Peiliang Chen

Enhancement of ZnO light emission via coupling with localized surface plasmon of Ag island film

Enhancement of the light emission of ZnO films was observed by coupling through localized surface plasmons. By sputtering Ag islands onto ZnO films, their band gap emission coming through the Ag island films was enhanced by threefolds, while the defect emission was quenched. The enhancement was found to be mainly dependent on the sputtering time of the Ag islands, which is related to the island size. Furthermore, the relative spectral position between the ZnO emission band and the localized surface plasmon resonance bands of Ag islands was found to be decisive for the enhancement or quenching of photoluminescence, indicating that the emission intensity of ZnO films can be controlled by the Ag island size and the localized surface plasmon resonance band position.

ULTRAVIOLET ELECTROLUMINESCENCE FROM ZNO/P-SI HETEROJUNCTIONS

Nominally undoped ZnO films were deposited by reactive sputtering on the lightly boron-doped (p−) and heavily boron-doped (p+) silicon substrates. The sputtered ZnO films were identified to be highly ⟨002⟩ oriented in crystallinity and n type in electrical conductivity. The current-voltage (I‐V) characteristics revealed that the ZnO∕p−‐Si heterojunction exhibited well-defined rectifying behavior while the ZnO∕p+‐Si heterojunction did not possess rectifying function. As for the ZnO∕p+‐Si heterojunction, it was electroluminescent to a certain extent in the visible region under sufficient forward bias with the positive voltage on the silicon substrate, while it emitted ultraviolet light characteristics of near-band-edge emission of ZnO under the reverse bias, which significantly dominated the visible emission. In contrast to the ZnO∕p+‐Si heterojunction, the ZnO∕p−‐Si heterojunction did not exhibit detectable electroluminescence (EL) under either forward or reverse bias. The I‐V characteristics and EL mechan...

Electrically pumped ZnO film ultraviolet random lasers on silicon substrate

The electrically pumped ultraviolet (UV) random lasing in c-axis oriented ZnO polycrystalline films has been demonstrated. For this demonstration, a metal-oxide-semiconductor structure of Au∕SiOx(x<2)∕ZnO film was fabricated on a silicon substrate. With ever-higher forward bias where the negative voltage was connected to the silicon substrate, the UV electroluminescence from such a ZnO-based device transformed from the spontaneous emission to the random lasing in the ZnO film. It is believed that the recurrent scattering and interference of the enough strong electroluminescent UV light in the in-plane random cavities formed in the ZnO film leads to electrically pumped UV random lasing.The electrically pumped ultraviolet (UV) random lasing in c-axis oriented ZnO polycrystalline films has been demonstrated. For this demonstration, a metal-oxide-semiconductor structure of Au∕SiOx(x<2)∕ZnO film was fabricated on a silicon substrate. With ever-higher forward bias where the negative voltage was connected to the silicon substrate, the UV electroluminescence from such a ZnO-based device transformed from the spontaneous emission to the random lasing in the ZnO film. It is believed that the recurrent scattering and interference of the enough strong electroluminescent UV light in the in-plane random cavities formed in the ZnO film leads to electrically pumped UV random lasing.

Fairly pure ultraviolet electroluminescence from ZnO-based light-emitting devices

Fairly pure ultraviolet (UV) electroluminescence (EL) was realized on a ZnO-based metal-insulator (SiOx,x⩽2)-semiconductor structure on a silicon substrate, which was easily fabricated by the reactive direct current sputtering and electron beam evaporation. The UV EL originated from the near-band-edge (NBE) emission of ZnO was achieved at room temperature when the device was under sufficient forward bias with the negative voltage applied on the silicon substrate. Moreover, the intermediate SiOx layer should be thick enough to confine the electrons in the conduction band of ZnO beneath the ZnO∕SiOx interface, which is critical for generation of NBE emission from ZnO.

