Kinetics and aging in atomic layer epitaxy ZnS:Mn ac thin-film electroluminescent devices

The kinetics of the aging of atomic layer epitaxy ac thin-film electroluminescent devices was studied. In a first series of experiments, we aged devices at different temperatures from 50 to 190 °C, and measured the steady-state transferred charge versus voltage characteristics. From monitoring Q_145 V, the charge transferred at 145 V, we could trace the relationship between Q_145 V and the aging time. The aging process was found to be temperature dependent, and we could deduce an activation energy of 0.34 eV. In a second series of experiments, devices were aged 16 h at room temperature and subsequently heat treated at different temperatures from 250 to 450 °C. Monitoring again Q_145 V, we found that the devices recover from aging following the relationship -k_recot=ln[Q_145 V/Q_145 V(t=0)], where t is the heat treatment time. The recovery rate constant k_reco was found to have an activation energy of 1.3 eV. In a last series of experiments we found the aging rate to be proportional with the transferred charge. Possibly aging is a process of defect creation at the interface near the substrate. For this creation thermal energy and the energy of the accelerated electrons are needed. The defects can be annihilated by heating the device above 350 °C. © 1997 American Institute of Physics.