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The lubrication needs of wind turbines vary with the operating conditions. To provide a dynamic lubrication scheme for wind turbines under variable conditions, this paper designs a dynamically adjustable lubrication scheme through parallel control of multiple influencing factors. Based on mid- and long-term loads, the proposed scheme fully considers the influence of various sudden changes in addition to slowly changing factors like load, operating hours, and speed, such as to dynamically adjust the injection flow as per the specific operating condition of the turbine. The ideal lubrication effect was tracked through the adjustment of the injection flow or injection time, and used to determine the optimal dynamic lubrication control strategy during turbine operation. The proposed control strategy overcomes the defects of the traditional fixed-time fixed-flow lubrication approach, and provides reasonable on-demand lubrication schemes for wind turbines in different operating conditions. The on-demand injection of lubricant prevents under- or over-lubrication, reduces the rate of mechanical failure, and extends the service life of wind turbines. Suffice it to say that the proposed control strategy can lower power generation cost and save energy, making wind turbines more profitable.

All-solid-state lithium-based batteries with inorganic solid electrolytes are considered a viable option for electrochemical energy storage applications. However, the application of lithium metal is hindered by issues associated with the growth of mossy and dendritic Li morphologies upon prolonged cell cycling and undesired reactions at the electrode/solid electrolyte interface. In this context, alloy materials such as lithium-indium (Li-In) alloys are widely used at the laboratory scale because of their (electro)chemical stability, although no in-depth investigations on their morphological stability have been reported yet. In this work, we report the growth of Li-In dendritic structures when the alloy material is used in combination with a Li6PS5Cl solid electrolyte and Li(Ni0.6Co0.2Mn0.2)O2 positive electrode active material and cycled at high currents (e.g., 3.8 mA cm−2) and high cathode loading (e.g., 4 mAh cm−2). Via ex situ measurements and simulations, we demonstrate that the irregular growth of Li-In dendrites leads to cell short circuits after room-temperature long-term cycling. Furthermore, the difference between Li and Li-In dendrites is investigated and discussed to demonstrate the distinct type of dendrite morphology., Li-In alloys are widely used as reference materials in the research field of solid-state lithium-based batteries. Here, the authors report and discuss the instability of Li-In electrodes towards sulfide solid electrolytes in all-solid-state batteries.

Fully depleted (FD) silicon-on-insulator (SOI) nMOSFETs fabricated using 0.2- $\mu \text{m}$ SOI technology with external body contact (EBC) and floating body (FB) structures are irradiated up to 500 krad(Si) using 60Co gamma rays under the transmission gate (TG) and OFF bias conditions, respectively. The threshold voltage shift of the back transistors due to radiation-induced charge trapping in the buried oxide (BOX) is used to characterize the total dose response of irradiated back transistors. The results indicate that, overall, the TG biased EBC transistors with various gate lengths are more sensitive to the total dose radiation than the OFF biased FB counterparts at low dose levels. Furthermore, for the shorter gate transistors with a supply voltage of 1.8 V, a relatively complex correlation exists between the total dose response and the gate length. In particular, the back transistor of the TG biased 0.20- $\mu \text{m}$ 1.8-V EBC transistor reveals smaller threshold voltage shifts than the OFF biased counterpart at approximately 500 krad(Si) because of the saturation of its threshold shift with increased doses, and a similar radiation response is observed for the TG biased 0.35- $\mu \text{m}$ EBC transistor with a supply voltage of 2.5 V. We found that the 2.5-V back transistors exhibited greater radiation hardness than the 1.8-V counterparts with the same bias configuration in most cases.

Lead-free has been a goal that people pursue due to the environmental pollution caused by lead in lead-based materials. K0.5Na0.5NbO3(KNN) is one of the most promising lead-free piezoelectric materials. Theoretically, the piezoelectric properties of single crystals are much better than those of polycrystalline materials. However, it is difficult to fabricate uniform KNN-based crystals by the high-temperature melt method because of volatilization of elements. This method also needs complicated equipment and is expensive. Here, a seed-free, solid-state crystal growth (SFSSCG) method was used to prepare Mn, Li, and Bi co-doped KNN crystals, which show an ultrahigh piezoelectric coefficient of about 1050 pC N−1, around one order of magnitude higher than that of pure KNN ceramics. Furthermore, the effective piezoelectric coefficient d33* of this crystal can reach 2290 pm V−1 at a unipolar electric field of 10 kV cm−1. This crystal also shows a high Curie temperature and good ferroelectricity. It is expected that the lead-free KNN-based single crystals fabricated by this simple method show promise for high performance ferroelectric and piezoelectric applications in industry and are environment-friendly.

