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A high-performance AlGaN/GaN-based ultraviolet photodetector with a field-enhanced mechanism for photocurrent collection is designed and fabricated in this work. In addition to the inherent polarization field, two additional sets of collection fields are formed from a 2DEG layer to a ITO thin film and from the 2DEG layer to a cathode electrode sinker. The effectiveness in the collection of photogenerated carriers is remarkably enhanced, which leads to a photocurrent of 6.6 mA/mm under the illumination of 365 nm-centered ultraviolet light at an intensity of 1.8 mW/cm2. With an in-built shallow isolation trench, the dark current is suppressed below 40 pA/mm under a device bias of 5.0 V. A photo-to-dark current ratio as high as 1.7 × 108, a record high photo-responsivity over 4.3 × 106 A/W, and a high gain of 1.46 × 107 under 365-nm light are demonstrated by the fabricated prototype, showing great competitiveness in state-of-the-art AlGaN/GaN-based ultraviolet photodetectors. [ABSTRACT FROM AUTHOR]

In this letter, the suppression of dynamic on-state resistance (RON) degradation for faster dynamic RON recovery is achieved by the multimesa-channel (MMC) structure in AlGaN/GaN high electron mobility transistors. The measurement results are discussed with the physical mechanisms investigated. The initial transient RON degradation is reduced in the MMC structure, resulting from the lower peak electric field around the drain-side gate edge in the trigate structure compared to that in a planar device. The faster dynamic RON recovery in MMC devices is attributed to the quick emission of electrons at sidewall traps of shallower energy levels. The energy levels of dominant traps at the sidewall and top interfaces are found to be 0.26 eV and 0.37 eV below the conduction band edge, respectively, verified by Technology Computer Aided Design simulations in agreement with the measurement data. [ABSTRACT FROM AUTHOR]

AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) have become a promising candidate for use in efficient power conversion applications. In order to realize converter circuit control function and overcurrent protection of device itself, we have designed, fabricated, and experimentallymeasured the Au-free AlGaN/GaN MIS-HEMTs with embedded current sensing structure. A floating ohmic current sensing electrode is inserted between source and gate electrode of which the sensing voltage signal can represent the drain current. We have achieved stable current sensing ratios at various operating conditions including quasi-static, transient state, and under high temperature. The proposed structure is highly useful in monolithic power integrated circuit on CMOS-compatible AlGaN/GaN technologies. [ABSTRACT FROM PUBLISHER]

In order to examine the feasibility of full wide-bandgap GaN-based converters in aerospace power conversion applications, this paper proposes a monolithic DC-DC buck converter design with integrated high-side gate driver, over-current protection, and pulse-width-modulation feedback control circuits based on full AlGaN/GaN MIS-HEMT configuration. After model calibration of the DC and transient behaviors with fabricated normally-ON and normally-OFF AlGaN/GaN MIS-HEMT devices, the DC-DC buck converter is simulated. The circuit converts the input 100 V down to an adjustable range at 1 MHz switching frequency. The over-current protection function can properly protect the converter at a preset over-current threshold. The converter can respond to the load current and line input voltage fluctuations due to the integrated feedback control. These results illustrate the performance of proposed all-GaN DC-DC power converter design. [ABSTRACT FROM AUTHOR]

In this paper, a normally-off AlGaN/GaN MIS-HEMT with improved threshold voltage (VTH) thermal stability is reported with investigations on its physical mechanism. The normally-off operation of the device is achieved from novel short argon plasma treatment (APT) prior to the fluorine plasma treatment (FPT) on Al2O3 gate dielectrics. For the MIS-HEMT with FPT only, its VTH drops from 4.2V at room temperature to 0.5V at 200 °C. Alternatively, for the device with APT-then-FPT process, its VTH can retain at 2.5V at 200 °C due to the increased amount of deep-level traps that do not emit electrons at 200 °C. This thermally stable VTH makes this device suitable for high power applications. The depth profile of the F atoms in Al2O3, measured by the secondary ion mass spectroscopy, reveals a significant increase in the F concentration when APT is conducted prior to FPT. The X-ray photoelectron spectroscopy (XPS) analysis on the plasma-treated Al2O3 surfaces observes higher composition of Al-F bonds if APT was applied before FPT. The enhanced breaking of Al-O bonds due to Ar bombardment assisted in the increased incorporation of F radicals at the surface during the subsequent FPT process. The Schrödinger equation of Al2OxFy cells, with the same Al-F compositions as obtained from XPS, was solved by Gaussian 09 molecular simulations to extract electron state distribution as a function of energy. The simulation results show creation of the deeper trap states in the Al2O3 bandgap when APT is used before FPT. Finally, the trap distribution extracted from the simulations is verified by the gate-stress experimental characterization to confirm the physical mechanism described. [ABSTRACT FROM AUTHOR]

