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Various miniaturized viscometers have been developed utilizing several fabrication methods. Among them, microfluidic paper-based analytical devices ( $\mu $ PADs) are becoming popular due to their fabrication ease, cost-effectiveness, and the fact that the flow can be carried out using the embedded capillaries themselves. Mostly, $\mu $ PADs are reported to be fabricated by a solid-ink printer, which has significantly high capital and operational cost. To overcome such drawbacks, a novel rapid prototyping method has been proposed, wherein the formation of the hydrophobic regions was created by polycaprolactone (PCL) filament using a 3-D printer. To leverage this, $\mu $ PAD as a viscometer, velocity, or time between two points with known distances was required, which was carried out by an amperometric approach, established by fabricating the integrated screen-printed electrodes intersecting the microchannel of the $\mu $ PAD. The time measurement was fully automated by a microcontroller, and the relative viscosity was calculated by comparing the time taken by the reference fluid with that of a test fluid to cover a known length. Such integrated, automated, and low-cost paper-based microviscometer was leveraged to measure and analyze the viscosities of various milk variants, which has an accuracy of >92%.

We demonstrate edge electron emission from flexible free-standing graphene paper (GP). The turn-on field is measured at 2.2 V/ $\mu{\rm m}$ , and the maximum emission current density at 3 ${\rm A}/{\rm cm}^{2}$ . The field emission properties of GP can be optimized by adjusting the thickness and annealing temperature. Because it is flexible, it can be shaped into different forms to meet the requirements of specific applications. The electron beam shape can range from a sheet electron beam to a cylindrical (hollow) electron beam.

Oxide-based thin-film transistors (TFTs) with a lateral in-plane electrode are self-assembled on paper substrates, and the electrical modulation effect of the in-plane electrode is investigated. A SiO2-based solid-electrolyte film with high specific capacitance is used as the gate dielectric, and the operation voltage is reduced to less than 2.0 V. The threshold voltage (Vth) of such paper TFTs is tuned from -0.98 to 0.94 V by different voltage biases on the in-plane electrode. The threshold voltage shift (ΔVth) can be described by ΔVth = -(CG2/CG1)VG2, where CG2 and CG1 are the in-plane electrode and bottom-gate specific capacitance values. High electrical performance with a current on/off ratio of 6 ×105 ~ 106, a subthreshold swing of 0.14 ~ 0.19 V/dec, and a mobility of 8.64 ~ 9.45 cm2/V·s is obtained at different in-plane electrode voltage biases. Such low-voltage paper TFTs are promising for low-cost and portable electronics.

Alternating-current-type inorganic powder electroluminescence (PEL) devices were successfully fabricated on four kinds of paper substrates, i.e., glossy paper, sticker paper, magazine paper, and newspaper. To protect the paper from wet chemical and heating processes during the formation of the PEL device, the paper substrate was coated with a spin-on-glass layer that served as a buffer layer. In spite of the fragility of paper, quite satisfactory results were obtained-the performance of paper-based PEL devices was almost equivalent to that of PEL devices on a plastic substrate. Extension of a substrate to paper, even to flimsy daily newspaper, will widen the opportunity of PEL devices as one of flexible and disposable displays.

This paper presents a parallel plate-type field emission device of potassium hydroxide-doped electrochemically reduced graphene oxide (GO) manufactured using highly oriented pyrolytic graphite through electrochemical exfoliation. The material properties of the GO were tested through Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The optimal electron emission characteristics of the device were as follows: turn-on field = 2.03 V/ $\mu \text{m}$ , field emission current $= \,\, 16.4~\mu \text{A}$ , and field emission enhancement factor = 8377. At an emission peak wavelength of 563.7 nm, the optimal device had a light flux of 4.21 lumens and an illumination of 140.3 lux. These properties can be utilized in various optoelectronic devices, such as nanoelectronics devices, sensors, electrochemical systems, and energy storage devices.

In this paper, a fully controlled photocatalytic reduction of graphene oxide (GO) sheets is presented in which electrical bias is applied in combination with UV illumination. It is proved that this controllability allows higher conductivities and lower UV illumination times for the achieved reduced graphene oxide (rGO) sheets, which are not allowed without gate voltage. We attribute the observed enhancement mechanism in photocatalytic reduction to electron accumulation at the ZnO/GO interface and decrement of recombination of photogenerated carriers. Then, we applied ZnO nanowires to reduce the GO sheets locally and realize rGO ribbons. The optoelectric response of the fabricated photodetector based on the realized rGO ribbon shows that by controlling the photocatalytic reduction, we can achieve a tunable/selective photodetector ( $\lambda _{\mathrm {incident}} = 520$ , 595, and 633 nm have been investigated). These functionalities allow tuning the output sensitivity of the device in response to different incident wavelengths along the fabrication process or even after the fabrication process. We believe that the presented approach introduces a new generation of tunable devices suitable for different application fields, including optoelectronics.

