Electroluminescence of silicon-rich silicon nitride light-emitting devices

Non-stoichiometric silicon nitride films with different excess Si concentrations were deposited by plasma-enhanced chemical vapor deposition (PECVD) under different NH₃/SiH₄ gas flow ratios. Room-temperature electroluminescence (EL) was observed from the films. And the peak of EL spectra remains at 600 nm, irrespective of the increase of the Si concentrations. It was found that at high electric fields the electrons were injected into the SRSN film via Fowler-Nordheim tunneling and trap assisted tunneling, while at low electric fields the electrons were injected via Poole-Frenkel conduction. The observed EL can be attributed to the relaxation of injected carriers down the lower defect states before recombination due to their longer recombination lifetime.