Evidence was presented that two electron traps observed in polycrystalline zinc oxide could be associated with complex intrinsic defects. One deep level, E1, could be assigned to an oxygen vacancy. The second deep level, E2, could consist of a cluster‐type defect associated with oxygen vacancies. The two traps were characterized using deep‐level transient spectroscopy. The energies of these traps were 0.15 and 0.24eV, the capture cross sections were 4 x 10-18 and 1 x 10-17cm2, and the emission rates at 300K were 2.0 x 106 and 1.3 x 105Hz, respectively. The relative concentrations of these traps varied uniformly as a function of the cooling rate of the zinc oxide from a sintering temperature of 1300C. The concentration of E1 decreased, while the concentration of E2 increased, with decreasing cooling rate.

Defect Clusters in Zinc Oxide. Simpson, J.C., Cordaro, J.F.: Journal of Applied Physics, 1990, 67[11], 6760