In this paper, we study the structural, optical and electro-optical properties of silicon rich oxide (SRO) films, with 6.2 (SRO₃₀) and 7.3 at.% (SRO₂₀) of silicon excess thermally annealed at different temperatures and used as an active layer in light emitting capacitors (LECs). A typical photoluminescence (PL) red-shift is observed as the silicon content and annealing temperature are increased. Nevertheless, when SRO₃₀ films are used in LECs, a resistance switching (RS) behavior from a high current state (HCS) to a low conduction state (LCS) is observed, enhancing the intense blue electroluminescence (EL). This RS produces a long spectral blue-shift (∼227 nm) between the EL and PL band, and it is related to structural defects created by a high current flow through preferential conductive paths breaking off Si-Si bonds from very small silicon nanoparticles (Si-nps) (Eδ (Si ↑ Si ≡ Si) centers). LECs with SRO₂₀ films do not present the RS behavior and only exhibit a slight shift between PL and EL, both in red spectra. The carrier transport in these LEC devices is analyzed as being trap assisted tunnelling and Poole-Frenkel through a quasi 'continuum' of defect traps and quantum dots for the conduction mechanism in SRO₃₀ and SRO₂₀ films, respectively. The results prove the feasibility of obtaining light emitting devices by using simple panel structures with Si-nps embedded in the dielectric layer.

An analysis of the luminescent center and its effect on the optical, electrical and electro-optical properties of silicon rich silicon nitride (SRN) films deposited by low pressure chemical vapor deposition is reported. As-deposited SRN films emit a broad photoluminescence (PL) spectrum in the visible range where the maximum peak shifts from ∼490 to ∼590 nm as the silicon excess increases. After thermal annealing, a PL blue-shift is observed and it is ascribed to a compositional-dependent change in the concentration of defect states within the films. A correlation between the PL peak energy with the optical band-gap indicates that the luminescence is related to the band tail carrier recombination in the SRN films. Light emitting capacitors (LECs) based on fluor-doped tin oxide SnO 2 :F (FTO)/SRN active layer/n-Si substrate emit a broad electroluminescent spectra where the maximum emission peak blue-shifts when the polarity is changed from reverse to forward bias. In the reverse bias, the electroluminescence (EL) is related to the states of valence band tail and Si dangling bonds (K 0 centers), while in the forward bias the EL is originated from electronic transitions from the conduction band minimum to K 0 centers. A model based on the trap assisted tunneling carrier transport is correlated with the proposed EL radiative recombination process in the FTO/SRN/n-Si structures. A discussion of the differences between the PL and EL spectra is reported. The results open new alternatives toward the development of Si-based light emitters where two different EL spectra can be obtained changing the polarity.

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