All-solid-state lithium batteries (ASSLBs) using sulfide solid electrolytes (SSEs) offer an attractive option for energy storage applications. Lithium anode is the ultimate goal for ASSLBs, but lithium-indium (Li-In) alloy anode is more widely utilized in lab testing owing to the quite stable interface and elimination for the risk of short circuit. However, vigorous growth of Li-In dendrites in SSE is discovered in the present work when a full cell (LiNbO3 coated LiNi0.6Co0.2Mn0.2O2//Li6PS5Cl//Li-In) is cycled in high loading and high rate. Our study demonstrates that Li-In anode is unstable towards SSEs at high current, which induces Li-In dendrite growth enclosing electrolyte particles and eventually results in cell death after a long cycling. The morphology and growth mechanism of Li-In dendrites are revealed by scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) analysis and density function theory (DFT) calculations. Moreover, the differences between Li and Li-In dendrites are systematically compared.

In order to develop new phosphorus–nitrogen-containing flame retardants, three novel compounds of DOPO-substituted aminophenyl-s-triazine (TAT-DOPO) with different P/N element ratios were synthesized by Kabachnik–Fields reaction. TAT-triDOPO possessing three DOPO units in one molecule exhibited the best thermal stability. Besides, TAT-triDOPO and TAT-hexaDOPO possessing active hydrogen displayed the characteristics of reactive-type retardant, while TAT-enneaDOPO without active hydrogen represented additive-type retardant. The influences of three TAT-DOPO compounds on the thermal stability, flame retardancy and mechanical properties of the cured EP composites were investigated. Compared with pure EP, the char yields of EP/TAT-DOPO were increased. The LOI value and the UL-94 ratings of EP/TAT-triDOPO with a 5% loading were improved to 34.0% and V-0 grade. The PHRR, THR and HRC of EP/TAT-triDOPO were decreased by 25.7%, 21.1% and 25.4%, respectively. Furthermore, the incorporation of TAT-triDOPO could also improve the flexural strength and elastic modulus of cured EP. It was explained that the existence of active hydrogen atoms within TAT-triDOPO molecule can act as effective chemical cross-linking points in EP network. Finally, based on the SEM and TGA-FTIR analysis of pyrolytic products of cured EP/TAT-DOPO, it was deduced that the prepared TAT-DOPO flame retardant could exhibit both condensed phase and gas phase flame-retardancy mechanism.

The development of halogen-free epoxy resins (EPs) has become a major concern in the field of electronic packaging materials because flame retardants containing halogen release toxic chemicals during combustion. In this article, a type of modified EP possessing multiple functionalities, including high flame retardancy and thermal property as well as low hygroscopicity, was prepared via a simple method by taking advantage of synergistic effects of organotitanate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The mechanical and thermal properties of the as-prepared EP/titanium (Ti)/DOPO system were characterized by dynamic mechanical analysis, glass transition temperature, differential scanning calorimetry, and so on. The results showed that the incorporation of organotitanate and DOPO into EP can not only enhance the decomposition temperature and residual char but also increase the glass transition temperature and limiting oxygen index (LOI) value. The EP/Ti/DOPO system reached UL94 V-0 rating with an LOI of 34.7%. Compared to pure epoxy, the peak heat release rate, heat release capacity, and total heat release of EP/Ti/DOPO were decreased by 33.3%, 35.1%, and 16.7%, respectively.

A continuous precipitation method for the synthesis of Ag2CO3/AgBr/Bi2WO6 nanocomposite photocatalyst is proposed. This method has the advantages of simple operation, short reaction time and no heating in the whole reaction process. XRD and HRTEM confirm that the composite is composed of Ag2CO3, AgBr and Bi2WO6. SEM indicates that the composite is nanometer sized and composed of small particles with a particle size of about 20 nm. The separation ability of photogenerated carriers in nanocomposite has been studied by photoluminescence (PL) test. The activity of the photocatalyst has been evaluated by the degradation of methyl blue (MB), methyl orange (MO) and rhodamine B (RhB). The results show that the photodegradation efficiency of the synthesized Ag2CO3/AgBr/Bi2WO6 nanocomposite on 8 mg/L RhB is 95.1% after 60 min of solar illumination and is still 62.1% after 4 times of recycling. The kinetic constant over Ag2CO3/AgBr/Bi2WO6 nanocomposite photocatalyst (0.03557 min−1) is more than 4.23, 1.23 and 2.23 times larger than over pure Ag2CO3 (0.00841 min−1), Bi2WO6 (0.02887 min−1) and AgBr (0.01595 min−1). The active species in photocatalytic system are ·OH, ·O2– and h+, which are proved by the free radical trapping experiment and electron paramagnetic resonance (EPR) analysis. The optical absorption properties of the prepared samples has been studied by UV–Vis DRS. The possible photocatalytic mechanism is also proposed.

