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Ga2O3 is one of the most suitable semiconductor materials for performing deep UV photoelectric detection. In this work, a self-powered deep UV photodetector based on a Ga2O3/BFO heterojunction is fabricated via solution spin-coating and metal-organic chemical vapor deposition (MOCVD) methods. Without biasing driven, the device achieves an extreme low dark current ( ${I}_{dark}$ ) of 8.38 fA, a photo-to-dark current ratio ( PDCR ) of $1.66\times10$ 5, a high specific detectivity ( ${D} \ast $ ) of $6.1\times 10^{12}$ Jones and an open-circuit voltage ( ${V}_{\textit {oc}}$ ) of 0.55 V responding to deep UV irradiation (254 nm in this work). Through analyzing the band diagram of the heterojunction, the intrinsic physical characteristics of the photodetector are discussed. Results show that the photodetector has excellent deep UV signal detecting ability, indicating that Ga2O3/BFO heterojunction is a potential candidate for performing self-powered deep UV photodetection.

In this study, phononic crystals reducing the earthquake effects will be determined and prototypes will be constructed which can give the opportunity to reduce the effects of seismic waves. Furthermore, test results will be discussed numerically and experimentally. A reasonable structure has been investigated for seismic waves in a low-frequency band by extracting band diagram based on finite element method. The wave propagation is numerically carried out depending on the experimentally obtained mechanical properties of the field. The optimum dimensions and arrangement of the periodic structure have been evaluated by numerical analysis. It is demonstrated that the shielding effect can be realized due to the impedance matching between the ground and seismic metamaterials. Impedance matching is the necessary condition for the maximum interaction of the seismic waves propagating in the field with the structure.

In this paper, the proposed design of H-shaped TFET has been discussed. This design is providing a high Ion/Ioff ratio with a better Ion. HfO2 is used for better tunnelling current. The controllability of gate voltage on the drain current improves as the gate area increases. We can obtain better outcomes for current in this design by altering the architecture. With this device, Different parameters such as unit parameter, analog parameter, and linearity parameter have been studied and investigated the output of the H-TFET. As unit parameters, the electric field, electric potential, energy band diagram, and non-local band-to-band tunnelling rate (BTBT) have all been observed. Second and third-order harmonics distortion (HD2, HD3), third-order current intercept point (IIP3), third-order intermodulation distortions (IMD3), and second and third-order voltage intercept point (VIP2, VIP3) are evaluated as linearity parameters that characterize the device’s distortions and linearity. We obtained Ion $${\text{=1.6x}10}^{-4}$$ A/μm,Ioff=2.1 $${\text{x}10}^{-19}$$ A/μm, Ion/Ioff=7.6 $${\text{x}10}^{14}$$ ,threshold voltage Vt=0.3449 V. © 2017 ElsevierInc.Allrightsreserved.

In this work, the junctionless (JL) feature is incorporated in a newly invented device called vertical super-thin body (VSTB) FET and a comparative exploration of DC and analog/RF figures of merit (FoM) is reported for various gate dielectric materials with high-k (Si3N4/HfO2) and low-k (SiO2) in this novel device through a properly calibrated Sentaurus TCAD tool. A significant minimization of short channel effects by Si3N4 and HfO2 is reflected in all the DC FoM. With respect to SiO2, off-state leakage current and on-to-off current ratio improves by five (three) orders of magnitude, whereas on current increases by 4.93 (11.83) μA for HfO2 (Si3N4). Further, using HfO2 (Si3N4) as gate dielectric instead of SiO2, induces a drop of 23.3 (13.91) mV/V in subthreshold swing. The core reason behind such beneficial impact of higher dielectric constant (er) on DC FoM is explained through off-state energy band diagram and bulk electrostatic potential of the device. Besides, though HfO2/Si3N4 increases gate capacitance (Cgg) and gate-drain capacitance (Cgd), both Cgg/Cgd exhibits extremely low values for all the gate dielectrics. Such an attribute helps in achieving higher unit gain cut-off frequency and gain-bandwidth-product. A higher er also influences other analog/RF parameters favorably. It is observed that compared to SiO2, HfO2 (Si3N4) enhances peak values of transconductance, intrinsic gain, transconductance frequency product, gain frequency product, and gain transconductance frequency product by 37.74 (13.16) μA, 48.08 (24.91), 0.832 (0.278) THz/V, 1.01 (0.465) THz, 34.3 (22.8) THz/V, respectively. This study is intended to establish a broader understanding about the influence of high-k gate dielectrics on the performance of JL VSTB FET.

In this letter, sub-10-nm air channel devices were fabricated with the aid of photolithography and focused ion beam (FIB) etching. Field emission (FE) properties of the device were measured under ambient conditions. The operation mechanism was discussed by means of current-voltage (I-V) curve fitting and energy band diagram analysis. On account of the extremely shrinking of nano-gap, record-high emission currents of $355.6~\mu \text{A}$ at 1 V were realized in air with a threshold voltage as low as 0.588 V. A cycle test of 200 times was also performed to verify and analyze the stability of the device. Importantly, the temporal response performance of the device was also measured. It demonstrated a high-speed and repeatable output waveform with a rise/fall time of $\sim 100$ ns. This study demonstrates a practical nano-fabrication technology to fabricate sub-10-nm air channel devices with ultra-low operating voltage, which can be utilized as an electrical element in high-speed and low-power integrated circuits.