A single atomic layer of graphene, integrated onto an undoped bulk substrate in a back-gated transistor configuration, demonstrates surprising strong photoconduction, and yet, the physical origin of the photoresponse is not fully understood. Here, we use a detailed computational model to demonstrate that the photoconductivity arises from the electrostatic doping of graphene, induced by the surface accumulation of photogenerated carriers at the graphene/substrate interface. The accumulated charge density depends strongly on the rate of charge transfer between the substrate and the graphene; the suppression of the transfer rate below that of carrier’s thermal velocity is an essential prerequisite for a substantial photoinduced doping in the graphene channel under this mechanism. The contact-to-graphene coupling (defined by the ratio of graphene–metal contact capacitance to graphene’s quantum capacitance) determines the magnitude of photoinduced doping in graphene at the source/drain contacts. High-performance graphene phototransistors would, therefore, require careful engineering of the graphene–substrate interface and optimization of graphene–metal contacts.

We present a computational study on hybrid nanomaterial-insulator-silicon solar cells where single-walled carbon nanotube or graphene forms the emitter as well as top conducting electrode on n-type crystalline silicon having a thin interfacial tunnel oxide. The effects of nanomaterial doping and tunnel oxide thickness on cell characteristics are modeled. Similar to bulk emitters, cell efficiency could be increased by chemical doping (p-type) of the nanomaterial. Unlike bulk, nanomaterial could get electrostatically doped (n-type) due to its low quantum capacitance, by the surface charge density in silicon. For chemically undoped graphene on lightly ( $10^{{16}}$ /cm $^{{3}}$ ) doped silicon, efficiency loss due to the electrostatic doping effect is $\sim 11$ %. A moderate p-type chemical doping (0.2 eV shift in Fermi level) of graphene reduces the aforementioned loss to $\sim 2$ %. The electrostatic doping effect in carbon nanotube-based cells is relatively small and independent to nanotube’s chemical doping. For tunnel oxide thickness $\ge 2$ nm, photogenerated carrier accumulation at silicon/oxide interface considerably enhances the electrostatic doping effect. The effect of tunnel oxide thickness variation on fill factor and open circuit voltage is shown to be qualitatively similar to standard bulk metal–insulator–silicon solar cells. Our model predicts an optimal oxide thickness of $\sim 1$ nm which confirms the experimental reports.

This paper investigates the plasma-spraying technique as applied to oxide cathodes compared with the conventional coating method. In the conventional oxide cathode manufacturing process, a carbonate powder layer BaSrCa(CO3) is either painted or sprayed onto the nickel-base material at room temperature after the carbonate powder has been mixed with a nitrocellulose binder to provide adhesion to the nickel surface. However, the by-products deposited due to the coating of the oxide cathode and the decomposing process, combined with the relatively weak adhesion resulting from this coating method, undermine the performance of the oxide cathode. Plasma spraying can produce a high-quality coating by applying a relatively inert medium using a high-temperature high-particle velocity process. Impacts on the performance of the plasma-sprayed oxide cathode, as compared with a conventionally coated oxide cathode, are presented. The experimental results show that the pulsed-current emission density of a plasma-sprayed oxide cathode is nearly twice that of the conventionally coated oxide cathode, whereas the evaporation rate of the plasma-sprayed oxide cathode is only 10% as much as the conventionally coated oxide cathode.

An electrophoretic display (EPD) cell with a triple-layered microcavity structure was fabricated using a convenient dry film resist. The inherent structural advantage arising from the function of the middle channel layer as a background colored state enabled the EPD to operate with two different-colored states by using a single type of electronic-ink particles, thereby eliminating the possible agglomeration of oppositely charged ink particles and supporting the potential application of the proposed structure to color the electronic paper. The preliminary operation of this new EPD structure was demonstrated as white and blue display states on a rigid glass exhibiting a contrast ratio of 1.5 : 1 with saturation voltages of + 30 and -30 V, respectively. Successful demonstrations on both the indium-tin-oxide-patterned glass and flexible polyethylene substrates are also provided.

