Enhancement of orange-yellow electroluminescence extraction from SiNx light-emitting devices by silver nanostructures.

A multilayer structure of ITO/SiNx/Ag/p/p(+)-Si/Au was fabricated to improve the extraction of the orange-yellow electroluminescence from SiNx-based light-emitting devices (LEDs), and an about 5 times enhancement of external quantum efficiency (EQE) was obtained. This improved light-extraction is mainly originated from the increase of root-mean-square roughness of ITO electrode and reflectivity at longer wavelength via the addition of elongated Ag nanostructures. For the structure with the dipolar resonance peak of Ag nanostructures far from the emission wavelength of SiNx matrix, the increased surface roughness of ITO electrode has a dominant effect on the improvement of the light-extraction. Moreover, the decrease of on-series resistance by the addition of Ag nanostructures due to its enhanced local electrical fields also has a benignant contribution to the improved EQE. Our work may provide a promising approach to improve the EQE of LEDs, which is not limited to SiNx matrix.