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In this work, single photon avalanche diodes (SPADs) were fabricated using the standard 180 nm complementary metal-oxide semiconductor process. Their small size of 15–16 μ m and low operating voltage made it possible to easily integrate them with readout circuits for compact on-chip sensors, particularly those used in the radiation sensor network of a nuclear plant. Four architectures were proposed for the SPADs, with a shallow trench isolation (STI) guard ring and different depletion regions designed to demonstrate the main performance parameters in each experimental configuration. The wide absorption region structure with PSD and a deep N-well could achieve a uniform electric field, resulting in a stable dark count rate (DCR). Additionally, the STI guard ring was implanted to mitigate the premature edge breakdown. A breakdown voltage was achieved for a low operating voltage of 10.75 V. The DCR results showed 286.3 Hz per μm2 at an excess voltage of 0.04 V. A photon detection probability of 21.48% was obtained at 405 nm.

A closed-form, analytical, and unified model for the surface potential from source to drain in nanowire (NW) gate-all-around (GAA) tunneling field effect transistors (TFETs) is proposed and validated. Foremost, the correctness of the dual modulation effect in GAA-TFETs is demonstrated. Building on that, the model comprehensively considers the effects of the channel depletion region, drain depletion region, and channel inversion charges. Furthermore, a compact current model for GAA-TFETs, based on the derived surface potential expression, is presented, with a discussion on ambipolar conduction—an essential factor for device model integrity. The model’s accuracy and flexibility are validated through TCAD simulations and measurement data from NW-GAA-TFETs, yielding promising results.

The piezophototronic effect has been widely explored to improve the performance of optoelectronic devices. However, modulation of piezoelectric charges varies with different energy band structures. Thus, it is important to investigate the specific role of the piezophototronic effect from a theoretical perspective. Herein, the piezophototronic effect in anisotype p‐Si/n‐ZnO heterojunction photodiodes with type‐II energy band diagrams through analytical derivation and numerical simulation is thoroughly studied. It is found that both the depletion region and quasineutral region have a decisive effect on photocurrent in their respective regions. Specifically, modulations of piezoelectric charges on depletion region current and quasineutral region current are opposite and compensate each other, resulting in reduced piezophototronic effect. Heterojunctions under short diode conditions are preferred for better piezophototronic effect as modulation on quasineutral region current is weakened while that on depletion region current remains unchanged. The effects of doping concentration, absorption coefficient, and minority carrier lifetime of semiconductor materials on device characteristics are also studied. This work provides deeper insight into the underlying device physics of the piezophototronic effect. [ABSTRACT FROM AUTHOR]

This work presents silicon-on-insulator (SOI) junction-less FETs (C-JLFET) with a pyramid P+ area within the buried oxide region (PP-JLFET). The Silvaco software analysis shows that the PP-JLFET with P+ area within the BOX layer has improved the ION/IOFF ratio of ~ 1010 and causes the proposed device to be suitable for logic operations. The principal concept of this paper concentrates on enhancing the depletion region for obtaining a smaller off-current (IOFF) ~ 10–15. Although the on-current (ION) reduced slightly, but this decrement is very small value. Also, another purpose is to achieve a better self-heating effect (SHE), which is obtained by embedding a silicon pyramid P+ area with a larger thermal conductivity than the buried oxide region. SHE improves from 308 to 325 K in the proposed device versus the conventional JLFET. Effects including carrier density, lattice temperature, SHE, and kink effect have been investigated, and the PP-JLFET results demonstrate that the proposed device improves the device characteristics versus C-JLFET. [ABSTRACT FROM AUTHOR]

Abstract:For the first time, in this research, we introduce ajunctionless tunneling FET (J-TFET) on a uniform p+starting junctionless FET to realize appreciable immunityagainst inherent high ambipolar current (Iamb). So, weutilize two isolated gates with appropriate workfunctionsover the channel and drain regions to create P+IP+N+charge distribution. This structure utilizes a spacebetween the gate-drain electrodes (SGD), to provide aP+IP+N+ structure thanks to the effective electronsdepletion on the drain side. Increasing the SGD, furthereffectively pulls up the bands near the interface betweenthe channel-drain regions, widens the tunneling width fortunneling to occur, and thus in turn reduces the Iamb from5.37×10-7 A/µm to 1.14×10-14 A/µm. Thus, we point outthat the proposed J-TFET can obtain on-current thatsatisfies the expectation of logic applications with highperformance and Ioff that meets the specifications of lowpower characteristics, a phenomenon that is rarelyaccessible with conventional TFETs.

