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Here, cobalt-doped copper bismuth oxide (Co-CuBi2O4) was synthesized via a facile hydrothermal method for photoelectrocatalytic (PEC) hydrogen production. The results disclosed that the 5% Co-doped CuBi2O4 has better PEC activity which is ∼3 fold higher than pristine CuBi2O4. The doping of cobalt in CuBi2O4 improves the interfacial charge transfer at an electrode/electrolyte interface and reduces the recombination rate of photogenerated electron-hole pairs. This higher performed 5% Co-doped CuBi2O4 photocathode further modified with TiO2-P25 to form a Co-CuBi2O4/TiO2 p‐n heterojunction. This Co-CuBi2O4/TiO2 photocathode displayed a photocurrent density of 330 μA cm−2 at +0.5 V vs. RHE which was ∼2 fold higher than Co-CuBi2O4. Because this p-n junction affords inner electric field in the space charge region that helps for further minimization of electron-hole recombination, which facilitate efficient charge separation and transport thereby enhance the PEC water reduction.

The pursuit of low power consumption, high charge collection efficiency (CCE), and high energy resolution is critical for the development of high performance GaN-based alpha-particle detectors. In this letter, we fabricated a low-voltage p-i-n GaN-based alpha-particle detector with superior energy resolution. The detector exhibits a very low leakage current of pA level even at −100 V and high CCEs of 31% and 92% at zero bias and reverse bias of 50 V, respectively. Meanwhile, the detector demonstrates a high energy resolution of 2.48% at −20 V. These excellent performances are attributed to the artificially enlarged path of alpha particles in the depletion region by employing the angular incidence measurement method and the high crystal quality of the epitaxial film grown on a single-crystal GaN substrate. In addition, the damage events caused by the alpha particles are also investigated using the Monte Carlo calculation. These results are anticipated to promote the research of radiation-hardened GaN-based detectors.

The Schottky barrier at the interface between the semiconductor phase and the metal phase has excellent rectification effect which can greatly facilitate the formation of the electron accumulation region. The interface electronic modulation can promote the formation of electron depletion layer in the gas sensing process, which is a powerful strategy to improve the sensing performance. In this work, ZnO–TiC composites were successfully prepared. XRD, TEM, BET and XPS characterizations of the ZnO–TiC composites were proformed to investigate the compositions and structures. The as-synthesized samples were applied to fabricate gas sensors to investigate their gas sensing performance. Compared to pure ZnO and TiC, the composites achieved high sensitivity (232 for 100 ppm aniline) and linear detection (R2 = 0.986) of aniline. The improvement of sensor performance is mainly attributed to the electronic modulation of Schottky barrier at the interface between ZnO and TiC. Our results indicate that the construction of ZnO-TiC Schottky barrier is a promising strategy for enhancing the performance of gas sensors.

We report GaN vertical trench MOS barrier Schottky (TMBS) diodes with embedded p-GaN shielding rings (SRs) and systematically investigate the impact of different structural parameters of the p-GaN SRs on the breakdown performance of the GaN-based vertical TMBS diodes by numerical simulation. The charge coupling effect by the embedded p-n junction at the bottom of the trench homogenize the electric field at the trench corner and alleviate the electric field crowding effect at the Schottky contact region, which can effectively avoid the premature breakdown and improve the reverse blocking capability of the TMBS diodes. The p-GaN SRs can also broaden the overlapped depletion region and shift the pinch-off point into the n−-GaN drift region, thus facilitating the 2-D depletion in the n−-GaN drift layer and boosting the breakdown performance of the conventional TMBS diodes. We found that the doping concentration, thickness, and the width of the p-GaN SRs are closely associated with the electric field distribution and the reverse breakdown characteristics of the GaN-based vertical TMBS diodes. The vertical TMBS diodes with optimal p-GaN SR parameters featured a dramatic improvement in the breakdown voltage from 907 to 1281 V, without an obvious degradation in the ON performance. The proposed TMBS diodes with a p-GaN SR structure can pave the way toward a high-performance GaN vertical power device for high-power and high-efficiency power switch applications.

A 2-D compact analytical model for the device potential of double metal double gate hetero-oxide Tunnel FET (DM DG Hetero-oxide TFET) has been developed in this work. The hetero-oxide (HfO2 + SiO2) and the double metal double gate allows improvement in current in the ON state of TFET as well as suppresses the ambipolar current in TFET curtailing both the limitations of TFET. Parabolic approximation method with required boundary conditions has been utilized to solve Poisson’s equation. Depletion region plays vital role in altering the potential of device in its proximity. Therefore, the depletion regions at drain and source are also considered for the modeling of the device. For this the effect of fringing field has been considered using the technique of conformal mapping in the depletion regions. The incorporation of the depletion region in potential modeling allows a precise modeling of the potential near channel-drain and source-channel junctions. The model results considering source and drain depletion region shows better match with simulation results. Validation of proposed model has done against simulation data using ATLAS TCAD SILVACO software. The compact analytical model developed here is found to have good agreement with the simulation framework.

For the first time, we report achieving a considerable output power density in metal-semiconductor field-effect transistors according to silicon-on-insulator technology (SOI MESFETs). Our main idea is to improve the breakdown voltage and the saturation current simultaneously and, therefore, the output power density of SOI MESFET devices by silicon dioxide engineering. Our silicon dioxide engineering consists of a step-shaped buried oxide (BOX) and an extra layer of silicon dioxide under the gate (SB-LO-SOI) in this work. A step-shaped in the channel area results in a more significant drain current due to increasing total carrier concentrations. Also, by omitting a part of the BOX and substituting it with n-doped silicon, the depletion layer changes, and the channel charges increase. Besides, the distribution of the electric field improves by the additional rectangular silicon dioxide layer under the gate as a result of extending the depletion layer. By having a premier electric field distribution, the breakdown voltage will enhance. According to the results, the breakdown voltage and the saturation current of the considered device improve by 130 % and 33 %, respectively, compared to the traditional one. As well as, the output power density of the considered device rises by 212 %. Thereupon, the SB-LO-SOI MESFET device outperforms the conventional SOI MESFET device in terms of electrical properties.

