Preparation of ZnGa2O4:Mn phosphor thin films as emitting layers for electroluminescent devices

Abstract

ZnGa2O4:Mn thin films as the emitting layer in thin-film electroluminescent (TFEL) devices have been prepared by rf magnetron sputtering and low-pressure chemical vapor deposition (CVD). The as-deposited thin films, regardless of preparation methods, were ZnGa2O4 which crystallized with a spinel structure. A green EL emission was realized in TFEL devices using as-deposited ZnGa2O4:Mn thin films as the emitting layer and a thick BaTiO3 ceramic sheet as the insulating layer. Maximum luminances of 0.7 and 7.6 cd/m2 were obtained in TFEL devices using as-deposited ZnGa2O4:Mn thin films prepared by the sputter and CVD techniques, respectively, when driven by a sinusoidal wave voltage at 1 kHz. In addition, a maximum luminance above 600 cd/m2 was obtained in TFEL devices using ZnGa2O4:Mn thin films postannealed at a temperature of about 1000 °C, regardless of preparation methods. The improvement of EL characteristics by postannealing ZnGa2O4:Mn thin-film emitting layers was mainly attributed to an improvement in the crystallinity of the emitting layers.