The La-Mg-Ni hydrogen storage alloys with A2B7/AB5 double phase were successfully prepared by vacuum melting combined with ball milling. The phase structure, electrochemical properties and the catalytic oxidation properties for BH4- of the (Mm1-xMgx)Ni2.485Co0.525Mn0.28Al0.21 (x=0.1-0.5 )alloys were investigated by XRD and electrochemical measurements. The results showed that (Mm1-xMgx)Ni2.485Co0.525Mn0.28Al0.21 alloys are composed of LaNi5 phase and (La, Mg)2Ni7 phase. Among the studied alloys, the electrochemical properties of the alloy with x=0.3 is the best, and the electrochemical properties of the alloy with x=0.3 is significantly better than that of the AB5-type hydrogen storage alloy, which is mainly due to the formation of (La, Mg)2Ni7 phase in the alloy. At the same time, the alloy with x=0.3 also shows a better catalytic oxidation effect on BH4-, which is also better than that of the AB5- type hydrogen storage alloy. The catalysis of (Mm1-xMgx)Ni2.485Co0.525Mn0.28Al0.21 alloy catalyst is related to its electrochemical performance. The catalysis of hydrogen storage alloys may have a positive correlation with its own electrochemical performance.

Liquid nitrogen has been working as an important medium in fire extinguishing and prevention, due to its efficiency in oxygen exclusion and heat removal. Such a technique is especially crucial for coal industry in China. We built a tunnel model with a temperature monitor system (with 36 thermocouples installed) to experimentally study heat and mass transfer of liquid nitrogen in non-homogeneous coal porous media (CPM), and expected to optimize parameters of liquid nitrogen injection in engineering applications. Results indicate that injection location and amount of liquid nitrogen, together with air leakage, significantly affect temperature distribution in CPM, and non-equilibrium heat inside and outside of coal particles. The injection position of liquid nitrogen determines locations of the lowest CPM temperature and liquid nitrogen residual. In the deeper coal bed, coal particles take longer time to reach thermal equilibrium between their surface and inside. Air leakage accelerates temperature increase at the bottom of the coal bed, which is a major reason leading to fire prevention inefficiency. Measurement fluctuation of CPM temperature may be caused by incomplete contact of coal particles with liquid nitrogen flowing in the coal bed. Moreover, the secondary temperature drop (STD) happens and grows with the more injection of liquid nitrogen, and the STD phenomenon is explained through temperature distributions at different locations.

Sericin has great potentials in biomedical applications for its good reactive activity, biocompatibility and biodegradability. However, the undesirable mechanical performance limits its application. Here, we developed a green, facile and economic approach to prepare sericin/polyvinyl alcohol (PVA) blend film. Further, silver nanoparticles (AgNPs) were synthesized in situ on the surface of sericin/PVA film via UV-assisted green synthesis method. Mechanical performance, swelling, mass losing and water retention tests showed the blend film had good mechanical performance, hygroscopicity, water retention capacity and low mass losing ratio. Scanning electron microscopy, fourier transfer infrared spectroscopy, X-ray diffractometry diffraction and X-ray photoelectron spectroscopy indicated the blending of PVA and sericin promoted the formation of hydrogen bond network between sericin and PVA, thus enhanced the mechanical performance and the stability of sericin, as well as the hygroscopicity and water retention capacity. UV irradiation and AgNPs modification did not affect the inner crystalline structure of sericin/PVA blend film. The inhibition zone and bacteria growth curve assay suggested AgNPs-sericin/PVA film had good antibacterial activities against E. coli and S. aureus. This novel AgNPs-sericin/PVA film shows great potentials in biomedical materials such as wound dressing and skin tissue engineering.

