Negative differential resistance and resistive switching behavior in broad-spectrum electroluminescent devices based on Si3N4/Si thin films deposited by E-beam

This work focuses on the study of the electro-optical properties of Si3N4/Si multilayer (ML) structures deposited by electron beam evaporation and thermally annealed to induce the silicon nanocrystals (Si-ncs) formation. The increase in band gap and the changes of photoluminescence spectra indicate a phase change of the material after thermal annealing (TA). However, the TA favored the diffusion of Si from Si-layers throughout Si3N4 layers losing the ML structure. This Si diffusion produced the formation of Si-nanopyramids at the ML/Si substrate interface as well as Si-ncs, as corroborated by transmission electron microscopy. Current density vs. electric field (E) curves showed the presence of a negative differential resistance (NDR) which is related to the annihilation of preferential conductive filaments (CFs) created by the Si-nanopyramids with Si-ncs. As the E exceeds -1 MV/cm, a resistive switching (RS) from a high resistance to low resistance state (LRS) was observed, where the ON/OFF ratio increases as the area of the devices decreases. In addition, a broad-spectrum electroluminescence (EL, white light) was obtained during the RS phenomenon reaching optical powers up to 3 nW. Once the LRS is reached, the E required to obtain EL reduces up to 28.7 %, thus improving the devices performance.