Crystallization and electroluminescence performance of the Er-doped polycrystalline Gd3Ga5O12 nanofilms fabricated by atomic layer deposition on silicon

Er-doped Gd2O3/Ga2O3 nanolaminates are fabricated by atomic layer deposition on silicon, which transform to polycrystalline Gd3Ga5O12 garnet (GGG) nanofilms after annealing above 900 degrees C. The Gd/Ga ratio approaching stoichiometry and Ga2O3 interlayers thinner than 1.5 nm are essential for the gallium garnet crystallization after annealing, while resulting in better film morphology in optoelectronic utilization, otherwise the Ga2O3 interlayers tend to segregate into micrometer grains on the surface. The impact-excitation of the doped Er3+ ions by hot electrons within the nanolaminate GGG:Er devices results in the characteristic Er3+ electroluminescence (EL) centered at 1530 nm, exhibiting the external quantum efficiency of 1.9% and decay lifetime of 1.27-2.47 ms. Stronger EL emissions and longer lifetime are obtained from the devices with the stoichiometry Gd/Ga ratio and better morphology. The electron conduction within the GGG matrix is ascribed to the trap-assisted tunneling mechanism above threshold electric field. This work further explores the deposition of nanolaminates with designed component and crystallinity, and the possibility of fabricating optoelectronic devices from Si-based garnet nanofilms.