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

Abstract

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.