Inductive power transfer (IPT), which employs the principle of electromagnetic induction, is widely applied to wireless charging applications. The efficiency of an IPT system is highly dependent on the quality factor (Q) of the power resonant tank. In this paper, a novel design on the structure of the resonant coil is used in the resonant tank to achieve a significantly high Q above 1000 for the IPT system. Compensating capacitors are used in both primary and secondary circuits to align the resonant frequencies in order for the system resonant status to be maintained by a frequency tracking circuit. The experimental results show that with a primary coil Q of 1200, the proposed IPT system allows power to be transferred at a maximum air gap distance to coil diameter ratio of 1.46 for a highest efficiency of 87% at the resonant frequency of 106 kHz. [ABSTRACT FROM AUTHOR]

During off-state, the influence of surface-trapped electron charges induced by high-field stress near the gate electrode of AlGaN/GaN power high-electron mobility transistor devices causes a reduction in two-dimensional electron gas (2DEG) carrier density at the heterointerface. In a pulse turn-on operation, the weakened 2DEG channel results in a higher on-state conduction resistance during the transient, known as the current collapse phenomenon. The phenomenon increases the switching loss by a higher on-state resistance and prolonged turn-on transition time, thus limits the device operating frequency range. In this paper, such a phenomenon is modeled, analyzed by Sentaurus TCAD simulation, and verified by the laboratory measurement data, with the emphasis on the influence of field plates toward the current collapse. The spatial distributions of trapped electrons and excess free electrons along the AlGaN surface are modeled and analyzed to arrive at the quantitative relationships among the trapped electron density, on-resistance increase, and the electric field distribution which provide a reliable criterion for current collapse reduction. It was found that, with a proper field plate design, it is possible to achieve an improvement on transient on-state resistance and the current recovery time. [ABSTRACT FROM AUTHOR]

This paper reports extensive modelling and analysis of the temperature dependence on the device characteristics of the AlGaN/GaN high electron mobility transistors (HEMTs). A physics-based model is proposed in this study in order to correctly predict the gate flat-band Schottky barrier height, energy band Fermi-level (EC–EF) at the AlGaN/GaN interface, two-dimensional electron gas sheet density, gate threshold and (ID–VG) at sub-threshold voltages, and drain current–voltage (ID–VD) characteristics under various high-temperature conditions. The analytical results are then verified by comparing with the laboratory measurement as well as the numerical results obtained from the Sentaurus TCAD simulation. The proposed model is found to be useful for power electronic device designers on the prediction of the AlGaN/GaN HEMT device performance under high-temperature operation. [ABSTRACT FROM AUTHOR]

This paper presents a practical methodology for realistic simulation on reverse characteristics of Wide Bandgap (WBG) SiC and GaN p-n junctions. The adjustment on certain physic-based model parameters, such as the trap density and photo-generation for SiC junction, and impact ionization coefficients and critical field for GaN junction are described. The adjusted parameters were used in Synopsys Medici simulation to obtain a realistic p-n junction avalanche breakdown voltage. The simulation results were verified through benchmarking against independent data reported by others. [ABSTRACT FROM AUTHOR]