Owing to the large built‐in field for efficient charge separation, heterostructures facilitate the simultaneous realization of a low dark current and high photocurrent. The lack of an efficient approach to engineer the depletion region formed across the interfaces of heterojunctions owing to doping differences hinders the realization of high‐performance van der Waals (vdW) photodetectors. This study proposes a ferroelectric‐controlling van der Waals photodetector with vertically stacked two‐dimensional (2D) black phosphorus (BP)/indium selenide (In2Se3) to realize high‐sensitivity photodetection. The depletion region can be reconstructed by tuning the polarization states generated from the ferroelectric In2Se3 layers. Further, the energy bands at the heterojunction interfaces can be aligned and flexibly engineered using ferroelectric field control. Fast response, self‐driven photodetection, and three‐orders‐of‐magnitude detection improvements are achieved in the switchable visible or near‐infrared operation bands. The results of the study are expected to aid in improving the photodetection performance of vdW optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract Owing to the large built‐in field for efficient charge separation, heterostructures facilitate the simultaneous realization of a low dark current and high photocurrent. The lack of an efficient approach to engineer the depletion region formed across the interfaces of heterojunctions owing to doping differences hinders the realization of high‐performance van der Waals (vdW) photodetectors. This study proposes a ferroelectric‐controlling van der Waals photodetector with vertically stacked two‐dimensional (2D) black phosphorus (BP)/indium selenide (In2Se3) to realize high‐sensitivity photodetection. The depletion region can be reconstructed by tuning the polarization states generated from the ferroelectric In2Se3 layers. Further, the energy bands at the heterojunction interfaces can be aligned and flexibly engineered using ferroelectric field control. Fast response, self‐driven photodetection, and three‐orders‐of‐magnitude detection improvements are achieved in the switchable visible or near‐infrared operation bands. The results of the study are expected to aid in improving the photodetection performance of vdW optoelectronic devices.

[Display omitted] • Photoelectrode containing PN junctions was synthesized by a simple method. • Photoelectrode achieved 91.5% full-spectrum absorption of sunlight. • Photoresponses mechanism of PN junctions was revealed regarding energy level structure, depletion region, and space charge. • Potential application of NiO-WO 3 -FTO photoelectrode in DSSCs was elucidated. In the current global energy crisis, dye-sensitized solar cells (DSSCs) with excellent performance and loaded with P/N type semiconductor heterojunctions (PN junctions) has attracted huge attention in renewable energy research. This study reports the unique energy level structure and synergistic effect of the PN junction interfaces in response to light. Photoelectrodes containing NiO–WO 3 nano-powder (NPs) layers were synthesized on fluorine-doped tin oxide (FTO) substrates by a simple method, which can respond to full-spectrum absorption of sunlight. In this study, the carrier densities in the P-type and N-type semiconductor heterojunctions at a light intensity of 2 SUN (2000 W/m2) were 1.38 × 1028 m−3 and 4.27 × 1028 m−3, respectively. These values are 2.7 and 1.9 times higher than those in dark conditions, indicating that the electrode excels in converting light into electrical energy, outperforming other reported results. Although PN junctions are often used in applications such as DSSCs and energy storage devices, the photoresponses of the heterojunction energy band structure still need to be elucidated. In this work, the analysis of the charge depletion region width revealed the electron transfer mechanism during the charge and discharge process under light illumination. Additionally, the electrochemical experiment demonstrated the impact of space charge at the interface on the energy levels. Furthermore, by studying the energy level structure of the PN junction, it was confirmed that the internal resistance decreases and the photocurrent increases under light conditions. The design and application flexibility of the PN junctions were verified based on these results and the possible applications of this photoelectrode in solar cells were elucidated. [ABSTRACT FROM AUTHOR]

A photodiode, a semiconductor device, is designed to convert light into an electric current. The piezo-phototronic effect, arising from the interplay of semiconductor properties, piezoelectric polarizations, and photo-excitations, presents a promising avenue for enhancing photodiode performance. This research is dedicated to analyzing the impact of the piezo-phototronic effects on p-Si/n-ZnO heterojunction photodiodes when subjected to 365 nm illumination, a situation more intricate than the commonly studied 648 nm illumination. Employing numerical simulation methods, we systematically investigated the influence of varying ZnO and Si lengths on the piezo-phototronic effect, with a focus on the depletion region and neutral region current perspectives. Our findings reveal that adjusting these lengths can heighten sensitivity at low currents or lead to increased base currents. Additionally, the study delves into the effects of doping concentration, minority carrier lifetime, and mobility on device characteristics. This investigation contributes essential insights for a comprehensive understanding of piezo-phototronic effects and establishes a foundational framework for the design of industrial devices. [Display omitted] • Optimal ZnO thickness is crucial for piezo-phototronic effect in photodiode. • Short Si thickness limits the exertion of piezo-phototronic effect. • Semiconductor properties (e.g., doping, absorption) have a significant impact on piezo-phototronic effect. [ABSTRACT FROM AUTHOR]