In this study, the frequency/voltage dependence of the dielectric constant (epsilon '), dielectric loss (epsilon ''), real/imaginary components of the complex electric modulus (M ', M ''), tangent loss (tan delta), ac electrical conductivity (sigma(ac)), real and the imaginary parts of the complex impedance (Z*), phase angle (theta) between resistance current, and capacitive current of the Al/(Coumarin: PVA)/p-Si structures were investigated using C/G-V-f measurements in wide range of frequency (10 kHz-1 MHz) and voltage (+/- 5 V) by 0.05 V steps. These parameters showed strong dependence on frequency and voltage due to the existence of surface states (N-ss), their life/relaxation time (tau), series resistance (R-s), and polarization processes. epsilon ' and epsilon '' values were found to be high at lower frequencies and this was explained by the fact that the interfacial dipoles have enough time to orient themselves in the direction of the signal and thus N-ss can easily follow it. M '-V and M ''-V plots both have a distinctive peak at depletion region and peak position shifts toward accumulation region with increasing frequency due to restructuring and reordering of N-ss under electric field and polarization. ln(sigma)-ln(f) plots for accumulation region show two linear parts with different slopes, and this provides an evidence to the existence of two different conduction mechanisms which correspond to intermediate and high frequency regions. The strong dispersion in epsilon ' and epsilon '' at lower frequencies was attributed to the N-ss, Maxwell-Wagner-type polarizations.

The 4H-SiC trench metal–oxide semiconductor field-effect transistor (MOSFET) with the grounded p+ shielding region is one of the commercial devices with superior gate oxide reliability. However, the introduced JFET region seriously increases the influence of quasisaturation (QS) on device electrical performances, resulting in the poor output and transfer characteristics. In order to investigate the mechanism of QS effect, the output characteristic is physically analyzed by monitoring the variations of the electric field, the electron concentration, the electron velocity, and the depletion layer inside the cell structure. It is demonstrated that the channel electrons are injected into the JFET current path from the channel region by a forward bias to the channel and JFET junction at QS state. Moreover, based on the Lombardi CVT model, the influence of QS effect on devices with different channel electron mobilities is first studied. An improved SiC trench MOSFET with two-level doped current spreading layers is proposed to decrease the JFET resistance and suppress the QS effect. The QS current and the peak transconductance are improved by 42% and 23%, respectively. The specific ON-state resistance is decreased by 10% and the figure of merit is improved by 7%.

The reliability of the integrated circuits (ICs) has become one of the greatest challenges with the increasing complexity of the electromagnetic environment. On this basis, an explicit difference in the damage location is observed in the high-power microwave (HPM) radiated CMOS inverters. The detailed damage mechanism analysis is performed. The analysis shows that the overcurrent-dominant failure and the latch-up-dominant failure are induced in positive and negative half radiation cycle respectively, resulting in the damage location discrepancy. The depletion region current $I_{\textrm {SS}}$ and the body current $I_{\textrm {body}}$ are derived from the established theoretical charge transport model. TCAD simulations demonstrate the junctional-overcurrent and latch-up process, empirical formula is obtained to explain the damage mechanism and predict the thermal damage location. The damage dependency on interference characteristics is discussed for further understanding. Corresponding experiments are performed using the six-integrated-inverters chip. The results support the theoretical charge transport model well.

Boron-doped diamond (B-diamond) metal–oxide–semiconductor (MOS) capacitor and MOS field-effect transistor (MOSFET) are fabricated on a flat diamond epitaxial layer. Their electrical properties and thermal stabilities after annealing at 500 °C are investigated. Annealing makes the leakage current density of the B-diamond MOS capacitor increase slightly. There is a larger stretch-out for the capacitance-voltage curve in the depletion region after annealing than that before annealing. The drain-current maxima for the as-fabricated and 500 °C-annealed MOSFETs are obtained as −0.49 and −0.60 mA/mm, respectively. Extrinsic transconductance maxima are 18.7 and $21.4~\mu \text{S}$ /mm, respectively. These obtained values are considerably larger than those obtained by the previously reported B-diamond MOSFETs.

In this paper, a 2D analytical potential model for n + SiGe Gate stacked linearly graded work function Vertical TFET (n + SiGe GS-LGW-VTFET) is developed with incorporating the effect of source and drain depletion region towards the channel. The proposed novel structure is developed from linearly graded for equalizing disruption of the work function having symmetric potential distribution effect on the device channel, which noticeably improve the device performance by reducing the short channel effect. The Poisson equation is solved in terms of channel surface potential and electric field using the parabolic approximation approach. This model also used some accurate analysis by employing the SiO2 and HfO2 with gate stacking method in order to increase the better gate control over the channel length. This model can initially forecast with the effect of gate-source voltage (Vgs) and drain-source voltage (Vds) thereafter gate oxide thickness, linearly graded work function, and SiGe mole fraction. The electric field is derived using the surface potential model, and thereafter, in order to extract the drain current characteristics, our suggested model accounts for the variables of the Kane model by integrating the band-to-band tunneling generation rate over the tunneling region. The proposed model efficiency has been confirmed by the drive characteristics of our model are in coincides nicely with that of simulation results.

Herein we introduce and investigate a new architectural design strategy for planar single gate field effect transistors (SG-FETs) that delivers advantages from all fronts of design, fabrication and performance perspectives. The amalgamation of schottky buried metal layer (BML) and charge plasma (CP) mechanism of doping in planar single gate architecture yields a novel type of FET called as CP-BML FET. Owing to the schottky BML induced depletion region created on the bottom side of device layer reduces effective device layer thickness (TSi) suppressing short channel effects (SCEs) including drain induced barrier lowering (DIBL) and threshold voltage roll-off. The proposed FET has been analyzed for DC and RF performance figure of merits (FOMs) and compared to counter part state of the art technologies with reference to ITRS performance projections. The proposed FET is also investigated the performance FOMs on for criticality of physical parameters including gate length (Lg), device layer thickness (TSi), BML workfunction (ϕBML). The ION and IOFF for proposed device at Lg = 20nm read at 730μ A/μ m and 7 × 10− 2 pA/μ m respectively. RF performance analysis reveal transition frequency (ft) of 390 GHz with SS $\simeq \ \text {75mV/dec}$ coherent with ITRS performance projections. It is found that ultra scaled (7 nm) proposed device exhibits intrinsic delay τ of 0.6 ps which is superior to ITRS projections of 1.71 ps at 28 nm technology node. The proposed device yields Pdyn of 0.248 fJ/μ m at Lg= 7nm implicating it to be potential candidate for low power with high performance application requirements.

