Effect of the structure on luminescent characteristics of SRO-based light emitting capacitors.

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.

DC and AC electroluminescence in silicon nanoparticles embedded in silicon-rich oxide films.

Electroluminescent properties of silicon-rich oxide (SRO) films were studied using metal oxide semiconductor-(MOS)-like devices. Thin SRO films with 4 at.% of silicon excess were deposited by low pressure chemical vapour deposition followed by a thermal annealing at 1100 degrees C. Intense continuous visible and infrared luminescence has been observed when devices are reversely and forwardly bias, respectively. After an electrical stress, the continuous electroluminescence (EL) is quenched but devices show strong field-effect EL with pulsed polarization. A model based on conductive paths--across the SRO film--has been proposed to explain the EL behaviour in these devices.