Nanostructured NiO thin film was prepared by the sol–gel spin-coating technique and used for low-concentration ammonia (NH3) detection at elevated temperatures. The x-ray diffraction (XRD) pattern confirms the cubic phase with a polycrystalline nature. Field-emission scanning electron microscopy (FESEM) shows uniform spherical-shaped grains and substantiates the evident porosity of the film. The film shows 94% of transmittance in the visible region and has an optical band gap of 3.64 eV. Hall measurement confirms the p-type conductivity at room temperature. X-ray photoelectron spectroscopy (XPS) reveals the presence and electronic states of nickel (Ni 2p3/2, 2p½) and oxygen (O 1s). Gas-sensing studies on the NiO film reveal that the response was comparatively deprived at low- (< 250°C), and high-temperature (> 250°C) regimes, demonstrating that the reaction directions are spontaneous, along with the rate of adsorption (and diffusion) being extremely slow, with the desorption process dominating the adsorption, resulting in a positive value of Gibbs free energy ( Δ G ). Especially, at a working temperature of 250°C, the film exhibits the limit of detection (LOD) at 0.2 ppm with a response of 1.91 × 102%, and a maximum response of 4.01 × 10 3 % toward 5 ppm of NH3 concentration. This remarkable response at low concentration is attributed to the smaller crystallite size and porosity. In addition, and more significantly, the working temperature reduces the depletion region between the grains. As a consequence, this lower the potential barrier and accelerates the diffusion rate. Hence, increasing the response. [ABSTRACT FROM AUTHOR]

In this work, we employed our newly established explicit photogain theory to probe physics in nanodevices at single device level. A single fitting of the explicit photogain theory to experimental photoresponses allows us to find important device parameters including surface depletion region width Wdep, doping concentration NA (or ND), carrier mobility $\mu _{\text{p}}$ (or $\mu _{\text{n}}$), minority recombination lifetime $\tau _{0}$ and surface recombination velocity Vsrv. These parameters are often difficult to calibrate using traditional semiconductor characterization techniques as the size of semiconductor devices scales down. The extracted parameters were verified with independent Hall effect measurements and other experiments. It shows that this technique is simple, nondestructive and accurate enough to probe the physics in nanodevices at single device level. [ABSTRACT FROM AUTHOR]

This paper presents an accurate analytical model of surface potential and drain current for a long channel dual material gate (DMG) tunneling field‐effect transistor (TFET) with the addition of nonlinear inversion charge developed at the channel/drain interface region, ambipolar characteristic, and quantum confinement. The model includes the effect of dual metal gate work function as it controls the threshold voltage without considering a fully depleted undoped channel region. The current model includes the effect of charge accumulation at the interface of two gates and an appropriate mathematical expression of nonlinear inversion charge developed at the interface of two gates has been derived from the two‐dimensional (2D) Schrodinger wave equation incorporating quantum confinement. The model is effective to capture transfer characteristics at Sub 10 nm body thickness. A high ION/IOFF ratio and less than 27 mV/decade subthreshold swing are achieved at 2 nm body thickness which is desirable for low power VLSI application. The proposed model has been compared and calculated by Sentaurus TCAD with fair accuracy and a good resemblance, including ambipolar characteristics at sub 10 nm body thickness has been achieved. [ABSTRACT FROM AUTHOR]

PbS quantum dot (QD) solar cells harvest near-infrared solar radiation. Their conventional hole transport layer has limited hole collection efficiency due to energy level mismatch and poor film quality. Here, how to resolve these two issues by using Ag-doped PbS QDs are demonstrated. On the one hand, Ag doping relieves the compressive stress during layer deposition and thus improves film compactness and homogeneity to suppress leakage currents. On the other hand, Ag doping increases hole concentration, which aligns energy levels and increases hole mobility to boost hole collection. Increased hole concentration also broadens the depletion region of the active layer, decreasing interface charge accumulation and promoting carrier extraction efficiency. A champion power conversion efficiency of 12.42% is achieved by optimizing the hole transport layer in PbS QD solar cells, compared to 9.38% for control devices. Doping can be combined with compressive strain relief to optimize carrier concentration and energy levels in QDs, and even introduce other novel phenomena such as improved film quality., (© 2024 Wiley‐VCH GmbH.)

