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Author Topic: Can anyone solve this chemical reaction?  (Read 2477 times)

Offline spyker

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Can anyone solve this chemical reaction?
« on: 02/10/2014 03:04:06 »
Hello everyone,

I have a question regarding to the chemical reactions between gallium nitride (GaN) wafer and other chemicals. FYI, i'm doing elctroless etching to fabricate porous GaN. To be honest, chemistry is not my field. So I have some difficulties to solve this chemical reactions. Could anyone can guide me to solve this chemical reactions?

GaN + HF + C2H5OH +H2O2 = ???

Thanks!  :)

[MOD EDIT - please phrase subjects as questions in line with AUP]
« Last Edit: 02/10/2014 16:14:46 by Georgia »


 

Offline chiralSPO

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Re: Chemical reactions
« Reply #1 on: 02/10/2014 03:40:33 »
I know about chemistry, but not etching specifically. Are all of these chemicals applied at the same time, or are they sequential washes? What is the GaN on? What concentration are the HF and H2O2?
 

Offline evan_au

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Re: Chemical reactions
« Reply #2 on: 02/10/2014 10:47:15 »
Do not try this experiment in your kitchen at home!
  • HF is quite vicious - use a fume cupboard. Most chemicals can be stored in glass - but this eats glass.
  • H2O2 can be nasty if it is concentrated
 

Offline spyker

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Re: Can anyone solve this chemical reaction?
« Reply #3 on: 03/10/2014 05:12:38 »
Yes, all the chemical was applied at the same time. But I forgot to mention that the GaN is in the form of wafer (solid).  That means I etch the GaN wafer using HF + C2H5OH +H202 solution with ratio 2:1:1. FYI, the concentration of HF about 49% and H2O2 about 30-32%. I was mixed the chemical first then I put GaN wafer into the solution for etching process. Is it possible the chemical reactions can be separated into two parts?

(1) HF + C2H5OH + H202 = ???
(2) GaN + product (1) = ???

Thanks!  ;)
 

Offline spyker

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Re: Can anyone solve this chemical reaction?
« Reply #4 on: 03/10/2014 05:18:21 »
Yeah, don't simply doing this experiment at home. I'm doing this experiment in the lab (fume cupboard) and I take a fully precautions while conducting this experiment.

 :D
 

Offline Bored chemist

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Re: Can anyone solve this chemical reaction?
« Reply #5 on: 05/10/2014 16:29:33 »
Chemical etchants for this sort of thing are more an art than a science. Somebody probably tried mixturs of things until they worked.
The HF supplies fluoride ions which will dissolve the gallium. The H2O2 oxidises the nitride- probably to nitrate and thus makes it soluble. It also oxidises the gallium.
The alcohol might simply be a solvent, or it might have some strange surfactant effect that produces the porous product.

Please note that some of the witch's brews used for etching are potentially explosive as well as toxic and corrosive.
 

Offline chiralSPO

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Re: Can anyone solve this chemical reaction?
« Reply #6 on: 06/10/2014 16:12:35 »
Chemical etchants for this sort of thing are more an art than a science. Somebody probably tried mixturs of things until they worked.
The HF supplies fluoride ions which will dissolve the gallium. The H2O2 oxidises the nitride- probably to nitrate and thus makes it soluble. It also oxidises the gallium.
The alcohol might simply be a solvent, or it might have some strange surfactant effect that produces the porous product.

Please note that some of the witch's brews used for etching are potentially explosive as well as toxic and corrosive.

Agreed with (almost) all of the above. I only disagree with the notion that the hydrogen peroxide oxidizes the gallium--presumably all of the gallium is already in the +3 state, which would not be oxidized further.

I would add that my guess is GaN + 4 HF → NH4+ GaF4 is the fastest reaction. The peroxide probably slowly oxidizes the ammonium ions to nitrate, but may be more to get rid of any organic residues, which the ethanol would help with... I don't know, but my gut tells me HF alone would suffice for etching GaN, but I'm sure there is a reason the standard procedure calls for the mixture.
 

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Re: Can anyone solve this chemical reaction?
« Reply #6 on: 06/10/2014 16:12:35 »

 

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