Z. H. Cen

Realization of n-Zn1−xMgxO∕i-ZnO∕SiOx∕n+-Si heterostructured n-i-n light-emitting diodes by low-cost ultrasonic spray pyrolysis

n-Zn1−xMgxO∕i-ZnO∕SiOx∕n+-Si heterostructured light-emitting diodes have been demonstrated by low-cost ultrasonic spray pyrolysis. The current-voltage measurement shows typical characteristics of a back-to-back diode due to the double Schottky barriers induced by the SiOx layer. Blue electroluminescence peaking at 460nm was observed at room temperature when a positive bias of ∼4V was applied on the Si substrate. The electroluminescence is suggested to be dominated by the donor-acceptor pair recombination in the i-ZnO layer, where the holes were injected from the valence band of Si into the acceptor level of i-ZnO.

Electrically tunable white-color electroluminescence from Si-implanted silicon nitride thin film

Visible electroluminescence (EL) with two composite bands, i.e., a violet band and a green-yellow band has been observed from Si-implanted silicon nitride thin films. By varying the intensity ratio of the two composite EL bands in terms of the injection current, strong white-color EL can be achieved at certain injection currents (e.g., ~265 mA/cm(2)). The observed transition in EL color from violet to white under different injection conditions is studied based on the understanding that the violet band is originated from silicon nitride matrix while the green-yellow band is related to the implanted Si. The Si-implanted silicon nitride thin film offers the possibility of electrically tunable white-light Si-based light emitters.

Annealing effect on the optical properties of implanted silicon in a silicon nitride matrix

Optical properties of implanted Si in a silicon nitride (Si3N4) thin film have been determined with spectroscopic ellipsometry based on the Tauc–Lorentz (TL) model and the Bruggeman effective medium approximation. It is shown that the suppressed dielectric functions of the implanted Si are dominated by the energy transitions related to the critical point E2. The effect of thermal annealing on the dielectric functions of the implanted Si has been investigated. The analysis of the dielectric functions based on the evolution of the TL parameters can provide an insight into the structural changes in the implanted Si embedded in the Si3N4 matrix caused by the annealing.

Evolution of electroluminescence from multiple Si-implanted silicon nitride films with thermal annealing

Influence of thermal annealing on electroluminescence (EL) from multiple-Si-implanted silicon nitride films has been investigated. A reduced injection current and an enhanced EL intensity have been obtained simultaneously by increasing the annealing temperature, which results in a higher EL quantum efficiency. In addition, four emission bands are identified, and their peak energies, intensities, and full widths at half maxima are found to change with annealing temperature. A model is proposed to illustrate the carrier transport, the mechanisms of the four emission bands, and the evolution of the EL bands with annealing as well. The two major bands and the minor ultraviolet band are explained in terms of the recombination of the injected electrons in either the silicon dangling-bond (≡Si0) states or the nitride conduction band with the injected holes in either the band tail states above the nitride valence band or the valence band itself, while the minor near infrared band is attributed to the Si nanocryst...

Split of surface plasmon resonance of gold nanoparticles on silicon substrate: a study of dielectric functions

The split of surface plasmon resonance of self-assembled gold nanoparticles on Si substrate is observed from the dielectric functions of the nanoparticles. The split plasmon resonances are modeled with two Lorentz oscillators: one oscillator at ~1 eV models the polarization parallel to the substrate while the other at ~2 eV represents the polarization perpendicular to the substrate. Both parallel and perpendicular resonances are red-shifted when the nanoparticle size increases. The red shifts in both resonances are explained by the image charge effect of the Si substrate.

Relationship Between Current Transport and Electroluminescence in

Relationship between current transport and electroluminescence (EL) in the system of excess Si distributed in SiO2 thin films synthesized with low-energy ion implantation has been examined. A linear relationship is found, and both of them follow a power law and are determined by the concentration and distribution of the excess Si in the oxide films. With the knowledge of the dependence of the transport on the concentration and distribution of the excess Si, one can predict the effect of the implantation recipe on the EL intensity.

\hbox{Si}^{+}

Room-temperature random lasing is achieved from an n-AlN/p-GaN heterojunction. The highly disordered n-AlN layer, which was deposited on p-GaN:Mg layer via radio frequency magnetron sputtering, acts as a scattering medium to sustain coherent optical feedback. The p-GaN:Mg layer grown on sapphire provides optical amplification to the scattered light propagating along the heterojunction. Hence, lasing peaks of line width less than 0.4 nm are emerged from the emission spectra at round 370 nm for the heterojunction under forward bias larger than 5.1 V. Lasing characteristics of the heterojunction are in agreement with the behavior of random lasers.

-Implanted

In this letter, Ni-rich NiO thin film is deposited on p-type Si substrate by dc magnetron sputtering to form a metal-insulator-semiconductor structure. The charge trapping in the Ni nanocrystals (nc-Ni) embedded in NiO matrix induces a flatband voltage shift and capacitance modulation, which could be used for memory applications. The charging of nc-Ni depends on the voltage polarity, as well as the charging time and magnitude of gate voltage. The capacitance modulation can be described by an equivalent circuit model.

\hbox{SiO}_{2}

Al nanocrystal (nc-Al)/Al2O3 nanocomposite thin films were synthesized by radio-frequency magnetron sputtering. The static dielectric constant (er) of the nanocomposite thin films was determined by the capacitance-voltage reconstruction technique which was able to correct for the influence of high current conduction in the thin films. In contrast to pure Al2O3, the nanocomposite has a much higher er and its er exhibits strong temperature dependence also. The higher er is attributed to the dipole effect of the Al–O dangling bonds due to the presence of nc-Al in the Al2O3 matrix. However, the dipole effect degrades at a higher temperature, which explains the observed decrease in er with increasing temperature.

Thin Films

Anomalous capacitance-voltage (C-V) characteristics of Al/Al-rich Al2O3/p-Si capacitors have been observed. The measured C-V curves exhibit rolloffs and frequency dispersion in the accumulation region and voltage stresses cause both horizontal and vertical shifts of the C-V curves. These anomalous behaviors are mainly due to the large current conduction and the charge trapping in the Al-rich Al2O3 layer. The anomalous C-V characteristics have been reconstructed based on a four-element circuit model. With the reconstructed C-V curves, the capacitance of the Al-rich Al2O3 layer and the charging-induced flatband voltage shift can be determined.