The Fourier-series-based insulated-gate bipolar transistor (IGBT) model has been very effective in simulating its switching behaviors and meanwhile, reflecting carrier dynamics. However, in turn-on process, such a model has difficulty in distinguishing the boundary between undepleted area and depletion layer of the drift region due to Gibbs phenomenon and therefore, cannot accurately describe the carrier behavior of carrier storage region (CSR). In this study, the Fourier-series-based model is modified to determine the more precise depletion layer edge for turn on. This is achieved by utilizing the actual characteristics of the carrier concentration gradient at the edge of CSR in turn-on process. Such a modified model is implemented in MATLAB/Simulink and it can better reflect the depletion layer and simulate the distribution of both the carrier concentration and electric field during turn-on process. It corrects the unreasonable voltage tail caused by the error of drift region voltage calculation in previous models. The results of the proposed model under both the resistive load and inductive load are in good agreement with TCAD. Such a modified model can more accurately simulate both carrier dynamics and switching behaviors in the turn-on process.

This article describes an analysis of the electric-field-dependence mechanism for cosmic ray failure in power semiconductor devices. Two major modes for the failure have been reported. One is bipolar transistor activation caused by carrier generation from impact ionization at the n−/n+ boundary. The other is Joule heating generated by an avalanche current in high electric fields. We clarified that a bipolar transistor activation mode had not occurred even under high electric field conditions for the drift layer width used in lower-voltage-class insulated-gate bipolar transistors (IGBTs) by evaluating the drift layer thickness dependence of the failure in time (FIT) in 1700 V devices from punchthrough to non-punchthrough with and without a p+ collector layer. We also clarified that the electric field averaged over the depletion layer width (applied voltage divided by the depletion layer width) is the critical factor for failure, rather than the maximum electric field, for the first time by observing a universal curve of the average electric field dependence of FIT in 750–6500 V IGBTs and diodes. To improve the cosmic ray durability of power semiconductor devices, lowering the electric field averaged over the depletion layer width is effective for device design.

Black silicon (b-Si) surfaces typically have a high density of extreme nanofeatures and a significantly large surface area. This makes high-quality surface passivation even more critical for devices such as solar cells with b-Si surfaces. It has been hypothesized that conformal dielectrics with a high fixed charge density ( ${{\boldsymbol{Q}}_{\boldsymbol{f}}}$ ) are preferred as the nanoscale features of b-Si result in a significant enhancement of field-effect passivation. This article uses 1-D, 2-D, and 3-D numerical simulations to study surface passivation of b-Si, where we particularly focus on the charge carrier control by | ${{\boldsymbol{Q}}_{\boldsymbol{f}}}$ | up to 1 × 1013 cm−2 under accumulation conditions. We will show that there is a significant space charge region compression in b-Si nanofeatures, which affects the charge carrier population control for moderate | ${{\boldsymbol{Q}}_{\boldsymbol{f}}}$ | up to a1 × 1012 cm−2. The average surface minority charge carrier density can be reduced by 70% in some cases, resulting in an equivalent reduction in area-normalized surface recombination losses if the effective surface recombination velocity ( ${{\boldsymbol{S}}_{{\rm{eff}}}}$ ) is limited by minority carriers. This provides a possible solution for the empirical ${{\boldsymbol{S}}_{{\rm{eff}}}} \propto 1/{\boldsymbol{Q}}_{\boldsymbol{f}}^4$ reported previously. We will also show that the situation is more complicated for surface passivation films where the ratio between the electron and hole capture cross section ( ${{\boldsymbol{\sigma }}_{\boldsymbol{n}}}$ / ${{\boldsymbol{\sigma }}_{\boldsymbol{p}}}$ ) is higher than 10 for p -type surfaces. For commonly used surface passivation films with a | ${{\boldsymbol{Q}}_{\boldsymbol{f}}}$ | larger than a1 × 1012 cm−2, there is little space charge compression for b-Si. Consequently, ${{\boldsymbol{S}}_{{\rm{eff}}}}$ simply scales with the surface area, i.e., there is no enhanced reduction of surface recombination by field-effect passivation on b-Si.

This article presents a simple yet powerful general pinning process model for 3-D pinned photodiodes (PPDs), which can be used to model PPDs with small dimensions (miniature PPDs). For the development of a pinning model, capable of dealing with different PPD shapes and dimensions, the charge population in the space charge region (SCR) is calculated. Moreover, to improve the model’s accuracy, the PPD inner region depletion mechanism is investigated, and the inner SCR width is extracted analytically. The model’s application in analyzing PPDs is verified with six previously published experimental results.

In this article, in addition to two commonly known noise parameters—dark count rate (DCR) and afterpulsing (AP)—we explore another interesting phenomenon–random telegraph signal (RTS) noise—during the transitional phase of the avalanching process. We present the properties of the RTS noise and their dependence on the biasing voltage and temperature. An analytical model is used to extract the dimension of the defects in the depletion region from the variation of the RTS noise current amplitude with biasing voltage. By comparing the DCR and AP of single-photon avalanche diode (SPAD) samples with different defect dimensions derived from the RTS noise properties, a trend that the SPAD with a larger defect dimension shows a higher DCR and AP is found.

