Increased Light Extraction of Thin-Film Flip-Chip UVB LEDs by Surface Texturing
Journal article, 2023
Ultraviolet light-emitting diodes (LEDs) suffer from a low wall-plug efficiency, which is to a large extent limited by the poor light extraction efficiency (LEE). A thin-film flip-chip (TFFC) design with a roughened N-polar AlGaN surface can substantially improve this. We here demonstrate an enabling technology to realize TFFC LEDs emitting in the UVB range (280-320 nm), which includes standard LED processing in combination with electrochemical etching to remove the substrate. The integration of the electrochemical etching is achieved by epitaxial sacrificial and etch block layers in combination with encapsulation of the LED. The LEE was enhanced by around 25% when the N-polar AlGaN side of the TFFC LEDs was chemically roughened, reaching an external quantum efficiency of 2.25%. By further optimizing the surface structure, our ray-tracing simulations predict a higher LEE from the TFFC LEDs than flip-chip LEDs and a resulting higher wall-plug efficiency.
AlGaN
light-emitting diode
ultraviolet
surface texturing
electrochemical etching
light extraction
Author
Michael Alexander Bergmann
Chalmers, Microtechnology and Nanoscience (MC2), Photonics
Johannes Enslin
Technische Universität Berlin
Martin Guttmann
Technische Universität Berlin
Luca Sulmoni
Technische Universität Berlin
Neysha Lobo Ploch
Ferdinand-Braun-Institut fur Hochstfrequenztechnik
Filip Hjort
Chalmers, Microtechnology and Nanoscience (MC2), Photonics
Tim Kolbe
Ferdinand-Braun-Institut fur Hochstfrequenztechnik
Tim Wernicke
Technische Universität Berlin
Michael Kneissl
Technische Universität Berlin
Ferdinand-Braun-Institut fur Hochstfrequenztechnik
Åsa Haglund
Chalmers, Microtechnology and Nanoscience (MC2), Photonics
ACS Photonics
2330-4022 (eISSN)
Vol. 10 2 368-373Microcavity laser breakthrough for ultraviolet light (UV-LASE)
European Commission (EC) (EC/H2020/865622), 2020-08-01 -- 2025-07-31.
Ultravioletta och blå mikrokavitetslasrar
Swedish Research Council (VR) (2018-00295), 2019-01-01 -- 2024-12-31.
Subject Categories
Other Physics Topics
Nano Technology
Condensed Matter Physics
DOI
10.1021/acsphotonics.2c01352
PubMed
36820322