In the doping , if the impurity atoms size higher the host atoms size ,shifting in X-Ray peaks ? or it depend on the dopant concentration also?
There aren't many atoms that have exactly the same size, but size does matter for dopants. What semiconductor are you interested in doping?
Dear Lior ,
thanks.in the n-type and p-type semiconductors in the Si ,please compare the impurity atoms size with the host atoms .
Regards,
The common dopants in Si are B (p) P and As (n); I'm sure you can find the atomic radii by yourself. The size difference in this case is important because it creates a disruption in the periodicity of crystal that extends beyond the size of the atom. This disruption can scatter free carriers, thus reducing their mobility. In Si the mobility degradation due to dopants is not large until high concentrations (~>E18) are obtained, where it starts dropping rather sharply.
Dear Dr Abbas R,
You may go through the following link:
http://personal.cityu.edu.hk/~appkchu/AP4120/8.PDF
Regards,
In the doping process, I think the size of the impurity should be selected in such a way that it should sit in the interstitial site. otherwise i think impurity could not be incorporated in the crystal structure of host material and If this size will not match then the impurity will remain a single atomic entity.
So therefore the size of impurity should be equal to or less than interstitial site/defect in crystal.
Vishal, I think that in Si and several other common semiconductors the dopants are electrically active when they are in substitutional positions, rather than interstitial positions. This is part of the reason why a high temperature anneal is needed after ion implantation (another reason is to recover implantation induced lattice defects)
Dear Lior ,
thanks.in the n-type and p-type semiconductors in the Si ,please compare the impurity atoms size with the host atoms and tell me doping lead to the peaks shifting or change in the peaks intensity.
Regards,
Hi Abbas
The size of impurity only affect the kinetic process of the impurity movement, e.g. Interstitial, Vacancy, Substantial, etc. And, from this point of view, it's not necessary for the dopants to be as same size as host atoms.
Cheers
Dear Abbas,
What peaks are you referring to? If you are talking about XRD peaks then typical doping levels of Si are quite low and should be somewhat challenging to measure (but not impossible).
As far as atomic sizes, this information is abundantly available with an easy google search, I'm sure you can find it by yourself.
Good luck
Lior
Dear Lior and everyone.
Thanks due to your valuable answers.
Best Regards,
Abbas
By asking a question I answer your question!
Is the size of any of the dopant atoms in Si, like boron (B), Aluminum (Al), Phosphor (P) or Arsenic (AS) is the same as the size of Si atom?
The size of different atoms cannot be the same. A consequence of difference in the sizes of atoms is their segregation coefficient.
Thank you everyone for the input, and apologies for the delay in responding. I will soon post a circuit diagram as suggested.
Thank you once again, David
Typically, for doping in any semiconductor, the size of the dopant atom does not matter. What makes a material a semiconductor (irrespective of size of its band gap)?
If the dopant atom can replace one of the host atoms and create an energy level within the band gap either close to the lower edge of conduction band (the host material becomes n-type semiconductor) or close to the upper edge of valence band (the host material becomes p-type semiconductor). It is important that the dopant impurity energy level becomes ionized at room temperature for a device such as a p-n junction to be useful at room temperature.
It is interesting to note that impurities used for making Si n-type or p-type, will not perform the same function if added in other materials such as GaAs.
I agree with the answer that size does not matter in the doping in case of semiconductor.
However My earlier answer was for the system where we dope rare earth for making the crystal luminescent or to synthesize nanophosphor etc.
Dear Dean ,
in Si n-type or p-type b y doping,doesn't change the peaks positions due to doping?
why ?
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Atomic, Molecular and Optical Physics