AlGaN-based deep UV LEDs grown on sputtered and high temperature annealed AlN/ sapphire

N. Susilo1, S. Hagedorn2, D. Jaeger3, H. Miyake4, U. Zeimer2, C. Reich1, B. Neuschulz1, L. Sulmoni1, M. Guttmann1, F. Mehnke1, C. Kuhn1, T. Wernicke1, M. Weyers2, and M. Kneissl1,2

Published in:

Appl. Phys. Lett., vol. 112, no. 04, pp. 041110 (2018).

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The performance characteristics of AlGaN-based deep ultraviolet light emitting diodes (UV-LEDs) grown by metalorganic vapor phase epitaxy on sputtered and high temperature annealed AlN/sapphire templates are investigated and compared with LEDs grown on epitaxially laterally overgrown (ELO) AlN/sapphire. The structural and electro-optical properties of the devices on 350 nm sputtered and high temperature annealed AlN/sapphire show similar defect densities and output power levels as LEDs grown on low defect density ELO AlN/sapphire templates. After high temperature annealing of the 350 nm sputtered AlN, the full widths at half maximum of the (0002) and (1012) reflections of the high resolution x-ray diffraction rocking curves decrease by one order of magnitude to 65 arc sec and 240 arc sec, respectively. The curvature of the sputtered and HTA AlN/sapphire templates after regrowth with 400 nm MOVPE AlN is with -80 km-1 much lower than the curvature of the ELO AlN/sapphire template of -160 km-1. The on-wafer measured output powers of 268 nm LEDs grown on 350 nm sputtered and high temperature annealed AlN/sapphire templates and ELO AlN/sapphire templates were 0.70 mW and 0.72 mW at 20 mA, respectively (corresponding to an external quantum efficiency of 0.75% and 0.78%). These results show that sputtered and high temperature annealed AlN/sapphire provide a viable approach for the fabrication of efficient UVC-LEDs with reduced complexity and thus reduced costs.

1 Institute of Solid State Physics, Technische Universiät Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
3 Evatec AG, Hauptstraße 1a, 9477 Trübbach, Switzerland
4 Department of Electrical and Electronic Engineering, Mie University, Mie 514-8507, Japan