Summary: We have demonstrated the gallium nitride (GaN)‐based betavoltaic (BV) cells with PN and PIN junction to investigate the relationship between the intrinsic GaN (i‐GaN) layer and power performance of BV cells. A short‐circuit current (ISC) and an open‐circuit voltage (VOC) of the fabricated BV cells were evaluated by using an electron‐beam (e‐beam) irradiation. The cell with PIN junction exhibited an improved ISC and VOC compared to the cell with PN junction. This is because the additional 200 nm‐thick i‐GaN layer extends the depletion region of BV cell, resulting in improved charge collection. When a 17 kV e‐beam irradiated into the fabricated GaN PIN BV cell, the device exhibited an ISC of 1.86 μA, a VOC of 2.23 V, a maximum output power (Pmax.out) of 2.74 μW, and a power conversion efficiency (PCE) of 4.5%, respectively. This PCE is the best value among GaN BV cell researches using 17 keV e‐beam irradiation. To study a role of i‐GaN layer in PIN BV cell, the technology computer‐aided design (TCAD) simulator was implemented. The effect of layer thickness and native defects in GaN material on the power performance of BV cell was evaluated. The power performance of PIN BV cell was degraded by introducing native defects in layers due to an increase of recombination rate. The BV cell with 500 nm‐thick i‐GaN layer exhibited better power performance when the electrons with average energy of Ni‐63 irradiated into device because the maximum absorption rate of electrons was well positioned in the depletion region. The experimental and simulated results showed that the introduction of i‐GaN layer and the optimization of parameters such as thickness and crystalline quality were important to improve the power performance of BV cells. [ABSTRACT FROM AUTHOR]

The gate–bulk/body voltage ${V}_{\text {gb}}$ -dependent effect of the source or drain–bulk/body junction capacitance ${C}_{j}$ that is originated from the variation in the gate-edge sidewall junction area due to the modulation of the channel depletion depth in the OFF-state region of bulk/PD-SOI MOSFETs is physically revealed. This ${V}_{\text {gb}}$ -dependent ${C}_{j}$ is accurately extracted from the measured S-parameters and newly modeled in the wide off-bias range. The geometry-dependent model and parameter extraction method are proposed to make the new ${C}_{j}$ model applicable in SPICE. [ABSTRACT FROM AUTHOR]

In the present article, the modeling of subthreshold current of asymmetric silicon-on-insulator (SOI) Junctionless Field Effect Transistors (JLFETs) is done. The switching properties are further investigated by formulating the subthreshold swing characteristics based on the minimum potential concept. The model adopts the effect of substrate-induced surface potential (SISP) effect as well as source/drain depletion region with necessary changes in the boundary conditions at the silicon-buried oxide (BOX) interface. The developed model is beneficial for the optimization of low power switching characteristics for SOI JLFETs. The model results are validated with the numerical simulation results obtained from Sentaurus TCAD simulator. [ABSTRACT FROM AUTHOR]

In the realm of organic solar cells (OSCs), the width of the depletion region at the anode interface is a critical factor that adversely impacts the open-circuit voltage ( V ) and the power conversion efficiency (PCE). To address this challenge, a novel approach involving a conjugated polyelectrolyte (CPE)-based composite, PCP-2F-Li:POM, has been developed. This composite serves as a solution-processed hole transport layer (HTL), effectively minimizing the depletion region width in high-performance OSCs. The innovative aspect of PCP-2F-Li:POM lies in its "mutual doping" mechanism. Polyoxometalate (POM) is utilized as a dopant, facilitating the formation of p-doped CPE and n-doped POM within the composite. This results in a substantial increase in doping density, nearly 2 orders of magnitude higher than that observed in unmodified CPE. Consequently, the width of depletion region is markedly reduced, shrinking from 76.4 to 6.0 nm. This reduction plays a pivotal role in enhancing hole transport via the tunneling effect. The practical impact of this development is notable. It leads to an increase in oc ) and the power conversion efficiency (PCE). To address this challenge, a novel approach involving a conjugated polyelectrolyte (CPE)-based composite, PCP-2F-Li:POM, has been developed. This composite serves as a solution-processed hole transport layer (HTL), effectively minimizing the depletion region width in high-performance OSCs. The innovative aspect of PCP-2F-Li:POM lies in its "mutual doping" mechanism. Polyoxometalate (POM) is utilized as a dopant, facilitating the formation of p-doped CPE and n-doped POM within the composite. This results in a substantial increase in doping density, nearly 2 orders of magnitude higher than that observed in unmodified CPE. Consequently, the width of depletion region is markedly reduced, shrinking from 76.4 to 6.0 nm. This reduction plays a pivotal role in enhancing hole transport via the tunneling effect. The practical impact of this development is notable. It leads to an increase in V oc from 0.84 to 0.86 V, thereby contributing significantly to an impressive PCE of 18.04% in OSCs. Moreover, the compatibility of PCP-2F-Li:POM with large-area processing techniques underscores its potential as a viable HTL material for future practical applications. Additionally, its contribution to the enhanced long-term stability of OSCs further bolsters its suitability for practical applications.

