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This paper investigates the Al2O3/AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (MOSHEMT) performance with post oxidation annealing (POA) process. First, the optimum annealing condition was found to be 400°C for 20 min. The transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy were used for material analysis. The hysteresis capacitance-voltage (C-V) measurement was also used to characterize the amount of traps at the Al2O3/AlGaN interface. It was found that the amount of the traps reduced after POA process. In addition, the performance of the MOSHEMT like gate leakage current, output current, subthreshold swing, off-state breakdown voltage, frequency response, and power characteristics were improved after POA process.

Cowell’s method of extracting barrier heights of top and bottom electrode metals in asymmetric metal-insulator-metal (MIM) tunneling diodes exhibiting Fowler-Nordheim tunneling is successfully automated. Pt-Al2O3-TiN MIM diodes with 5 nm insulator thickness are used in demonstration. Conditions assuring successful application of Cowell’s method and its automation are discussed.

Resistive random-access memory (RRAM) has shown great potential for neuromorphic engineering, due to its ability of emulating neural network and simple structure. To mimic the brain-learning behavior, two types of neural actions, short-term plasticity (STP) and long-term potentiation (LTP), should be imitated perfectly. In this work, we propose a unique RRAM cell with a double switching layer, in which a 2D material is embedded as a separation layer. Within a proper voltage range of stress, the mobile oxygen ions are blocked by the single atomic layer, and hence the subsequent relaxation of oxygen ions leads to a volatile switching characteristic. Owing to this volatile characteristic, the proposed device can mimic neural actions, STP and LTP, by a simple pulse train with different repetitions and frequencies without the complicated pulse settings of spike-timing-dependent plasticity (STDP). For various learning algorithms in future brain-inspired applications, different switching materials with different bind energies and relaxation times of oxygen ions can be utilized.

This paper uses H2O2 oxidation technique to grow Al2O3 on AlGaN/GaN heterostructure. The H2O2-grown-Al2O3 is served as a sensing membrane and a surface passivation layer. The contact angle of the ion-sensitive field-effect transistor (ISFET) with the H2O2-grown-Al2O3 is improved from 66.5° to 40.6° and this phenomenon indicates that the hydrophile characteristic is improved after the H2O2 treatment. The drain-source current ( $I _{\textrm {DS}}$ ) is improved $\sim 32$ % after the H2O2 oxidation due to the passivation effect. In addition, extrinsic transconductance ( $\mathrm{g}_{m}$ ) characteristics of the transistors are investigated. The pH sensitivity is also improved from 41.6 to 55.2 mV/pH for the ISFET with H2O2-grown-Al2O3. Furthermore, the ISFET with the H2O2 treatment exhibits better transient characteristics compared with the ISFET without the H2O2 treatment. The sensitivity parameter ( $\beta $ ) and the relationship between surface potential ( $\psi _{s}$ ) and pH value are investigated by theoretical calculation. The hysteresis phenomenon and the drift effect can be improved using the present H2O2-grown Al2O3 as the sensing membrane and the passivation layer.

Comparative studies for TiO2-passivated Al0.25Ga0.75N/GaN heterostructure FETs (HFETs) and TiO2-dielectric MOS-HFETs using nonvacuum ultrasonic spray pyrolysis deposition technique are made. Optimum device performances are obtained by tuning the layer thickness of TiO2 to 20 nm. High relative permittivity ( $k$ ) of 53.6 and thin effective oxide thickness of 1.45 nm are also obtained. Pulse-IV, Hooge coefficient ( $\alpha _{H}$ ), Transmission Electron Microscopy, and atomic force microscope have been performed to characterize the interface, atomic composition, and surface flatness of the TiO2 oxide. Superior improvements for the present TiO2-dielectric MOS-HFET/TiO2-passivated HFETs are obtained, including 47.6%/23.8% in two-terminal gate–drain breakdown voltage (BV $_{\rm GD})$ , 111%/22.2% in two-terminal gate-drain turn-ON voltage ( $V_{\mathrm{{\scriptscriptstyle ON}}})$ , 47.9%/39.4% in ON-state breakdown (BV $_{\rm DS})$ , 12.2%/10.2% in drain–source current density ( $I_{\rm DS})$ at $V_{\rm GS} = 0$ V ( $I_{\rm DSS0})$ , 27.2%/11.7% in maximum $I_{\rm DS}$ ( $I_{\rm DS, max})$ , 3/1-order enhancement in on/off current ratio ( $I_{\mathrm{{\scriptscriptstyle ON}}} / I_{\mathrm{{\scriptscriptstyle OFF}}})$ , 58.8%/17.6% in gate-voltage swing linearity, 25.1%/13.2% in unity-gain cutoff frequency ( $f_{T})$ , 40.6%/24.7% in maximum oscillation frequency ( $f_{\max })$ , and 33.8%/15.6% in power-added efficiency with respect to a Schottky-gated HFET fabricated on the identical epitaxial structure. The present MOS-HFET has also shown stable electrical performances when the ambient temperature is varied from 300 to 450 K.

