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Abstract: Temperature-dependent characteristics of ZnO Schottky diodes with Iridium (Ir) contact electrodes were investigated. Using Norde model, it was found that the effectively Schottky barrier heights of Ir on n-ZnO were around 0.837, 0.829, 0.801, 0.750 and 0.719eV when measured at 25, 30, 50, 100 and 150°C, respectively. Using Cheung’s method, it was found that Schottky barrier heights between Ir and the n-ZnO were 0.824, 0.823, 0.789, 0.743 and 0.740eV when measured at 25, 30, 50, 100 and 150°C, respectively. The large Schottky barrier heights suggest that Ir is a potentially useful material for ZnO-based ultraviolet Schottky barrier photodetectors and metal–semiconductor-metal photodetectors. [Copyright &y& Elsevier]

Abstract: Amorphous-Si:H/SiO2 multilayers were fabricated on various substrates by alternatively changing the ultra-thin amorphous Si films deposition and in situ plasma oxidation processes. Uniform silicon nanodots with controllable size were formed by combining the rapid thermal annealing and furnace annealing techniques as revealed by cross-sectional transmission electron microscopy. Light-emitting diodes based on Al/(nc-Si/SiO2) multilayers/Si substrate/Al structures were fabricated and electrically driven luminescence was demonstrated at room temperature. It was found that the substrate had a significant impact on the carrier injection efficiency and the luminescence intensity. The turn-on voltages of the device on p+-Si and p-Si substrate were 2.2 and 8V, respectively. Meanwhile, electroluminescence intensity of the device on p+-Si substrate was five times higher than that on p-Si substrate under the same power supply, which means the heavily doped substrate is helpful for enhancing the carrier injection efficiency. [Copyright &y& Elsevier]

Abstract: Phosphorous-doped and boron-doped amorphous Si thin films as well as amorphous SiO2/Si/ SiO2 sandwiched structures were prepared in a plasma enhanced chemical vapor deposition system. Then, the p–i–n structures containing nano-crystalline Si/ SiO2 sandwiched structures as the intrinsic layer were prepared in situ followed by thermal annealing. Electroluminescence spectra were measured at room temperature under forward bias, and it is found that the electroluminescence intensity is strongly influenced by the types of substrate. The turn-on voltages can be reduced to 3 V for samples prepared on heavily doped p-type Si (p+-Si) substrates and the corresponding electroluminescence intensity is more than two orders of magnitude stronger than that on lightly doped p-type Si (p-Si) and ITO glass substrates. The improvements of light emission can be ascribed to enhanced hole injection and the consequent recombination of electron–hole pairs in the luminescent nanocrystalline Si/ SiO2 system. [Copyright &y& Elsevier]

Abstract: In this paper, we report the detailed RF and microwave characterization of planar interdigitated (PID) varactors fabricated on Ba0.6Sr0.4TiO3/Ba0.4Sr0.6TiO3 double-layer thin film deposited by pulsed laser deposition (PLD) on the MgO substrate. In particular, the dependences of the PID varactors’ performance (i.e. tunability and quality factor) on the physical design parameters, such as finger spacing and width, are investigated. It was found that both the capacitance and tunability of the PID varactors show strong dependence upon the finger spacing. This dependence can be divided into the linear part (when the finger spacing is large) and non-linear part (when the finger spacing is small). The finger width also affects the capacitance and tunability, although to a much lesser degree. The relations between the physical design parameters and the varactors’ performance provide useful scaling information for accurate and optimized varactor design. The relation between the quality-factor (Q-factor) and the bias voltage is also revealed and explained using an equivalent circuit model. [Copyright &y& Elsevier]

Abstract: One-dimensional all solid-state microcavities (MCs) based on amorphous silicon-nitride films have been fabricated in plasma enhanced chemical vapor deposition system. Spectral narrowing and enhancement of room temperature photoluminescence due to the modulation effect in MCs were observed. The modulated luminescence behavior in MCs was further studied by angular dependent luminescence measurements. The distinct cavity mode energy shifting and variation of luminescence intensity with the detect angle were observed, which reflected the directionality of emission properties in the planar MCs. The deviation of the measured angular dependent energy shifting from the theory prediction was discussed as being related to the structure properties of the MCs. [Copyright &y& Elsevier]

Abstract: We report the fabrication of ZnO-based metal–insulator–semiconductor (MIS) and metal–semiconductor–metal (MSM) photodetectors. With 5V applied bias, it was found that photocurrent to dark current contrast ratios of the ZnO MSM and MIS photodetectors were 2.9×102 and 3.2×104, respectively. It was also found that measured responsivities were 0.089 and 0.0083A/W for the ZnO MSM and MIS photodetectors, respectively, when the incident light wavelength was 370nm. Furthermore, it was found that ultraviolet (UV) to visible rejection ratios for the fabricated ZnO MSM and MIS photodetectors were 2.4×102 and 3.8×103, respectively. [Copyright &y& Elsevier]

Abstract: GaN films were grown on patterned-Si(111) substrates by metal organic chemical vapor deposition (MOCVD). Arrays of rectangular stripes and squares, with a 3.5-μm height and different lateral dimensions were patterned and etched on Si substrates using inductively coupled plasma reactive ion etching. A low temperature 24-nm-thick AlN (grown at 720°C) was used as the seed layer for growing GaN films of 0.3- to 2-μm thick. For ridges wider than 2μm, crack-free flat-top GaN films were obtained with a surface roughness of ∼0.7nm. Localized Raman spectroscopy was conducted to study the stress distribution in the GaN films on Si ridges and squares. Substantial stress relaxation was observed in GaN on patterned Si area. The crystalline microstructure of GaN films was characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and atomic force microscopy. [Copyright &y& Elsevier]

We employ the method of laser interference crystallization carried out by using a phase-shifting grating mask (PSGM) to fabricate nanocrystal Si with a two-dimensional (2D) patterned distribution within a 10 nm thick a-Si:H single layer grown on a SiO2/Si or fused quartz substrate by the plasma-enhanced chemical vapor deposition technique. The results of atomic force microscopy, cross-section transmission electron microscopy and high resolution transmission electron microscopy show that Si nano-crystallites are formed and selectively located in the discal regions within the initial a-Si:H layer, which are patterned with the same 2D periodicity of 2.0 μm as the PSGM. The diameter of each discal region is about 250 nm and the height is about the same as the thickness of a-Si:H layers. These results demonstrate that the present method is promising for the fabrication of various patterned nc-Si arrays for device applications simply by changing the geometry of the mask. [Copyright &y& Elsevier]

Abstract: The authors report the fabrication of ZnO-based metal-oxide-semiconductor field effect transistors (MOSFETs) with a high quality SiO2 gate dielectric by photochemical vapor deposition (photo-CVD) on a sapphire substrate. Compared with ZnO-based metal-semiconductor FETs (MESFETs), it was found that the gate leakage current was decreased to more than two orders of magnitude by inserting the photo-CVD SiO2 gate dielectric between ZnO and gate metal. Besides, it was also found that the fabricated ZnO MOSFETs can achieve normal operation of FET, even operated at 150°C. This could be attributed to the high quality of photo-CVD SiO2 layer. With a 2μm gate length, the saturated I ds and maximum transconductance (G m ) were 61.1mA/mm and 10.2mS/mm for ZnO-based MOSFETs measured at room temperature, while 45.7mA/mm and 7.67mS/mm for that measured at 150°C, respectively. [ABSTRACT FROM AUTHOR]