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Proceedings Paper

Selective wet etching of AlInN layers for nitride-based MEMS and photonic device structures
Author(s): Ian M. Watson; Chang Xiong; Erdan Gu; Martin D. Dawson; Francesco Rizzi; Katarzyna Bejtka; Paul R. Edwards; Robert W. Martin
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Paper Abstract

Processing of GaN-AlInN-GaN epitaxial trilayers into 3-dimensional microstructures, using a combination of vertical dry etching and lateral wet etching, is discussed. The AlInN layers were grown so as to have an InN mole fraction close to the value of 17% required for lattice matching with GaN. Inductively coupled plasma etching with chlorine-argon gas mixtures was used to define mesa features with near-vertical sidewalls. Refluxing aqueous solutions of nitric acid of 2 molar concentration allowed highly selective lateral etching of the AlInN interlayers exposed on the mesa sidewalls, providing a novel sacrificial layer technology for the III-nitride materials. Lateral etch rates of 0.14-0.21 μm/hr were observed for 100-nm AlInN interlayers. Two distinct applications are discussed. In one example, lateral etching of an AlInN layer was used to expose the underside of epitaxial GaN disks for fabrication of planar microcavities. Here, retention of an optically smooth GaN (0001) surface on the underside of the disks is critical. Microbridges with potential for development as sensors were also demonstrated, and the deformation of these structures provides a sensitive probe of the local strain state of the undercut GaN layer.

Paper Details

Date Published: 24 April 2008
PDF: 11 pages
Proc. SPIE 6993, MEMS, MOEMS, and Micromachining III, 69930E (24 April 2008); doi: 10.1117/12.781881
Show Author Affiliations
Ian M. Watson, Univ. of Strathclyde (United Kingdom)
Chang Xiong, Univ. of Strathclyde (United Kingdom)
Erdan Gu, Univ. of Strathclyde (United Kingdom)
Martin D. Dawson, Univ. of Strathclyde (United Kingdom)
Francesco Rizzi, Italian Institute of Technology (Italy)
Katarzyna Bejtka, Univ. of Strathclyde (United Kingdom)
Paul R. Edwards, Univ. of Strathclyde (United Kingdom)
Robert W. Martin, Univ. of Strathclyde (United Kingdom)


Published in SPIE Proceedings Vol. 6993:
MEMS, MOEMS, and Micromachining III
Hakan Urey, Editor(s)

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