This study investigates the interface between the active layer and contacts in organic photovoltaics (OPVs) since the contact materials strongly affect the energy barrier at the interfaces. The interfacial characteristics are simply defined as a resistance–capacitance ( R–C ) shunt pair and extracted by fitting the impedance spectra to the equivalent circuit model. A change in the energy barrier is found to affect the values of R and C at the interface and the carrier transition time. In addition, the effect of electron buffer layer (TiO2) thickness on the interfacial characteristics is analyzed using an impedance spectroscopy. The interfacial area between the hole buffer layer (MoO3), and the active layer affects the values of R and C at the interface.

A device design technique for nanowire FETs for low power capability beyond 10 nm technology node is proposed using 3D numerical simulation and physical analysis. The subthreshold kink effect enables the use of low supply bias without compromising performance. The proposed technique overcomes the fundamental and thermal voltage-limited subthreshold swing (SS). As end of technology roadmap is being approached, many solutions to extend Moore’s Law have been proposed. As the leakage current, mainly coming from the short-channel effects (SCEs), is becoming a limiting factor, the supply bias, i.e. VDD, has to decrease as the channel dimension continues to shrink. However, in order to provide a good CMOS logic, on-off current ratio, which is linked to SS, has to maintain at least three orders. Such limitation has prevented the supply bias from further scaling down. It would be a great deal if we can reduce SS. In SOI-based MOSFETs, floating body effects (FBEs) have addressed a concern for design, especially for a partially depleted body. Fully depleted SOI (Fig. 1) is considered a simpler device as FBEs are minimized. Among FBEs, the kink effect in subthreshold regime and in strong inversion due to impact ionization was once a big issue for the concern of raised off leakage current (Ioff). Nontheless, such concern has long gone since fully depleted SOI emerged. For the kink mechanism, the quasi neutral body in which the injected holes are stored is needed (Fig. 2), but it does not exist in fully depleted devices. Among nonplaner emerging transistors, gate-all-around (GAA) nanowire MOSFET shows superior SCE control due to excellent electrostatics. The GAA channel is usually design with a small diameter to meet the scale length requirement. FBEs are never of concern in the strongly depleted body. We found that using a proper scheme of channel doping, the subthreshold kink is observed. Furthermore, if the kink is away from VGS = 0 V, Ioff is not influenced. Using such technique, we were able to lower SS to less than 60 mV/dec. Fig. 3 shows the GAA n-MOSFET for simulation with gate length (L) of 5 nm, gate oxide thickness of 0.4 nm, channel doping of 1e19 cm^-3 and source/drain doping of 1e20 cm^-3 following ITRS. The high channel doping is intended to create a quasi neutral body for FBEs to effect. Such doping level is now a viable option as in-situ doping has become widely accepted. Fig. 4 shows IDS versus VGS characteristics, where the subthreshold kink at high drain bias is observed. Fig. 5 shows IDS versus VGS characteristics for different channel doping levels, indicating high doping is needed. Figs. 6 and 7 show hole density at different biases, respectively. As can be seen, holes are being accumulated when VGS is set to the condition for the kink to occur. A kink-assisted steep SS scheme was proposed for GAA MOSFETs using in-situ doping technique. Though additional channel doping induces impurity scattering and hence degrades drive current, the benefit from steep SS could overwhelm such drawback if designed properly when seeking for lower supply bias. Figure 1

This letter demonstrates and investigates AlGaN/GaN metal–insulator–semiconductor ultraviolet photodetector (MIS-UV-PD) with a cost-effective wet oxidation technique. The H2O2 oxidation technique is adopted to grow an insulator layer. The material qualitative and semiquantitative analyses of the H2O2-grown aluminum oxide are studied by energy dispersive X-ray spectroscopy The performances of the present MIS-UV-PD with different H2O2 treatment time are also investigated. The MIS-PD with 5-min H2O2 treatment time has the optimum performances. The dark current is suppressed from 4.23 nA to 5.15 pA at −10 V. The responsivity and the UV to visible rejection ratio are enhanced to $1.03\times 10^{\mathrm {\mathbf {-2}}}$ A/W and $3.38\times 10^{\mathrm {\mathbf {5}}}$ . Moreover, the noise equivalent power and detectivity are determined to be $4.8\times 10^{\mathrm {\mathbf {-11}}}$ W and $4.52\times 10^{\mathrm {\mathbf {10 }}}$ cmHz $^{\mathrm {\mathbf {0.5}}}$ W $^{\mathrm {\mathbf {-1}}}$ . This cost-effective oxidation technique provides a simple approach to fabricate AlGaN/GaN MIS-UV-PD and its performances are also improved.

This paper proposed Al 2 O 3 deposition by ultrasonic spray pyrolysis (USP) method as an insulator layer for Al 2 O 3 /AlGaN/GaN metal-insulator-semiconductor ultraviolet photodetector (MIS-UV-PD) applications. The composition of USP-grown Al 2 O 3 was confirmed by X-ray photoelectron spectroscopy. The refractive index and transmittance characteristics of USP-grown Al 2 O 3 were also characterized. The Al 2 O 3 /AlGaN/GaN MIS-UV-PD performances with different Al 2 O 3 thickness (30, 20, and 15 nm) were investigated. The responsivity was 1.3 × 10 -3 /7.5 × 10 -3 /0.83 A/W, UV-to-visible rejection ratio was 2.34 × 10 3 /1.37 × 10 4 /3.18 × 10 5 , and the detectivity was 2.78 × 10 8 /1.26 × 10 9 /1.17 × 10 11 cmHz 0.5 W -1 for the MIS-UV-PD with 30-/20-/15-nm-thick Al 2 O 3 . It was found that the performances of MIS-UV-PD with 15-nm Al 2 O 3 as the insulator layer are much better than the MIS-UV-PD with 20and 30-nm Al 2 O 3 .

