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Facet formation for laser diodes on nonpolar and semipolar GaN
J. Rass1, T. Wernicke2, R. Kremzow1, W. John2, S. Einfeldt2, P. Vogt1, M. Weyers2, and M. Kneissl1,2
1 Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany
2 Ferdinand-Braun-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, D-12489 Berlin, Germany
Published in:
phys. stat. sol. (a), vol. 207, no. 6, pp. 1361-1364 (2010).
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Personal use of this material is permitted. However, permission to reprint/republish this material for
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Abstract:
Different technologies have been evaluated in order to create
vertical and smooth facets for GaN-based laser diodes on nonand
semipolar substrates. Laser assisted scribing and cleaving
proved to be a suitable method to create c-, a- and m-plane facets
for devices grown on nonpolar, polar and semipolar GaN
planes. The RMS roughness measured by atomic force microscopy
was found to be less than 1 nm. Semipolar facets showed
tilted or multifaceted cleavage planes. Dry etching using
inductively coupled plasma etching (ICP) resulted in vertical
facets for devices grown on polar c-plane GaN, while the facets
of semipolar (11 2) GaN on sapphire exhibited a slight tilt
depending on the crystal orientation. Wet chemical postprocessing
of semipolar facets can improve the tilt angle but suffers
from a roughening of the facets due to selective dislocation
etching. By using a focussed ion beam (FIB) it is possible to
create vertical and smooth facets independent of the crystal
orientation.
Keywords:
etching, GaN, ion-beam applications, laser diodes
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