Over the past decade, the direct methanol fuel cell (DMFC) has been considered as a potential candidate of power sources for portable electronics due to its high energy density and environmental friendly operation. However, the use of diluted fuel loading and active fuel mixer/pump limits the DMFC's efficiency and operating time dramatically. The disadvantages become more severe in microscale DMFCs which require high conversion efficiency within a small physical space to meet the strict working specifications. In this paper, a low-power micro fuel supplier with programmable concentration regulation was designed and fabricated by using microelectromechanical system technology. The prototype adopted surface-tension pumping as the primary driving force to deliver fuel at zero power consumption. In addition, a well-arranged microfluidic capillary network was used to regulate the fuel concentration. A pulse-power actuated bubbler switch was embedded in the capillary network to achieve the liquid flow control dynamically and to adjust the fuel concentration for micro-DMFC ( \muDMFC) reaction. Both electrolysis and thermal bubble actuations were investigated in this paper for their effective operations in the prototype. The advantage of precise and low-power fuel regulation within a compact system volume makes the proposed fuel delivery subsystem a suitable candidate for future on-chip \muDMFC development. [ABSTRACT FROM AUTHOR]

Abstract: For the past decade, extensive mathematical modelling has been conducted on the design and optimization of liquid-feed direct methanol fuel cells (DMFCs). Detailed modelling of DMFC operations reveals that a two-phase flow phenomenon at the anode and under-rib convection due to the pressure difference between the adjacent channels both contribute significantly to mass-transfer in a DMFC and its output performance. In practice, comprehensive simulations based on the finite volume technique for two-phase flow require a high level of numerical complexity in computation. This study presents a complexity-reduced mathematical model that is developed to cover both phenomena for a realistic, but fast, in computation for the prediction and analysis of a DMFC prototype design. The simulation results are validated against experimental data with good agreement. Analysis of the DMFC mass-transfer is made to investigate methanol distribution at anode and its crossover through the proton-exchange membrane. From a comparison of the influence of two-phase flow and under-rib mass-transfer on DMFC performance, the significance of gas-phase methanol transport is established. Simulation results suggest that both the optimization of the flow-field structure and the fuel cell operating parameters (flow rate, methanol concentration and operating temperature) are important factors for competitive DMFC performance output. [Copyright &y& Elsevier]

The originally proposed superjunction (SJ) power MOSFET structure with interdigitated p-n columns is highly recognized for its higher voltage-blocking capability and lower specific ON-state resistance. However, in practice, the performance of 54 devices is greatly handicapped due to difficulties in the formation of perfect charge-balanced p-n columns by the limitation of fabrication process technology, particularly, for devices with small p-n column widths at low voltage ratings, Recently developed structures of polysilicon-flanked and oxide-bypassed SJ MOSFETs are to overcome the conventional 5,1 device fabrication limitation. The follow-up development on extending the scope of these recently reported device structures to lateral 5,1 structures, which is suitable for SJ power integrated circuits, Is reported for the first time, In this paper, detailed descriptions of the progressive development and the technical advancement of several Si MOSFET structures are presented with both simulation and experimental results. [ABSTRACT FROM AUTHOR]

The superjunction MOSFET power devices, such as p-n column superjunction (named SJ or CoolMOS) devices and oxide-bypassed (OB) devices, are highly recognized for their higher blocking capability and lower on-state resistance. However, the performance of SJ devices is greatly handicapped due to difficulties in formation of perfect charge-balanced SJ p-n columns by the current process technology, especially for devices with small widths and voltage ratings below 180 V. OB devices can be an alternative in this voltage region, which utilize the well established oxide thickness control in fabrication instead of the difficult doping control as in SJ devices. However, OB drift region electric field distribution is not as optimal as that in SJ devices. Gradient oxide-bypassed (GOB) structure enhances the performance of OB devices so that it can achieve a performance comparable to that of an ideal p-n column SJ device in the medium voltage range, and at the same time, requires simple process technology. Complete descriptions on the GOB device and related design issues are presented in this paper. Fabrication issues are also discussed with possible sacrificial materials and etchants for making the vertical graded oxide sidewalls. Design cases for 80, 120, and 180 V GOB devices are also illustrated for better understanding in the device. [ABSTRACT FROM AUTHOR]