Enhancement-mode AlGaN/GaN MOSHEMTs have been widely used in power electronic applications thanks to its superior electrical characteristics [1, 2]. Several methods have been proposed to fabricate E-mode AlGaN/GaN HEMTs like gate recess [3], F− doping at the AlGaN barrier layer [4], and p-type GaN cap layer [5]. Nevertheless, the high threshold voltage and high output current is hard to obtain simultaneously for the E-mode AlGaN/GaN HEMT. Recently, the E-mode AlGaN/GaN MOSHEMT is realized by integrating two of the above methods to obtain higher Ids and more positive V t [6, 7]. This work proposes gate structure engineering by integrating three processes, including gate recess, fluorine doped barrier layer and in-situ chlorine doped Al 2 O 3 gate dielectric layer to realize the E-mode AlGaN/GaN MOSHEMT. The present MOSHEMT shows higher output current density and more positive threshold voltage than the MOSHEMTs which use gate recess and fluorine doping techniques.

1, 8-Diiodooctane (DIO) has been known for its role of improving the polymer morphology and enhancing performance of polymer bulk heterojunction (BHJ) solar cell. In this work, the impedance spectroscopy was used to investigate the interface of poly(4,8-bis-alkyloxybenzo(1,2-b:4,5-b′)dithiophene-2,6-diyl-alt- (alkyl thieno(3,4-b) thiophene-2-carboxylate)-2,6-diyl) (PBDTTT-C):PC 70 BM in BHJ with DIO as additive. Based on our results, we were able to simulate the device into an equivalent circuit model, which allows us to conveniently analyze the organic/organic interfacial contact in the organic photovoltaic (OPV) device. Thus, we demonstrate that the impedance spectroscopy can an effective approach in characterizing the donor/acceptor interfaces, such that a direct correlation can be established between the morphology and the device performance of BHJ devices.

Composite HfO2/Al2O3-dielectric In0.2Ga0.8As/Al0.24Ga0.76As metal–oxide–semiconductor high-electron-mobility transistors (MOS-HEMTs) by using RF sputtering/ozone water oxidization, respectively, are investigated. In comparison with a conventional Schottky-gate device on the same epitaxial structure, an Al2O3 liner was chemically formed for the present MOS-HEMT to improve interfacial quality and decrease gate leakages. Moreover, a high-k HfO2 layer was further deposited on the Al2O3 liner to enhance the gate modulation capability. The present MOS-HEMT with the devised HfO2/Al2O3 dielectric stack has demonstrated excellent switching characteristics, including superior subthreshold slope (S.S.) of 70 mV/dec and high drain–source current (IDS) on–off ratio of up to 6 orders. Improved direct-current (DC), radio-frequency (RF), and high-temperature device performances of the present design are also comprehensively studied in this work.

This paper investigates the temperature-dependent performances of AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT). The gate dielectric layer and surface passivation layer are formed by the H 2 O 2 oxidation technique. The gate dielectric quality is estimated by the breakdown electric field (EBD) and low-frequency noise. The capacitance-voltage (C-V) hysteresis characteristics of MOS and Schottky diodes at 300/480 K are also studied. An appropriate thermal model is used to investigate the self-heating effect and calculate the effective channel temperature (T eff ). The dc performances of the present MOS-HEMT are improved at 300/480 K, as compared with a Schottky-barrier HEMT (SB-HEMT), including output current density, maximum extrinsic transconductance (gm,max), gate voltage swing, gate-drain leakage current (IGD), specific ON-resistance (RON), three-terminal OFF-state breakdown voltage (BVOFF), and subthreshold swing. Factors that cause IGD and BVOFF are analyzed by the temperature-dependent measurement. The passivation effect of the present MOS-HEMT is also confirmed by the surface leakage measurement. The devised MOS-HEMT demonstrates superior thermal stability to the reference SB-HEMT. The present-design is promising for high-temperature electronic applications.

Gate-all-around (GAA) MOSFETs relevant for the 11.9-nm CMOS technology node are optimized with device dimensions following the scale length rule. Variability in transistor performance due to systematic and random variations is estimated with the aid of TCAD 3-D device simulations, for these well-tempered GAA structures. The tradeoff between read stability and write-ability of 6-T static RAM cell designs implemented with GAA MOSFETs with either square or rectangular nanowire channel regions is then investigated, and a calibrated transistor \({\boldsymbol {{I}}}\) – \({\boldsymbol {{V}}}\) compact model is used to estimate cell yield. The results indicate that a rectangular (thin and wide) channel design achieves the optimal balance between the read yield and write yield and hence provides for the lowest minimum cell operating voltage, estimated to be \(\sim 0.45\) V, as well as smaller cell area.

