Er‐Doped MgAl₂O₄ Nanofilms Enabling Highly Efficient Near‐Infrared Electroluminescence from the Silicon‐Based MOS Devices Fabricated by Atomic Layer Deposition

Abstract Er³⁺‐doped polycrystalline MgAl₂O₄ (MAO:Er) spinel nanofilms are deposited via atomic layer deposition, and the metal‐oxide–semiconductor light emitting devices are fabricated. The crystallinity and morphology of the MAO:Er nanofilms are explored by modifying the annealing temperatures, Al₂O₃/MgO ratios and Er₂O₃ dopant cycles. The similar electroluminescence (EL) emissions peaking at 1530 nm indicates the identical crystal field environment for the doped Er³⁺ ions. The concentration quenching is verified to occurs via the energy transfer among the neighboring Er³⁺ ions. The optimal device (800 °C‐annealed, Al₂O₃/MgO ratio close to stoichiometry, Er³⁺: 1.85 mol%) yields the highest external quantum efficiency of 28%, the power efficiency of 0.32% and the optical power density of 14.62 mW cm⁻². The smooth MAO:Er spinel nanofilms with the low refractive index and high resistance ensure the highly efficient light extraction and the generation of energetic electrons for the impact excitation of Er³⁺ ions. The trap‐assisted tunneling under operation electric field dominates the conduction mechanism for the EL emissions. The estimated decay lifetime of 1154.4 µs and a large‐stimulated emission cross‐section in the order of 10⁻¹⁵–10⁻¹⁴ cm² are revealed from the EL emissions. Intense near‐infrared emissions from these Si‐based MAO:Er devices have great potential in the optoelectronic applications.