Recent advances in CMOS scaling have made circuits more and more sensitive to errors and dysfunction caused by ionizing radiation, even at ground level, requiring accurate modeling of such effects. Besides generation, transport, and collection of radiation-induced excess carriers, another phenomenon, called funneling, has to be modeled for an accurate prediction of soft errors. The funneling effect occurs when the radiation track crosses a space charge region and generates excess carriers with a density higher than the doping close to it. These carriers distort the electric field of the space charge region, deeply changing the transport mechanism, from diffusion in a field-free semiconductor to drift. The objective of this work is to include funneling as part of the generalized lumped devices model in order to obtain a complete tool for SPICE-compatible simulations of single-event effects (SEEs). The latter approach has been recently proposed to simulate radiation-induced charges in the silicon substrate and is based on the so-called generalized lumped devices that simulate charge generation, propagation, and collection using standard circuit simulators. The generalized devices are here extended to include funneling and used to simulate an alpha particle impinging on the bulk of nMOS and pMOS transistors. The results obtained are validated with TCAD numerical simulations. Finally, an static random-access memory (SRAM) struck by an alpha particle is analyzed. The model predicts that the occurrence of a soft error, i.e., flipping of memory state, may depend on whether or not there is funneling. This justifies the need for accurate modeling of funneling phenomena to predict SEEs in ICs.

The main focus of this framework is the preparation of CdTe nanocrystalline thin films (~120 nm) on single crystal p-Si wafers (270 μm) with Miller index (100) using thermal evaporation. Then, the In/n-CdTe/p-Si/Al solar cell was successfully fabricated. The dark I–V characteristics for the fabricated solar cell have been determined in range of 300–375 K and an applied voltage range of − 2 to 2 V. The fabricated solar cell's behavior was thoroughly explained. As a result, the important parameters for the fabricated solar cell such as the rectification ratio $${\text{RR}}$$ , the junction resistance $$R_{{\text{J}}}$$ , ideality factor of solar cell n, the shunt resistance $$R_{{{\text{sh}}}}$$ , the series resistance $$R_{{\text{s}}}$$ , the barrier height created at the interface between the CdTe thin film and the p-Si wafer $$\phi_{b}$$ , the energy of trap level $$E_{{\text{t}}}$$ and the activation energy of carriers’s recombination in the depletion region $$\Delta E$$ were determined. Finally, the Poole–Frenkel $$\beta_{{{\text{PF}}}}$$ and Schottky $$\beta_{{\text{S}}}$$ parameters were computed.

Sensors are part of a safe laboratory, working space and closed environment. In view of this, a sensing material for ammonia (NH3) vapour, nickel oxide (NiO) has been investigated to improve its quality as a sensor. The transparent nanostructured NiO thin films were deposited on glass substrates by sol-gel spin coating method at different molar concentrations (0.4 M, 0.6 M and 0.8 M). The NH3 sensing studies reveal that 0.6 M film shows admirable response of 403 (75 ppm), and also it has good response and recovery times (110 s and 33 s) for 25 ppm at room temperature. These features of the film are attributed to low surface roughness, small grain size and higher surface to volume ratio compared to other films. In presence of air ambience, the electrons at film surface are chemisorbed by oxygen molecules and thereby cause an increase of the depletion layer. Once the film is exposed to the analyte gas NH3, the depletion layer decreases because of electrons returning back to the conduction band (CB). These electrons are then de-excited to the valence band (VB) and recombine with holes (annihilation of holes). At the same time, the trapping of electrons by Ni(OH)2 and creation of holes by oxidation of Ni2+ into Ni3+ increases the hole concentration at VB, followed by a reduction of recombination rate of electrons and holes. All these processes decrease the potential barrier between the grains and thereby cause the Fermi level (EF) to shift towards VB. These processes remarkably enhance the sensing behaviour of the film. Importantly, the prepared NiO thin film behaves as a n-type sensor at room temperature for NH3; and therefore, termed as pseudo-n-type.

To improve the performance of semiconductor photoelectrodes for water splitting, the amount of band bending in the depletion layer of a semiconductor should be accurately ascertained, since it dete...

In2O3 vertical nanostructures (VNS) are fabricated using a glancing angle deposition (GLAD) technique upon an In2O3 thin film (TF) on a n-type silicon (n-Si) substrate. Analysis using high-resolution transmission electron microscopy (HRTEM) and high-resolution x-ray diffraction (HRXRD) revealed that the In2O3 VNS are amorphous in nature. An average ~4.5-fold enhancement in absorption was observed and a microscopic origin was proposed for observed bandgap changes for the n-Si/In2O3 TF/GLAD In2O3 VNS and bare n-Si/In2O3 TF samples in the visible region due to surface-related trap states or oxygen vacancies. The improvement in photodetection was attributed to the presence of a large number of surface-related trap states at the edge of metal contacts. The fabricated VNS detector possesses enhanced photosensitivity (~1.7-fold) due to an efficient photogating effect in the depletion region. A maximum detectivity of ~12.8 × 107 Jones was observed for the n-Si/In2O3 TF/GLAD In2O3 VNS device, which possesses ~15.6-fold enhanced detectivity as compared to the bare n-Si/In2O3 TF device.

In this paper, we propose a novel Silicon on Insulator (SOI) Metal Semiconductor Field Effect Transistor (MESFET) with an embedded GaN layer (GL-SOI-MESFET) for modifying the electric field distribution. The main idea of this work is based on using a high breakdown field material (GaN), for amending the electric field and potential distribution near the drain region, and as a result, the breakdown voltage of the proposed structure will be higher than a conventional structure (C-SOI-MESFET). The breakdown voltage (VBR) of the GL-SOI-MESFET at the Ids = 55 mA/mm and Vgs = − 1 V has been achieved ~21 V whereas the VBR in the C-SOI-MESFET is 16 V. The proposed structure shows the improvement of DC and RF characteristics versus the C-SOI-MESFET. For obtaining the best results to improve the structure performance, dimensions of the GaN layer have been optimized. Also, by amending potential distribution and changing the depletion region between the gate and drain sides, the gate-drain capacitance reduces. The effects like the electric field, the potential distribution, breakdown voltage, the kink effect, the self-heating effect, power gains, and parasitic capacitances are investigated and the proposed structure results have superior DC and radio frequency (RF) performances compared with the conventional MESFET structure.