In recent decades, all-solid-state lithium batteries have gained enormous attention due to the improved safety performance and high specific energy. However, the brittle nature of sulfide-based solid electrolytes and poor interface compatibility limit the long-cycle stability and high rate performance of ASSLBs. The utilization of a thick solid electrolyte further reduces the cell-level energy and power. Herein, we prepare a thin sulfide electrolyte film (65 μm) using modified Li6PS5Cl and poly (ethylene oxide) (PEO). Under a high loading of 4.46 mA h cm−2, the assembled cell employing this electrolyte film with LiNi0.7Co0.2Mn0.1O2 cathode and lithium-indium alloy anode maintains a 1000 stable cycles with 74% capacity retention and average 99.85% coulombic efficiency at 60 °C. The cell-level energy and power are increased by an order of magnitude compared with traditionally prepared solid-state batteries. An excellent specific power of 374.7 W kg−1 is delivered at the initial cycle. This modified electrolyte film is expected to be commercially produced in the near future.

The Na0.5K0.5NbO3 single crystal was successfully grown by a seed-free solid-state crystal growth method using super-low content of LiBiO3 as a sintering aid. Microstructure, piezoelectric, ferroelectric and dielectric properties were investigated. The results show that well-paralleled lamellar ferroelectric ordering domains structure are present and no crack can be seen inside the single crystal. The best piezoelectric and dielectric properties (at 1 kHz) of d33 = 265 pC/N, Pr = 27.4 μC/cm2, e = 738, tanδ = 0.04 appear at x = 0.40at% for (1-x)Na0.5K0.5NbO3-xLiBiO3 single crystal. A higher remnant polarization Pr of 36.3 μC/cm2 were obtained at x = 0.45 at%.

Large Na0.5K0.5NbO3 (NKN) piezoelectric single crystals were obtained by seed-free solid-state crystal growth method, which is a traditional sintering grain growth process, with LiBiO3 used as a sintering aid. The largest dimension of the single crystals obtained was 11 mm × 9 mm × 3 mm. In addition to the LiBiO3 doping content, temperature, and time effect of the crystal growth process was systematically investigated and considered from the kinetics point of view. With the assistance of Avrami analysis, parameters relevant to the crystal growth process were determined. Laue diffraction and transmission electron microscopy suggested an orthorhombic symmetry for the single crystalline structure. Dielectric-frequency-temperature measurements revealed an orthorhombic-tetragonal and tetragonal-cubic phase transition at 155°C and 405°C, respectively, both of which are typical of first-order transitions, and have a well-defined thermal hysteresis. Rayleigh analysis was performed regarding to the extrinsic reversible and nonreversible piezoelectric properties, and the result suggested a dominant intrinsic reversible piezoelectric contribution of 91.5% under E0 = 1 kV/cm AC amplitude. Such a single crystal growth process route is low cost and a relative simple preparation process.

The ~3 μm fluorescence was investigated in the Ho2O3-doped transparent tellurite glass-ceramic for the first time. The branching-ratios and emission cross-sections were calculated. The glass-ceramics had high branching-ratio (20.5%) and large emission cross-section (1.76 × 10−20 cm2) corresponding to Ho3+:5I6→5I7 transition. After crystallization, the ~3 μm fluorescence intensity increased obviously excited by 640 nm laser diode. The broadband fluorescence about 3 μm was observed under excitation by a 1950-nm thulium-doped fiber lasers. The increased ~3 μm fluorescence intensity and narrowed spectrum demonstrated the Ho3+ ions embedded into the crystalline phase. These results indicate that the tellurite glass-ceramics may be a promising material for mid-infrared lasers.

In an attempt to improve thermal and flame-retardant properties of epoxy resins efficiently, a new reactive phosphorus-containing curing agent called 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl-(phenylimino)-(4-hydroxyphenyl)me-thane (DOPO-PHM) was synthesized and was combined with 4,4′-diaminodiphenyl methane (DDM) to co-cure epoxy resins (E51), which covalently incorporated halogen-free DOPO organ groups into the epoxy networks. The chemical structure of this curing agent was confirmed by FTIR, 1D, and 2D NMR spectra. A reaction mechanism during the preparation was proposed, and the electron effect on the stabilization of the carbocation was discussed. Various DDM/DOPO-PHM molar ratios were used to get the materials with different phosphorus contents. Their dynamic mechanical, thermal, and flame-retardant properties were evaluated by dynamic mechanical thermal analysis, thermogravimetric analysis, and limiting oxygen index (LOI) respectively. All samples had a single Tg, showing that these epoxy resins were homogeneous phase for long-term use in spite of adding DOPO-PHM. Both char yields (under nitrogen and air atmospheres) increased with the increasing of phosphorus content and the LOI values increased from 24.5 for standard resin to 33.5 for phosphorus-containing resins, indicating the significant enhancement of thermal stability and flame retardancy. POLYM. ENG. SCI., 54:1192–1200, 2014. © 2013 Society of Plastics Engineers

