Luminescence from metal-oxide-semiconductor devices with Eu3+-doped CeO2 films on silicon: From broadband to monochromatic emission

We report on the transformation from broadband to monochromatic orange-red emission for the electroluminescence (EL) from the metal-oxide-semiconductor (MOS) devices with europium (Eu3+)-doped CeO2 films annealed at various temperatures as the light-emitting layers. Under the bias voltages exceeding 8 V, the 800 °C-annealed MOS device exhibits dominant Eu3+-related emission at 590 nm with a full width at half maximum of only ∼2 nm. In contrast, the 400 °C-annealed MOS device is activated into broadband emissions associated with the defects in the CeO2 host. Also, the two distinct EL behaviors can co-exist by annealing the CeO2:Eu3+ film at 600 °C. It has been demonstrated that the defect- and Eu3+-dependent EL are related to the Poole-Frenkel (P–F) and trap-assisted tunneling (TAT) electrical conduction mechanisms, respectively. The MOS device with a tunable EL is significant due to its potential applications, e.g., optoelectronic integration.