Abstract: The existing direct methanol fuel cell (DMFC) systems are fed with a fixed concentration of fuel, which are either a diluted methanol solution or an active fuel delivery driven by an attached active pump. Both approaches limit the power conversion density or degrade the overall efficiency of the DMFC system significantly. Such disadvantages become more severe in small-scale DMFCs, which require a high conversion efficiency and a small physical space suitable for portable electronics. In this paper, passive fuel delivery based on a surface tension driving mechanism was designed and integrated in a laboratory-made prototype to achieve consumption depending on fuel concentration and power-free fuel delivery. Unidirectional methanol-to-water smooth flow is achieved through the capillaries of a Teflon PTFE (polytetrafluoroethylene) membrane based on the difference in liquid surface tension. The prototype was demonstrated to exhibit a better polarization performance and to last for an extended operating time compared to conventional DMFCs. Its high efficiency and load regulation performance were also demonstrated in contrast to an active DMFC supplied with a constant concentration fuel. The fuel delivery driven by the liquid surface tension effect demonstrated here is believed to be more applicable for future small-scale DMFCs for portable electronics. [Copyright &y& Elsevier]

Abstract: The micro-electro-mechanical systems (MEMS) inertia sensors, such as silicon microgyroscopes, utilize linear momentum to detect the plane-motion information. Their sensing sensitivity is proportional to the amount of linear momentum created by the linear actuator within the sensor. In this paper, a new driving scheme is proposed to enhance the linear momentum with a larger linear displacement during actuation. In our implementation, the displacement can be 1.8 times or higher than that of achievable using the conventional form of actuation for the same system voltage. Or, if for the same actuation displacement, the proposed scheme can reduce the system voltage by at least 25% to be suitable for low-voltage system integration. [Copyright &y& Elsevier]

The performance of specific on-state resistance (Ron,sp) versus breakdown voltage (Vbr) of a superjunction power MOSFET device is constrained by the quality of its sidewall junctions formed by neighbouring p and n columns in the drift region. The p–n junction quality, which is inevitably affected by the inter-column dopant diffusion in practice, will limit the Ron,sp–Vbr device performance if no compensation measure is taken. A detailed study of the influence of sidewall junction quality on performance at various column widths under given thermal process conditions was carried out through process and device simulations. The study discovers the practical optimal performance of superjunction (SJ) DMOS and UMOS structures under the influence of dopant inter-column diffusion. Analysis of the phenomenon shows that the degradation of the breakdown voltage is caused by the p and n column charge imbalance. Practical SJ performance equations, which model the influence reasonably well, are derived in the paper. These equations can be used to predict the practical performance of an SJ device under given thermal conditions, which in turn guides us to the compensation measures required to achieve better performance. [ABSTRACT FROM AUTHOR]

Presents a study that described research work on the design and fabrication of current sensor suitable for smart power integration in lateral insulated-gate bipolar transistor (IGBT) structure. Design of integrated current sensor; Variations of current sensing ratio at different temperatures; Conclusion.

Presents a study that proposed a novel folded gate LD metal oxide semiconductor transistor (FG-LDMOST) with the properties of low-on resistance and high transconductance. Information on how the FG structure was formed; Investigation of the FG concept; Fabrication of FG-LDNOS on 4-5 &Ω; cm n-type <100> lightly doped substrate using complementary metal oxide semiconductor (CMOS) compatible process technology.

Proposes a concise circuit suitable for integration and with gate drive capability to provide the complete function of overcurrent safe operating area protection for the lateral insulated gate bipolar transistor. Importance of overcurrent protection scheme; Description of operational principle.

