Photonic crystal based control of directionality in GaN based LEDs

Thomas M. Mercier, Chirenjeevi Krishnan, Peter J. Shaw, Pavlos G. Lagoudakis, Martin D.B. Charlton

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Citation (Scopus)

Abstract

LED surface structuring has been widely used to increase light extraction[1]. Due to the high refractive index of the thick GaN epitaxy layers, most emitted light becomes trapped and reabsorbed by the epitaxial layers. While random structuring can effectively scatter trapped light out of the LED, it gives little control over the resulting beam-shapef[2]. Photonic crystals however provide a means to simultaneously improve light extraction efficiency and control beam directionality. Furthermore, P-side up LEDs normally utilize a transparent top contact layer in order to allow top light emission whilst maintaining good electrical properties. In this paper we investigate a novel photonic crystal LED configuration with a nontransparent metal top contact layer, and cylindrical holes etched through the top contact layer and deep into the underlying epitaxy. In this novel configuration light emission is only possible from the etched holes giving rise to extreme beam steering effects. We utilize broadband spectroscopic reflectometry to experimentally investigate beam shape and optical properties from fabricated devices. We observe a range of achievable beam patterns with extreme deviations from the normal Lambertian. We investigate the effect of square and triangular photonic crystal lattices on beam directionality.

Original languageEnglish
Title of host publicationLight-Emitting Devices, Materials, and Applications XXIV
EditorsJong Kyu Kim, Michael R. Krames, Martin Strassburg
PublisherSPIE
ISBN (Electronic)9781510633674
DOIs
Publication statusPublished - 2020
Externally publishedYes
EventLight-Emitting Devices, Materials, and Applications XXIV 2020 - San Francisco, United States
Duration: 3 Feb 20206 Feb 2020

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume11302
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Conference

ConferenceLight-Emitting Devices, Materials, and Applications XXIV 2020
Country/TerritoryUnited States
CitySan Francisco
Period3/02/206/02/20

Keywords

  • Directionality
  • GaN
  • LEDs
  • Photonic Crystals

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