A high-resolution active-matrix microencapsulated electrophoretic display (EPD) driven by polycrystalline-silicon thin-film transistors (poly-Si TFTs) with integrated drivers has been developed for the first feasibility study of electronic paper. The poly-Si TFTs were fabricated with a low temperature process below 425/spl deg/C. Microencapsulated electrophoretic material was coated on the TFT backplane, which was driven at 18 V. The resolution of the display is quarter VGA (video graphics array), and pixel pitch is 131 ppi (pixels per inch). As a result, this display offers a wide viewing angle, high contrast ratio and nonvolatilization of data. In addition, four-level grayscale images were also achieved by using an area ratio grayscale (ARG) driving method.

We present an approach to mass produce high-quality graphene on insulator substrate. Ni dots with single or few grains were achieved by annealing. Electron backscattered diffraction indicated that almost all of the Ni dots had (111) surface that is parallel to the substrate. Single-layer graphene with good crystalline quality has been grown on Ni dots. The patterned graphene films were transferred to insulating substrates by wafer bonding and etch back technique, which resulted in zero misalignment, low contamination, and high yield (>90%). Graphene-based field-effect transistors with self-aligned gate were fabricated with this method, which demonstrate the potential of this method as a candidate for mass production of graphene transistors.

International audience; This paper presents the methodology, implementation and application of a full-band quantum transport model based on the non-equilibrium Green's function formalism and the empirical pseudopotentials. In particular the paper reports the treatment of heterojunctions between lattice matched semiconductors, comprising a gradual transition region described according to a virtual crystal approximation. Our approach entails several numerical techniques to make the full-band quantum transport method computationally affordable, and thus enable robust and efficient self-consistent device simulations. Then we employ our simulation scheme for the analysis of some exemplary devices based on quantum tunnelling, such as an Esaki tunnelling diode, as well as n-and p-type heterojunction Tunnel FETs. In particular we investigate the influence on the current-voltage characteristics of the width of the heterojunction transition region. We observe that a gradual transition region mainly affects the device characteristics by lengthening the tunnelling path at the heterojunction, which has a different impact on device current depending on the external bias conditions.

We demonstrate that the residual carbon concentration in the drift region can have a significant impact on the reverse leakage, breakdown voltage, and breakdown stability of GaN-on-GaN vertical diodes. Two generations (Gen1, Gen2) of polarization-doped p-n junctions with different C concentrations were compared, in terms of avalanche voltage, avalanche instability, and deep-level concentration. The original results collected within this paper show that: 1) both generations of devices can safely reach the avalanche regime; diodes with a lower residual CN have a higher reverse leakage and a lower avalanche voltage, due to an uneven distribution of the electric field; 2) the presence of residual carbon can lead to breakdown walkout, i.e. a recoverable increase in breakdown voltage under reverse-bias stress. Specifically, devices with higher C concentration show a fully-recoverable breakdown walkout, whereas the breakdown voltage is stable in devices with lower C concentration; and 3) steady-state photocapacitance measurements confirm the presence of CN in both generations, and are used to assess the relative difference in concentration between Gen1 and Gen2, even for levels below secondary ion mass spectroscopy (SIMS) sensitivity. The results described in this paper indicate the existence of a trade-off between breakdown voltage (increasing by improving compensation) and breakdown stability (improving by reducing CN concentration) and are of fundamental importance for the optimization of GaN power devices.

In this paper, a microfluidic device is introduced based on direct current (dc) dielectrophoresis for the separation of circulating tumor cells from normal blood cells. Differential sidewall electrodes are designed inside the channel and two middle-channel outlets are located after the end of the electrodes, which are assigned to collect the normal blood cells. A maximum dc potential of 3 V is applied to the electrodes, resulting in a differential dielectrophoretic forces acting on the cells. This paper involves isolating MCF-7 breast cancer cells from white blood cells (WBCs) and red blood cells (RBCs), eliminating the demand for primary RBC lysis. Numerical simulation results revealed that the differential electrodes not only suppressed successfully the need for high applied voltages by dc dielectrophoresis but also diminished the joule heating effects. Besides that, the arrangement of the differential electrodes was observed to play a critical role in the separation performance. In particular, designing the outlets, as well as adjusting the electrode potentials, has effectively assisted the device to be tunable for different cancer cells even with different radii. More strikingly, the ability of the device to deflect the waste cells (WBCs and RBCs) to out of the microchannel prior to the cancer cells was proven to positively affect the separation efficiency and purity. The proposed device was capable of separating different cells leveraging various diameters with capture purity and efficiency of higher than 83% and 100%, respectively.