In GaN Schottky barrier diodes (SBD), there is a trade-off between the turn-on voltage and the leakage current. In this study, recess-free 4 nm-thin-barrier AlGaN/GaN SBDs with minimal leakage current as well as excellent turn-on voltage homogeneity are developed, which enable better electrical control to pinch off the 2DEG channel under the anode region and avoids trap introduced in the barrier etching process. In detail, the effect of reverse stress on the SBD performance is initially explored by using differential conductance, and then, the anode-to-cathode distances and temperatures dependence of SBDs output characteristics are systematically studied. The fabricated thin-barrier GaN SBDs show a turn-on voltage of ∼0.75 V and a low level leakage current of 9.66 × 10−10 (1.91 × 10−8) A/mm at 300 (423) K, which is among the lowest reported values at the comparable reverse bias voltage and temperature. Moreover, structure parameters of the thin-barrier AlGaN/GaN SBD are systematically modeled and optimized by the TCAD simulations, including anode metal work function, Al mole fraction, the anode-to-cathode distance, and slanted anode angle. The introduction of slanted anode is found to have significant effect on the improvement of reverse breakdown voltage and leakage current characteristics. [ABSTRACT FROM AUTHOR]

The micromachined gyroscope is rapidly gaining popularity as a rate sensor for application in areas such as automotive and aerospace systems, where low power consumption, high sensitivity, low temperature drift and good stability are prerequisites. In this paper, the overall design and fabrication process of a reactive ion-etched inertial resonant gyroscope based on the capacitive sensing principle is reported. The experimental results are also discussed. [ABSTRACT FROM AUTHOR]

Presents information on a smart power synchronous rectifier (SPSR). Design; Characteristics; Performance parameters of SPSR.

In this paper, a new actuation scheme for the push-pull electrostatic microelectromechanical systems comb drive actuators is proposed. The displacement amplitude excited by the new form of driving voltages can be more than three times as large as that which is achievable using the conventional form for the same applied system voltage. [ABSTRACT FROM AUTHOR]

Presents a study which proposed a design of integrated current sensor for lateral insulated-gate bipolar transistor power devices. Details on the design of the lateral current sensor; Conclusions.

Photovoltaic responses, including photovoltage, photocurrent, illuminated J-V curve, and light-to-electricity power conversion efficiency, were investigated in chemical-solution-derived polycrystalline and epitaxial (Pb0.97La0.03)(Zr0.52Ti0.48)O3 (PLZT) thin films sandwiched between different metal and oxide electrodes. The epitaxial PLZT films with Au/PLZT/Nb-doped SrTiO3 structure exhibited about one order of magnitude larger photocurrent and efficiency over the randomly oriented polycrystalline PLZT films with Au/PLZT/Pt structure due to the high crystalline quality with the reduced defects and enhanced depolarization field. The illuminated J-V curve was approximately linear for both polycrystalline and epitaxial PLZT thin films. The nonzero photovoltaic outputs in the unpoled films were induced by asymmetric interfacial Schottky barriers. The illuminated J-V curve shifted toward the positive voltage direction after positive poling and toward the negative voltage direction after negative poling, and the enhancement of efficiency only occurred when the polarization direction accorded with the direction of Schottky barrier difference at the two electrode interfaces. Thickness dependences of photovoltage, photocurrent, and light-to-electricity conversion efficiency were also examined. It was observed that photovoltage linearly increased with film thickness while both photocurrent and efficiency exponentially increased with the decrease in thickness. Furthermore, at a fixed small film thickness, efficiency was also found to increase reciprocally with the decrease of incident UV intensity. [ABSTRACT FROM AUTHOR]

Ferroelectric (Pb0.97,La0.03)(Zr0.52,Ti0.48)O3 thin films in different thicknesses were fabricated on Pt/Ti/SiO2/Si substrates through a sol-gel process. Film thickness dependence of photoinduced current was investigated under the illumination of ultraviolet light. A theoretical model was developed to describe the thickness-dependent photocurrent. Both the theoretical model and experimental results showed that the photocurrent increases exponentially with the decrease in film thickness. However, photocurrent may drop in the films with the very small thickness of tens of nanometers and below in which the small size effect of ferroelectricity is considered. This model also reveals the relationship between the photocurrent and the internal electric field or remnant polarization and predicts a small diffusion current in the opposite direction at very low field or polarization region. These results provide useful guides for the design of ferroelectric film photovoltaic devices. [ABSTRACT FROM AUTHOR]

