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Enhanced light extraction efficiency of far-ultraviolet-C LEDs by micro-LED array design

J. Rass, H.K. Cho, M. Guttmann, D. Prasai, J. Ruschel, T. Kolbe, and S. Einfeldt

Published in:

Appl. Phys. Lett., vol. 122, no. 26, pp. 263508, doi:10.1063/5.0154031 (2023).


AlGaN-based far-UVC light emitting diodes (LEDs) with an emission wavelength of 233 nm were fabricated in the form of micro-LED arrays with emitter diameters ranging from 1.5 to 50 µm. The mesa was plasma etched with a sidewall angle of 45°–50°, and insulator layers made of SiNx or SiO2 were deposited. While the external quantum efficiency (EQE) of the LEDs with SiNx showed only a small dependency on the micro-LED diameter, the LEDs using SiO2 showed an increase in the peak EQE by a factor of four as compared to large area devices. This enhancement is attributed to a strong increase in the light extraction efficiency due to total internal reflection and re-direction at the inclined mesa, allowing TM-polarized light emitted in the plane of the quantum well to be extracted through the sapphire backside of the chips.

Ferdinand-Braun-Institut (FBH), Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany

© 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1063/5.0154031

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