Room temperature electrically pumped ultraviolet random lasing from ZnO nanorod arrays on Si

We report the electrically pumped ultraviolet random lasing from ZnO nanorod arrays on Si. Metal-insulator-semiconductor structures in a form of Au/SiO(2)/ZnO-nanorod-array were fabricated on Si. Such devices exhibit random lasing when the Au electrode is applied with a sufficiently high positive voltage. In this context, in the region adjacent to SiO(2)/ZnO-nanorod-array interface, stimulated emission from ZnO occurs due to population inversion and, moreover, light is scattered by the nanorods and SiO(2) films. Therefore, random lasing proceeds due to optical gain achieved by the stimulated emission and multiple scattering.

Electroluminescence of SnO2∕p-Si heterojunction

Polycrystalline SnO2 film of tetragonal rutile structure with an optical band gap of 3.9eV was formed by oxidation process at 1000°C on electron beam evaporation deposited Sn film. Room temperature electroluminescence from the SnO2∕p-Si heterojunction was observed at 590nm when the device was under sufficient forward bias with the positive voltage applied on the p-Si substrate. It is proposed that the electrons in the conduction band of SnO2 relax to defect states that resulted from the dangling bonds at the surface of the small SnO2 grains and then radiatively recombine with the holes in the valence band.

Electrophotoluminescence of ZnO film

The electric-field-controlled photoluminescence (PL), i.e., electrophotoluminescence (EPL) of ZnO film has been investigated via a ZnO-based metal-insulator-semiconductor (MIS) structure on a silicon substrate applied with different biases. Compared with the PL of ZnO film in the case where there is no bias on the MIS structure, the positive bias with negative voltage applied on silicon substrate significantly enhances the near-band-edge ultraviolet emission while suppressing the deep-level-related visible emissions, whereas the negative bias hardly changes the PL of ZnO film. The mechanism for EPL of ZnO film is proposed in terms of the electric-field effect on the bending of energy bands of ZnO.

347nm ultraviolet electroluminescence from MgxZn1−xO-based light emitting devices

347nm ultraviolet (UV) electroluminescence (EL) originated from the near-band-edge emission of MgxZn1−xO was realized on a MgxZn1−xO-based metal-insulator (SiO2)-semiconductor (MIS) structure on a silicon substrate. Compared with the EL performance of the MgxZn1−xO∕n+-Si heterojunction, the MgxZn1−xO-based MIS structure exhibited much stronger and purer UV emission while much weaker visible emissions. This is ascribed to the carrier accumulation beneath the MgxZn1−xO∕SiO2 interface as the MIS structure is under forward bias, which significantly increases the radiative interband recombination rate and therefore the UV emission from MgxZn1−xO.

Photoluminescence of Tb3+ doped SiNx films grown by plasma-enhanced chemical vapor deposition

Room temperature photoluminescence (PL) properties of the Tb3+ ion implanted nonstoichiometric silicon nitride (Tb3+:SiNx) and silicon dioxide (Tb3+:SiOx) were studied. The films were deposited by plasma-enhanced chemical vapor deposition and then annealed at different temperatures for 1h in flowing N2 before or after the implantation. Results show that there are four intense PL peaks due to the intra-4f transitions of Tb3+ in the wavelength from 470to625nm for both kinds of films. Moreover, after postannealing at 1000°C, the integrated PL intensity of Tb3+:SiNx is much higher than that of Tb3+:SiOx. The energy transfer from the defect related energy levels to the Tb3+ ions will enhance the D45→Fk7 (k=3–6) luminescence of Tb3+ ions.

Electrically pumped ultraviolet random lasing from ZnO-based metal-insulator-semiconductor devices: Dependence on carrier transport

The electrically pumped ultraviolet (UV) random lasing and carrier transport of ZnO-based metal-insulator-semiconductor (MIS) structures on Si substrates have been systematically investigated. With the increase of positive bias voltage on the gates of the MIS devices, the current-voltage (I-V) characteristics manifest a normal curved I-V region where the current increases with the bias, followed by a negative differential resistance (NDR) region. Moreover, the UV electroluminescence from the devices in the normal region is transformed from spontaneous emission into increasingly intensive random lasing; while, that in the NDR region is transformed from random lasing into very weak spontaneous emission. The reason for the effect of NDR on the random lasing from the devices has been tentatively explored.