The stability and magnitude of photovoltage response in (Pb0.97La0.03)(Zr0.52Ti0.4g)O_3 (PLZT) ferroelectric thin films were investigated in the present work. Photovoltage degrading in multi-cycle ultraviolet (UV) light illumination was observed in Au/PLZT/Pt sandwich capacitor configuration and in-plane polarized configuration with a pair of top Au interdigital electrodes. For the in-plane polarized configuration, which had a greatly enhanced electrode gap, the reduction ratio of photovoltage during multi-cycle UV illumination was significantly smaller hence the stability of photovoltage was greatly improved over the sandwich capacitor configuration. Trapping of photo-induced charges and polarization screening at the ferroelectric-electrode interfaces were found to be the major cause for the degrading of photovoltage in ferroelectric films. Furthermore, for the Au/PLZT/Pt capacitor, the magnitude and even the polarity of the photovoltage were remarkably affected by the asymmetric interfacial Schottky barriers due to the small photovoltage magnitude determined by the small film thickness. [ABSTRACT FROM AUTHOR]

Photovoltaic effect in ferroelectric materials exhibits potential for applications of sensors and remote controls in micro-electro-mechanical systems, and a systematic evaluation on the photovoltaic behavior in ferroelectric materials becomes important. However, as a critical parameter that determines the photovoltaic output in ferroelectric thin films, the film thickness effect on photocurrent output has not been investigated for thin film samples. In this work, a theoretical model has been developed to describe the thickness-dependent photocurrent in (Pb0.97La0.03)(Zr0.52Ti0.48)O3(PLZT) thin films with a sandwich electrode structure. This model indicates that photocurrent increases exponentially with the decrease in film thickness. Therefore, a significantly enhanced photocurrent can be expected in thinner PLZT films. The predicted thickness dependence of the short circuit photocurrent was also supported by our experimental results. [ABSTRACT FROM AUTHOR]

A new partial silicon-on-insulator (SOI) formation technology and the associated RF LDMOSFET device structure on silicon bulk substrate are proposed in this paper. The same technology can also be applied to enhance the quality factor of the integrated on-chip microinductors. The proposed technology is able to reduce both drain/substrate parasitics and leakage current tier devices fabricated on bulk substrate. At the same time, the approach overcomes the thermal problem encountered by devices fabricated on full-SOI substrate. To demonstrate the technology, both partial-SOI LDMOSFET and microinductor devices were fabricated on bulk wafer with their RF performance verified by laboratory measurements. [ABSTRACT FROM AUTHOR]

Presents a study which proposed a novel silicon radio frequency metal oxide semiconductor field-effect transistor structure with a dummy-gate incorporated between the active gates. Analysis of the structure of the transistor; Experimental details; Conclusions.

A good magnetic field sensor should exhibit high sensitivity, low power consumption, and low output offset to accurately detect small fields. In this work, the high sensitivity in magnetoresistance variation (ΔR) is achieved by the AlGaN/GaN fin-shaped high electron mobility structure, in comparison to that of planar structures. A physical based analysis is presented to describe the influence of the fin width dimension on the ΔR dependency under magnetic fields. The sensitivity is expressed as a function of geometric parameters, electron mobility, and two-dimensional electron sheet density, with relaxation of polarization, shoulder density distribution, and sidewall trapped charges considered. Devices were fabricated, and a high sensitivity is observed in laboratory measurements on devices at narrower fin widths. At the fin width of 50 nm, the measured device has a sensitivity of 0.76 Ω/μΤ2 at the magnetic flux of 85 μΤ. The sensor's power consumption is as low as 48 μW, and the minimum magnetic flux detectable is at 20 μΤ. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) high-temperature Hall sensors are strongly required in various applications such as in the automotive and aircraft engines and in the diagnostic system of the thermonuclear reactors. In this paper, we propose a novel Hall sensor based on the wide-bandgap GaN-based materials on a single chip with greatly reduced area which can simultaneously detect 3D magnetic fields at high temperature up to 650 K. The device is analysed and demonstrated by performing the technology computer-aided design simulations, and significantly improved performances are achieved by employing space isolation and passivation scheme to effectively reduce the carrier interference from each dimension. Finally, high current-related magnetic sensitivities are found and the typical values are 128.6, 88.1, and 49.9 V A−1 T−1 on x, y and z axes, respectively, at room temperature. And the temperature coefficients are as low as −286.4, −366.8, and −202.9 ppm K−1, respectively. Moreover, dramatically improved cross-sensitivities are revealed and the maximum value is less than 1.0% at B ≤ 1.0 T which is much lower compared with other currently reported data. The work provides a new technical approach to realize a single-chip 3D magnetic sensor which is promising especially for high-temperature applications. [ABSTRACT FROM AUTHOR]