This letter utilizes ultrasonic spray pyrolysis (USP) to deposit Al2O3 as the passivation layer of GaN light-emitting diodes (LEDs). The composition of Al2O3 is analyzed by X-ray photoelectron spectroscopy. The refractive index and transmittance of USP-grown Al2O3 are investigated. The thickness of Al2O3 is determined to be 70 nm, which is close to the optimum from antireflection theorem calculation for the wavelength of 455 nm. The coverage quality and thickness are confirmed by transmission electron microscopy. The light output power (LOP) of USP-grown-Al2O3-passivated InGaN/GaN LED is improved from 321 mW to 347 mW compared with an LED without passivation. The forward voltage ( \(V_{\mathrm {\mathbf {F}}}\) ) and series resistance ( \(R_{\mathrm {\mathbf {s}}}\) ) are not subject to significant variations but the shunt resistance ( \(R_{\mathrm {\mathbf {SH}}}\) ) is increased after Al2O3 passivation. LED chips with Al2O3 and SiO2 passivation are packaged as LED lamps. Devices passivated by USP-grown Al2O3 show slightly better LOP performance than those passivated by plasma-enhanced chemical vapor deposition-grown SiO2.

FinFETs have been made successfully for mass manufacturing on bulk and silicon-on-insulator wafers. When choosing the bulk option, additional process steps are needed for substrate leakage suppression. Typically, heavy substrate doping for punchthrough stopping between the source and drain is used, but precise control of the doping profile to prevent its up-diffusion into the channel has been a challenging task, especially for continuously shrinking device dimension. In this paper, we propose a stack gate structure with doping-free substrate while punchthrough leakage can be suppressed. The proposed technique can be integrated in conventional gate-last high-k metal gate process. Both polysilicon and metal gates are shown to be feasible in the proposed stack gate based on 3-D TCAD simulation. In addition, the stack gate structure without substrate doping is immune to its random dopant fluctuations.

Enhanced light extraction efficiency (LEE) of high-power GaN-based light-emitting diodes (LEDs) is achieved by inserting a self-assembled SiO2 nanosphere monolayer between the substrate and backside reflectors. Due to the presence of concave surfaces and photonic crystal-like air voids, downward photons emitted from multiple quantum well toward 3-D backside reflectors, could be reflected, scattered, and redirected into arbitrary directions for light extraction. These textured 3-D backside reflectors with an SiO2 nanosphere monolayer could also extract the lateral light inside device into the normal direction and improve LEE. As compared with a conventional LED without a backside reflector and an LED with a planar hybrid backside reflector, at 350 mA, the studied device with a 3-D hybrid backside reflector exhibits 136.4% (165%) and 23.6% (27.4%) enhancements in light output power (luminous flux) without the degradation of electrical properties. Higher light intensities in light emission mapping image and far-field pattern are also obtained. These results show that a textured 3-D backside reflector could be easily formed by inserting an SiO2 nanosphere monolayer to significantly enhance the performance of high-power GaN-based LEDs.

This letter demonstrates and investigates AlGaN/GaN ultraviolet photodetector (UV-PD) with a simple passivation process. The hydrogen peroxide (H2O2) oxidation technique is adopted to complete the passivation. The results of chemical analysis suggest that the Al and Ga dangling bonds react with the oxygen atoms. This passivation process effectively reduces the side-wall surface states, which also suppress the dark current to 11 pA. In addition, the photo response and the UV to visible rejection ratio of the PD with H2O2 passivation process are enhanced to 8.1×10-3 A/W and 2.3×103 when the PD is biased at -10 V. The noise equivalent power and the detectivity are determined to be 1.63×10-8 W and 1.33×108 cmHz0.5W-1. The simple passivation technique improves the AlGaN/GaN UV PD performances effectively.

Most photovoltaics operate at high temperature under sunlight. In this work, the thermal instability of diiodooctane-based high-efficiency bulk heterojunction (BHJ) organic photovoltaics (OPVs) is studied. The BHJ layers were heated to various temperatures to investigate the changes in their physical properties using atomic force microscopy phase images. The mobilities of the carriers were characterized at various temperatures using the space-charge-limited current method, and the carrier lifetime was calculated by applying impedance spectroscopy to the simulated equivalent circuit of the OPV devices.

Comparative studies of double δ-doped InAlAs/InGaAs metal-oxide-semiconductor metamorphic high electron mobility transistors (MOS-MHEMTs) with different compressive-strained and tensile-strained channel structures have been made. In addition to the strain engineering of the heterostructure, the MOS-gate design is also integrated by using the cost-effective H2O2 oxidization technique. The tensile (compressive)-strained channel is devised by the In0.52Al0.48As/In0.41Ga0.59As (In0.52Al0.48As/In0.63Ga0.37As) heterostructure. Device characteristics with respect to different channel structures are physically studied. The impact-ionizationrelated kink effects in MHEMTs are significantly suppressed by the MOS-gate. Atomic force microscopy (AFM) and low-frequency noise (LFN) analysis were used to study the surface roughness and interface quality. As compared to the compressive-strained MOSMHEMT and conventional Schottky-gate devices, the present tensile-strained MOS-MHEMT design has demonstrated improved transconductance gain (gm), current drive, intrinsic voltage gain (AV), and power performance. © The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0031412jss] All rights reserved.

