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, f or 2 h. in air, and then quenched to room temperature. Defect concentration s in these samples at the sintering temperatures and at room temperature an d below were calculated using a refined defect model. Using the calculated electron concentrations and assuming a constant electron mobility of 100 cm (2)/Vs, conductivities at room temperature were calculated and compared wit h 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 w as estimated to be similar to2.0 eV. Using the experimental conductivities and the calculated electron concentrations, the electron mobilities were ca lculated between 70 and 300 K. The results show that the temperature depend ence of the mobility in undoped ZnO is similar to that in ZnO single crysta ls observed in other works, and heavy Mn doping significantly reduces the e lectron mobility below room temperature probably due to impurity scattering . The role of Mn on the electrical conductivity of ZnO could be understood. (C) 2001 Elsevier Science Ltd. All rights reserved.