We report in this paper the design and fabrication of single-chip alternating current-LEDs (AC-LEDs) by monolithically integrating, for the first time, high-breakdown Schottky barrier diodes (SBDs) and micro-LED arrays using III-nitride LED epi-wafers of standard specs for volume production. A technique of cyclic mixed-etching has been introduced to restore the surface of inductively coupled-plasma (ICP) etching processed gallium nitride to device quality for fabricating high-breakdown Schottky junctions. Proof-of-concept single-chip AC-LED devices and a prototype driver-free white AC-LED lamp were demonstrated, showing high-efficiency LED emission, high chip area utilization efficiency, low power loss of the on-chip SBD bridge rectifier, and good luminous efficacy of the prototype AC-LED lamp. This paper paves the way toward mass-producing reliable and low-cost driver-free AC-LED lamps for solid-state lighting with existing LED manufacturing infrastructures.

This paper reports an industry standard monolithic 555-timer circuit designed and fabricated in the in-house silicon carbide (SiC) low-voltage bipolar technology. This paper demonstrates the 555-timer integrated circuits (ICs) characterization in both astable and monostable modes of operation, with a supply voltage of 15 V over the wide temperature range of 25 °C–500 °C. Nonmonotonic temperature dependence was observed for the 555-timer IC frequency, rise time, fall-time, and power dissipation.

Efficiency roll-off defined as the rapid efficiency drop by increasing the electrical current density is a major issue in the design of novel organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF). In this paper, it is shown that efficiency enhancement and suppression of efficiency roll-off in TADF OLEDs can be accomplished by broadening the exciton generation zone by precisely tuning the doping concentration of the TADF emissive material in the host matrix. This universal and simply tunable parameter can be applied to any TADF OLED to further enhance its performance characteristics. In this paper, a typical TADF OLED with realistic parameters is numerically investigated by solving the charge carrier transport and excitonic equations and taking into account all relevant processes such as triplet–triplet annihilation, triplet–polaron, and singlet–triplet quenching, and (reverse) intersystem crossing. It is shown that the internal quantum efficiency (IQE) decreases at very low and very high doping densities due to exciton distribution nonuniformity and charge balance factor reduction, respectively. Power efficiency depends on the IQE as well as the potential drop across the emissive layer and decreases at very low doping densities even for a perfectly balanced device; however, the reduction for an unbalanced device is much more substantial. For a perfectly balanced device with an emissive layer thickness of 30 nm, at a current density of 10 mAcm−2, the IQE can be increased from 18% to more than 58% by decreasing the doping concentration from ${c}= {15}$ % to 0.5%. Power efficiency reaches its peak value of 38 lm/W at 1.4% doping.

A novel plasma Charge Accumulative Model (pCAM) by calculating time-integrated Fowler–Nordheim (FN) tunneling charges and field of the gate dielectric in plasma processes is proposed in this paper. Our prior studies have developed and presented a quantitative FinFET plasma recording device by an effective fin-shaped field effect transistor (FinFET) contact-to-metal coupling structure to record and quantify plasma ion charges created in FinFET backend processes. In this paper, a precise analytical model is proposed to model the magnitude of plasma ion charges, time-integrated stressing field, and the criteria of the plasma process for optimum FinFET process technology. The new pCAM is highly matching with the measurement result of 16- and 7-nm FinFET wafers. The model can be adapted to practically estimate the plasma damage with different charge types, process parameters, and ion distribution; it can optimize the FinFET process and further understand the plasma damage mechanism in charging processes of 7-nm FinFET and beyond.

To develop an efficient thermal design for gallium-nitride (GaN) high-electron-mobility transistors (HEMTs) that usually hold a super-high-power density, it is essential to accurately predict the junction temperature. In GaN HEMTs, the heat transfer process is dominated by thermal spreading resistance. Moreover, the phonon mean free paths (MFPs) of GaN are comparable with the channel layer thickness and the heat spot width. Thus, a ballistic effect emerges, resulting in the invalidity of Fourier’s heat conduction law. Therefore, Fourier’s law-based thermal resistance model should be reexamined and modified for this case. In this paper, we used the phonon Monte Carlo (MC) method to investigate the thermal spreading resistance in a ballistic-diffusive regime for GaN HEMTs. Our simulation results indicate that the ballistic effect significantly altered the temperature distributions within channel layers and resulted in a dramatic increase in the thermal resistance when compared with Fourier’s law-based predictions. Furthermore, a semiempirical thermal resistance model with a fitting parameter was derived. This model can accurately address the issues of thermal spreading and the ballistic effect. This paper can provide a more in-depth understanding of the thermal spreading resistance in a ballistic-diffusive regime, and it can be useful for the prediction of junction temperatures and for the thermal management of HEMTs.