Al0.3Ga0.7N/AlN/GaN metal-oxide-semiconductor high electron mobility transistors (HEMTs) grown on Si substrates by using ozone water oxidation method are investigated. Superior improvements of 52.2% in two-terminal gate-drain breakdown voltage (BVGD), 30.3% in drain-source current density (IDS) at VGS = 0 V (IDSS0), 43.6% in maximum IDS (IDS,max), 34.7% in maximum extrinsic transconductance (gm,max), and 52.7%/34.3% in unity-gain cutoff/maximum oscillation frequency (fT/fmax) are achieved as compared with a reference Schottky-gated HEMT. Thermal stability is studied by conducting temperature-dependent characterizations of devices at ambient temperatures of 300-550 K. Time-dependent electrical reliability analyses for the devices stressed in off-state (VGS = -20 V and VDS = 0 V) for 0-60 h and on-state (VGS = 2 V and VDS = 20 V) for 0-20 h are also made to physically investigate the dominant degradation mechanisms. Excellent reliability and thermal stability at 300-550 K are achieved by the present design.

A feasible device design methodology for bulk FinFETs is proposed. An optimal yet simple process technique is shown to achieve good performance while maintaining low leakage current with thin gate-to-substrate isolation oxide and moderately doped substrate. In contrast, high substrate doping underneath the fin and thick isolation oxide are usually needed to prevent substrate leakage in conventional bulk FinFETs. A design window accounting for isolation oxide thickness and substrate doping level is proposed for low power and high performance application. Sufficient substrate doping (in the mid-10 18 cm −3 range) and proper isolation oxide of 10s nm are suggested based on our performance projection.

We have measured surface photovoltage (SPV), photoreflectance (PR), and photoluminescence (PL) spectra of two InAlAs/InxGa1 − xAs/InAlAs metamorphic high-electron mobility transistor (MHEMT) structures. One possesses a V-shaped InxGa1 − xAs (x = 0.3–0.5–0.3) tensile-strained channel in In0.5Al0.5As/InxGa1 − xAs/In0.5Al0.5As heterostructures, and the other is an In0.42Al0.58As/In0.53Ga0.47As/In0.42Al0.58As MHEMT structures with InxGa1 − xAs (x = 0.53) compressively-strained channel grown on GaAs by molecular beam epitaxy. The comparison of SPV, PR, and PL spectra facilitates the identification of channel-well transitions in the MHEMT structures with different InxGa1 − xAs channels. Inter-subband transitions, Fermi-level energies, and built-in electric field of the two MHEMT structures with dissimilar InxGa1 − xAs channel are evaluated and discussed from the experimental analyses of SPV, PR and PL measurements. The results showed that the design of tensile-strained MHEMT structure enhances sheet-carrier density and avoids surface-roughness scattering by increasing V-shape electric field between the two channel interfaces. The electron mobility of the tensile-strained MHEMT structure is hence being promoted.

This paper investigates enhanced device characteristics of AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (HEMT) (MOS-HEMT) fabricated by using hydrogen peroxide (H2O2) oxidation technique which demonstrates the advantages of simplicity and cost effectiveness. A 13-nm-thick Al2O3 oxide was grown upon the surface of AlGaN barrier layer and served as the gate dielectric layer and the surface passivation layer at the same time to effectively decrease gate leakage current and prevent RF current collapse, which are the critical issues of nitride HEMTs. Enhanced device performances of dc, RF, power, and reliability of the present MOS-HEMT are comprehensively investigated as compared with a conventional Schottky-gate HEMT.

In this paper, a novel three-phase five-level inverter is proposed. The proposed topology constructed of 12 power switches and 12 diodes to achieve a three-phase five-level AC Y-connected output. The output line-to-line voltage is five levels and total harmonic distortion is lower. Compared to the traditional three-phase inverters, the proposed three-phase five-level inverter can achieve the five output voltage levels with fewer components. In this paper, the details of the mode analyses and control schemes are discussed. An experimental prototype with input voltage 500 V, output power 6 kW, THD 3.62%, and efficiency 98.40% is implemented to verify the theory and feasibility of the proposed topology.

In the present study, a time-multiplexing current balance (TMCB) current-mode boost converter is proposed to improve the transient performance. Generally, the crossover frequency of a conventional boost converter is limited to half or less than the right-half-plane (RHP) zero to ensure the system stability. The transient performance of a conventional boost converter is degraded due to its limited bandwidth. The proposed TMCB boost converter extends its bandwidth and moves the RHP zero to a higher frequency to improve the transient performance using two inductors in one channel. Besides, the small signal model of dual phase system which considers cross-couple effect and offset correction is presented. The proposed converter requires an extra inductor and a slight increase in the size of the printed circuit board layout and die size. Using time multiplexing, two inductors were operated in an interleaved phase at a switching frequency of 5 MHz rather than a single inductor system operated at a switching of 10 MHz for the same ripple required. Experimental results show that the TMCB technique is effective in correcting the mismatch in the current of the inductors even if the difference between the inductors is large. Furthermore, the proposed converter can improve the settling time from 52 to 22 μs due to an extended bandwidth.