The transparent nature of photovoltaic (PV) cell can replace the windows and facades in conventionally integrated buildings to harvest energy from natural sunlight and spontaneously generate electric power for various mankind applications. To demonstrate this idea, Ti-doped BiFeO3 (BFTO) lead-free ferroelectric material was explored as an active material in Pt/CuCrO2/BFTO/WS2/ITO PV cell where WS2 formed the n-type electron transport material (ETL), an unconventional p-type CuCrO2 was responsible for the hole-transportation (HTL) and bottom ITO and Pt top electrodes, were employed to extract the electrical properties of the device. A single heterojunction PV unit yielded a large short-circuit current density (JSC) and an open-circuit voltage (VOC) of 2.60 mA/cm2 and 0.95 V, respectively, which resulted in an improved efficiency of 100 orders or more as compared to the plain BFO based PVs. Different structural and absorption studies performed on 5% and 10% Ti-doped BFO revealed lower bandgap for 5% (2 eV) and thus higher absorption in visible region. The elevated ferroelectricity in 5% BFTO along with the indispensable driving force offered by ETL and HTL promoted enhanced band bending and thus efficient carrier separation and extraction in the heterostructure. A well-defined band diagram was proposed to explain the PV operating mechanism. For the integration of the transparent PV, a series connection of two 1 × 1 cm PV unit cells has been demonstrated to offer a significant amount of photogenerated voltage. This establishes the prospects of ferroelectric heterojunctions to realize PV power generation sources for emerging electronic applications.

In the present article, we conceptually develop some understanding of the Peltier heat resulting at the rectifying junction between a metal and an n-type semiconductor with a depleted space charge layer (“the Schottky barrier”) as well as two Ohmic contacts between a metal and an n-type semiconductor with an enriched space charge layer, and two dissimilar metals chosen as three instructive examples via “the thought experiment,” based upon the energy band diagram of metal and semiconductor. Additionally, we briefly discussed on the difference between the contact potential and diffusion potential, both of which proved to be a thermodynamic reversible potential as well that influences greatly the Peltier coefficient. We concluded that the reduction in the kinetic energy of more energetic electrons passing through the rectifying junction as well as the two Ohmic contacts is accompanied by the Peltier heat evolution. By contrast, the enhancement in the kinetic energy of less energetic electrons passing through the rectifying junction as well as the two Ohmic contacts is associated with the Peltier heat absorption. The Peltier heat evolution and absorption resulting at the rectifying junction as well as the two Ohmic contacts can be well understood in terms of reduction/enhancement in the kinetic energy of electrons crossing the junction, respectively, under the isothermal constraint of a couple of junctions. The rectifying junctions provide Peltier effects more markedly than the two Ohmic contacts. This idea provides in particular a basis for the thermoelectric generator (batteries) and it can be extended to other rectifying junctions such as a p-n junction and another Ohmic contact between metal and p-type semiconductor with an enriched space charge layer.

Polaritons in anisotropic materials result in exotic optical features, which can provide opportunities to control light at the nanoscale1-10. So far these polaritons have been limited to two classes: bulk polaritons, which propagate inside a material, and surface polaritons, which decay exponentially away from an interface. Here we report a near-field observation of ghost phonon polaritons, which propagate with in-plane hyperbolic dispersion on the surface of a polar uniaxial crystal and, at the same time, exhibit oblique wavefronts in the bulk. Ghost polaritons are an atypical non-uniform surface wave solution of Maxwell's equations, arising at the surface of uniaxial materials in which the optic axis is slanted with respect to the interface. They exhibit an unusual bi-state nature, being both propagating (phase-progressing) and evanescent (decaying) within the crystal bulk, in contrast to conventional surface waves that are purely evanescent away from the interface. Our real-space near-field imaging experiments reveal long-distance (over 20 micrometres), ray-like propagation of deeply subwavelength ghost polaritons across the surface, verifying long-range, directional and diffraction-less polariton propagation. At the same time, we show that control of the out-of-plane angle of the optic axis enables hyperbolic-to-elliptic topological transitions at fixed frequency, providing a route to tailor the band diagram topology of surface polariton waves. Our results demonstrate a polaritonic wave phenomenon with unique opportunities to tailor nanoscale light in natural anisotropic crystals.

Investigating heterointerfaces with test structures is crucial for fabricating electronic and photonic devices. Recently, we proposed and developed a PbS colloidal quantum dot/ZnO/Si hybrid infrared detector for infrared-sensitive optoelectronic devices on silicon-based large-scale integrated circuits. The conventional circular transfer length method (CTLM) is commonly used for evaluating Ohmic contact. To apply the CTLM to a heterointerface junction, we propose a coaxial CTLM (CCTLM) that includes a circular electrode in the middle and doughnut-shaped outer contact electrodes. The proposed test structure can be identified and quantitatively analyzed for the junction type (Ohmic or Schottky) by changing the electrode area. By using the CCTLM test structure for n-type ZnO/n-type Si heterojunctions and X-ray photoemission spectroscopy measurements, we identified the heterojunction as the Schottky type via the CCTLM and estimated the band diagram of the heterojunction.

In this paper, we investigated TiO2 as gate dielectric to achieve the large dielectric constant. The ultra high-k value over 30 was obtained by Capacitance–Voltage measurement of Al/Ti/TiO2/Si Metal-Insulator–Semiconductor (MIS) capacitor. Among as deposited, rapid thermal annealing (RTA) at 750 °C and 1000 °C, the RTA at 750 °C showed the lowest gate leakage current. It implies that TiO2 has optimum RTA temperature having the lowest leakage current. When TiO2 is annealed at 750 °C, the phase of TiO2 changes to anatase and interfacial layer between TiOx and Si was formed. While TiO2 is annealed at 1000 °C, the phase of TiO2 changes to rutile and diffusion of silicon atoms was clearly observed and it causes the silicide formation. Based on measurement data, we proposed the energy band diagram of Al/TiO2/Si MIS capacitors. This diagram shows that the energy band gap of RTA at 750 °C is expanded while that of RTA at 1000 °C is contracted. In addition, TiO2 with RTA at 550 °C was tested to confirm leakage current and it shows lower leakage current than RTA at 750 °C as we expected. This result confirmed that optimum RTA temperature of TiO2 would exist under 750 °C.

