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

    Fingerprint

    Light emitting diodes
    light emitting diodes
    Quantum efficiency
    reflectors
    quantum efficiency
    potassium hydroxides
    Anisotropic etching
    Potassium hydroxide
    augmentation
    output
    Growth temperature
    Substrates
    Tin oxides
    Sapphire
    Leakage currents
    eutectics
    indium oxides
    Indium
    Eutectics
    tin oxides

    Keywords

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

    ASJC Scopus subject areas

    • Electrical and Electronic Engineering
    • Physics and Astronomy (miscellaneous)

    Cite this

    High light-extraction GaN-based vertical LEDs with double diffuse surfaces. / Lee, Ya-Ju; Kuo, Hao Chung; Lu, Tien Chang; Wang, Shing Chung.

    In: IEEE Journal of Quantum Electronics, Vol. 42, No. 12, 01.12.2006, p. 1196-1201.

    Research output: Contribution to journalArticle

    Lee, Ya-Ju ; Kuo, Hao Chung ; Lu, Tien Chang ; Wang, Shing Chung. / High light-extraction GaN-based vertical LEDs with double diffuse surfaces. In: IEEE Journal of Quantum Electronics. 2006 ; Vol. 42, No. 12. pp. 1196-1201.
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    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.",
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