In this work, we fabricated vertical organic thin film transistors (VOTFTs) with lead phthalocyanine (PbPc) as the active layer and analyzed the operating characteristics and current transfer mechanism of VOTFTs. The results show that the quiescent output current of VOTFTs is not saturated, and the output current can be modulated by requiring different gate voltages. The switching parameters of the VOTFTs are ton = 2.5 μs, toff = 3.5μs, and the switching characteristic time reaches the microsecond level. When a sine wave dynamic signal is applied to the gate electrode, the cut-off frequency fc = 77 kHz. The experimental results demonstrate that short channel and vertical structure of VOTFTs make up for organic semiconductor material defects of low carrier mobility and realize high speed and low driving voltage of organic devices. Electric field intensity of depletion layer in the gate region is 7×107V/m, and high electric field intensity makes carriers tunneling become the major transport mode. The tunnel injection model is used to analyze the carrier transport inside the transistor. The results show that the operating current of the transistor conforms to the tunneling effect theory.

Silicon technology is dominant in electronics and optoelectronics. The cut-off wavelength of silicon is less than 1.1 $$\upmu$$ m due to the bandgap, limiting applications of silicon in communication, sensing, and light harvesting. A new strategy for infrared photodetection is presented by integrating silicon and PbSe colloidal quantum dots (CQDs), which combines advantages of silicon devices and PbSe-CQDs. In this study, we introduce a silicon-based photodetector that is sensitive to infrared light with spectral response from 405 nm to 1550 nm. The device can deliver a high responsivity of 648.7AW− 1 and a fast response of 32.3 $$\upmu$$ s at 1550 nm. Besides, the detectivity and the external quantum efficiency of the device reached 7.48 × 1010 Jones and 6.47 × 104%, respectively. The performance of the device originates from the photovoltage generated at the interface between the silicon and the quantum dots. This photovoltage changed the width of the depletion layer to realize detection. These results indicate that the silicon-based quantum dot infrared photodetectors prepared by this method have application prospects in the field of optoelectronics.

In this research, for determining the effects of the (Gr-PVP) interfacial layer, two types of diodes (Au/n-Si and Au/(Gr-PVP)/n-Si) were performed on the same n-Si wafer with the same ohmic and rectifier contacts. Graphene-doped PVP nanocomposite film was grown on the n-Si wafer by a spin-coating method. Therefore, the basic electrical parameters of them were extracted from the I-V and Z-V-f characteristics and compared in detail. The higher values of n and lower values of BH obtained from Cheung's functions compared to TE theory were ascribed to their voltage-dependent. The frequency-dependent diffusion potential (V-D), doping-donor atoms (N-D), depletion layer width (W-D), surface potential (psi(s)), R-s, and BH values of the MPS diode were also extracted from the impedance characteristics in the frequency range of 10-10(3) kHz.

In this article, novel sandwich-structured surface plasmon ultraviolet (UV) photodetectors based on ZnO thin films with engineered rear metal electrode were fabricated by radio-frequency magnetron sputtering. An exhaustive study about the impact of a dissimilar metallic layer (Au and Pt) on the structural, optical, and electrical properties of the device was carried out. The carrier collection property of the sandwich structure devices has the advantages of horizontal and vertical joint collection. In theory, adding a new metal semiconductor layer introduces a contact area and increases the resistance. An ultra-low dark noise current of less than 2.0 × 10–7 A and a responsivity exceeding 1.6 A/W were achieved with the prepared ZnO-based UV-PDs in the rear metallic electrode mode. The devices based on the ZnO/Pt/ZnO and MgZnO/Pt/MgZnO sandwich structures show high responsivity and fast response. This study provides a depletion layer width method for the fabrication of high-response UV photodetectors for surface plasmon-based materials by integrating metal semiconductor nanostructures. A homogeneous two-layer UV photodetector is constructed, which changes the traditional single-layer device structure and overcomes drawbacks of the single device structure.

This study investigates the charge injection barrier at the phthalocyanine (H2Pc)/Pd using accumulated charge measurement (ACM). Because the hole injection barrier is relatively small, the voltage ...

In this work, vertical NiO/Ga2O3 heterojunction diodes (HJDs) integrated with SiNx/Al2O3 double-layered insulating field plate (FP) structures have been demonstrated. With the additional post-annealing, the resultant diode exhibits a decreased differential specific on-resistance ( $\text{R}_{\mathrm{ on,sp}}$ ) of 5.4 $\text{m}\boldsymbol{\Omega } \cdot $ cm2 and an enhanced breakdown voltage (BV) of 1036 V. The improved performance is attributed by the combination of the FP-suppressed crowding electric field at the device edge and the reduced trap density at the NiO/Ga2O3 interface. In particular, the near-unity ideality factor has been achieved for this p-n HJD at an elevated temperature of 275 °C, indicating that the diffusion current is dominated. The high-temperature operation capability is owing to the quality improvement of NiO/Ga2O3 interface, where the Shockley-Read-Hall (SRH) recombination mediated by deep-level defects within the depletion region is thus suppressed.

We present a systematic study of how graphitic carbon nitride (g-C3N4) in combination with Al2O3 can be used as a double dielectric to control threshold and flat band voltage in capacitance-voltage (C-V) characteristics of an a-IGZO metal-insulator-semiconductor (MIS) device fabricated on ITO substrate. We study temperature dependence of C-V characteristics for Al2O3 based MIS structures with and without g-C3N4 in the oxide. The effective dielectric constants are estimated in both cases. We show that g-C3N4 in combination with Al2O3 can be used as an effective dielectric with larger relative permittivity than either of them. It also leads to positive threshold shift without affecting the active interface at the semiconductor. The carrier density in the semiconductor is measured from the depletion region showing small variation with respect to frequency and temperature.

Effect of an isolated Ge nanowire embedded in an n-doped Si on electron beam induced current is simulated by a Monte Carlo calculation algorithm. A circular nano-contact is used to collect the current generated by the use of primary energy of 5 or 10 keV in a perpendicular configuration along a line passing through the contact center. The nanowire, considered as a recombination center, is vertically positioned beneath the contact. Calculation takes into account various parameters such as a nano-scale depletion zone under the nano-contact, the depth of the nanowire, and its size. The surface recombination velocity is taken equal to zero. Competition between both carriers collected by the nano-contact and those captured by the nanowire is studied. Both processes are affected by the depth of the nanowire and by the primary energy. Moreover, the nanowire–Si contact behaves as a nano-scale hetero-junction, and hole storage in the nanowire leads to accentuation of energy band bending, especially in the longitudinal direction of the nanowire. Consequently, tunnel recombination would be present.