This article reports an analysis of the fringing capacitances of an ion-implanted double-gate (DG) junctionless (JL) field-effect transistors (FETs). The actual nonintegrable Gaussian function of the ion-implanted channel has been replaced by an integrable Gaussian-like vertical channel doping profile to model the fringing capacitances of the DG JLFET. The boundary conditions for the source and drain depletion regions of the uniformly doped channel has been modified according to the nonuniformly doped channel using the conformal mapping technique. In this method, the gate-oxide capacitance is transformed to the source and drain fringing capacitances using an empirical multiple coefficient ${m}$ whose value is determined by matching the model result with the ATLAS TCAD simulation data for their best fitting. It is shown that unlike the uniformly doped device, the fringing capacitances are different for the front and back gates. Furthermore, the nonlinear bias-dependent potential profile along the channel leads to different fringing capacitances at the source and drain of the proposed device. The dependence of the fringing capacitances (and ${m}$) on the doping profile and bias conditions are investigated in detail. Accordingly, analytical expressions for the fringing capacitances are extracted. The model results are verified by the TCAD simulations. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we introduce several kinds of volatile anti-solvents to prepare a fully-reacted perovskite film, thereby obtaining a high-efficiency solar cell. The volatility of the solvent strongly influences the uniformity and porosity of the PbI 2 film, and thus affects the uniformity and compactness of the obtained perovskite film. Scanning electron microscopy (SEM) revealed that the perovskite film fabricated by the ethanol treatment method was very dense and exhibited a smoother surface. At the same time, the compositions of the perovskite films produced using different volatile solvents were determined via X-ray diffraction (XRD), and it was found that the film fabricated by the ethanol treatment method completely reacted with no residual PbI 2. The ethanol treated sample was characterized by UV–vis spectroscopy and current density-voltage (J-V) measurements, and the best absorbance, a fill factor of 0.73, short circuit current density, J sc , of 22.1 mA cm-2, an open circuit voltage, V oc , of 1.04 V and a photoelectric conversion efficiency, PCE, of 16.8% were obtained. Graphical abstract Image 1 Highlights • Conventional method produces residual PbI 2. • Residual PbI 2 deteriorates solar cell photoelectric performance. • Ethanol removes residual PbI 2. [ABSTRACT FROM AUTHOR]

In recent years, self-powered Schottky ultraviolet (UV) photodetectors (PDs) have attracted great attention due to their low manufacturing cost and zero-bias response. However, the development of high-performance self-powered Schottky devices is limited by the weak light response due to the internal weak electric field. Here, we introduce a Mg x Zn 1-x O capping layer on ZnO and fabricate a ZnO/Mg x Zn 1-x O heterojunction Schottky UV PD by using the sol-gel method. The improved device exhibits excellent self-powered characteristics and stability, specifically, an increase of 909% in photocurrent, an improvement of more than one order of magnitude in responsivity, and an improved linear dynamic region (LDR: 33.7 dB). The introduction of the Mg x Zn 1-x O capping layer is responsible for the improved device performance, resulting in enhanced built-in electric field and depletion region width due to the increase of the Schottky barrier, thereby facilitating the separation and transport of photogenerated carriers. This work provides an effective way to fabricate high-performance self-powered ZnO Schottky UV PDs. • ZnO/Mg x Zn 1-x O (x = 0∼0.25) Schottky UV photodetector prepared by sol-gel method. • Increasing Mg content can enhance the self power supply of devices. • The maximum linear dynamic region of the devices reaches 33.7 dB. • The photoresponse of the devices are improved by an order of magnitude. • High LDR and R are from increased schottky barrier and depletion region width. [ABSTRACT FROM AUTHOR]