Increase the inversion degree in Er-doped MgGa2O4 spinel nanofilms to obtain strong electroluminescence

Abstract

The GaO/MgO/ErO nanolaminates are fabricated by atomic layer deposition and crystallized into Er-doped MgGaO spinel (MGS:Er) nanofilms after annealing, with their electroluminescence (EL) performance characterized. The annealing above 600 °C achieves the polycrystalline spinel nanofilm, and the crystallization is promoted by the higher annealing temperature and GaO/MgO ratio. The dopant Er ions preferably substitute into the octahedron sites occupied by Ga ions in ordinary spinel and Mg in anti-spinel lattice, while the inversion degree is confirmed to increase with the reduction of GaO/MgO ratio and annealing temperature, resulting the relatively enhanced secondary EL at 1542 nm. This perturbation by Er-substitution into anti-spinel sites improves the emission intensity and excitation efficiencies, the main EL emission peaking at 1531 nm from the optimal MGS:Er device exhibits the excitation efficiency reaching 5.8 %, with the enhanced electrical injection realizing the maximum EL intensity above 17.3 mW/cm. The fluorescence lifetime of these MGS:Er devices is established in the range of 371–760 μs, which decreases mainly with the Er concentrations. The prototype device using the near-stoichiometric GaO/MgO ratio shows the operation time of 1.12 × 10 s. This work explores the fabrication of Si-based spinel nanofilms with designed composition and special microstructure, and their practical application in optoelectronics.