Glancing angle deposition technique was used to fabricate Ag nanoparticles (NPs) capped TiO2 Nanowire (NW) array structure for capacitive memory application. Electron microscopes confirmed the sandwiched structure of Ag NPs between TiO2 thin-film (TF) and NW. The average length of the vertical TiO2 NW and diameter of Ag NPs (with density ~1012 cm2) were found to be ~ 350 nm ±5 nm and ~3.2 nm ± 0.4 nm, respectively. An enhanced photoluminescence was observed in case of Ag NPs capped TiO2 NWs due to the presence of high carriers as compared to bare TiO2 NW. The capacitance (C) - voltage (V) hysteresis was measured for both Ag NPs capped TiO2 NW and bare TiO2 NW at different sweeping voltage (±3V to ±10 V) at 1 MHz frequency. A high capacitive memory window of 7.12 V was obtained for Ag NP capped TiO2 NW at ±10 V with an excellent endurance upto 1000 cycle. Significantly lesser charge loss of 23% was obtained after a span of 104 s with a hole and electron loss of 10.6% and 17.8% respectively. The program and erase process in the device was explained with the help of a band diagram.

A titanium oxynitride (TiOxNy) resistive random-access memory (RRAM) with write-once-read-many-times (WORM) characteristics is proposed. The TiOxNy resistive switching (RS) layer with a thickness of 62 nm was fabricated using a thermal nitridation process of an evaporated Ti metal film. The residual Ti layer with a thickness of 8 nm is used as the bottom contact. The Al/TiOxNy/Ti/n+-Si RRAM shows a large memory window of 107 at a low read voltage of 0.2 V. Stable high-resistance state (HRS) and low-resistance state (LRS) are observed in the endurance test for 104 read cycles. High read-disturb immunity can be found for over 104 s. The energy band diagram, carrier conduction and the RS mechanisms of the RRAM are investigated.

Herein, ${p}$ – type CdO thin films coated onto ${n}$ – type Si crystals are employed to form metal oxide semiconductor field effect transistors (MOSFET). In the broken gap design, the valence band edge of Si substrates centered at 5.25 eV is aligned at conduction band edges of CdO centered at 5.20 eV. The construction of the energy band diagram indicated that the devices could reveal a deep built in potential of 4.68 eV. The device is fabricated by the thermal evaporation technique under vacuum pressure of 10−5 mbar. CdO thin films grown onto Si thin crystals form a randomly distributed nanorod-like grains of rod length and diameter of $\sim 2.0 {\mu m}$ and 160 nm, respectively. In addition, ${n}-$ Si/ ${p}-$ CdO heterojunctions displayed typical diode characteristics with ideality factors of ~1.40 and barrier height of 0.67 eV. As passive mode devices, the C-V curves displayed enhanced PMOS channel with the ability of capacitance depletions in a wide range of frequency (10M–1.0 GHz). The depletion width of the device widens from 7.0 nm to 660 nm in that frequency domain. Moreover, the biased and unbiased impedance spectra analyses in the frequency domain of 1.0M–1.0 GHz, indicated the voltage controllability of the devices when operated as microwave cavities. The magnitude of the reflection coefficient spectra indicated the ability of using the MOSFET devices as high pass filters. The features of the ${n}-Si\textit {/p}$ -CdO heterojunctions nominate them for use as microwave band filters, PMOS field effect transistors and as frequency and voltage controlled tunable capacitors

An acidified SnO2/rGO aerogel (ASGA) is an attractive contributor in ethanol gas sensing under ultralow concentration because of the sufficient active sites and adsorption pores in SnO2 and the rGA, respectively. Furthermore, a p-n heterojunction is successfully constructed by the high electron mobility between ASP and rGA to establish a brand-new bandgap of 2.72 eV, where more electrons are released and the surface energy is decreased, to improve the gas sensitivity. The ASGA owns a specific surface area of 256.1 m2/g, far higher than SnO2 powder (68.7 m2/g), indicating an excellent adsorption performance, so it can acquire more ethanol gas for a redox reaction. For gas-sensing ability, the ASGA exhibits an excellent response of Ra/Rg = 137.4 to 20 ppm of ethanol at the optimum temperature of 210 °C and can reach a response of 1.2 even at the limit detection concentration of 0.25 ppm. After the concentration gradient change test, a nonlinear increase between concentration and sensitivity (S-C curve) is observed, and it indirectly proves the chemical adsorption between ethanol and ASGA, which exhibits charge transfer and improves electron mobility. In addition, a detailed energy band diagram and sensor response diagram jointly depict the gas-sensitive mechanism. Finally, a conversed calculation explains the feasibility of the nonlinear S-C curve from the atomic level, which further verifies the chemical adsorption during the sensing process.

In this paper, a new perovskite photodetector based on Graphene/reduced Graphene oxide/Perovskite material system has been investigated. A rigorous study through design of high speed and high sensitivity photodetector has been conducted to achieve an optimum device performance. The proposed photodetector was studied using 3D Atlas Silvaco simulator with regard to dark current, energy band diagram, electric field profile, photo to dark current ratio (PDCR), responsivity, sensitivity and detectivity. Our findings demonstrate the outstanding ability of the proposed Graphene electrode scheme to reduce the undesirable shadowing effect and enhance the collection mechanism. Besides, reduced graphene oxide interlayer with high conductivity plays a crucial role for high efficient charge transportation. The proposed design displays 10 times photocurrent improvement when compared to the conventional design Au/TiO2/Perovskite photodetector. The proposed device displays a high value of responsivity of 340 A/W, a 100 GHz bandwidth with 10 µs transient response, and significant PDCR of 646.4, high detectivity of 2.61 × 1013 (Jones) and high sensitivity of 6.46 × 104. In addition, the proposed photodetector shows ruggedness under high temperature condition. This modeling strategy is able to direct other researchers in the design and development of efficient perovskite optoelectronic devices.