A high frequency Surface Acoustic Wave (SAW) filter which is the key point of the SAW sensor is made by MEMS technology. The SAW filter used for sensors needs to have the factors of high frequency, low loss and high quality factor. In order to satisfy the performance of the factors, the SAW delay lines of Electrode Wave Control Single Phase Unidirectional Transducer (EWC/SPUDT) are used in the filter. This transducer can be considered as the networks of connection of some units of IDTs and the loss of device can be effectively reduced. Based on the Coupling of Modes (COM) theory and equivalent circuit modal, the mixed matrix (P matrix) of the transducers can be deduced, and further, the response of the delay lines can be obtained. According to the calculated results, a mask layout is made. Then the SAW delay line is completed and found to agree with the theoretical simulation. Its center frequency is 503 MHz and insertion loss is low enough for use of sensors.

Tb 0.3 Dy 0.7 Ho x Fe 1.95 ( x =0.00, 0.05, 0.10, 0.15, 0.20, 0.35, 0.50, 0.65) quaternary alloys were prepared by arc-melting and followed by annealing. The phases present and structure of the alloys were determined using a D8-Advance X-ray diffractometer. The magnetostriction of the alloys was studied by standard strain gauge technique. The dependence of Ho content on the structure, magnetostriction and density of the alloys was investigated in detail. The research results showed that Ho-doping did not change MgCu 2 -type cubic Laves structure in Tb 0.3 Dy 0.7 Fe 1.95 . When Ho content x ≤0.2, rich rare earth phase presented in the alloys increased and magnetostriction of the alloys reduced evidently with increasing x , but for alloys with x >0.2, the content of rich rare earth phase started to reduce and the magnetostriction increased quickly, especially at low magnetic field in the alloy with x =0.65 due to separation of rich rare earth phases on the surface of the alloy.

A four-finger InGaAs/InP double heterojunction bipolar transistor is designed and fabricated successfully by using planarization technology. The emitter area of each finger is 1 ? 15?m2. The breakdown voltage is more than 7 V, the maximum collector current could be more than 100 mA. The current gain cutoff frequency is as high as 155 GHz and the maximum oscillation frequency reaches 253 GHz. The heterostructure bipolar transistor can offer more than 70mW class-A maximum output power at W band and the maximum power density can be as high as 1.2W/mm.

The layer structure of InGaAs/InP double heterojunction bipolar transistor (DHBT) is designed to enhance the frequency performance and breakdown voltage. The composition-graded base structure is used to decrease the base transit time. The InGaAs setback layer and two highly doped InGaAsP layers are used to eliminate the conduction band spike of the collector. The submicron-emitter InGaAs/InP DHBT is fabricated successfully. The base contact resistance is greatly decreased by optimization of contact metals. The breakdown voltage is more than 6 V. The current gain cutoff frequency is as high as 170 GHz and the maximum oscillation frequency reached 253 GHz. The DHBT with such high performances can be used to make W-band power amplifier.

We design and fabricate an InGaAs/InP double heterostructure bipolar transistor (DHBT). The spike of the conduction band discontinuity between InGaAs base and InP collector is successfully eliminated by insertion of an InGaAs layer and two InGaAsP layers. The current gain cutoff frequency and maximum oscillation frequency are as high as 155 and 144 GHz. The breakdown voltage in common-emitter configuration is more than 7 V. The high cutoff frequency and high breakdown voltage make high-speed and high-power circuits possible.

A new proposed Metal-Insulator-Metal (MIM) serie capacitor model for Monolithic Microwave Integrated Circuit is presented. The MIM serie capacitor model covers the frequency range up to 40 GHz for millimeter-wave circuit design application. The parasitic elements of model are extracted by parameters fitting optimization between the measured S-parameters and model simulated result. The relationship between the optimized parasitic element values and the dimension data of capacitor structure can be expressed.