This paper proposes a robust to defects and short length device (RDSLD), a newly in-plane resonant tunneling diode (RTD), and its ac-modeling with the minimum length of 3 nm. The proposed structure has robust performance in the presence of defects. It also has a high degree of flexibility in tuning electronic specifications. By using bipolar doping and a special h-boron nitride barrier pattern, these unique features are obtained. The simulation results verify that the proposed structure has the potential for replacing conventional RTD diodes. Such that the peak-to-valley ratio (PVR) and the maximum current of 4500, 450 nA for perfect bowtie and 3.45, 1256 nA for rhombic barrier shape structure are obtained, respectively. Also, negative differential resistance (NDR) is observed in all of the structures with vacancy and impurity defects. The effect of the geometrical parameters on the charge transmission of the device is another issue that is addressed in this paper. Furthermore, the analytical and numerical capacitance model parameters are presented.

Quantum dot (QD) white light-emitting diodes (LEDs) are promising devices in illumination and display applications, and the low thermal stability of QDs is one of the biggest problems limiting their practical use. In this paper, we proposed a metal-based inverted packaging (MIP) structure to enhance the thermal performance and stability of QD white LEDs. The results indicate that the thermal power of LED chips can greatly increase the surface temperature of QD white LEDs, especially that of the color-converted layer and the base. Therefore, the LED chip was separated from the QD layer and isolated with low thermal conductivity layers of air and glass using the MIP structure. This successfully reduces the base temperature and constrains the thermal power of the LED chip on the upper phosphor layer, thus enhancing the thermal performance for the QD layer. Consequently, MIP-QD white LEDs have a small deviation of 57.3 K in their correlated color temperature (CCT) and a deviation of 0.29 in their color rendering index (CRI) at injection power values in a wide range of 0.08–1.3 W, with mean values of 4382 K and 90.3, respectively. Moreover, these devices have negligible reduction in their electroluminescence intensity, and CCT and CRI values after aging for 10 h under severe conditions at an injection power of 0.9 W. Consequently, this paper can provide a general guide to enhance the thermal performance and stability of QD white LEDs by separating the thermal power of the LED chip from the QD layer.

Photodetectors (PDs) based on organic–inorganic hybrid materials such as graphene and perovskites have recently emerged at the forefront of the research in optoelectronic devices. Despite the remarkable progress in the performance of optoelectronic devices based on hybrid materials, some aspects such as stability have so far not been thoroughly addressed. This paper serves to demonstrate a fully inkjet-printed PD fabricated by hybrid perovskite (CH3NH3PbClx-3I3) layer between the two graphene electrodes as graphene/perovskite/graphene (GPG) heterostructure. The fully inkjet-printed GPG PD is found to be effective for the visible light region, which can be attributed by the high uniformity and low defects of the printed materials. Thus, the GPG PD achieves a high responsivity of 0.53 A/W. Fully inkjet-printed hybrid perovskite PD demonstrated in this paper unveils the facile, potentially large-scale and cost-effective methods for fabrication of hybrid perovskites-based optoelectronic devices, including PDs and solar cells.

The dielectric screening property of a semiconductor is very crucial for the electrical characteristics of a MOSFET, and which can be described mathematically by Poisson equation via the permittivity. While the theory and experiments have corroborated the permittivity reduction of nanoscale Si, this paper studies the electrical characteristics of MOSFETs considering the reduced channel permittivity by quantum transport simulations. It is found that the channel permittivity reduction may mitigate the short-channel effects, showing subthreshold swing improvement and threshold voltage shift of MOSFETs in nanoscale. Compared to quantization effects, the positive and negative impacts of the channel permittivity reduction on the devices in particularly nanoscale have been investigated. This paper elucidates the necessity of considering semiconductor permittivity reduction for nanoscale device design and simulations.

In recent years, triboelectric nanogenerators (TENGs) have been increasingly attracting attention owing to the ability for converting multiple mechanical energy into electricity. In this paper, we first propose a multifunctional conductive copper tape-based TENG (CCT-TENG) that is constructed completely using one piece of conductive copper tape. The triboelectric pairs, supporting structure, and conductive electrode were composed using bottom paper, silicone oil, and copper foil, all of which came from one roll of conductive copper tape. The approximate output power density of the CCT-TENG reached $240.1~\mu \text{W}$ /cm2. By spraying the aqueous solution of LiCl onto the surface of the bottom paper, a CCT-TENG incorporating LiCl was fabricated and used as a self-powered active sensor to detect the relative humidity (RH) of the environment. The obtained results revealed that the humidity sensor had good humidity response, response linearity, and reversibility. In addition, the RH was reflected by the brightness of light-emitting diodes (LEDs) that was driven by the humidity sensor. This paper realizes a promising, affordable, and portable integration of power supply systems and sensing systems, which can promote the application of TENG in the field of electronic detection device and environment monitoring.

