Fabrication technology for high light-extraction ultraviolet thin-film flip-chip (UV TFFC) LEDs grown on SiC

Burhan K. Saifaddin, Abdullah Almogbel, Christian J. Zollner, Humberto Foronda, Ahmed Alyamani, Abdulrahman Albadri, Michael Iza, Shuji Nakamura, Steven P. DenBaars, James S. Speck

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


The light output of deep ultraviolet (UV-C) AlGaN light-emitting diodes (LEDs) is limited due to their poor light extraction efficiency (LEE). To improve the LEE of AlGaN LEDs, we developed a fabrication technology to process AlGaN LEDs grown on SiC into thin-film flip-chip LEDs (TFFC LEDs) with high LEE. This process transfers the AlGaN LED epi onto a new substrate by wafer-to-wafer bonding, and by removing the absorbing SiC substrate with a highly selective SF6 plasma etch that stops at the AlN buffer layer. We optimized the inductively coupled plasma SF6 etch parameters to develop a substrate-removal process with high reliability and precise epitaxial control, without creating micromasking defects or degrading the health of the plasma etching system. The SiC etch rate by SF6 plasma was ∼46 μm hr–1 at a high RF bias (400 W), and ∼7 μm hr–1 at a low RF bias (49 W) with very high etch selectivity between SiC and AlN. The high SF6 etch selectivity between SiC and AlN was essential for removing the SiC substrate and exposing a pristine, smooth AlN surface. We demonstrated the epi-transfer process by fabricating high light extraction TFFC LEDs from AlGaN LEDs grown on SiC. To further enhance the light extraction, the exposed N-face AlN was anisotropically etched in dilute KOH. The LEE of the AlGaN LED improved by ∼3× after KOH roughening at room temperature. This AlGaN TFFC LED process establishes a viable path to high external quantum efficiency and power conversion efficiency UV-C LEDs.
Original languageEnglish (US)
Pages (from-to)035007
Issue number3
StatePublished - Jan 31 2019
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2022-06-10
Acknowledgements: This work was funded by the King Abdulaziz City for Science and Technology (KACST), the Technology Innovations Center (TIC) program, and the KACST-KAUST-UCSB Solid State Lighting Program. The authors are appreciative of the support of the Solid State Lighting and Energy Electronics Center (SSLEEC) at UCSB. The authors acknowledge the UCSB-Collaborative Research in Engineering, Science and Technology (CREST) Malaysia project. A portion of this work was conducted in the UCSB nanofabrication facility and part of the NSF NNIN network (ECS-0335765), as well as the UCSB MRL, which is supported by the NSF MRSEC Program (DMR05-20415). This work was also supported by the National Science Foundation Graduate Research Fellowship Program (Grant No. 1650114). The authors would also like to thank the cleanroom staff at UCSB nanofabrication facility, especially Brian Thibault and Don Freeborn.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

ASJC Scopus subject areas

  • Materials Chemistry
  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering
  • Condensed Matter Physics


Dive into the research topics of 'Fabrication technology for high light-extraction ultraviolet thin-film flip-chip (UV TFFC) LEDs grown on SiC'. Together they form a unique fingerprint.

Cite this