This studies the thermal effects on a polymer solar cell, consisting of conjugated poly(3-hexylthiophene) (P3HT) and fullerence derivative [6,6]-phenyl-C 61 butyric acid methyl ester (PCBM) composites with high concentrations of 3–5 wt%. Improved light absorption, crystalline degree and molecular distribution of highly concentrated of P3HT:PCBM blended films are achieved after the thermal treatment. Additionally, the photocurrent density and power conversion efficiency (PCE) of the present polymer solar cells with 5 wt% P3HT:PCBM film are enhanced by more than sixfolds and sevenfolds, respectively. The 130 °C-treated polymer solar cell with 4 wt% P3HT:PCBM film has a superior PCE of 3.6% under AM1.5 illumination at 100 mW/cm 2 due to an enhanced separation efficiency of excitons and balanced carrier mobility.

Impact of device structure variability of silicon nanowire FETs is assessed and SRAM design implication is presented based on 3-D numerical simulation. Both the conventional and junctionless nanowire FETs are shown to be sensitive to structural variation whereas the former is more tolerable. Both the circular wire and non-circular wire cases for feasible SRAM design with a focus on read/write noise margin are included in our study.

This paper proposes a highly integrated dual-side dual-output (DSDO) switched-capacitor (SC) converter with only two flying capacitors. Generally, a dual-phase voltage doubler and an inverter are used to supply positive and negative voltages for thin film transistor-liquid crystal display (TFT-LCD) gate drivers, respectively. Four flying capacitors, eight pin-outs for the four flying capacitors, and 16 power switches are necessary for their operations in the driver integrated chip (IC). The proposed DSDO SC converter combines both dual-phase voltage doubler and inverter converter in one channel through the use of time multiplexing technique with minimal performance degradation. As a result, the proposed converter not only reduces the number of flying capacitors from four to two, but also removes four IC pin-outs for lower cost and more compact size. Moreover, the 16 required power switches are reduced to 12, resulting in an approximated 27% decrease of the silicon area.

This work investigates temperature-dependent device characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) grown by a metal-organic chemical vapor deposition (MOCVD) system, and passivated by using hydrogen peroxide (H2O2) oxidation method. The present oxide-passivated AlGaN/GaN HEMT can effectively improve device performances, including current drive, transconductance, gate-drain forward turn-on voltage (Von), and gate-drain reverse breakdown voltage (BVGD) at 300–480 K. In addition, improved RF and power performances have also been achieved as compared with an unpassivated device. The present oxide-passivated AlGaN/GaN HEMT is promising for high-temperature and high-power monolithic microwave integrated circuit (MMIC) applications.

Al0.2Ga0.8As/In0.2Ga0.8As metal-oxide-semiconductor pseudomorphic high electron mobility transistors (MOS-pHEMTs) with different shifted -gate structures have been comprehensively investigated in this work. The present -gate MOS-pHEMTs were fabricated by using techniques of ozone water oxidation and shift exposure. Gate length (LG) reduction, surface oxide passivation, and field-plate structure are achieved at the same time by the devised -gate processing. By using the same optical mask set, devices with different LG/field-plate lengths (LFP )o f 1.2/0μm, 0.8/0.4 μm, and 0.6/0.6 μm were fabricated upon the identical epitaxial layer structure. Device performances including device gain, current drive, off/on-state breakdown, high-frequency characteristics, power characteristics, and high-temperature stability up to 450 K, are investigated with respect to different LG/LFP lengths in this work.

This brief reports, for the first time, an oxide passivated AlGaN/GaN high electron mobility transistor by using the hydrogen peroxide (H2O2) treatment. Characterizations by using electron spectroscopy for chemical analysis and transmission electron microscopy have been performed to verify the formation of surface oxide on the AlGaN barrier layer. The present design has demonstrated superior improvements of 41% in the maximum drain/source current density IDS,max; 39% in the drain/source saturation current density at zero gate bias IDSSO, 47% in the maximum extrinsic transconductance gm,max, 53.2% in the two-terminal gate/drain breakdown voltage BVGD 36% in the cutoff frequency fT, and 20% in the maximum oscillation frequency fmax, as compared with an unpassivated conventional device.

In this paper, a current mode boost converter using window transient enhancement (WTE) and overshoot suppression (OSS) technique is presented for digital still camera (DSC) applications. The peak-to-peak transient overshoot voltage demand of a DSC motor driver is generally within 4%-5% of the regulated value. However, conventional boost converters usually fail to pass this criterion during large load transient. The OSS technique reduces the overshoot voltage when load current changes from heavy to very light. Experimental results show that compared with the use of a conventional current mode boost converter, the use of the technique reduces drop voltage about 62% and overshoot voltage about 51% when the load current has a load step of 400 mA. Moreover, the settling time improves to 43%, which is better than in the conventional case of a 400 mA load current step. The overhead of the silicon area is about 4.5% to achieve the overshoot reduction. The estimated high performance demonstrates that it is suitable for DSC applications.