Multiple-channel GaN heterostructures have been used to improve the device performance of high electron mobility transistors (HEMTs). The object is to achieve highly linear transconductance, low ON-resistance, and large output current. However, the complicated situation of the multiple channels made it difficult to model multiple-channel HEMTs. We report an analytical model of the electron population and the energy band diagram of multiple-channel GaN heterostructures. It is established based on the continuity of electric displacement vector at various interfaces and the electric neutrality of the whole heterostructure. The double-channel, triple-channel, four-channel, and ten-channel heterostructures have been investigated, and the calculation results are compared with the numerical self-consistent Schrodinger–Poisson solution to show the feasibility of the model.

A 365 nm AlxGa1-xN-based ultraviolet light-emitting diodes (LEDs) with double Al composition gradient last quantum barrier and hole supply layer structure has been studied. Experimental results show that the proposed structure enhances the carrier injection efficiency and suppresses the overflow of electrons. The introduction of three-dimensional hole gas further enhances the hole injection efficiency. As a result, the wall plug efficiency and electroluminescence intensity are significantly improved. In addition, the carrier concentration and the radiative recombination rate in the active region of the quantum well increases. Looking at the energy band diagram, one sees that the double Al composition gradient structure leads to higher electron blocking and alleviates the hole blocking effect. Overall, we conclude that the double Al composition gradient structure provides a pathway to achieve high-efficiency ultraviolet LEDs.

The emergence of additive manufacturing and the advances in structural optimization have boosted the development of tailored cellular materials. These modern materials with complex architectures show higher structural efficiency when compared to traditional materials. In particular, truss-like cellular structures show great potential to be applied in lightweight applications due to their large strength/stiffness to mass ratio. Besides lightweight, these materials may exhibit incredible vibration isolation properties known as phononic band gaps. The present investigation addresses the topology optimization of two-dimensional (2D) truss-like cellular structures. The formulation aims to find the optimal geometrical and mechanical properties of each truss element to create a material exhibiting outstanding vibration (elastic wave) isolation at a certain frequency range (band gap). A new method to handle the non-differentiation of repeated eigenvalues, as well as mode switching, is proposed, where P-norms are used to create continuous approximation for extreme frequency values for all wave vectors of the band diagram. Results show that the proposed formulation is effective and avoids convergence problems associated to mode switching and to repeated eigenvalues.

This work exclusively illustrates dual-metal double gate Ge pocket tunnel field effect transistor (DMG-DG-Ge pocket TFET) with hetero gate dielectric. This structure includes dual-metal gate and hetero-dielectric as well. Extensive TCAD simulation analysis is carried out to illustrate how the device transfer characteristics changes in different regions with respect to various parameters such as, the work-function of tunneling gate and auxiliary gate variations, lengths ratio of tunneling gate and auxiliary gate, and the dielectric constants of homo/hetero dielectrics involved. Here, optimization of dual metal gate work-function is done along with dual gate metal length ratio. To optimize the device behavior hetero gate dielectric HfO2 and SiO2 are considered over the source-channel interface and channel-drain interface, respectively. The enhanced device transfer characteristics obtained are explained and verified with the energy band diagram and tunneling length. The reported device structure achieves ION/IOFF = 5.05 × 1011 and sub-threshold slope (SS) as 15.9425 mV/decade along with the reduced ambipolar current. An increase in ION/IOFF ratio by the order of four as compared to Ge-pocket TFET, is reported with reasonably high ON current for sub 0.5 V supply. This enables the device for low power applications. In addition to this, for the complete analog and RF characterization of the proposed device structure, transconductance, parasitic capacitance, cut-off frequency, intrinsic delay, energy-delay product, transconductance generation factor etc. are also illustrated in detail here. Further, the energy efficiency of the device is also analyzed and justifies for its low power high-speed applications.

The impedance–frequency and capacitance–voltage characteristics of metal/polyethylene oxide (PEO)/Si (MOS) capacitors at thicknesses relevant to transistor technology are measured with and without CsClO4. Basic understanding of the impedance frequency and voltage characteristics of this MOS system is established in spin-coated films in the thickness range from 6 nm to 19 nm, as determined from capacitance measurements and transmission electron microscopy. Estimates of the dielectric constant, energy band diagram, charge trap density, and conductivity in ultrathin PEO are obtained. Simple equivalent circuits based on resistive and capacitive elements that reflect the physical system are used to model the measured impedance frequency trends and compare films with and without CsClO4 in the polymer matrix. This study reveals the electrical properties of PEO near the limits of thickness scaling, toward memory and neuromorphic device applications.

This paper demonstrates the effect of ferroelectric gate oxide on the electrostatic doped nanotube tunnel field-effect transistor (FE-ED-NTTFET). The proposed device is a dopingless device, and the electrostatic doped method is used for the operation of the device. For electrostatic doped operation, the operating source voltage (VS) for the proposed device is −1.2 V. The intrinsic doping is used throughout the device. The thin ferroelectric material with a width of 2 nm is used as the gate oxide, to improve the performance of the proposed FE-ED-NTTFET device. For the detailed investigation of the proposed FE-ED-NTTFET device, the following parameters are taken into consideration such as device parameters, analogue parameters, and linearity parameters. In device parameters, energy band diagram, quasi Fermi-level of electron and hole, electron/hole mobility, electric filed, non-local tunneling (BTBT), and hole/electron concentration are taken into consideration. In analogue parameters ON current, OFF current, ION/IOFF current ratio, threshold voltage, and sub-threshold swings are considered. For small-signal analysis linearity parameters such as TGF, cut-off frequencies, HD2, HD3, VIP2, VIP3, IIP3, and IMD3 have been discussed. The proposed FE-ED-NTTFET device shows the higher ON current (ION) 6.24uA, lower OFF current (IOFF) order of 10−17 A, higher ION/IOFF current ratio 1*1012, and better sub-threshold swing (SS) 12 mV/decade for gate voltage (VGS) 1.2 V.

