Engineering mesa fabrication for optimized performance of AIGaN-based far-UVC LEDs

H.K. Cho¹, J. Rass¹, C. Netzel¹, M. Guttmann¹, J. Ruschel¹, K. Gehrke¹, T. Kolbe¹, and S. Einfeldt¹

Published in:

IEEE Photonics Technol. Lett, vol. 38, no. 23, pp. 1917, doi:10.1109/LPT.2026.3735196 (2026).

Abstract:

The fabrication technologies for mesas in AlGaNbased far-UVC LED chips were investigated using inductively coupled plasma (ICP) etching. The etch rate decreased withincreasing BCl3/Cl2 gas ratio which is attributed to reduced Cl radicals and non-volatile byproducts, and it increased withan increasing RF bias likely due to ion-assisted etching. The mesa sidewall angle was tuned via ICP/RF powers and the usedmask: A SiO2 hard mask yielded steep/vertical (~90) sidewalls, while a positive photoresist mask together with a thermallyinduced reflow step enabled shallow/ only slightly inclined (~20°) sidewalls. For 233 nm far-UVC LEDs with SiNx insulation, veryshallow mesa sidewalls (~20°) modestly enhanced the output power, whereas LEDs with ~45° sidewalls exhibited a slowerdecline in optical power during aging.

Keywords:

Deep UV, light emitting diodes (LEDs), mesaangles, plasma etch, reliability, chip geometry.far-UVC, far-UVC LED, LEDs, LED, inductively, ICP, Etching, CL, RF, SiNx, output power, aging, Indexes, UV, Light emitting diodes, light emitting diode, light-emitting-diodes, diode, plasma etch, Reliability, reliabilities, geometry

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