[SI-LIST] Re: Doping effects.
- From: Teh Lip Khoon <lkteh@xxxxxxxxxxxxxx>
- To: rfengg@xxxxxxxxx
- Date: Fri, 21 Mar 2003 13:06:53 +0800
Hi George,
Conductivity is given by quN where q is the electronic charge, u is the
mobility of carrier and N is effective carrier concentration. Increasing the
doping concentration will increase N, as well as dopant ion concentration. At
low to medium dose, that's fine. An increase in conductivity is achieved.
However, if the doping concentration is high, you start having a lot of dopant
ions sitting in the crystal lattice of Si. This can cause strain in the
Si lattice. Also, the dopant ions in high concentration causes carrier
scattering due to interaction of the charged carrier with the dopant ion. When
you have such a situation, the carrier mobility suffers. Therefore the
conductivity of your silicon is not going to increase much. The name for
heavily-doped silicon is "degenerate", and they are seldom used in typical
semiconductor application.
Regards,
LK
GEORGE VARGHESE wrote:
> Hi all,
> If doping increases the conductivity of Silicon , why cant we
> attain superconductivity with heavy doping of a material? Whats the
> phenomenon that limits the conductivity if we actually do increase carriers
> by doping?
>
> Thanks and regards,
> George.
>
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