The work explores the conduct of composition graded amorphous silicon carbon alloy (aSixC1-x: H) as window layer on graded band gap amorphous silicon (p+aSixC1-x: H/i-aSi:H/n+aSi1-xGe x:H) solar cells, for the first time. The working principle of the proposed structure is interpreted with the aid of energy band diagram. Experimentally validated parameters were adopted for the simulation of the proposed structure. It is observed that the proposed structure is efficient in delivering conversion efficiency (η) of 15.39% at 300 K on reducing its window layer thickness to 5 nm, which is commensurate to other announced amorphous silicon solar cells. The momentous cutback in thickness of one of the active layer leads to lesser material demand and diminishes the overall manufacturing cost. Further, the effect of variation in temperature on the proposed structure has been evaluated and observed that the performance remain almost unaltered. Furthermore, the proposed solar cell structure is compared with our previous work and state of art of single junction amorphous silicon solar cell structures.

International audience; A dielectric transmittance filter composed of subwavelength grating sandwiched between two few-layers distributed Bragg reflectors (DBRs) is proposed with the aim of being compatible with CMOS technology and to be tunable by lithographic means of the grating pattern without the need of thickness changes, in the broad spirit of metamaterials. The DBR mirrors form a Fabry-Perot (FP) cavity whose resonant frequency can be tuned by changing the effective refractive index of the cavity, here, by tailoring the in-plane filling factor of the grating. The structure has been studied and designed by performing numerical simulations using Fourier Modal Method (FMM). This filter proves to have high broad angular tolerance up to ±30˚. This feature is crucial for evaluating the spectral performance of narrow-band filters especially the so-called Ambient light sensors (ALS). By analyzing the transmittance spectral distributions in the band diagram, it is found that the angular tolerance is due to coupling between the FP and the guided mode inside the cavity in analogy to resonances occurring within multimode periodic waveguides in a different context.

We present a detailed study on the crystal structure of 0.10 mol% Ta-doped β-Ga2O3 crystals before and after annealing treatment in air by high-resolution X-ray diffraction and Raman spectroscopy, as well as the detection of point defects through the variation of photoluminescence excitation (PLE) and photoluminescence (PL) with temperature. Based on the experimental data, the band diagram of the 0.10 mol% Ta-doped β-Ga2O3 crystal is constructed. The crystal quality of the 0.10 mol% Ta-doped β-Ga2O3 crystal was improved after annealing treatment. The PL spectra exhibited two ultraviolet emission bands (UV ∼3.59 eV, UV′ ∼3.22 eV) and a blue emission band (BB ∼2.73 eV) , which are ascribed to the recombination of self-trapped excitons at the trigonal OI and OII sites and gallium vacancies in the (2−) charge state (tetrahedral site), respectively. The work function of the 0.10 mol% Ta-doped β-Ga2O3 crystal increased from 5.28 eV to 5.38 eV as a result of annealing treatment.

This paper presents a detailed study of the current-voltage (I-V) and capacitance-voltage (C-V) measurements made on a CdS/CdTe based solar cell by numerical modeling. Implementation of the simulated cell having a superstrate configuration was done with the help of SCAPS program using defect density model. The I-V characterisation includes window and absorber layer optimisation based on various factors including the impurity doping concentration, thickness and defect density. The energy band diagram, spectral response and currentvoltage plot of the optimised cell configuration are shown. C-V characterisation (Mott-Schottky analysis) of the solar cell is conducted at different low frequencies to determine the flatband potential, carrier concentration and to validate the reliability of the results. The optimum device performance was obtained when the active layer was 2 ?m thick with a doping level of 1?1015/cm3.

Tuning Schottky barrier height is crucial to optimize the performance of Schottky junction devices. Here, we demonstrate that the Schottky barrier height can be tuned with the voltage from a triboelectric nanogenerator (TENG). Schottky barrier heights at both ends are increased after the treatment with the voltage generated by the TENG. The electric field generated by the impulse voltage of the TENG drives the diffusion of the ionized oxygen vacancy in a CuO nanowire, which induces the nonuniform distribution of the ionized oxygen vacancy. The positively charged oxygen vacancy accumulates at the contacted interface of Pt and the CuO nanowire, and it impels the conduction and valence bands to bend downwards. The Schottky barrier height is raised. A theoretical model based on the energy band diagram is proposed to explain this phenomenon. This method offers a simple and effective avenue to tune the Schottky barrier height. It opens up the possibility to develop a high-performance Schottky sensor by tuning the Schottky barrier height.