An efficient electron injection/hole blocking layer, N-[3-(trimethoxysily)propyl]ethylenediamine that was grafted onto zinc oxide (ZnO/PEDA-TMS), was used in inverted polymer light-emitting diodes (PLEDs). PEDA-TMS induced a strong dipole directed towards ZnO, which was enhanced by vacuum energy level shifts of ultra-violet photoelectron spectroscopic observations, reducing the barrier height between ZnO and the emissive layer. The effect of annealing ZnO on the performance of PLEDs was analyzed using an electron-only device and capacitance–voltage ( C – V ) characterization. Following annealing at 300 °C, ZnO provided effective electron injection and blocked holes, which enhanced the recombination of the electrons and holes. The eletroluminescence efficiency of an inverted PLED with a ZnO/PEDA-TMS layer is comparable to that of a conventional device. The electron injection mechanism of the inverted device can be explained by C – V behaviors, which are correlated with the threshold voltage and turn-on voltage.

A novel Γ-gate Al0.24Ga0.76As/In0.15Ga0.85As metal-oxide-semiconductor (MOS) high-electron-mobility transistor (MOS-HEMT) by using methods of ozone water oxidation and shifted exposure has been comprehensively investigated. Effective gate-length reduction, improved gate insulation, and formations of a field plate and a full surface passivation within the drain-source region are simultaneously achieved. The present Γ-gate MOS-HEMT has demonstrated superior device performances, including improvements of 523% (12.8%) in two-terminal gate-drain breakdown, 137% (36.1%) in on-state drain-source breakdown, 16.1% (11.8%) in maximum extrinsic transconductance (gm, max), 34.5% (9.7%) in intrinsic voltage gain (AV), 27.8% (16.2%) in power-added efficiency, 34.5% (19.8%) in minimum noise figure (NFmin) , and 28%/39.3% (11.4%/21.6%) in unity-gain cutoff frequency/maximum oscillation frequency (fT/fmax), as compared to a conventional Schottky-gate (MOS-gate) device fabricated upon the same epitaxial structure by using an identical optical mask set. Investigations of optimum extracted parasitics, small-signal device parameters, and high-temperature device characteristics at 300 K-450 K are also made in this work.

This paper presents a high integrated dual-side dual-output (DSDO) switched-capacitor (SC) regulator with only two flying capacitors. Generally, a dual-phase voltage doubler and an inverter are used to supply positive and negative voltage for TFT-LCD gate drivers, respectively. Four flying capacitors, eight pin-outs, and sixteen power switches are necessary for their operations in the driver integrated chip (IC). The proposed DSDO SC regulator combines both dual-phase voltage doubler and inverter converter into one channel through the use of time multiplexing technique at the cost of little performance degradation. As a result, it not only diminishes the number of flying capacitor from four to two but also removes four IC pin-outs for low cost and compact size. Beside, sixteen necessary power switches are reduced to twelve for decreasing about 27% silicon area.

The hydrogen sensing and response characteristics of a catalytic Pd/GaN metal-semiconductor (MS) Schottky diode are systematically studied in this paper. The current-voltage characteristics, hydrogen detection sensitivity ratios, Schottky barrier height variations, adsorption heat, and transient responses for different hydrogen concentration are measured over wide temperature range. The Pd/GaN Schottky diode reveals a remarkable capability of hydrogen detection at high temperature and relatively wide operating temperature range under bipolarly applied voltages. Experimentally, extremely low hydrogen concentration for 14 ppm H2 in air can be detected. A very high hydrogen detection sensitivity ratio of 12744 and a large Schottky barrier height variation Δφb of 253 meV are obtained when a 9970 ppm H2 in air gas is introduced at 300 K. In addition, according to the van't Hoff equation, the hydrogen adsorption heat value of the studied device is calculated as -18.24 kJ mole. Finally, considerably short response time is found in the studied device.

A novel transparent Al-doped ZnO (AZO)-gated Al0.2Ga0.8As/In0.2Ga0.8As pseudomorphic high-electron mobility transistor (pHEMT) has been comprehensively investigated. The proposed AZO-gated pHEMT has demonstrated superior temperature-dependent performance, including two-terminal gate-drain breakdown/turn-on voltages of - 63/3.4 (-56.4/3.4) V, an intrinsic voltage gain AV of 257 (176), and a gate voltage swing of 1.18 (1.13) V at 300 (450) K. An excellent thermal threshold coefficient ∂Vth/ΘT of -1.8 mV/K was also obtained. A conventional Au-gated device with the same gate dimensions of 1 × 100 μm2 was also fabricated in comparison. In addition, high optical transmittance values of 82%-98% for incident energy values of 1.24-3.54 eV are achieved in the AZO film. The present AZO-gated HEMT has demonstrated three-terminal tunable optical responsivity due to a photovoltaic effect. Photosensing characteristics under different radiation wavelengths of white light, red light (632 nm), and near infrared (980 nm) are also studied.

