Hi,
We have worked on this a lot in our group, using CitricaAcid:Hydrogen Peroxide
in the appropriate concentration.  The ratio will tune which concentration of Al
in AlGaAs you can and cannot etch.  See the references below.  If you don't have
access, I can send you 1 or 2 in PDF format.

-Bill

4 records found in Compendex for: ((((adesida) WN AU) AND ((citric acid) WN AB))
AND ((selective) WN AB)), 1990-2004
                Select all on page  |   Select range:to     |   Clear all on
page   |   Clear all selections

 1.  Comparative study of wet and dry selective etching processes for
GaAs/AlGaAs/InGaAs pseudomorphic MODFETs
Tong, M. (Univ of Illinois); Ballegeer, D.G.; Ketterson, A.; Roan, E.J.; Cheng,
K.Y.; Adesida, I. Source: Journal of Electronic Materials, v 21, n 1, Jan, 1992,
p 9-15
Database: Compendex
Abstract / Links  |  Detailed Record / Links


 2.  Process for enhancement/depletion-mode GaAs/InGaAs/AlGaAs pseudomorphic
MODFETs using selective wet gate recessing
Tong, M. (Univ of Illinois); Nummila, K.; Seo, J.-W.; Ketterson, A.; Adesida, I.
Source: Electronics Letters, v 28, n 17, Aug 13, 1992, p 1633-1634
Database: Compendex
Abstract / Links  |  Detailed Record / Links


 3.  Selective wet etching characteristics of lattice-matched InGaAs/InAlAs/InP
Tong, M. (Univ of Illinois); Nummila, K.; Ketterson, A.A.; Adesida, I.; Aina,
L.; Mattingly, M. Source: Journal of the Electrochemical Society, v 139, n 10,
Oct, 1992, p L91-L93
Database: Compendex
Abstract / Links  |  Detailed Record / Links


 4.  InAlAs/InGaAs/InP MODFET's with uniform threshold voltage obtained by
selective wet gate recess
Tong, M.; Nummila, K.; Ketterson, Andrew; Adesida, Ilesanmi; Caneau, C.; Bhat,
Rajaram Source: IEEE Electron Device Letters, v 13, n 10, Oct, 1992, p 525-527
Database: Compendex
Abstract / Links  |  Detailed Record / Links




---- Original message ----
>Date: Thu, 11 Dec 2003 16:58:10 -0800 (PST)
>From: Sai Raghav Parasa 
>Subject: [mems-talk] High Selectivity for GaAs over AlAs for Wet Chemical
Etching
>To: mems-talk@memsnet.org
>
>Hi all,
>
>Can you give 3 best etchants which have high selectivity for GaAs over AlAs for
Wet Chemical Etching?
>
>The etchant should best etch GaAs but should not attack AlAs.
>
>Thanks,
>Bye,
>Parasa,
>University of Kassel, Germany.
>
>
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