This paper clarifies the correct transmission mechanism, misattributed in the previous research, of a hydrogenated amorphous silicon thin-film transistor (a-Si:H TFT) device. Complete drain current–gate voltage ( ${I}_{\text {D}}$ – ${V}_{\text {G}}$ ) transfer characteristics including the forward and backward gate sweeps (gate voltage carried out in the OFF-state $\to $ on-state and the ON-state $\to $ OFF-state) are performed, and the physics models of an energy-band schematic are clearly explained. This paper reveals that the ${I}_{\text {D}}$ – ${V}_{\text {G}}$ curve stretch-out behavior of the subthreshold region is due to the leakage of the Poole–Frenkel region. At the Poole–Frenkel regions, electrons transfer to the drain terminal, and holes remain in the valance band of the a-Si:H bulk. The remaining holes represent the positive voltage and cause the electron barrier height lowering. This causes an increase in subthreshold current of the subthreshold region. Finally, three experiments are performed to prove the correctness of these models, and the a-Si TFTs device improvement methods will be proposed to enhance the stability and performance of product of the a-Si TFTs.

In this paper, we propose a novel reconfigurable ferroelectric FET (R-FEFET), which can reconfigure its operation between volatile and nonvolatile modes during run-time by dynamically modulating its hysteresis. The R-FEFET comprises of two gates with ferroelectric (FE) in both the gate stacks. One of these terminals serves as a regular gate, while the other is used as a control to introduce reconfigurability. Employing Landau–Khalatnikov equation-based FEFET model, we extensively analyze the device characteristics in both FinFET and planar technologies. We show that by changing the control voltage between 0 and 1 V, the hysteresis width (HW) can be modulated between 1.1 and 0.3 V. In addition, we show the device characteristics and advantages that R-FEFETs possess to overcome the drawbacks encountered with gate leakage in standard FEFETs. The hold margins in the nonvolatile mode of R-FEFETs increase by ~ $10\times $ with respect to standard FEFETs, and the drive current strengths in the volatile mode show 13% improvements when compared to standard FETs. Using the proposed R-FEFETs, we examine a low-power nonvolatile memory design in Part II of this paper.

Because of the predicted shortage of fossil fuels in the future, public interest in utilizing solar energy for photovoltaic (PV) electricity has exponentially increased in recent years. In particular, interest in the building integration of PVs is growing worldwide, and the use of building-integrated PVs (BIPVs) is one of the fastest growing segments of the PV industry. Luminescent solar concentrators (LSCs) are one of the possible approaches for BIPVs. However, the high cost and poor stability of the dyes or quantum dots used in conventional LSCs prevent the widespread adoption of electricity generation through the LSC-based solar energy. Therefore, inorganic phosphors with long lifetime and photostability under ultraviolet (UV) excitation and moisture are favorable luminescent materials for LSCs. In this paper, thin-film LSCs using commercial inorganic phosphors are proposed. The thin-film LSCs with different inorganic phosphors were examined. The phosphor concentration and relative position of the thin phosphor layer were investigated to determine the suitable structure of a thin-film LSC. This paper aimed to achieve an understanding of thin-film LSCs by using inorganic phosphors and to provide useful guidelines for future commercialization.

International audience; Abstract:This paper details an extraction procedure to fully model the transient self-heating of transistors from a GaN HEMT technology. Frequency-resolved gate resistance thermometry (f-GRT) is used to extract the thermal impedance of HEMTs with various gate widths. A fully scalable analytical model is developed from the experimental results. In the second stage, transient thermoreflectance imaging (TTI) is used to bring deeper insights into the HEMTs' temperature distribution by individually extracting the transient self-heating of each finger. TTI results are further used to successfully validate the f-GRT results and the modeling of the thermal impedance. Overall, f-GRT is demonstrated to be a fast and robust method for characterizing the transient thermal characteristics of a GaN HEMT. For the first time to the authors' knowledge, a scalable model of the thermal impedance is extracted fully from experimental results.

In the domain of printed electronics (PE), field-effect transistors (FETs) with an oxide semiconductor channel are very promising. In particular, the use of high gate-capacitance of the composite solid polymer electrolytes (CSPEs) as a gate-insulator ensures extremely low voltage requirements. Besides high gate capacitance, such CSPEs are proven to be easily printable, stable in air over wide temperature ranges, and possess high ion conductivity. These CSPEs can be sensitive to moisture, especially for high surface-to-volume ratio printed thin films. In this paper, we provide a comprehensive experimental study on the effect of humidity on CSPE-gated single transistors. At the circuit level, the performance of ring oscillators (ROs) has been compared for various humidity conditions. The experimental results of the electrolyte-gated FETs (EGFETs) demonstrate rather comparable currents between 30%–90% humidity levels. However, the shifted transistor parameters lead to a significant performance change of the RO frequency behavior. The study in this paper shows the need of an impermeable encapsulation for the CSPE-gated FETs to ensure identical performance at all humidity conditions.