The time zero dielectric breakdown characteristics of MOSCAP with ultra-thin EOT high-k metal gate stacks are studied. The TZDB results show an abnormal area dependence due to the series resistance effect. The series resistance components extracted from the Fowler–Nordheim tunneling relation are attributed to the spreading resistance due to the asymmetry electrodes. Based on a series model to eliminate the series resistance effect, an area acceleration dependence is obtained by correcting the TZDB results. The area dependence follows Poisson area scaling rules, which indicates that the mechanism of TZDB is the same as TDDB and could be considered as a trap generation process.

We investigate the effects of NO annealing and forming gas (FG) annealing on the electrical properties of a SiO2/SiC interface by low-temperature conductance measurements. With nitrogen passivation, the density of interface states (DIT) is significantly reduced in the entire energy range, and the shift of flatband voltage, ΔVFB, is effectively suppressed to less than 0.4 V. However, very fast states are observed after NO annealing and the response frequencies are higher than 1 MHz at room temperature. After additional FG annealing, the DIT and ΔVFB are further reduced. The values of the DIT decrease to less than 1011 cm−2 eV−1 for the energy range of EC − ET > 0.4 eV. It is suggested that the fast states in shallow energy levels originated from the N atoms accumulating at the interface by NO annealing. Though FG annealing has a limited effect on these shallow traps, hydrogen can terminate the residual Si and C dangling bonds corresponding to traps at deep energy levels and improve the interface quality further. It is indicated that NO annealing in conjunction with FG annealing will be a better post-oxidation process method for high performance SiC MOSFETs.

Noise performance of AlGaN/GaN HEMT has received more and more worldwide attention in recent years. In this paper, a MMIC process in AlGaN/GaN technology has been developed. A LNA design is based on a AlGaN/GaN HEMT noise model and a complete model library of passive elements under the optimum bias for LNA design. The paper describes modeling, bias dependence of small-signal and noise parameters, circuit design of the LNA using noise model without transistor noise measurement, and demonstrates a NF of 2 dB at 8GHz.

88 nm-gate InP-based InAlAs/InGaAs HEMTs with the gate width of 75 μm have been designed and fabricated. They exhibited a current gain cutoff frequency (f T ) of 204 GHz and a maximum oscillation frequency (f max ) of 352 GHz at a drain-source voltage (V ds ) of 1.5 V and a gate-source voltage (V gs ) of 0 V. Excellent DC characteristics were also demonstrated with the DC peak transconductance (g m, max ) of 918 mS/mm and the maximum current density of 635 mA/mm.

The configuration of a novel C-band spatial power combiner in waveguide is introduced. Employing the optimized Klopfenstein tapered slot antenna arrays, the waveguide-based power combiner based on 2times4 arrays at C band (3.6-4.4 GHz) was made. Its size is 70 mmtimes98 mmtimes170 mm and it is implemented by using eight commercial GaAs MMIC power amplifiers. CW power combiner measurements were performed with output power greater than 20 W (CW) at the frequency range from 3.6 to 4.4 GHz, where the maximum saturation output power is 46.82 dBm (48.08 W) at 4.35 GHz. The corresponding linear gain is about 9.5 dB,the PAE is approximately 26% and the efficiency is about 75%.

In this paper, A12O3 ultrathin film used as the surface passivation layer for AlGaN/GaN high electron mobility transistor (HEMT) is deposited by thermal atomic layer deposition (ALD), thereby avoiding plasma-induced damage and erosion to the surface. A comparison is made between the surface passivation in this paper and the conventional plasma enhanced chemical vapor deposition (PECVD) SiN passivation. A remarkable reduction of the gate leakage current and a significant increase in small signal radio frequency (RF) performance are achieved after applying Al2O3+BCB passivation. For the Al2O3+BCB passivated device with a 0.7 μm gate, the value of fmax reaches up to 100 GHz, but it decreases to 40 GHz for SiN HEMT. The fmax/ft ratio (≥ 4) is also improved after Al2O3+BCB passivation. The capacitance–voltage (C–V) measurement demonstrates that Al2O3+BCB HEMT shows quite less density of trap states (on the order of magnitude of 1010 cm−2) than that obtained at commonly studied SiN HEMT.

