Visible electroluminescence (EL) has been reported from semitransparent Au film/extra thin Si-rich silicon oxide film/p-Si diodes at room temperature. The Si-rich silicon oxide films, with thickness of about 40 Å, were grown using the magnetron sputtering technique. At forward bias of 4 V, EL spectra with peak energy of 1.9 eV and full width at half maximum of 0.5 eV can be observed from diodes with such extra thin Si-rich oxide films having not been annealed. EL peak energy shows a small red shift under low forward bias but does not shift again when increasing the bias further. Annealing at 800 °C, EL spectra widen and show several shoulders at about 1.5, 2.2, and 2.4 eV, and the EL peak energy shows blue shift with increasing forward bias. These results are shown to be consistent with light emission at several types of luminescence centers in the Si-rich silicon oxide films.

We report a study on gamma irradiated porous Si. The electron paramagnetic resonance study on porous Si irradiated by gamma rays shows that the observed signals come from an intrinsic defect, a Si dangling bond, at the interface of Si/SiOx in porous Si. The photoluminescence measurements show that the gamma irradiation not only increases the intensity of the photoluminescence but also greatly improves its stability. The spectra of the Fourier transform infrared absorption show that the gamma irradiation is an effective method for accelerating oxidation of porous Si. All experimental results can be explained by the increase of the oxidation layer thickness which decreases the nonradiative recombination probability of electron-hole pairs.

We have systematically studied the evolution of the optical properties of free-standing porous silicon (PS) films during thermal oxidation at 200 °C in air by measuring of the PL, IR, optical absorption and Raman scattering spectra. After thermal oxidation for 200 h, the PL peak energies of free-standing PS films focus on a small energy range centered around 1.61 eV. In this case, a conclusion that the sizes of nanometer silicon particles (NSPs) decrease with increasing time of thermal oxidation is obtained by theoretical fitting for Raman scattering spectra. The evolution of transmission curve is quite complicated (which redshifts first and then blueshifts during thermal oxidation), and can be explained by a model including the quantum confinement effect in the NSPs and the influence of the Si–O bonds on the surface of NSPs. Meanwhile, no focusing of the optical absorption edge of free-standing PS films is found. Experimental results clearly indicate that there is no simple correlation between the PL energies and the sizes or the energy gaps of NSPs. These results can be explained by the quantum confinement/luminescence center model.

Articles you may be interested inRoom-temperature 1.54 μm electroluminescence from Er-doped silicon-rich silicon oxide films deposited on n + -Si substrates by magnetron sputtering Electroluminescence from semitransparent Au film/ SiO 2 /(amorphous-Si/SiO 2 ) superlattice/ p-Si structure Mechanism and performance of forward and reverse bias electroluminescence at 1.54 μm from Er-doped Si diodes

Nanometer SiO2/nanometer Si/nanometer SiO2 double-barrier (DB) structures, with Si layers having eleven different thicknesses from 2 to 4 nm, were deposited on n+–Si substrates using the magnetron sputtering technique. Strong electroluminescence (EL) from semitransparent Au film/DB/n+–Si structure was observed under reverse bias in a range of about 5–7 V. It is found that every EL spectrum of the structure can be decomposed into two Gaussian bands with peaks at around 1.85 and 2.25 eV, and their intensities and current swing synchronously with increasing nanometer Si layer thickness; the periodic length of swing is consistent with half of the de Broglie wavelength of the carriers. A comparison was carried out between EL from the Au/DB/n+–Si structure under reverse bias and that from the Au/DB/p–Si structure under forward bias reported previously.