Far-ultraviolet-C (Far-UVC) light-emitting-diodes (LEDs) offer a promising technology for the disinfection of surface, air, water, food and airborne disease transmission in occupied spaces, including COVID-19 (SARS-CoV-2) and other viral diseases, when it is meticulously designed, engineered, and applied. Research should continue on both the safety and efficacy of AlGaN-based Far-UVC LEDs, as well as the material choices and device designs to develop highly efficient solid-state UV germicidal irradiation (UVGI) at 222 nm emission to replace toxic low-pressure mercury lamps emitting at 253.7 nm. However, the key issue of hole concentration inside the multi-quantum-wells (MQWs) of AlGaN-based Far-UVC LEDs with high Al-contents is quite critical. Therefore, theoretical studies of AlGaN-based Far-UVC LEDs may suggest sufficient evidence for immediate consideration and implementation for the epitaxial growth of 222 nm-band Far-UVC LED technology during this world-wide health crisis. In this paper, the initial design of the Al-graded p-AlGaN hole source layer (HSL) on the performances of Far-UVC LED was compared with conventional bulk p-AlGaN HSL (non-graded)-based LED devices. For the evaluation of the device's performances, the energy band diagram, internal quantum efficiency (IQE), electrons and holes concentration, radiative recombination rate, and current density vs voltage characteristic were compared. It was found that LEDs at 222 nm emission without using the undoped (ud)-AlGaN final-quantum-barrier (FQB) and only keeping the Al-graded Mg-doped p-AlGaN HSL showed high carrier injection into the MQWs. The variation in the energy band diagram around the p-AlGaN electron-blocking layer (EBL)/p-AlGaN HSL region and p-AlGaN HSL/p-GaN contact-layer (CL) indicates that the introduction of the Al-graded p-AlGaN HSL, as well as the special choice of Al composition at the interfaces, are quite promising for the enhancement of hole injection toward MQWs. The simulation results suggest that the proposed structure of the Al-graded p-AlGaN HSL after omitting the ud-AlGaN FQB structure in the Far-UVC LED is quite useful for achieving high peak efficiency, as well as for suppressing the efficiency droop when compared to the conventional bulk Far-UVC LED. After introducing a new design of 40 nm-thick p-AlGaN HSL in the Far-UVC LED, the radiative recombination rate in the first two quantum-wells of MQWs has been improved up to ∼50%. The enhanced radiative recombination rate is attributed to the enhanced level of electron and hole concentrations by ∼26% and 53%, respectively, in the MQWs. Ultimately, after removing the ud-AlGaN FQB and using 40 nm-thick Al-graded (Al: 100% to 20%) p-AlGaN HSL, the efficiency droop has been remarkably reduced from ∼39% (Bulk-LED) to ∼19% in the new design of Far-UVC LED structure.

In the quest of the origin of direct and indirect nature of bandgap of zinc-blende (ZB) phase Boron Antimonide and Bismuth (BSb, BBi), a systematic density functional theory (DFT) calculation is carried out, considering the full-potential linearized augmented plane wave (FPLAPW) basis sets in the Modified Becke-Johnson (mBJ) exchange correlation (XC) potential. Including the Generalized Gradient Approximation Perdew-Burke-Ernzerh (PBEsol) XC functional, a fully relaxed and optimized lattice constants, (5.23, and 5.52 A) are obtained for BSb and BBi respectively. The optimized lattice constant serves as a basis for the calculation of optoelectronic properties like electronic density of state (DOS), band diagram, and optical absorption coefficient. The BSb offers a wider direct ( Γ - Γ ) bandgap of 2.804 eV compared to the indirect ( Γ - X ) one of 0.997 eV, while BBi exhibits a narrower direct ( Γ - Γ ) bandgap of 422 meV compared to the indirect ( Γ - X ) one of 1.046 eV. The computed total and partial DOS (TDOS, PDOS) brings out the better insight for foundation of indirect and direct nature of bandgap in BSb and BBi respectively. The calculated optical absorption spectra is in consistent with this direct and indirect nature of bandgap of BSb and BBi. Consequently, BSb become a promising contender for photovoltaic applications and BBi for IR application.

Diamond like semiconductors (DLS) have emerged as candidates for thermoelectric energy conversion. Towards understanding and optimizing performance, we present a comprehensive investigation of the electronic properties of two DLS phases, quaternary Cu2HgGeTe4 and related ordered vacancy compound Hg2GeTe4, including thermodynamic stability, defect chemistry, and transport properties. To establish the thermodynamic link between the related but distinct phases, the stability region for both is visualized in chemical potential space. In spite of their similar structure and bonding, we show that the two materials exhibit reciprocal behaviors for dopability. Cu2HgGeTe4 is degenerately p-type in all environments despite its wide stability region, due to the presence of low-energy acceptor defects VCu and CuHg and is resistant to extrinsic n-type doping. Meanwhile Hg2GeTe4 has a narrow stability region and intrinsic behavior due to the relatively high formation energy of native defects, but presents an opportunity for bi-polar doping. While these two compounds have similar structure, bonding, and chemical constituents, the reciprocal nature of their dopability emerges from significant differences in band edge positions. A Brouwer band diagram approach is utilized to visualize the role of native defects on carrier concentrations, dopability, and transport properties. This study elucidates the doping asymmetry between two solid-solution forming DLS phases Cu2HgGeTe4 and Hg2GeTe4 by revealing the defect chemistry of each compound, and suggests design strategies for defect engineering of DLS phases.

This paper primarily focuses on the performance enhancement of cadmium sulfide/cadmium telluride (CdS/CdTe) solar cells by replacing CdS window with zinc sulfide (ZnS)/CdS bilayer window. The comparative analysis of ther�mally evaporated CdS and ZnS/CdS heterostructure-based CdTe solar cells was done by employing structural, morphological, optical, and electrical analy�sis. Core objective of the work was to reduce the absorption loss at window layer by widening the total transmittance of window system for CdTe absorber. In addition, interface behavior was studied using advanced spectroscopic tech�niques, which help to analyze the diffusion. For the first time, to the best of our knowledge, ultraviolet photoelectron spectroscopy measurement has been employed on all the layers of the present superstrate structure to estimate the energy band diagram. Further, their suitability in a multi-layer graded bandgap structure was correlated to the final device parameters, concerning economic viability. Along with the fill factor increment (55% to 73%) offered by the ZnS/CdS bilayer window, limitation posed by the single-layer CdS win�dow has been discussed. Replacement of CdS by ZnS/CdS bilayer window has enhanced the conversion efficiency from 3.73% to 7.12%.

