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

Er 3+ ‐doped polycrystalline MgAl 2 O 4 (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, Al 2 O 3 /MgO ratios and Er 2 O 3 dopant cycles. The similar electroluminescence (EL) emissions peaking at 1530 nm indicates the identical crystal field environment for the doped Er 3+ ions. The concentration quenching is verified to occurs via the energy transfer among the neighboring Er 3+ ions. The optimal device (800 °C‐annealed, Al 2 O 3 /MgO ratio close to stoichiometry, Er 3+ : 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 Er 3+ 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 cm 2 are revealed from the EL emissions. Intense near‐infrared emissions from these Si‐based MAO:Er devices have great potential in the optoelectronic applications.