The n-type silicon integrated-back contact (IBC) solar cell has attracted much attention due to its high efficiency, whereas its performance is very sensitive to the wafer of low quality or the contamination during high temperature fabrication processing, which leads to low bulk lifetime τbulk. In order to clarify the influence of bulk lifetime on cell characteristics, two-dimensional (2D) TCAD simulation, combined with our experimental data, is used to simulate the cell performances, with the wafer thickness scaled down under various τbulk conditions. The modeling results show that for the IBC solar cell with high τbulk, (such as 1 ms–2 ms), its open-circuit voltage Voc almost remains unchanged, and the short-circuit current density Jsc monotonically decreases as the wafer thickness scales down. In comparison, for the solar cell with low τbulk (for instance, < 500 μs) wafer or the wafer contaminated during device processing, the Voc increases monotonically but the Jsc first increases to a maximum value and then drops off as the wafer's thickness decreases. A model combing the light absorption and the minority carrier diffusion is used to explain this phenomenon. The research results show that for the wafer with thinner thickness and high bulk lifetime, the good light trapping technology must be developed to offset the decrease in Jsc.

An optimized modeling method of 8 × 100 μm AlGaN/GaN-based high electron mobility transistor (HEMT) for accurate continuous wave (CW) and pulsed power simulations is proposed. Since the self-heating effect can occur during the continuous operation, the power gain from the continuous operation significantly decreases when compared to a pulsed power operation. This paper extracts power performances of different device models from different quiescent biases of pulsed current–voltage (I–V) measurements and compared them in order to determine the most suitable device model for CW and pulse RF microwave power amplifier design. The simulated output power and gain results of the models at Vgs = −3.5 V, Vds = 30 V with a frequency of 9.6 GHz are presented.

In this paper, the off-state breakdown characteristics of two different AlGaN/GaN high electron mobility transistors (HEMTs), featuring a 50-nm and a 150-nm GaN thick channel layer, respectively, are compared. The HEMT with a thick channel exhibits a little larger pinch-off drain current but significantly enhanced off-state breakdown voltage (BVoff). Device simulation indicates that thickening the channel increases the drain-induced barrier lowering (DIBL) but reduces the lateral electric field in the channel and buffer underneath the gate. The increase of BVoff in the thick channel device is due to the reduction of the electric field. These results demonstrate that it is necessary to select an appropriate channel thickness to balance DIBL and BVoff in AlGaN/GaN HEMTs.

AlGaN/GaN HEMT gate leakage increasing induced by passivation was investigated by employing double gate surface leakage test structure, circle and rectangular Schottky contact structure and metal float gate structure. It was demonstrated that surface leakage is not a major contributor to increasing of gate leakage. Increase of gate leakage depends on augmenting of Schottky contact edge effect and inhibiting "visual gate" between gate and drain

A novel salicide body-contacted structure compatible with bulk silicon process is presented in this paper for partially depleted SOI nMOSFETs. Simulation results show that the structure can eliminate the kink effect effectively and the drain breakdown voltage is improved considerably.

p/sup +/ polysilicon and n/sup +/ polysilicon were used as the gate material for fully-depleted SOI NMOS transistors. It's found that n-channel transistors with p+ poly gates require lower channel doping levels than their n/sup +/ poly counterparts, leading to easier formation of depleted film and control of the threshold voltage. The low channel doping results in improved source-drain breakdown characteristic.

The threshold voltage of fully depleted silicon-on-insulator (SOI) MOSFET with channel lengths down to the deep-submicrometer range has been investigated. By applying Gauss's law, a quasi-two-dimensional analytical threshold voltage model for ultra-thin SOI fully depleted MOSFET's including the short-channel effect (SCE) is achieved. Furthermore, we consider further the threshold voltage of FDSOI MOSFET and in particular the value of the surface potential at threshold. It is shown that the surface potential at FDSOI MOSFET threshold may differ significantly from 2 /spl phi/ i. We extend this model by accounting for surface potential about P+ poly-silicon gate, a closed form expression for the threshold voltage is obtained and compared with experimental data for several SOI FD MOSFET's.

This paper describes the total dose radiation performance of CMOS/SOI 4 Kb SRAMs fabricated in a radiation hardened partially depleted SOI CMOS technology. The SRAM adopts 1 K/spl times/4 architecture. It achieves a fast access time 30 ns and chip size 3.6 mm/spl times/3.84 mm. Memory functionality does well after a total dose irradiation up to 5/spl times/10/sup 5/ rad(Si) under 3 V power supply. This meets the needs in military and aerospace fields. It is the first time that the radiation effects on SOI VLSI were investigated in China.

