and reduces internal reflection. Experiments with laboratory-fabricated AlGaInP devices of conventional design demonstrated a 32% improvement in the luminous intensity at 20 mA for the device with the AAO layer. This letter shows by theory and experiment that AAO films can be used as a low-cost, easily implemented surface nano-roughening for improving extraction efficiency of AlGaInP LEDs.

Original languageEnglish
Pages (from-to)428-430
Number of pages3
JournalIEEE Photonics Technology Letters
Volume20
Issue number6
DOIs
Publication statusPublished - 2008 Mar 15

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

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