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Organic light emitting diodes are fabricated based on metal-free phthalocyanine (H2Pc) doped into tris-(8-hydroxyquinoline) aluminium (Alq3). The device structure is ITO/NPB (30 nm)/Alq3: H2Pc(30 nm)/BCP(20 nm)/Alq3(20 nm)/Al. In the light-emitting layers, H2Pc concentrations are varied from 0 wt% to 100 wt%. The emissions around 708 nm and 800 nm appear at low concentrations, while the emissions around 910 nm and 930 nm appear at high concentrations. The emissions around 708 nm and 800 nm are from H2Pc monomers. The emissions around 910 nm and 930 nm are from H2Pc aggregates. The dominant mechanism in the doped devices is direct charge trapping.

We fabricate organic thin films using the copolymer of methyl methacrylate and glycidyl methacrylate (PMMA-GMA) as a gate dielectric with a simple top-contact structure. Copper phthalocyanine (CuPc) TFTs are fabricated and the influences of annealing on the performance are studied. The mobilities increase from 2.5×103 cm2/Vs to 4.2×103 cm2/Vs and threshold voltages decrease from -18 V to -10 V after annealing. The good performances of the devices approach those obtained with inorganic gate dielectric materials such as silicon dioxide under the same technical conditions. It is fully proven that PMMA-GMA is a competitive candidate as an excellent gate insulation layer.

ZnO films were deposited by low-pressure metal organic chemical vapour deposition on epi-GaN/Al2O3 films and c-Al2O3 substrates. The structure and optical properties of the ZnO/GaN/Al2O3 and ZnO/Al2O3 films have been investigated to determine the differences between the two substrates. ZnO films on GaN/Al2O3 show very strong emission features associated with exciton transitions, just as ZnO films on Al2O3, while the crystalline structural qualities for ZnO films on GaN/Al2O3 are much better than those for ZnO films directly grown on Al2O3 substrates. Zn and O elements in the deposited ZnO/GaN/Al2O3 and ZnO/Al2O3 films are investigated and compared by x-ray photoelectron spectroscopy. According to the statistical results, the Zn/O ratio changes from Zn-rich for ZnO/Al2O3 films to O-rich for ZnO/GaN/Al2O3 films.

The axis of the integrated superluminescent light source was tilted with respect to the output facet normal for lasing suppression. A new phenomenon (lasing suppression) was observed in the tilted integrated device. Three new schemes were proposed and demonstrated further to suppress the lasing by analysing the reason for lasing in the tilted structure. The lasing was suppressed successfully at high pumping levels, and high superluminescent powers (more than 300 mW) were obtained at a pulsed condition with the spectral full width at half maximum of 25-30 nm.

ZnO homojunction light-emitting diodes are fabricated on Si(100) substrates by plasma assisted metal organic chemical vapour deposition. A p-type layer of nitrogen-doped ZnO film is formed using radical N2O as the acceptor precursor. The n-type ZnO layer is composed of un-doped ZnO film. The device exhibits desirable rectifying behaviour with a turn-on voltage of 3.3V and a reverse breakdown voltage higher than 6V. Distinct electroluminescence emissions centred at 395 nm and 490 nm are detected from this device at forward current higher than 20 mA at room temperature.

The N–Ag codoped ZnO films are deposited on quartz glass substrates by ultrasonic spray pyrolysis technology. The results indicate that the p-type conductivity in ZnO films is greatly enhanced by the double acceptor codoping of N and Ag compared with that of Ag- and N-monodoped ZnO films, and the N–Ag codoped low-resistivity p-type ZnO films with the resistivity of 1.05 Q-cm, relatively high carrier concentration of 5.43 × 1017 cm-3, and Hall mobility of 10.09 cm2 V-1s-1 are obtained under optimized conditions. This achievement confirms that p-type ZnO with acceptable properties for optoelectronic applications could be realized by simultaneous codoping with two potential acceptors.

For ZnO/diamond structured surface acoustic wave (SAW) filters, performance is sensitively dependent on the quality of the ZnO films. In this paper, we prepare highly-oriented and fine grained polycrystalline ZnO thin films with excellent surface smoothness on the smooth nucleation surfaces of freestanding CVD diamond films by metal organic chemical vapour deposition (MOCVD). The properties of the ZnO films are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectrum. The influences of the deposition conditions on the quality of ZnO films are discussed briefly. ZnO/freestanding thick-diamond-film layered SAW devices with high response frequencies are expected to be developed.

