Doping is one of the way to reduce the bandgap of ferroelectrics/any materials. By doing so we create many defects in the system. these defects have a role on electrical conductivity (AC/DC). Is there any way to determine how electrical conductivity varies as band gap decreases. How to create a balance between them.
Therefore, the band gap is a major factor determining the electrical conductivity of a solid. Substances with large band gaps are generally insulators, those with smaller band gaps are semiconductors, while conductors either have very small band gaps or none, because the valence and conduction bands overlap.
I agreed with Hadi Jabbar Alagealy . You also can get ac conductivity from dielectric measurement.
Abhinay Sreeram ,
The conductivity of a given material depends on both intrinsic (as energy bandgap) and extrinsic (as doping, defects, ...) factors.
- The energy bandgap plays a paramont role in this purpose. Usually, with decreasing the energy bandgap EG of a given material, the conductivity increases because of the strong exponential increaseof its intrinsic free electron and hole densities following a law as exp~(-EG/2kT);
- Decreasing EG induces another increase of the conductivity through an increase of both electron and hole mobilities ue and uh as a result of a decrease of their respective effective masses m*e and m*h since u scales as 1/m* and m* scales approximatly as 1/EG.
- Decreasing EG also induce an increase of the static dielectric constant (epsilon S) which means that Coulomb interactions Vij are more strongly screened since Vij scale as 1/(rij*epsilon S). This results in much reduced potential interaction energies.
- All these effects may affect in turn the behavior of extrinsic factors as doping impurities and defects as follows:
- Donor and acceptor ionization energies will get smaller both because of smaller m* but also because of larger epsilon S. Donor and acceptor ionization will be more efficient and it induces more free electrons and holes available in the system increasing in this way the conductivity.
- As to the defects, their behavior is more complicated, but they are less efficient because of their screening by increasing free carrier (electrons and holes) densities and by increasing static dielectric constant.
- As to ferroelectricity the effects are also more complicated but, in principle, decreasing EG induces similar effects as above for a ''normal'' insulator or semiconductor with specific ones as to ferroelectricity itself. More particularly, ferroelectricity is affected mainly by combined effects due to increasing free carrier concentrations and increasing dielectric constant and how they affect the ferroelectric hysteresis property of a given material . These effects are likely to induce in turn a decrease of several hysteresis properties as hysteresis energy, remnant electric fields,...
I hope this may help you.
Best regards,
Professor A. Kadri
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