High light-extraction GaN-based vertical LEDs with double diffuse surfaces

Ya Ju Lee, Hao Chung Kuo, Tien Chang Lu, Shing Chung Wang

Research output: Contribution to journalArticle

48 Citations (Scopus)

Abstract

High light-extraction (external quantum efficiency ∼40%) 465-nm GaN-based vertical light-emitting diodes (LEDs) employing double diffuse surfaces were fabricated. This novel LED structure includes one top transmitted diffuse surface and another diffuse omnidirectional reflector (ODR) on the bottom of a LED chip. The diffusive ODR consists of a roughened p-type GaN layer, an indium-tin-oxide (ITO) low refractive index layer, and an Al layer. The surface of the p-type GaN-layer was naturally roughened while decreasing the growth temperature to 800 °C. After flip-bonding onto a Si substrate by AuSn eutectic metal and laser lift-off processes to remove the sapphire substrate, an anisotropic etching by dilute potassium hydroxide (KOH) was employed on the N-face n-GaN layer to obtain transmitted diffuse surfaces with hexagonal-cone morphology. The double diffused surfaces LEDs show an enhancement of 56% and 236% in light output power compared to single side diffused surface and conventional LEDs, respectively. The devices also show a low leakage current in the order of magnitude of 10-8 A at -5 V and a calculated external quantum efficiency of about 40%. The high scattering efficiency of double diffused surfaces could be responsible for the enhancement in the device light output power.

Original languageEnglish
Pages (from-to)1196-1201
Number of pages6
JournalIEEE Journal of Quantum Electronics
Volume42
Issue number12
DOIs
Publication statusPublished - 2006 Dec 1

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Keywords

  • Double diffuse surfaces
  • GaN
  • Light-emitting diodes (LEDs)
  • Light-extraction efficiency

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

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