A novel type of integrated InGaAsP superluminescent light source was fabricated based on the tilted ridge-waveguide structure with selective-area quantum well (QW) intermixing. The bandgap structure along the length of the device was modified by impurity free vacancy diffusion QW intermixing. The spectral width was broadened from the 16 nm of the normal devices to 37 nm of the QW intermixing enhanced devices at the same output power level. High superluminescent power (210 mW) was obtained under pulsed conditions with a spectral width of 37 nm.

ZnO thin films with the c-axis orientation on the (0001) sapphire substrate were grown by metal-organic chemical vapour deposition. It was demonstrated that the VI/II precursor flow-rate ratio can influence strongly on the structure and opto-electrical properties. With the increasing VI/II ratio of 130:1, the full width at half maximum of (0002) peak in x-ray diffraction is only 0.184°, the near-band-edge emission enhances remarkably and the intensity ratio of the near-band-edge emission to the deep-level emission reaches 237:1 in the photoluminescence spectrum. At the same time, the resistivity and mobility increases to 3.28×102Ωcm and 25.3 cm2V-1s-1. These facts indicates that the quality of the ZnO thin films could be improved by increasing the VI/II flow rate ratio during the growth.

Novel structure GaAs/InGaAs/AlGaAs pseudomorphic modulation-doped field-effect transistors (MODFETs) with a buried p-i-n dipole layer and a 200 nm buffer layer have been fabricated. According to the calculation, the dipole buried layer not only results in the very thin buffer layer required, but also enhances the density of two-dimensional electron gas. The measured transconductances of these MODFETs, with a gate length of 2 µm and a drain-source spacing of 5 µm, are as high as 320 mS/mm and the measured maximum drain currents of the typical devices are higher than 500 mA/mm.

ZnO thin films have been grown on C-plane sapphire substrates by plasma-enhanced metal-organic chemical vapour deposition. The samples are then annealed at a higher temperature. The resistivity, concentration of electron, mobility and optically pumped threshold of both as-grown and annealed films are investigated. Furthermore, their structural and optical properties are also examined with x-ray diffraction, emission spectra and optical transmission spectra. The results indicate that the quality of ZnO thin films can be improved by annealing.

Room temperature photoluminescence (PL) spectra of InAs self-assembled quantum dots (QDs) deposited on a GaAs/InP and InP substrate are investigated. From the PL spectra, we find that the peak position of InAs QDs appears redshift from 0.795 to 0.785 eV after we insert a thin tensile GaAs layer between InAs QD layer and InP buffer layer. In order to explain this phenomenon in theory, we examine the strain tensor in InAs quantum dots by using a valence force field model and use a five-band kp formalism to obtain the electronic structure. The calculated results show that the ground transition energy decreases from 0.789 to 0.780 eV when the thin GaAs layer is inserted. Therefore, the PL peak position should appear redshift as shown in the experiment.

p-ZnO:As is prepared by the GaAs interlayer doping method. The potential applications of p-ZnO:As are evaluated by applying it into the construction of a p-ZnO/n-GaN heterojunction, though its hall, electrochemical capacitance-voltage and photoluminescence results show a hole concentration at the level of ~1017 cm−3 and a good optical quality. Ultraviolet random lasing is detected from the studied device under forward bias. Specific lasing modes are confirmed to originate from p-ZnO:As by further introducing the p-ZnO/MgO/n-GaN heterostructure. The resulting random lasing phenomena demonstrate the promising prospects in device application of p-ZnO:As fabricated by using our methods.

Reproducible p-type phosphorus-doped ZnO (p-ZnO:P) films are prepared on semi-insulating InP substrates by metal-organic chemical vapour deposition technology. The electrical properties of these films show a hole concentration of 9.02 × 10 17 cm−3, a mobility of 1.05 cm2/Vs, and a resistivity of 6.6 Ω · cm. Obvious acceptor-bound-exciton-related emission and P-induced zinc vacancy (VZn) emission are observed by low-temperature photoluminescence spectra of the films, and the acceptor binding energy is estimated to be about 125 meV. The local chemical bonding environments of the phosphorus atoms in the ZnO are also identified by x-ray photoelectron spectra. Our results show direct experimental evidence that PZn–2VZn shallow acceptor complex most likely contributes to the p-type conductivity of ZnO:P films.