As most trivalent lanthanides are hypersensitive, surface photovoltage (SPV) that is associated with charge separation in a space charge region of a semiconductor might become a new method for harv...

In this work, copper (Cu2+) substituted zinc ferrite (CuxZn1-xFe2O4 (0 ≤ x ≤ 1)) hollow micro-nanospheres were synthesized using a facile solvothermal and annealing technology. We investigated the effects of Cu2+ substitution on morphology, structure and gas sensing properties of CuxZn1-xFe2O4 hollow micro-nanospheres. The results confirmed the successful substitution of Zn2+ with Cu2+ and the cations redistribution. In addition, the testing results revealed that CuxZn1-xFe2O4 (0.25 ≤ x ≤ 1) based sensors showed significantly enhanced responses to low concentration acetone vapor. Especially, Cu0.75Zn0.25Fe2O4 and CuFe2O4 displayed high responses of 2.37 and 2.43 to 0.8 ppm acetone at 125 °C respectively, while that of ZnFe2O4 was only 1.17. Moreover, CuFe2O4 demonstrated an excellent sensor response, ultra-low limit of detection and remarkable selectivity. The fast response speed and high stability of CuFe2O4 sensor further indicated that it was promising to apply for practical medical diagnosis. The enhanced sensing properties of Cu0.75Zn0.25Fe2O4 and CuFe2O4 sensors were explained by the effect of Cu2+ on lattice cation distribution, electron depletion layer thickness and adsorbing capacity.

In the field-effect transistors based on the wide-band-gap nitride heterostructures, the dielectric layers are in widespread use as one of the main elements in the active regions of the devices and the passivation layers. Stringent requirements are imposed on the dielectrics in terms of the high dielectric capacitance, large band-gap energy, and the coating integrity. Furthermore, the films must withstand high electric fields and have a low surface state density in the dielectric/semiconductor interface. For these purposes, the low temperature films grown by plasma-enhanced chemical vapor deposition, atomic layer deposition (ALD), and plasma-enhanced deposition are usually used as effective coatings. The ALD films of Al2О3, SiNх (Si3N4), SiON, and ALD AlN are used most often, and offer the greatest promise for the AlGaN/GaN heterostructures. The influence of the passivation of the ALD Al2O3, SiNx, and SiON coatings of various thicknesses on the change of the charge and the density of the states of the AlGaN/GaN heterostructures is investigated. The physical parameters of the structures are estimated by the C–V characteristics measured on various frequencies and the I–V characteristics. It is demonstrated, according to the examined energy band diagrams of the structures at various control voltages, and estimation of the elemental composition of the films by the method of Auger electron spectroscopy, that the reason for the generation of a high positive charge at the deposition of the ALD Al2O3 and SiNx films is the occurrence of an additional piezoelectric charge in the buffer layer of AlGaN. It is demonstrated that use of the SiON films with the oxygen concentration in them higher than 3% does not result in the generation of an additional positive charge but can initiate current fluctuations during the measurement of the I–V characteristics. A possible mechanism of carrier transport in the space charge region resulting in such fluctuations is discussed.

© 2020, Springer Science+Business Media, LLC, part of Springer Nature.This paper reports that frequency response on profile of C–V–ƒ and G/ω–V–ƒ characteristics of spin-coated nanographite (NG)-doped polyvinylpyrrolidone (PVP)/n-Si structures in a wide frequency (1 kHz–5 MHz) and voltage (± 3 V) ranges at room temperature. Hereby, the basic parameters of the structure such as diffusion potential (VD), doping donor density (ND), Fermi energy level (EF), maximum electric field (Em), depletion layer thickness (Wd), and barrier height (ΦB) are derived by using the intercept and slope of C−2–V–ƒ plot for each frequency. Additionally, the energy density distribution of surface states (Nss) and their relaxation time values (τ) are also attained from the conduction method and their values are found as 4.999 × 1012 eV−1 cm−2 and 2.92 µs at 0.452 eV, and 3.857 × 1012 eV−1 cm−2 and 164 µs at 0.625 eV, respectively. The lower Nss values are the consequence of passivation effect of the used nanographite (NG)-PVP polymer interlayer. As a result, the polymer interlayer based nanographite (NG)-PVP is candidate instead of the widely used oxide/insulator layer for the purpose of decreasing the surface states or dislocations.

An Al2O3 thin film is assembled on an unin- tentionally doped ZnO for metal–insulator–semiconductor (MIS) capacitors. Leakage current density ( ${J}$ ), capacitance–voltage ( ${C} - {V}$ ) properties, and their thermal stabilities are investigated. The ${J}$ -values for the MIS capacitors before and after annealing at 300 °C are lower than $2.0 \times 10^{-7}$ A/cm2 at a gate voltage of −10.0~10.0V. Frequency-dependent ${C}-{V}$ characteristic shows a stable maximum capacitance for the MIS capacitor before annealing. However, it decreases dramatically at 1 MHz for that after annealing at 300 C, which is attributed to the change of ZnO channel resistance. Flat band voltage shifts in the–curves after annealing at 300 C are one order lower than those before annealing, indicating the decrease of positive fixed charge density in the Al2O3 film. There are ledge phenomena for hysteresis characteristics in the curves, which result possibly from the delayed evacuation of minority carriers in deep depletion region. By considering the Fowler–Nordheim tunneling model, band configurations of the Al2O3/ZnO heterojunctions are clarified to be straddling gap structures with conduction band offsets larger than 1.3 eV.

