Polarity dependence in Cl2-based plasma etching of GaN, AlGaN and AlN

Matthew D. Smith, Xu Li, Michael J. Uren, Iain G. Thayne, Martin Kuball*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

1 Citation (Scopus)


This work compares Cl2-based inductively-coupled plasma (ICP) etching of N-polar and III-polar AlxGa1-xN, including GaN and AlN. For the etch processes of this study, etch rates of AlxGa1-xN decreased with increasing Al:Ga alloy ratio. A 750 W ICP power, 175 W platen power Cl2/Ar ICP process exhibited etch rates in the range 160–450 nm/min for AlxGa1-xN with the precise rate depending on alloy composition and material polarity, and etch rate selectivity between AlN and GaN of 3.0 for III-polar material and 1.6 for N-polar material. Cl2/Ar/O2 processes with 650 W ICP power and 50 W platen power showed an overall reduction in etch rate in the range 2–360 nm/min for AlxGa1-xN with precise rate depending on alloy composition and material polarity. These O2 containing chemistries demonstrated significantly greater etch rate selectivity for N-polar materials (8–80) compared to III-polar materials (1.8–1.9). A correlation between GaN etch rate, surface roughening and selectivity was observed, and the possible reasons behind the polarity dependence of etch rate selectivity are discussed.

Original languageEnglish
Article number146297
JournalApplied Surface Science
Publication statusPublished - 20 Apr 2020

Bibliographical note

Funding Information:
This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) Grant GaN-DaME (EP/P00945X/1) .

Publisher Copyright:
© 2020 Elsevier B.V.

Copyright 2020 Elsevier B.V., All rights reserved.


  • Etching
  • GaN
  • Plasma
  • Polarity
  • Selective
  • Semiconductors

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