This paper presents an optoelectronics-based compact equivalent circuit model of an n-Ge/p-Ge1– x Sn x /n-Ge1– x Sn x heterojunction phototransistor (HPT). This paper includes the static electrical and optical characteristics of the device, Gummel characteristics, effect of temperature, and overall noise analysis of HPT based on various parametric variations. We then investigate the effect of parasitic capacitance on the noise performance of the HPT. The estimated results show that the signal-to-noise ratio (SNR) is strongly dependent on not only the operating frequency but also the operating temperature and applied base-bias voltage. Estimated performance shows that SNR of HPT >90 dB up to 100 GHz and >80 dB up to 50 °C can be achieved, which ensured the operation of the device as high-speed and low-noise detector.

In this paper, a novel vertical phototransistor was reported and compared with planar phototransistors for the first time. As compared with the planar phototransistors, the vertical ones exhibited much better photoelectric performance, which is attributed to an ultrashort photo-generated holes transfer distance and a stronger excitons dissociating electrical field due to their ultrashort channel length (tens of nanometers). Moreover, in order to examine the transport and trapping of different carrier charges separately, the impact of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) dopant on the performance of planar and vertical phototransistors was investigated. The vertical devices exhibited an ultrahigh responsivity (~6600 A/W) as well as an excellent detectivity ( $\sim 7\times 10^{15}~\text{Jones}$ ) and a fast photoresponse (rise time of 0.28 s), whereas slight changes were observed in the planar ones with doping of PCBM. The high performance of the blend vertical phototransistors is due to the trapping of the photo-generated electrons with PCBM and the effective transport of holes due to the ultrashort channel length. This paper provided a promising pathway for low-cost, high-performance phototransistors.

The instability of amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) under ultraviolet (UV) light was thoroughly investigated in this paper. Unlike in a darkened state, an off-state leakage current can be found in the dual-sweep I–V transfer curve of a-IGZO TFTs under UV light illumination. Furthermore, despite the same UV light condition, the forward sweep and reverse sweep show different I–V curves, representing two different physical mechanisms. First, the subthreshold swing degradation and threshold voltage shift to the negative direction in the forward sweep are due to the total channel barrier lowering and can be confirmed by changing the light exposure region. Second, in the reverse sweep, the suggested back-channel leakage current can be controlled by dual-gate TFTs. UV light exposure of the metal–insulator–semiconductor–metal structure verifies that the off-state leakage current passes through the back channel in a reverse sweep. Finally, the physical mechanism links between forward and reverse sweeps have comprehensive interpretation in this paper.

In this paper, an analytical model has been developed to observe the recombination losses involved in a tunnel oxide passivated contact solar cell with a carrier-selective layer constituting polycrystalline silicon (poly-Si). The main focus of this paper is to observe the contribution of each component of recombination current density and its effect on open-circuit voltage, Voc. The effect of emitter saturation current density (Joe), surface recombination velocity, substrate thickness, and doping density of carrier-selective layer on Voc has been presented. The analysis indicates that Voc = 766 mV can be achieved for Joe = 2 fA/cm2, and a doping density of poly-Si > 1021cm−3 in a c-Si/SiO2/poly-Si contact for a 50- $\mu \text{m}$ -thick substrate in case of ideal surface passivation. For identical conditions, Voc attains a lower value of 750mV for a 180- $\mu \text{m}$ -thick substrate. The dependence of Voc on bandgap of tunnel layers has also been observed by considering other materials like Si3N4 and SiC. These results from the analyticalmodel have been compared with results froma simulation using automat FOR simulation of HETerostructures v2.5 and have been found to be in good agreement with each other.

In this paper, we have developed a physics-based analytical model for the electrical characteristics of passivated silicon carrier-selective contact (CSC) solar cells and validated it with numerical simulations. The model comprises analytical solutions of: 1) the Poisson equation, accurately capturing the level of inversion and accumulation at the crystalline silicon (c-Si) layer interfaces, and 2) the recombination current capturing the various recombination mechanisms at work in the solar cell. The calculations establish that CSC solar cells have the potential to achieve an efficiency greater than 26% even when both c-Si interfaces have realistic SRV values of 100 cm/s. The model helps illustrate the physics underlying the performance of CSC solar cells for variation in key device parameters such as surface recombination velocities, bulk lifetime, contact layer doping, and amorphous silicon (a-Si) thickness amongst others. By circumventing the need for resource-intensive numerical simulations, the analytical model described in this paper can assist in the design and development of high-performance CSC solar cells.