Constructing p-n heterojunction is considered as an effective approach to improve gas-sensing performance of nanomaterials, and the general focus is that the formation of a p-n junction can effectively broaden the electron-depletion layer, enhancing the amount of the adsorption oxygen, and being beneficial to the improvement of the gas-sensing performance. However the widening of the depletion layer can only contribute to the improvement of the sensitivity, the effect of p-n junction on other sensing parameters is still not well understood. Herein, the In2O3/Co3O4 core/shell hierarchical heterostructures (In2O3/Co3O4 HHS) are investigated to discern how p-n junction alters the sensing process. The construction of p-n junction can effectively adjust Fermi level, influence the oxidation ability of the adsorbed oxygen and significantly heighten the selectivity of sensing materials, resulting in superior sensing activity. Especially, In2O3/Co3O4 HHS exhibits obviously enhanced gas sensing performance toward formaldehyde at 180 °C with high response and good selectivity. Our findings promote the recognition of the important role of electronic structure on gas sensing performance and provide a new strategy to design sensing materials for gas detection.

This article reports that Hetero-interfacial-thermal resistance (HITR) due to phonon scattering and weak electron–phonon coupling at hetero-interfaces, can impact stacked Si gate-all-around (GAA) nanosheet field effect transistor (NSHFET) self-heating effect (SHE) and reliability. We have investigated the HITR of Si/SiO2 and Si/metal-silicides on SHE of vertically stacked Si GAA NSHFET. Our simulation predictions reveal that a very noticeable effect of the HITR of Si/ M0 at front end of line (FEOL) and back end of line (BEOL) interface (FEOL/BEOL) is that the hot-spot location is shifted into the channel away from drain depletion region, which affects the device SHE and degrades device performance. The impact of nanosheet width ( ${W}_{NSH}$ ) and sheets stacking number ( ${N}$ ) on device SHE and drive current degradation with and without HITR effect are also studied. It is revealed that wider nanosheets with lower HITR can be a better device design choice for heat mitigation in high performance logic transistors.

The various structures of ferroelectric tunnel junctions (FTJs) are widely studied. Among them, metal-ferroelectric-semiconductor (MFS) FTJs show great tunneling electroresistance (TER) ratio by forming a depletion region. However, the poor ferroelectricity of hafnia on semiconductor electrodes degrades the TER ratio. This study employed high-pressure annealing with forming gas to improve the ferroelectric properties of MFS FTJs. We achieved a high 2Pr value ( $47.54~\mu \text{c}$ /cm $^{2}$ ) and large TER ratio (22) in MFS FTJ for a 6 nm thick hafnia layer annealed at high pressure (200 atm) with forming gas. This work helps improve the quality of interface between a semiconductor and ferroelectric layer to increase the ferroelectricity of MFS stack devices.

The space charge region (SCR) is a majority carrier-depleted region in a semiconductor. The width of this region and the size of the potential drop across it control photochemical charge separation...

The quasi-static capacitance–voltage (QSCV) characteristics of 10-nm-gate-length double-gate N-type metal–oxide–semiconductor field-effect transistors (NMOSFETs) with Si, Ge, InAs, $$ {\hbox{In}}_{0.53} {\hbox{Ga}}_{0.47} {\hbox{As}} $$ , and GaAs as channel materials are studied and simulated using Silvaco ATLAS three-dimensional (3D) technology computer-aided design (TCAD) software. The QSCV approach offers the advantage of immunity against frequency dependence effects and the ability to measure small capacitances in the 100 fF range. In this device, we consider the self-consistent solution of Schrodinger’s equation with Poisson’s equation. The splitting of the conduction band into multiple subbands is considered, while there is no doping in the channel region. The effects of metal gate electrode engineering, channel engineering (Si, Ge, GaAs, $$ {\hbox{In}}_{0.53} {\hbox{Ga}}_{0.47} {\hbox{As}} $$ , and InAs), and different channel thicknesses with $$ \left( {{\hbox{Al}}_{2} {\hbox{O}}_{3} } \right) $$ as gate oxide having thickness of 0.8 nm on the QSCV characteristics are studied. A comparison of the QSCV characteristics is carried out for the above-mentioned channel materials, revealing a significant reduction in the inversion-mode QSCV characteristics for all the materials due to quantization that results in a decrease in the overall gate-to-channel capacitance and hence increases the threshold voltage of the MOS device. The QSCV characteristics are also useful to measure the oxide thickness, flat-band voltage, threshold voltage, maximum depletion region thickness, charge distribution in the dielectric, interface trap charge, and interface states between the channel and gate oxide before device fabrication.

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.

In this study, Au/n-Si structures with PVP polymer interlayer were fabricated and characterized using capacitance/conductance-voltage-frequency (C/G-V-f) measurements. Obtained electrical parameters were found to be sensitive to frequency due to polymer interlayer, changes of traps/states (D-it/N-ss) level, interfacial/dipole polarization. The dispersion in C and G in depletion region is due toN(ss)/polarization, while the dispersion in accumulation region is due to interlayer/series resistance (R-s). The voltage-dependent profiles ofN(ss)andR(s)were derived using the methods of low-high frequency capacitance/Hill-Coleman and Nicollian-Brews, respectively. The width of depletion layer (W-d) and barrier height (phi(B)) values increase with increasing frequency almost linearly. On the other hand,R(s)decreases with increasing frequency whereas the maximum electric field (E-m) exhibits opposite behavior. The high frequency C/G-V plots were corrected to reveal theR(s)effect on them. The experimental results indicate that the growth of PVP interlayer by spin coating at the Au/n-Si interface yields a preferable and suitable device compared to devices with conventional insulating interlayer due to some advantages of polymer interlayers such as low-cost/weight, flexibility, and easy grown processes.

This article presents an experimental, room temperature, low-frequency noise characterization of germanium n-channel fin-field-effect transistors (finFETs) integrated on silicon. After determining the dominant mechanism in the noise spectrum, the main parameters associated with the noise mechanism are extracted and evaluated as a function of fin width from a planar-like (100 nm) up to narrow fin (20 nm) for 1- $\mu \text{m}$ length devices. The main findings are that the 1/ ${f}$ noise plays an important role in the Ge n-finFETs, whereby the trap density profiles in the gate-stack are quite uniform and have a lower level than in n-/p-channel Ge planar MOSFETs. In addition, a generation-recombination (GR) component was found in 160-nm-length devices, which is caused by GR centers located in the depletion region.

