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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Silicon nanocrystals (Si-ncs) are excellent candidates for the development of optoelectronic devices. Nevertheless, different strategies are still necessary to enhance their photo and electroluminescent properties by controlling their structural and compositional properties. In this work, the effect of the stoichiometry and structure on the optical properties of silicon rich oxide (SRO) films in a multilayered (ML) structure is studied. SRO MLs with silicon excess gradually increased towards the top and bottom and towards the center of the ML produced through the variation of the stoichiometry in each SRO layer were fabricated and confirmed by X-ray photoelectron spectroscopy. Si-ncs with three main sizes were observed by a transmission electron microscope, in agreement with the stoichiometric profile of each SRO layer. The presence of the three sized Si-ncs and some oxygen related defects enhances intense violet/blue and red photoluminescence (PL) bands. The SRO MLs were super-enriched with additional excess silicon by Si+ implantation, which enhanced the PL intensity. Oxygen-related defects and small Si-ncs (<2 nm) are mostly generated during ion implantation enhancing the violet/blue band to become comparable to the red band. The structural, compositional, and luminescent characteristics of the multilayers are the result of the contribution of the individual characteristics of each layer.

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Luminescent silicon-rich dielectric materials have been under intensive research due to their potential applications in optoelectronic devices. Silicon-rich nitride (SRN) and silicon-rich oxide (SRO) ilms have been mostly studied because of their high luminescence and compatibility with the silicon-based technology. In this chapter, the luminescent characteristics of SRN and SRO ilms deposited by low-pressure chemical vapor deposition are reviewed and discussed. SRN and SRO ilms, which exhibit the strongest photoluminescence (PL), were chosen to analyze their electrical and electroluminescent (EL) properties, including SRN/SRO bilayers. Light emiting capacitors (LECs) were fabricated with the SRN, SRO, and SRN/SRO ilms as the dielectric layer. SRN-LECs emit broad EL spectra where the maximum emission peak blueshifts when the polarity is changed. On the other hand, SRO-LECs with low silicon content (~39 at.%) exhibit a resistive switching (RS) behavior from a high conduction state to a low conduction state, which produce a long spectrum blueshift (~227 nm) between the EL and PL emission. When the silicon content increases, red emission is observed at both EL and PL spectra. The RS behavior is also observed in all SRN/SRO-LECs enhancing an intense ultraviolet EL. The carrier transport in all LECs is analyzed to understand their EL mechanism.