We report our simulation on the electric field effect of Bi thin film. Band diagram and carrier concentrations of the Bi channel at different surface potentials have been obtained by numerically solving Poisson's equation. In the calculation, the anisotropic characteristic of effective mass for carrier concentration and conductivity have been considered. The carrier densities were calculated from Fermi-Dirac integral. The conductivity effective mass ratio of electron and hole have been calculated to verify how the gate bias voltage affects the conductance of the Bi channel. The result shows that the Debye length in Bi is ~10 nm and nearly independent of the bias voltage. The dependency of conductance on gate bias is also discussed.

The core-level and valence band electronic structure of the n-GaAs (100) has been studied by synchrotron-based high-resolution photoelectron spectroscopy after irradiation by an Ar+ ion beam with energy Ei = 1500 eV and fluence Q = 1 × 1015 ions/cm2. Conversion of the conductivity type of the surface layer and formation of a p–n structure have been observed. The p-surface layer thickness (d ~ 5.0 nm) and band structure were experimentally determined from the Ga3d photoelectron spectrum by separation and analysis of the low intense n-type bulk contribution from deeper layers. A band diagram of the p–n junction formed on the n-GaAs surface by Ar+ ion bombardment was reconstructed. The p–n junction proved to be unexpectedly narrow compared to the extended tail of the implanted ion depth distribution.

In this study, we present an ambipolar conduction and RF stability performance for a Germanium Source Dual Halo Dual Dielectric Triple Material Surrounding Gate Tunnel FET (Ge(SRC)-DH-DD-TM-SG-TFET). The energy band diagram of the device will be derived using the Stern Stability Factor. The minimum tunneling length is expressed using low-k Silicon dioxide (SiO2) and high-k Hafnium oxide (HfO2) as dual dielectric material. Then the band to band tunneling (BTBT) rate tunneling generation rate will be derived using Kane’s model. In terms of frequency efficiency the proposed device with SiO2/HfO2 as gate dielectric is good enough to attain high cut-off frequency (fT) of 94.22 GHz is observed at drain to source voltage of VDS = 1 V. Efforts have also been made to properly assess the potential of the two halo doped regions regions. An expression for transconductance is proposed and the model is validated using 3-D Silvaco Atlas TCAD device simulator. In addition, to demonstrate the advantage of using Ge(SRC)-DH-DD-TM-SG-TFET dual dielectric halo doping in circuit applications, the transient response of the conventional TFET germanium source is compared with the low and high-k dielectric halo doping Ge(SRC) TFET.

Two-dimensional (2D) semiconductors, such as transition-metal dichalcogenides (TMDs), have attracted immense interest due to their excellent electronic and optical properties. The combination of single and multilayered 2D TMDs coupled with either Si or II-VI semiconductors can result in robust and reliable photodetectors. In this paper, we report the deposition process of MoSe2-layered films using pulsed laser deposition (PLD) over areas of 20 cm2 with a tunable band gap. Raman and X-ray diffraction indicates crystalline and highly oriented layered MoSe2. X-ray photoelectron spectroscopy shows Mo and Se present in the first few layers of the film. Rutherford backscattering demonstrates the effect of O and C on the surface and film/substrate interface of the deposited films. Ultraviolet-visible spectroscopy, Kelvin probe, photoelectron spectroscopy, and electrical measurements are used to investigate the band diagram and electrical property dependence as a function of MoSe2 layers/thickness. As the MoSe2 thickness increases from 3.5 to 11.4 nm, the band gap decreases from 1.98 to 1.75 eV, the work function increases from 4.52 to 4.72 eV, the ionization energy increases from 5.71 to 5.77 eV, the sheet resistance decreases from 541 to 56.0 kΩ, the contact resistance decreases from 187 to 54.6 Ω·cm2, and the transfer length increases from 2.27 to 61.9 nm. Transmission electron microscopy (TEM) cross-sectional images demonstrate the layered structure of the MoSe2 with an average interlayer spacing of 0.68 nm. The fabricated MoSe2-Si photodiodes demonstrate a current on/off ratio of ∼2 × 104 orders of magnification and photocurrent generation with a 22.5 ns rise time and a 190.8 ns decay time, respectively.

Oxygen-terminated type IIa (OT-IIa) diamond with oxygen suspended in the form of a ketone bond (C O) was synthesized via acid treatment. The Fermi level at 3.23 eV below the conduction band minimum for the OT-IIa diamond surface was measured experimentally, while that at 0.97 eV for the bulk was calculated theoretically. An acceptor model of the surface states was developed, employed, and combined with an upward-bending band diagram to compensate this energetic band difference between the surface and bulk of OT-IIa diamond. A Schottky barrier height of 3.15 eV between gold and the OT-IIa diamond was also measured. In addition, we also inferred the downward-bending band diagram for the surface of oxygen-terminated p-type diamond doped with boron. This work complements the semiconductor theory concerning diamond and will be helpful to analyze and improve the performance of devices based on oxygen-terminated diamond.

We report on the electroluminescent and I–V characteristics of the n-InAs/n-InAsSb/p-InAsSbP heterostructure grown by metalorganic vapor-phase epitaxy. In the spectral range of 0.23–0.29 eV, the high-intensity electroluminescence at a temperature of T = 77 K has been observed. The position of the maximum of the main emission band ( $$h\nu $$ ~ 0.24 eV) has shown a noticeable blue shift with increasing forward bias. Based on the investigations, a conclusion about the existence of a type-II staggered heterojunction at the InAs0.84Sb0.16/InAs0.32Sb0.28P0.40 heterointerface has been drawn, which is confirmed by the calculated energy band diagram.