High-k TiO 2 -dielectric Al 0.25 Ga 0.75 N/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs) grown on Si substrates by using nonvacuum ultrasonic spray pyrolysis deposition technique are reported for the first time. The effective oxide thickness is 1.45 nm with layer thickness/dielectric constant of 20 nm/53.6. Pulse I-V and low-frequency noise spectra (1/f) are conducted to characterize the interface property. The gate leakage current I GD is decreased by three orders at V GD = -50 V as compared with a reference Schottky-gate device. Superior device characteristics are achieved for the present MOS-HEMT (Schottky-gate HEMT) for the gate dimensions of 1 μm × 100 μm including drain-source current density I DS at V GS = 0 V (I DSS0 ) of 384 (342) mA/mm, maximum I DS (I DS , max ) of 650 (511) mA/mm, maximum extrinsic transconductance (g m , max ) of 107 (110) mS/mm, two-terminal gate-drain breakdown voltage (BVGD) of -155 (-105) V, turn-ON voltage (VON) of 3.8 (1.8) V, ON-state breakdown (BVDS) of 139 (94) V, gate-voltage swing of 2.7 (1.7) V, and ON/OFF current ratio (I ON /I OFF ) of 4.5 x 10 5 (3.5 x 10 2 ).

This letter reports, for the first time, the Al 2 O 3 -passivated AlGaN/GaN high electron mobility transistors (HEMTs) by using the nonvacuum ultrasonic spray pyrolysis deposition (USPD) technique. The Al 2 O 3 was devised as the surface passivation layer to effectively suppress leakage current and to reduce RF drain current collapse. The surface oxide has been characterized by using electron spectroscopy for chemical analysis, energy-dispersive X-ray spectroscopy, and transmission electron microscopy (TEM). With respect to an unpassivated device, the Al 2 O 3 -passivated HEMT has demonstrated superior improvements of 24.2% in maximum drain-source current (I DS,max ), 33.6% in maximum extrinsic transconductance (g m,max ), 46.8% in two-terminal breakdown voltage (BV GD ), and 45.3% in three-terminal off-state breakdown voltage (BV off ). The corresponding improvements achieved are 9.1%, 16.1%, 61.3%, and 55.7% for I DS,max, gm,max, BV GD , and BV off , respectively, as compared with passivation in Si 3 N 4 HEMTs. Besides, reduced interface density (Dit) and about two-order decreases in the leakage current are also achieved in the Al 2 O 3 -MOS diode using USPD with respect to a Si 3 N 4 -MIS diode.

In this study, the authors propose non-conventional phase-change memory programming schemes using a comprehensive model, which integrates the underlying electrical and thermal theories. Various pulsing schemes aiming to reduce operation power without compromising performance are assessed based on a calibrated model. Our results suggest that optimisation of power consumption can be done simply by design of pulsing techniques.

This letter used ultrasonic spray pyrolysis deposition (USPD) to deposit SnO2:F, Al2O3, and InGaZnO thin films to, respectively, serve as the bottom gate, gate dielectric layer, and channel layer of a thin-film transistor. For comparison, the sputter-deposited InGaZnO thin film was prepared as the reference sample. X-ray diffraction and X-ray photoelectron spectroscopy were used to observe the crystal structure and oxygen vacancy of the InGaZnO thin films. The optical characteristics were observed using the photoluminescence spectrum and an optical spectrometer. The InGaZnO-based TFT deposited by USPD shows competitive electrical characteristics compared with the sputter-deposited one. However, the USPD-deposited InGaZnO-based TFT has unstable negative bias illumination stress characteristic. Nevertheless, this letter provides an alternative and relatively cost-effective method for fabricating InGaZnO TFTs.

X‐band gain amplifiers, consisting of a symmetrically‐graded‐channel In0 425 Al0.575As/InxGa1 –xAs (x = 0.5 ?> 0.65 —? 0.5) metamorphic high electron mobility transistor (SGC‐MHEMT) and a pseudomorphic‐channel In0 425Al0 575As/In0 65Ga0.35As MHEMT (PC‐MHEMT), respectively, have been successfully investigated. The devised SGC‐MHEMT (PC‐MHEMT) amplifier circuit has demonstrated superior small‐signal gain of more than 15.7 (14.5) dB within the X‐band frequency regime. In addition, the SGC‐MHEMT amplifier also demonstrates superior gate‐voltage swing (GVS) characteristics as compared to the PC‐MHEMT amplifier. The improved tolerance for gate‐bias variations makes the proposed design suitable for high‐power and high‐linearity monolithic microwave integrated circuit (MMIC) applications.

A 26–38 GHz millimeter-wave (MMW) band sub-harmonic mixer has been designed using a 0.15-μm GaAs pseudomorphic high-electron-mobility transistor (pHEMT) technology. The anti-parallel diode pair (APDP) configuration as the basic unit in this sub-harmonic mixer design to suppress the fundamental frequency signals is used. The radio-frequency (RF) and the local oscillator (LO) signals are imported by two Lange couplers in the proposed design, with four pairs of APDPs connected in a ring structure. Superior RF/LO-to-IF (intermediate-frequency) and 2LO-to-RF/IF isolations have been achieved. The sub-harmonic mixer circuit has also exhibited excellent conversion loss of 13.7 dB with LO power of 13 dBm. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2135–2138, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23595