Nowadays, the importance of the blood particles separation is undeniable in medical fields and there are different sorts of separation methods accordingly. Acoustic cell separation is chosen in this paper. Also, numerical methods have been used to study the effect of geometrical factors on the separation of the particles before spending time and expenses in a trial and error manner experimentally. We have implemented a plenary finite-element-based simulation of separating blood particles such as white blood cells and platelets in an acoustic field using standing surface acoustic waves. In this paper, unlike previous works in which the channel is rectangular; the channel is trapezoidal in order to make the separation more efficient. By changing the trapezoidal leg angle, WBC’s distance from the midline will be different. The designed device is a bio-MEMS channel containing two inlets which are for the sheath flow and for the blood particles, a trapezoidal main channel, and three outlets. Two aluminum interdigital transducers are located on the LiNbO3 substrate. For creating the acoustic force, we have applied an alternating voltage to transducers. Blood particles will be moved toward the acoustic nodes because of the positive acoustic contrast factor. Since acoustic radiation force depends on the size of the particles and their compressibility, cells can be sorted according to their diameter and compressibility; hence, particles will be separated. For optimizing the device, we have changed the trapezoidal channel angle, the input voltage, and the flow rate.

To effectively solve the crosstalk issue in high-density crossbar array (CBA), high rectifying characteristics should be introduced in the resistance random-access memory (ReRAM) device, and in-depth understanding of the affecting factors on rectifying properties is essential for the large-scale application of ReRAM. In this paper, a high-performance self-rectifying device with CMOS compatible Pd/HfO2/TaO x /Ta structure was demonstrated in a 1-kb CBA. Forming-free, self-compliance, and high uniformity characteristics were successfully achieved. By modulating the thickness of the HfO2 rectifying layer, the rectifying ratio of device could be achieved as high as $\sim 2\times 10^{\textsf {3}}$ under ±3 V at low-resistance state (LRS). It was also experimentally confirmed that the selected unit cell in high-resistance state (logically the “ OFF” state) was stably readable when it was surrounded by unselected LRS (logically the “ ON” state) cells, in an array of up to $32 \times 32$ cells. Furthermore, a model based on interfacial barrier modulation and defects trapping/detrapping was proposed to elucidate the impact of the dielectric thickness on the self-rectifying characteristics of the device. The results presented in this paper provide a great potential for selector-free high-density memory applications.

In part I of this paper, we developed physical insights into the role and impact of acceptor and donor traps—resulting from C-doping in GaN buffer—on avalanche breakdown in AlGaN/GaN HEMT devices. It was found that the donor traps are mandatory to explain the breakdown voltage improvement. In this paper, silicon doping is proposed and explored as an alternative to independently engineer donor trap concentration and profile. Keeping in mind the acceptor and donor trap relative concentration requirement for achieving higher breakdown buffer, as depicted in part I of this paper, silicon & carbon codoping of GaN buffer is proposed and explored in this paper. The proposed improvement in breakdown voltage is supported by physical insight into the avalanche phenomena and role of acceptor/donor traps. GaN buffer design parameters and their impact on breakdown voltage as well as leakage current are presented. Finally, a modified Si-doping profile in the GaN buffer is proposed to lower the C-doping concentration near GaN channel to mitigate the adverse effects of acceptor traps in GaN buffer.

Because of charge trapping in GaN HEMTs, dc characteristics of these devices are not representative of high-frequency operation. The advanced spice model GaN model presented in Part I of this paper is combined with a Shockley–Reed–Hall-based trap model, yielding a comprehensive FET model for GaN HEMTs which can accurately model GaN devices exhibiting trapping-related dispersion effects. Measurement results of the dc and pulsed output and transfer characteristics of a commercially available GaN HEMT are presented, trapping in the device is modeled, and excellent fit to the measured data is shown. This paper presents an accurate model of trapping which is validated for eight different quiescent bias points of pulse measurements, with quiescent drain voltage ranging from 5 to 20 V and quiescent gate voltage ranging from −2.8 to −3.8 V, and a large range of gate and drain voltages to which the device was pulsed in the pulse measurements and at which the device was measured in the dc measurements, with gate voltage ranging from −4 to 0.4 V and drain voltage ranging from 0 to 40 V. This paper also presents high-frequency (10 GHz) large-signal RF validation of the model for optimal complex load condition.