A new modified Angelov current—voltage characteristic model equation is proposed to improve the drain—source current (Ids) simulation of an AlGaN/GaN-based (gallium nitride) high electron mobility transistor (AlGaN/GaN-based HEMT) at high power operation. Since an accurate radio frequency (RF) current simulation is critical for a correct power simulation of the device, in this paper we propose a method of AlGaN/GaN high electron mobility transistor (HEMT) nonlinear large-signal model extraction with a supplemental modeling of RF drain—source current as a function of RF input power. The improved results of simulated output power, gain, and power added efficiency (PAE) at class-AB quiescent bias of Vgs = −3.5 V, Vds = 30 V with a frequency of 9.6 GHz are presented.

The Ni/Ti/Ni multilayer ohmic contact properties on a 4H-SiC substrate and improved adhesion with the Ti/Au overlayer have been investigated. The best specific contact resistivity of 3.16 × 10−5 Ωcm2 was obtained at 1050 °C. Compared with Ni/SiC ohmic contact, the adhesion between Ni/Ti/Ni/SiC and the Ti/Au overlayer was greatly improved and the physical mechanism under this behavior was analyzed by using Raman spectroscopy and X-ray energy dispersive spectroscopy (EDS) measurement. It is shown that a Ti-carbide and Ni-silicide compound exist at the surface and there is no graphitic carbon at the surface of the Ni/Ti/Ni structure by Raman spectroscopy, while a large amount of graphitic carbon appears at the surface of the Ni/SiC structure, which results in its bad adhesion. Moreover, the interface of the Ni/Ti/Ni/SiC is improved compared to the interface of Ni/SiC.

Material structures and device structures of a 100-GHz InP based transferred-electron device are designed in this paper. In order to successfully fabricate the Gunn devices operating at 100 GHz, the InP substrate was entirely removed by mechanical thinning and wet etching. The Gunn device was connected to a tripler link and a high RF (radio frequency) output with power of 2 mW working at 300 GHz was obtained, which is high enough for applications in current military electronic systems.

The effect of the annealing time and annealing temperature on Ni/Ge/Au electrode contacts deposited on the n-type InP contact layer has been studied using a circular transmission line model. The minimum specific contact resistance of 3.2 × 10−7 Ωcm2 was achieved on the low-doped n-type InP contact layer with a 40 s anneal at 425 °C. In order to improve the ohmic contact and reduce the difficulty in the fabrication of the high doped InP epi-layer, the doping concentration in the InP contact layer was chosen to be 5 × 1018 cm−3 in the fabrication of transferred electronic devices. Excellent differential negative resistance properties were obtained by an electron beam evaporating the Ni/Ge/Au/Ge/Ni/Au composite electrode on an InP epi-layer with a 60 s anneal at 380 °C.

In this paper, 0.15-μm gate-length In0.52Al0.48As/In0.53Ga0.47As InP-based high electron mobility transistors (HEMTs) each with a gate-width of 2 × 50 μm are designed and fabricated. Their excellent DC and RF characterizations are demonstrated. Their full channel currents and extrinsic maximum transconductance (gm,max) values are measured to be 681 mA/mm and 952 mS/mm, respectively. The off-state gate-to-drain breakdown voltage (BVGD) defined at a gate current of −1 mA/mm is 2.85 V. Additionally, a current-gain cut-off frequency (fT) of 164 GHz and a maximum oscillation frequency (fmax) of 390 GHz are successfully obtained; moreover, the fmax of our device is one of the highest values in the reported 0.15-μm gate-length lattice-matched InP-based HEMTs operating in a millimeter wave frequency range. The high gm,max, BVGD, fmax, and channel current collectively make this device a good candidate for high frequency power applications.

Mesa etching technology is considerably important in the Gunn diode fabrication process. In this paper we fabricate InP Gunn diodes with two different kinds of chlorine-based etchants for the mesa etching for comparative study. We use two chlorine-based etchants, one is HCl-based solution (HCl/H3PO4), and the other is Cl2-based gas mixture by utilizing inductively coupled plasma system (ICP). The results show that the wet etching (HCl-based) offers low cost and approximately vertical sidewall, whilst ICP system (Cl2-based) offers an excellent and uniform vertical sidewall, and the over-etching is tiny on the top and the bottom of mesa. And the fabricated mesas of Gunn diodes have average etching rates of ~ 0.6 μm/min and ~ 1.2 μm/min, respectively. The measured data show that the current of Gunn diode by wet etching is lower than that by ICP, and the former has a higher threshold voltage. It provides a low-cost and reliable method which is potentially applied to the fabrication of chip terahertz sources.