Selective etching of GaAs relative to Al0.3Ga0.7As

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Can anyone please help me with the selective etching of GaAs w.r.to Al0.3Ga0.7As..
I have tried out many compositions using the citric acid and hydrogen peroxide and none of them given in the literature work...Please help

Ravi
 
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Selective etching might require an electric current or polarization. Also Al is perhaps better etch with a fluoride or chloride ion present. HF/HCl in HNO3 might work. Be very careful with HF - it's nasty stuff.

However, I'm not familiar with Al-Ga-As.
 
Thanks for the reply..but i am afraid we cannot use corrosive acids like HF.. So please tell if u are familiar with acids like citric acid, succinic acid.etc..
 
Have you already done the literature search? I looked up gaas etching on Google, and got this one on the first page:

Liao, C., Houng, M., and Wang, Y. "Highly Selective Etching of GaAs on Al0.2Ga0.8As Using Citric Acid/H2O2/H2O Etching System". Electrochem. Solid-State Lett., Volume 7, Issue 11, pp. C129-C132 (2004)
http://dx.doi.org/10.1149/1.1803072
 
You don't have to use HF - it can be enough to add F- (for example sodium fluoride) to get the same effect. Still, you have to be cautious.

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