Modification of the crystallinity and electroluminescence properties of Er-doped MgGa2O4 spinel nanofilms by inserting Al2O3 nanolayers

Abstract

In pursuit of better electroluminescence (EL) performance from Er-doped MgGa_xAl_yO₄:Er (MGAO:Er) spinel nanofilms, multiple Al₂O₃ nanolayers are inserted into the Ga₂O₃/MgO/Er₂O₃ nanolaminates by atomic layer deposition. The Al₂O₃ interlayers result in a higher crystallization temperature, while the changes in lattice constant and binding energy verify the finite substitution of Ga by Al ions in spinel lattice by inserting sufficient Al₂O₃ nanolayers. The comparison confirms the difference in crystallization due to the intact Al₂O₃ nanolayers, rather than the change in inversion degree of spinel lattice, results in the different EL spectra. The EL excitation efficiency of the optimal device (4 Al₂O₃ nanolayers, 700 °C-annealed) reaches 4.5 %, with the maximum emission intensity of 14.5 mW cm⁻². The EL devices based on MGAO:Er nanofilms annealed at 600–700 °C exhibit significantly improved operation stability, the device utilizing appropriate Al₂O₃ interlayers (4 layers in a ∼80 nm film) achieves the stable operation during continuous electrical injection for more than 10 days, benefiting from the quasi-crystalline structure and smooth morphology of the MGAO:Er spinel nanofilms. This work further reveals the changes in lattice crystallinity by the regulation of component and annealing temperature of oxide nanolaminates, and contributes to the silicon-based optoelectronic application of artificially designed nanofilms.