M. Guttmann1,2, N. Lobo-Ploch2, H. Gundlach3, F. Mehnke1, L. Sulmoni1, T. Wernicke1, H.K. Cho2, K. Hilbrich2, A. Külberg2, M. Friedler2, T. Filler2, I. Käpplinger4, D. Mitrenga4, C. Maier4, O. Brodersen4, T. Ortlepp4, U. Woggon3, S. Einfeldt2 and M. Kneissl1,2
J. Phys. D: Appl. Phys., vol. 55, no. 20, pp. 205105, doi:10.1088/1361-6463/ac5145 (2022).
AlGaN-based far ultraviolet-C (UVC) light emitting diodes (LEDs) with a peak emission wavelength below 240 nm typically show a long-wavelength tail at >240 nm that is detrimental to the use of the devices for skin-friendly antisepsis. We present the development of far-UVC LEDs with reduced long-wavelength emission using a HfO2/SiO2-based distributed Bragg reflector (DBR) filter. When the DBR filter is directly mounted on an LED package, the long-wavelength emission around 250 nm is reduced by two orders of magnitude while the transmitted output power is reduced down to 18%-27% of the initial value for DBR filters with cut-off wavelengths at 237-243 nm. As the transmission through the DBR filter depends strongly on the angle of incidence of the radiation, the transmitted output power of the spectrally pure far-UVC radiation can be doubled when an additional collimating lens is used on top of the LED package before passing through the filter.
1 Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut gGmbH, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
3 Institute of Optics and Atomic Physics, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
4 CiS Forschungsinstitut für Mikrosensorik GmbH, Konrad-Zuse-Str. 14, 99099 Erfurt, Germany
far-UVC, LED, AlGaN, spectral purity, dielectric filter, HfO2/SiO2
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