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 electro luminescent devices was studied. In a first series of experiments, we aged devices at different temperatures from 50 to 190 degrees C, and m easured the steady-state transferred charge versus voltage characteris tics. From monitoring Q(145V), the charge transferred at 145 V, we cou ld trace the relationship between Q(145V) and the aging time. The agin g process was found to be temperature dependent, and we could deduce a n activation energy of 0.34 eV. In a second series of experiments, dev ices were aged 16 h at room temperature and subsequently heat treated at different temperatures from 250 to 450 degrees C. Monitoring again Q(145V), we found that the devices recover from aging following the re lationship - k(reco)t = ln[Q(145V)/Q(145V)(t = 0)], where t is the hea t 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 fo und the aging rate to be proportional with the transferred charge. Pos sibly aging is a process of defect creation at the interface near the substrate. For this creation thermal energy and the energy of the acce lerated electrons are needed. The defects can be annihilated by heatin g the device above 350 degrees C. (C) 1997 American Institute of Physi cs.