Modulated Epitaxial Lateral Overgrowth of AlN for Efficient UV LEDs

V. Kueller1, A. Knauer1, C. Reich2, A. Mogilatenko1, M Weyers1, J. Stellmach2, T. Wernicke2, M. Kneissl2, Z. Yang3, C.L. Chua3, and N.M. Johnson3

Published in:

IEEE Photonics Technol. Lett., vol. 24 , no. 18, pp. 1603-1605 (2012).

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Abstract:

A reduction of the threading dislocation density in AlN layers on a sapphire from 1010 cm-2 to 109 cm-2 was achieved by applying epitaxial lateral overgrowth (ELO) of patterned AlN and sapphire templates. By varying the growth temperature, it is possible to influence the lateral growth rate and modulate the thickness before coalescence. With a two-step growth at two different temperatures, up to 11-µm thick crackfree layers were achieved. Using these ELO AlN templates, the light emitting diode (LED) output power was >1 mW dc at 295 nm and ≈ 4mW at 324 nm which is a significant increase compared to planar templates. The usefulness of modulated ELO AlN templates for ultraviolet LEDs has thus been validated.

1 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, D-12489 Berlin, Germany
2 Institute of Solid State Physics, Technische Universität Berlin, Berlin 10623, Germany
3 Palo Alto Research Center, Palo Alto, CA 94304 USA

Index Terms:

Epitaxial growth, epitaxial layers, light emitting diodes (LEDs), semiconductor materials.