Deep Traps and Mechanism of Brightness Degradation in Mn-doped ZnS Thin-Film Electroluminescent Devices Grown by Metal-Organic Chemical Vapor Deposition

Evidence from deep level transient spectroscopy (DLTS) and Fourier transform infrared spectroscopy (FTIR) measurements strongly supported the assertion that the degradation mechanism of ZnS:Mn AC thin-film electroluminescent (ACTFEL) devices is mainly due to the deep electron trap, E t, which comes from the Mn activators reacting with water molecules. The photoluminescence measurements revealed that the Mn-related E t trap behaves like a nonradiative center. Furthermore, the X-ray diffraction experiments indicate that the crystallinity of ZnS:Mn phosphor films were destroyed in some degree by the E t trap. As a result, poor brightness characteristics including lower brightness and higher threshold voltage were obtained when samples become aged.