Polycrystalline Er-doped Y3Ga5O12 nanofilms fabricated by atomic layer deposition on silicon at a low temperature and the exploration on electroluminescence performance

Atomic layer deposition of Er-doped yttrium aluminum gallium garnet nanofilms with tunable crystallization and electroluminescence properties

Polycrystalline erbium-doped Y₃(Al_xGa_1-x)₅O₁₂ (Er-YAGG) nanofilms with various Al/Ga compositions are deposited on silicon using atomic layer deposition followed by annealing at different temperatures. The Al/Ga ratios and the corresponding annealing temperatures required for crystallization are confirmed by investigating the diffraction patterns and micro-morphologies. The co-alloying of Al and Ga compositions controllably changes the lattice constant and impacts the grain growth. The crystal-field splitting of doped Er³⁺ ions is also modified, manifesting different electroluminescence (EL) spectra that also indicate the crystallization of garnet matrices. The EL performance of a device based on the Y₃Al₂Ga₃O₁₂ nanofilm (1.39 at% Er dopant) annealed at 900 °C is improved due to the adjustment of morphology and microstructural perturbations that are beneficial for radiative transition. The optimal EL device exhibits a low onset voltage of ∼25 V and a maximum external quantum efficiency of 3.29%. The excitation cross-section under electrical pumping is estimated to be 1.18 × 10^-15 cm². The carrier transport of these co-alloyed Er-YAGG devices conforms to the Poole-Frenkel mechanism. Both the EL decay lifetime and the device operation time increase with the incorporation of Ga within the Er-YAGG nanofilms. These Er-YAGG devices with tunable optoelectronic properties manifest promising potential for the engineering of light sources compatible with CMOS technology.

Bright white electroluminescence from polycrystalline dysprosium-doped yttrium gallium garnet nanofilms fabricated by atomic layer deposition on silicon

Bright white emission is obtained under electrical excitation from dysprosium doped Y₃Ga₅O₁₂ garnet (YGG:Dy) nanofilms fabricated by atomic layer deposition on silicon substrates. Electroluminescence (EL) composed of yellow (580 nm) and blue (482 and 492 nm) emission corresponds to the CIE chromaticity coordinates of (0.3568, 0.3807) and a CCT of ∼4700 K and can be used for lighting and displays. The crystallization and micro-morphology of polycrystalline YGG:Dy nanolaminates are explored by adjusting the annealing temperature, Y/Ga ratio, Ga₂O₃ interlayer thickness and Dy₂O₃ dopant cycle. The near-stoichiometric device annealed at 1000 °C presents optimal EL performance with the maximum external quantum efficiency and the optical power density reaching 6.35% and 18.13 mW cm^-2, respectively. The EL decay time is estimated to be 273.05 μs, with a large excitation section of 8.33 × 10^-15 cm². The conduction mechanism is confirmed to be the Poole-Frenkel mode under operation electric fields and the impact-excitation of Dy³⁺ ions by energetic electrons results in emission. Bright white emission from Si-based YGG:Dy devices can provide a new route to developing integrated light sources and display applications.