Defect chemistry and electrical characteristics of undoped and Mn-doped ZnO

Undoped and Mn-doped ZnO samples were sintered at 1373, 1473, and 1573 K, for 2 h, in air, and then quenched to room temperature. Defect concentrations in these samples at the sintering temperatures and at room temperature and below were calculated using a refined defect model. Using the calculated electron concentrations and assuming a constant electron mobility of 100 cm2/Vs, conductivities at room temperature were calculated and compared with experimental ones. The agreement between the experimental and calculated conductivities is very good for all the samples of undoped and Mn-doped ZnO. In the Mn-doped ZnO case, the ionisation energy of the Mn defect in ZnO was estimated to be ∼2.0 eV. Using the experimental conductivities and the calculated electron concentrations, the electron mobilities were calculated between 70 and 300 K. The results show that the temperature dependence of the mobility in undoped ZnO is similar to that in ZnO single crystals observed in other works, and heavy Mn doping significantly reduces the electron mobility below room temperature probably due to impurity scattering. The role of Mn on the electrical conductivity of ZnO could be understood.