I did some doping in a semiconductor and I have observed a shift from indirect band gap to direct. Prestine material has indirect band gap while doped material has Direct Band gap. My Question is, Is this is possible according to Theory or not?
I did some doping in a semiconductor and I have observed a shift from indirect band gap to direct. Pristine material has indirect band gap while doped material has Direct Band gap. My Question is, Is this is possible according to Theory or not?
Hi
can you tell me, how do you find that the band gap of your sample is changed from indirect to direct band gap?
Hi
can you tell me, how do you find that the band gap of your sample is changed from indirect to direct band gap?
It is in principle possible. At low doping concentration of a semiconductor, one introduces atomic (i.e. localised) states inside the gap. By increasing the doping concentration, these atomic states overlap and form new bands. Etc.
Nisar Muhammad : My pleasure. The following are two publications relevant to your main question:
Article Possible Indirect to Direct Bandgap Transition in SnS2 via N...
Article Possible electric field induced indirect to direct band gap ...
For the general theory of doping semiconductors, you may wish to consult any good book on Solid State Physics, such as that by Ashcroft & Mermin.
The earliest green LED (70-80's) is made out of an indirect bandgap material GaP by nitrogen doping, which makes it "quasi-direct", the same general idea mentioned in Dr. Farid's answer. One could increase the doping concentration to enhance the absorption. It leads to the formation of an impurity band that does not have a well defined bandgap and has a poor electronic mobility. See this paper for an evolution of the electronic structure with changing N doping level in GaP:N: https://coefs.uncc.edu/yzhang47/files/2018/07/GaPNPRB.pdf .
Respected Yong Zhang,
Thanks for your kind response and valuable suggestion.
Your Sincere,
Nisar
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