Effects of intergranular capacitance and resistance dispersion on polycrystalline semiconductor impedance

In the present work we focused on the effects, often disregarded, of the intergranular barrier fluctuations on the total impedance of polycrystalline structures. These fluctuations come from the discreteness nature and random distribution of ionized donors at the polycrystal, which are responsible of forming the intergranular barriers. Firstly, we used a numerical model that takes into account the point character of the involved donors and found that resistances and capacitances present distributions that become narrower with the grain size. Secondly, we built a bricklayer model with capacitances and resistances taken from the found distributions and calculated the total impedance, focusing on tin oxide as an example. We found the total polycrystal capacitance and resistance dependence on the specific dispersions of intergranular capacitances and resistances. •We studied the effect of intergranular barrier fluctuations in the polycrystalline semiconductor impedance.•We found the total polycrystal capacitance and resistance as a function of intergranular capacitances and resistances.•We found that it is important to take into account dispersions in the brick layer model for polycrystals with small grains.