Hello,

A GaAs/AlGaAs selective etchant is

1.5 (%50 Citric Acid soln) : 1 H2O
%50 Citric acid solution has mass ratio of 1:1 of Citric Acid and H2O
Moon E.,A. , Journal of Applied Physics : vol84 pp3933

But selectivity does not mean that it does not touch AlGaAs.  It also
mentions past works on selective GaAs/AlGaAs etching.

Selectivity strongly depends on Al mole fraction and usually not strong I
guess !
Also Some others use NH4OH based solutions but I don't have experience with
that.

Oray Orkun Cellek
[email protected]
Middle East Technical University, EE Dept., Turkey


----- Original Message -----
From: "Lihua Li" 
To: 
Sent: Sunday, December 09, 2001 10:26 PM
Subject: [mems-talk] AlGaAs-GaAs


> Hi all,
>
> I need GaAs substrate with thin film of AlGaAs on top
> of it. Any information regarding the vendor is
> appreciated.
>
> Also, does anyone know the etchant which will etch
> GaAs but not attack AlGaAs?
>
> Thanks!
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