An edge termination structure with enhanced field-limiting rings (enhanced FLRs) is proposed to stabilize the breakdown voltage against the surface charge. The pitches of the enhanced rings are designed to mitigate the electric field and expand the depletion layer, which leads to an improvement of the breakdown voltage. In addition, the enhanced FLR is insensitive to surface charge because the field plates completely cover the n− layer. Simulation results indicated that the enhanced FLR did not have any fluctuation of breakdown voltage against surface charge density from 0 to ${1}\times {10}^{{13}}\,\,\text {cm}^{{-}{2}}$ , whereas conventional structures did have fluctuation. To examine the validity of the concept, we fabricated a silicon carbide (SiC) merged p-i-n Schottky diode with the proposed structure. DC bias stress tests at 150 °C over 1000 h demonstrated the breakdown voltage stability of the enhanced FLR.

In this letter, we report a large-area lateral AlGaN/GaN-on-Si power rectifier as diode with low turn-on voltage. The lateral field-effect rectifier (LFER) is based on a normally-off HEMT in reverse conduction with very low threshold-voltage and shorted gate-source terminal. A p-GaN gate module was used to realize the normally-off HEMT. The large-area LFER achieves a turn-on voltage of down to 0.2 V, a specific on-resistance of 10.8 $\text{m}\Omega \times {\mathrm {cm}}^{2}$ , a maximum current of above 9 A with a gate width of 87 mm, and a leakage current of $57~\mu \text{A}$ /mm at a blocking voltage of 500 V. Test structures exhibit a breakdown voltage of 676 V. The effect of different depletion zone lengths, temperature influences and distribution on the turn-on voltage are investigated. Finally, this work shows that this approach of a p-GaN LFER has a great potential for rectifiers for next-generation power electronics.

International audience; In Cu(In,Ga)Se 2 (CIGS) thin-film solar cells, laterally inhomogeneous distributions of point defects may induce electrostatic potential fluctuations and thus reduce the open-circuit voltage (V oc). In the present work, we investigate possible origins of fluctuating potentials and estimate the amplitude of fluctuations and V oc losses in solar cells with various [Ga] in the CIGS absorber, with different buffer layers and with different durations of an RbF postdeposition treatment (PDT). Electron-beam-induced current measurements were employed to study the local difference in the width of the space-charge region (w SCR). It is shown that the amplitude of fluctuations in the w SCR depends significantly on the choice of buffer system and on the duration of the RbF PDT. In addition, energy-dispersive X-ray spectroscopy and cat-hodoluminescence measurements reveal that band-gap fluctuations do not have substantial impact on the device performance. Finally, some of the investigated cells were exposed to light soaking, which was found to be a means to reduce the detected electrostatic potential fluctuations and also to increase the effective electron diffusion length in the CIGS absorber for a part of the investigated cells.

Hematite (Fe2O3) is a well-known oxide semiconductor suitable for photoelectrochemical (PEC) water splitting and industry gas sensing. It is widely known that Sn doping of Fe2O3 can enhance the device performance, yet the underlying mechanism remains elusive. In this work, we determine the relationship between electronic structure, optical properties, and PEC activity of Sn-doped Fe2O3 by studying highly crystalline, well-controlled thin films prepared by pulsed laser deposition (PLD). We show that Sn doping substantially increases the n-type conductivity of Fe2O3, and the conduction mechanism is better described by a small-polaron hopping (SPH) model. Only 0.2% Sn doping significantly reduces the activation energy barrier for SPH conduction from at least 0.5 eV for undoped Fe2O3 to 0.14 eV for doped ones. A combination of X-ray photoemission, X-ray absorption spectroscopy, and DFT calculations reveals that the Fermi level gradually shifts toward the conduction band minimum with Sn doping. A localized Fe2+-like gap state is observed at the top of the valence band, accounting for the SPH conduction. Interestingly, different from the literature, only 0.2% Sn doping in Fe2O3 significantly improves the PEC activity, while more Sn decreases it. The improved PEC activity is partially attributed to an increased band bending potential which facilitates the charge separation at the space charge region. The reduced activation energy barrier for SPH will facilitate the transport of photoexcited carriers for the enhanced PEC, which is of interest for further carrier dynamics study.

Dynamic hot-carrier (HC) degradation can be effectively suppressed in four-terminal low-temperature poly-Si (LTPS) thin film transistors (TFTs) with a carrier injection terminal. In order to enhance the reliability of the four-terminal LTPS TFTs, geometry effect of the carrier injection terminal, such as width and location, on the dynamic HC degradation is systematically studied. It shows that a wider carrier injection terminal, which provides more carriers injection, can suppress the degradation more effectively. As for the location, if the injection terminal is adjacent to the edge of the drain depletion region, which extends into the channel at the falling time of the gate voltage pulses, the four-terminal TFTs can provide the best immunity to the dynamic HC degradation. The proposed optimization scheme can greatly enhance the reliability of LTPS TFTs, and the mechanism can be understood based on the nonequilibrium p-n junction degradation model.

To develop a high sensitive and low temperature NO2 gas sensor, the novel BiVO4/Cu2O heterojunctions were synthesized by a modified metal organic decomposition method to decorate BiVO4 nanoplates using Cu2O nanoparticles for enhancement of BiVO4 sensing performance to NO2. The structure and morphology of BiVO4, Cu2O and BiVO4/Cu2O composites were characterized by XRD, SEM and TEM spectra. The results indicate that the BiVO4/Cu2O heterojunctions are composed of monoclinic BiVO4 nanoplates with the thickness about 1.0–1.2 μm and 30–40 nm diameters of cubic Cu2O nanoparticles. The gas-sensing tests display that the composite exhibits rapid and linear responses to low concentration NO2 (from 100 ppb to 8.0 ppm), the highest response reaches 4.2 towards 4 ppm NO2 at 60 °C and relative humidity of 28.3%, which is more than 2 times of pure BiVO4 at the same condition. The enhanced sensing properties benefit from the novel p-n heterojunction between BiVO4 and Cu2O, which forms a depletion layer at the interface, leading to resistance increase of composites in NO2. The work demonstrates the as-synthesized BiVO4/Cu2O is a promising sensing material to detect NO2 gas.