# How to dope a semiconductor with an elemnt which sublimates?

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1. Jan 18, 2016

### Prins

Hi there
Im working in a solid state lab
I have a semiconductor, lets say 'AB'
nowim trying to dope it with a new element 'C' to form 'AB(1-x)Cx'
im using bridgman technique for this purpose,,,that is heating all the ingredients together
now the problem is that the element C sublimates before A or B melt
So im not getting the required yield
Any suggestions.
thanks

2. Jan 18, 2016

### e.bar.goum

Presumably you've checked the literature to see if anyone else has used this dopant and semiconductor, and if so, how they achieved it?

I'm pretty ignorant about doping semiconductors, and you've given us very little detail, but could you use a different technique, such as ion-implantation?

3. Jan 18, 2016

### Prins

Actually this is a matelial of sorts

4. Jan 18, 2016

### Prins

Any we have the apparatus for this method only...so options are limited

5. Jan 21, 2016

### Hyo X

Lets assume AB is GaAs. Is element C substituting only into the B sites? AB (1-x) Cx or both sites A(1-x/2)B (1-x/2) Cx?

If you can control the atmosphere around the AB so that even if C is a gas, AB is exposed to high concentration 100% C, does that help?

6. Jan 21, 2016

### Prins

First, C substitutes only B

Second, Well that is how im trying to do it. Putting the things inside an evacuated tube and then heating. But as i said,, im not getting the desired yield

7. Jan 21, 2016

### Hyo X

By yield you mean dopant concentration? How do you characterize dopant concentration?

You could try cycling the material. run the process with the dopant, then take the doped crystal and melt it and cycle it again. run it many times to increase the dopant conecntration slowly.

8. Jan 21, 2016

### Prins

well im trying to get AB(.9)c(.1)

so after doing the math i should get 5% atomic percentage
but EDS of sample shows it to be only nearly 1%

9. Jan 23, 2016

### MarkPercival

You say you're doing this inside an evacuated tube, presumably evacuated to exclude air to prevent oxides and such from forming. If this is a sealed tube and not actively being pumped while you're trying to make your end product, when your component C sublimates you no longer have a vacuum, you have C in vapor state, what Hyo X called the atmosphere within the tube. Can you add an excess of your component C to raise the vapor pressure enough to push it back into solution in the melt? I'm assuming that you've already checked that C is indeed soluble in A+B throughout the temperature range you have to work in, that is, from melting point of A+B to solidification.

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