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As capping of MBE-grown compound semiconductors; novel opportunities to interface science and device fabrication

Grepstad, J. K.; Husby, H.; Borg, A.; Fimland, B. O.; Bernstein, R. W. and Nyholm, R. LU (1994) In Physica Scripta 1994(T54). p.216-225
Abstract

In situ condensation of an amorphous cap of the high vapour pressure element (i.e. As, Sb) has been found to provide effective protection of molecular beam epitaxy grown compound semiconductor surfaces against ambient contamination. Most work reported so far relates to arsenic-capped AlGaAs. Detailed investigation with surface sensitive structural (RHEED, LEED) and chemical (XPS) probes confirms that the protective cap is conveniently removed by annealing in ultrahigh vaccum environments at a temperature in excess of similar 350 °C. Clean AlxGa1-xAs(001) surfaces with different atomic reconstructions and corresponding (Al)Ga: As composition ratios are now routinely prepared by this technique, and thus offers an... (More)

In situ condensation of an amorphous cap of the high vapour pressure element (i.e. As, Sb) has been found to provide effective protection of molecular beam epitaxy grown compound semiconductor surfaces against ambient contamination. Most work reported so far relates to arsenic-capped AlGaAs. Detailed investigation with surface sensitive structural (RHEED, LEED) and chemical (XPS) probes confirms that the protective cap is conveniently removed by annealing in ultrahigh vaccum environments at a temperature in excess of similar 350 °C. Clean AlxGa1-xAs(001) surfaces with different atomic reconstructions and corresponding (Al)Ga: As composition ratios are now routinely prepared by this technique, and thus offers an ideal testing ground for compound semiconductor surface and interface research. Reconstruction-dependent reactivity at metal/GaAs(001) interfaces is demonstrated, using surface sensitive synchrotron radiation photoelectron spectroscopy. Exploiting the protection offered by the As (Sb) cap for device fabrication purposes (e.g. in selective area epitaxy), demands a suitable method of pattern definition in the amorphous arsenic layer. The cap is shown to be chemically stable versus exposure to standard photolithographic processing chemicals, including photoresist, developer, and acetone (the photoresist solvent). However, the temperature required for thermal decapping is grossly inappropriate for photoresist curing. A novel technique of reactive decapping in a beam of hydrogen radicals (H‒) is shown to be effective at room temperature. This innovation makes pattern definition in the As cap compatible with standard photolithography, and test structures with similar 5 μm linewidth is demonstrated. Scanning electron micrographs unveil the presence of arsenic cap residues along the photoresist mask edges. Moreover, trace amounts of surface gallium oxide and carbon impurities were found with core-level photoelectron spectroscopy. The technique thus needs further refinement, before being useful in fabrication of compound semiconductor device structures. © 1994 IOP publishing Ltd.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physica Scripta
volume
1994
issue
T54
pages
10 pages
publisher
Institute of Physics Publishing Ltd.
external identifiers
  • Scopus:2342501687
ISSN
0031-8949
DOI
10.1088/0031-8949/1994/T54/054
language
English
LU publication?
yes
id
8408ff76-6a89-4458-82ea-ae723d796ce0
date added to LUP
2016-04-29 11:16:00
date last changed
2016-09-13 15:20:03
@misc{8408ff76-6a89-4458-82ea-ae723d796ce0,
  abstract     = {<p>In situ condensation of an amorphous cap of the high vapour pressure element (i.e. As, Sb) has been found to provide effective protection of molecular beam epitaxy grown compound semiconductor surfaces against ambient contamination. Most work reported so far relates to arsenic-capped AlGaAs. Detailed investigation with surface sensitive structural (RHEED, LEED) and chemical (XPS) probes confirms that the protective cap is conveniently removed by annealing in ultrahigh vaccum environments at a temperature in excess of similar 350 °C. Clean Al<sub>x</sub>Ga<sub>1-x</sub>As(001) surfaces with different atomic reconstructions and corresponding (Al)Ga: As composition ratios are now routinely prepared by this technique, and thus offers an ideal testing ground for compound semiconductor surface and interface research. Reconstruction-dependent reactivity at metal/GaAs(001) interfaces is demonstrated, using surface sensitive synchrotron radiation photoelectron spectroscopy. Exploiting the protection offered by the As (Sb) cap for device fabrication purposes (e.g. in selective area epitaxy), demands a suitable method of pattern definition in the amorphous arsenic layer. The cap is shown to be chemically stable versus exposure to standard photolithographic processing chemicals, including photoresist, developer, and acetone (the photoresist solvent). However, the temperature required for thermal decapping is grossly inappropriate for photoresist curing. A novel technique of reactive decapping in a beam of hydrogen radicals (H‒) is shown to be effective at room temperature. This innovation makes pattern definition in the As cap compatible with standard photolithography, and test structures with similar 5 μm linewidth is demonstrated. Scanning electron micrographs unveil the presence of arsenic cap residues along the photoresist mask edges. Moreover, trace amounts of surface gallium oxide and carbon impurities were found with core-level photoelectron spectroscopy. The technique thus needs further refinement, before being useful in fabrication of compound semiconductor device structures. © 1994 IOP publishing Ltd.</p>},
  author       = {Grepstad, J. K. and Husby, H. and Borg, A. and Fimland, B. O. and Bernstein, R. W. and Nyholm, R.},
  issn         = {0031-8949},
  language     = {eng},
  month        = {01},
  number       = {T54},
  pages        = {216--225},
  publisher    = {ARRAY(0x97fefb0)},
  series       = {Physica Scripta},
  title        = {As capping of MBE-grown compound semiconductors; novel opportunities to interface science and device fabrication},
  url          = {http://dx.doi.org/10.1088/0031-8949/1994/T54/054},
  volume       = {1994},
  year         = {1994},
}