It was discovered that the dielectric constant of the electrodes substantially determines the photovoltaic output in (Pb0.97La0.03)(Zr0.52Ti0.48)O3 ferroelectric thin films. With the screening charges distributed extensively away from the electrode interfaces, the use of the electrodes with a high dielectric constant gives rise to dramatically enhanced magnitude of photocurrent in photovoltaic thin films, and extremely high photovoltaic efficiency is theoretically predicted to be possible in ferroelectric ultrathin films or nanostructures. [ABSTRACT FROM AUTHOR]

Photovoltaic effect in ferroelectric thin films with thickness below 100 nm was investigated through both theoretical and experimental approaches. Unprecedented high photovoltaic power conversion efficiency around ∼0.28% was achieved with epitaxial (Pb0.97La0.03)(Zr0.52Ti0.48)O3 ferroelectric thin films, which is about 2 orders of magnitude higher than the reported in literature for ferroelectrics. Theoretical analysis indicated that efficiency can be further significantly improved by reducing the thickness in nanoscale. Extremely high efficient bulk photovoltaic effect is predicted in high quality ferroelectric ultrathin films. [ABSTRACT FROM AUTHOR]

The stability of photovoltage in WO3-doped (Pb0.97La0.03)(Zr0.52Ti0.48)O3 (PLWZT) ferroelectric thin films was investigated. For in-plane polarized configuration, with a greatly enhanced electrode gap, the reduction ratio of photovoltage during multicycle UV illumination was significantly smaller and stability of photovoltage was greatly improved over the sandwich capacitor configuration. The ferroelectric-metal interfacial effects including Schottky barriers and polarization screening due to the trap of photoinduced charges at interfaces were found to determine the magnitude, stability, and even the polarity of the photovoltage, particularly for the electrode-sandwiched PLWZT thin films. [ABSTRACT FROM AUTHOR]

A correction to the article "Thickness effects on photoinduced current in ferroelectric (Pb0.97La0.03)(Zr0.52Ti0.48)O3 thin films," by Meng Qin, Kui Yao, Yung C. Liang, and Santiranjan Shannigrahi in issue 101 (2007) is presented.

In this paper, an observation of drain current instability on p-GaN gate AlGaN/GaN HEMTs is reported. Contrary to the Schottky gate AlGaN/GaN HEMTs, which show stable and consistent Id – Vd curves under different pulsed conditions, the Id – Vd curves for p-GaN gate AlGaN/GaN HEMTs show a dispersion in the saturation region under the same pulse conditions, which cannot be explained by the trapping of electrons in the material. A model considering the trapping of holes in the p-GaN gate under different gate and drain biases is proposed to explain this new phenomenon. [ABSTRACT FROM AUTHOR]

Considering energy band alignment and polarization effect, ferroelectric BiFeO3 thin films are proposed as the photoanode in a monolithic cell to achieve unassisted photocatalytic water splitting. Significant anodic photocurrent was observed in our epitaxial ferroelectric BiFeO3 films prepared from sputter deposition. Both negative polarization charges and thinner films were found to promote the anodic photocatalytic reaction. Ultraviolet photoelectron spectroscopy proved that the conduction and valence band edges of BiFeO3 straddle the water redox levels. Theoretical analyses show that the large switchable polarization can modify the surface properties to promote the hydrogen and oxygen evolutions on the surfaces with positive and negative polarization charges, respectively. [ABSTRACT FROM AUTHOR]

Proposes a quasi-resonant PWM converter topology for unity power factor application. Achievement of zero-voltage transition conditions for both the main and auxiliary switching devices; Clamping of the blocking voltage at a relatively low level during off period; Analysis of the operating modes of the converter.