Selective wet etching of AlInN layers for nitride-based MEMS and photonic device structures

I.M. Watson, C. Xiong, E. Gu, M.D. Dawson, F. Rizzi, K. Bejtka, P.R. Edwards, R.W. Martin

Research output: Contribution to journalArticle

7 Citations (Scopus)

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.
LanguageEnglish
JournalProceedings of SPIE the International Society for Optical Engineering
Volume6993
DOIs
Publication statusPublished - 28 Apr 2008

Fingerprint

Photonic devices
Nitrides
Wet etching
Etching
Micro-electro-mechanical Systems
Photonics
microelectromechanical systems
MEMS
nitrides
etching
photonics
Lateral
Nitric Acid
Dry etching
Microcavities
Plasma etching
Argon
Chlorine
Inductively coupled plasma
mesas

Keywords

  • photonics
  • GaN layers
  • vertical dry etching
  • lateral wet etching

Cite this

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title = "Selective wet etching of AlInN layers for nitride-based MEMS and photonic device structures",
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.",
keywords = "photonics, GaN layers, vertical dry etching, lateral wet etching",
author = "I.M. Watson and C. Xiong and E. Gu and M.D. Dawson and F. Rizzi and K. Bejtka and P.R. Edwards and R.W. Martin",
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T1 - Selective wet etching of AlInN layers for nitride-based MEMS and photonic device structures

AU - Watson, I.M.

AU - Xiong, C.

AU - Gu, E.

AU - Dawson, M.D.

AU - Rizzi, F.

AU - Bejtka, K.

AU - Edwards, P.R.

AU - Martin, R.W.

N1 - Available in: MEMS, MOEMS, and Micromachining III (Proceedings Volume) Proceedings of SPIE Volume: 6993 Editor(s): Hakan Urey Date: 28 May 2008 ISBN: 9780819471918

PY - 2008/4/28

Y1 - 2008/4/28

N2 - 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.

AB - 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.

KW - photonics

KW - GaN layers

KW - vertical dry etching

KW - lateral wet etching

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