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where do I get cheap wafers?

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Posted by pineappleCoward on June 22, 2008, 12:14 am
 
Can anyone tell me where to get a few (2-4) wafers for cheap?  My only
requirement is that I want both N and P type wafers.  Don't care about
size, dopant, orientation, etc.  Test grade is fine as long as they
aren't coated!

Posted by Eeyore on June 22, 2008, 12:39 am
 


pineappleCoward wrote:


Hey sunshine, the wafers are SILICON ! PURE SILICON.

You want to dope them, then find a specialist and specify the dopant and
quantity or dope them yourself.

Graham


Posted by coj on June 22, 2008, 8:15 am
 Eeyore wrote:

Most Solar wafers are grown *intentionally doped* at a bulk resistivity
of around 1 ohm.cm (whether multicrystalline, CZ or float zone)

Boron is the dopant used for most p type wafers (the majority of
manufacturers) and Phosphorous can be used for n type (a rarity in Solar
cells).

There are process steps (spinning doped layers or diffusions) to add the
emitter layer but these need temperatures up to 1000C to work.

I don't know of anyone who could supply doped wafers with no coating,
the OP might try etching or grinding off any layers already on a solar cell.

What size does the OP need ? What are you going to do with them ?

coj

Posted by Eeyore on June 22, 2008, 11:13 am
 

coj wrote:


Hmmm. Defer. I KNOW a III-IV crystal grower and wafer maker btw. Not especially
relevant nt to this conversation bit I though I'd mention it along with the
flood showers available least you get contaminated with HF.

'Togging up' is fun too after a perverse fashion. Had to do that in a few
places.



I have found Google very useful in these instances.

Graham


Posted by coj on June 22, 2008, 9:33 pm
 Eeyore wrote:

Wafers are doped (or not) depending on what they are going to be used
for. III-V (three five) can be made intrinsic for amplifiers (e.g MMICs)
etc. where they don't want resistive leakage paths between the
components. All solar cells I believe are made on doped bulk material
(although the IC industry would presumably require undoped).


Me too but thankfully not everyday now. It's a pain to do and then
realise you need to nip out again.


I doubt any manufacturers would be interested in requests for a couple
of cells and I think the Chinese seem to be snapping up any excess
available. PV Crystalox make tonnes of Si PV Wafers per year in the UK
and there are a lot of other manufacturers world wide. Maybe the OP
could contact a University that does small scale cell experiments and
may have a couple of spare wafers ?

But consider etching off layers from a cell, I believe Astropower may
have had a whole business once in recycling semiconductor industry wafers.

--
coj


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