Relationship between variable range hopping transport and carrier density of amorphous In2O3-10 wt. % ZnO thin films

The electrical transport characteristics in amorphous Zn doped In2O3 films have been investigated in the range from 2 x 10(17) cm(-3) to 6 x 10(20) cm(-3) of the carrier concentration N-e. For films with N-e > 3 x 10(20) cm(-3), it is found that the Hall mobility mu(H) is limited by ionized impurity scattering. However, for films with N-e < 1 x 10(20) cm(-3), the N-e, dependence of mu(H) is given by the relation of mu(H) proportional to N-e(1/3). The temperature T dependence of resistivity rho(T) changes from exhibiting metallic behavior with d rho/dT > 0 to insulating behavior with d rho/dT < 0 near N-e approximate to 1 x 10(20) cm(-3) with decreasing N-e. The transport mechanism of carriers in the high-resistivity region is discussed by considering a model based on the Ioffe-Regel criterion. For the film with highest resistivity with N-e approximate to (5 - 6) x 10(17) cm(-3) among the present films, the rho(T) show a change from Mott variable-range hopping (rho proportional to exp T-1/4) to rho proportional to expT(-1/2) at approximately 10K with decreasing temperature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745055]