Dear Abir,

The energy gap is inversely proportional to the dielectric constant and proportional to the number of atoms per cubic centimeter.

If your band gap decreases while epsilonr decrease then there must be a more pronounced decrease in the density of the atoms. Which means that the interatomic distance increases.

I would like rthat you follow my paper in the link:Article A new theory for band gap shrinkage

Best wishes

Abdelhalim abdelnaby Zekry

Dear Sir,

Thanks a bunch for such a clear explanation. I have one more question. In my doped structure there are three C-N bonds and 27 Ga-N bonds. Should I take average of them as the interatomic distance?

Dear Md Abir Hassan ,

You can consider that your material is basically GaN and it is dop3ed by carbon to make it n-type. Then it is a three five compound and you can estimate it with formula given in the given paper in the first post.

Then you can consider that the doping my cause BGN as given. So, without BGN it is expected to get slightly higher bandgap than that really existing.

Best wishes