I doped my semiconductor thin film. In lower dopant concentration there is a increase in band gap. But higher dopant concentration leads to reduction in Band gap.
Dear Mina, that you mean the bandgap is the result of some measurement technique, may be it is only an interpretation of measurements. Please specify your film material and the method used for Eg determination and the value of Eg change, estimated carrier density.
Many reasons are possible, vanishing of exciton recombination band, Eg renormalization , see e.g. https://www.nature.com/nmat/journal/v13/n12/full/nmat4061.html
Good luck!
IS Vasil’evskii refers to a very relevant paper. When doping leads to suppression of screening, theoretically one moves to the Hartree-Fock (or exchange-only) limit, where band gaps are generally overestimated (insofar as the band-gap energy is concerned, the correlation part of the one-body potential in band-structures calculations counters the exchange part of the one-body potential). The mechanism underlying the increase in the band gap as a consequence of the suppression of screening, is entirely distinct from that underlying the Burstein-Moss band-gap shift.
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