Abstract
A postannealing technique has been used to make double-insulating SrS:Ce thin film electroluminescent (EL) devices. This technique has the effect of lowering the substrate temperature during SrS:Ce deposition, and also of improving the luminance and emission color with blueshift. Using this technique, the controllability of thin film processing and reproducibility of the devices have also been improved. A suitable annealing temperature is about 720°C. The device has a luminance of 320 cd/m2 and improved color coordinates, x=0.18 and y=0.35, using a 1-kHz drive frequency. The devices have also been evaluated as to EL properties and film crystallinity. In particular, a novel way of directly measuring the transient electric field across the active layer has been proposed.