We demonstrate that unidirectional and backscattering immune propagation of terahertz optical waves can be achieved in a topological valley-Hall waveguide made of graphene nanohole plasmonic crystals. In order to gain deeper physical insights into these phenomena, the band diagram of graphene nanohole plamsonic crystals has been investigated and optimized. We found that a graphene plasmonic crystal with nanohole arrays belonging to the $C_{6v}$ symmetry group possesses gapless Dirac cones, which can be gapped out by introducing extra nanoholes such that the symmetry point group of the system is reduced from $C_{6v}$ to $C_{3v}$. Taking advantage of this feature, we design a mirror symmetric domain-wall interface by placing together two optimized graphene plasmonic crystals so as to construct valley-polarized topological interface modes inside the opened bandgap. Our computational analysis shows that the valley-Hall topological domain-wall interface modes can be achieved at an extremely deep subwavelength scale, and do not rely on the application of external static magnetic fields. This work may pave a new way to develop highly-integrated and robust terahertz plasmonic waveguides at deep-subwavelength scale., 7 pages, 7 figures

In this study, a device design of single-gated feedback field-effect transistors (FBFETs) is proposed to achieve latch-up behaviors with high current gains. The latch-up mechanism is examined by conducting an equivalent circuit analysis, and the band diagram, I–V characteristics, memory window, subthreshold swing, and on/off current ratio are investigated using a commercial device simulator. The proposed FBFETs exhibit memory windows wider than 3.0 V, subthreshold swings less than 0.1 mV/decade, the on/off current ratios of approximately 1010, and on-currents of approximately 10−5 A at room temperature. The superior device characteristics and controllable memory windows open the promising possibility of FBFETs as the next-generation electronic devices.

In this article, an n-type double-gate low-temperature polysilicon (LTPS) TFT is investigated. Previous work has confirmed that the hot-carrier effect will cause impact ionization. Here we observed that, after hot-carrier stress (HCS), the transfer curve in the saturation region has a negative $\text{V}_{\mathrm {th}}$ shift, and a hump is also observed. The reverse output characteristic shows that gate induced drain leakage (GIDL) of the transistor gradually increases and the subthreshold swing (S.S.) has a tendency to collapse. In structures with longer lightly doped drain (LDD) lengths, the electric field at both source/drain side can be effectively dispersed. Thereby, an extended LDD can reduce the overall degradation, and a physical model of explanation is proposed. By using the energy band diagram, we clarify how the additional electron hole pairs affect the output property. Next, Silvaco TCAD simulation is utilized to illustrate the electric field distribution and validate the physical model.

The conductive and transparent properties of ZnO/Cu/ZnO sandwich structures were investigated in this study. The I–V curves of single ZnO films with different thicknesses were recorded and plotted. The linear I–V curves confirmed the ohmic conduction mechanism for the ZnO thin films in the ZnO/Cu/ZnO sandwich structures. Moreover, the energy band diagram of the ZnO/Cu interface showed that the interface between ZnO and Cu exhibited ohmic contact behavior. The resistivity of the ZnO/Cu/ZnO sandwich structures (with thicknesses between 20/5/20 nm and 80/5/80 nm) ranged from 2.25 × 10−4 Ω cm to 9.72 × 10−4 Ω cm. The lowest resistivity (i.e., 2.25 × 10−4 Ω cm) occurred in the 20/5/20 nm thin film. In the ZnO/Cu/ZnO sandwich structures, the electrons are transported vertically through the upper ZnO thin film and transported horizontally in the sandwiched Cu thin film. Ohmic conduction behavior was verified throughout the conduction path in the ZnO/Cu/ZnO sandwich structure. The transmittance measurement in the visible region of the structures showed that the sandwiched ZnO layers increased the transmittance of the 5 nm Cu thin film. In addition, the transmittance of the ZnO/Cu/ZnO sandwich structure was dependent on the thickness of the sandwiched ZnO layers. The 60/5/60 nm sandwich structure exhibited the best enhancement effect on transmittance. The thickness dependence was found to be due to the destructive interference between the reflected light at the ZnO/Cu and Cu/ZnO interfaces in the ZnO/Cu/ZnO sandwich structures.

This paper investigated the design and TCAD simulation of heterojunction Tunnel Field Effect Transistor (TFET) with dual gate material. The proposed device structure is designed with narrow bandgap semiconductor material InGaAs (0.74 eV) at source region and wider energy bandgap InP (1.34 eV) at channel and drain regions. The narrow bandgap at source/channel junction improves the tunneling generation rate and the wider bandgap at drain/channel junction reduces the ambipolar behavior. In addition to heterojunction, the dual work function at gate Metal (M1) and Metal (M2) and HfO2/SiO2 stacked dielectric helps to improve the band-gap narrowing as well as reduced leakage current. The proposed device electrical parameters such as Surface potential, energy band diagram, electric field, transconductance and drain current has been analyzed. The simulation results show significant improvement in ON current (10−5A/μm) and reduced OFF current (10−12A/μm) in the proposed device structure. The presented result reveals that the InGaAs/InP heterojunction stacked dielectric TFET is a good candidate for low power applications.

In this work, we fabricated charge-trapping MemTransistors (CTMTs) on a germanium (Ge) substrate with a single-charge-trapping-layer gate-stack or a double-charge-trapping-layer gate-stack. We first constructed the energy band diagram of two gate stacks using transmission electron microscope (TEM) images and by X-ray photoelectron spectroscopy analysis. We deposited Al2O3 as a tunneling layer and a barrier layer using an atomic layer deposition (ALD) system while depositing HfO2 by ALD as the charge-trapping layer whose conduction band offset with respect to Al2O3 is 1.74 eV. Next, we demonstrated the memory characteristics of the CTMTs. By implementing the double-charge-trapping-layer gate-stack on the CTMT, we were able to enlarge the memory windows by 372 mV, improve the retention by 2.7%, and reduce the read disturbance. Furthermore, we demonstrated the synaptic device characteristics of the CTMTs. With the optimization of pulse schemes, we reduced the nonlinearity of potentiation ( $\alpha _{\text {p}}$ ) and depression ( $\alpha _{\text {d}}$ ) from 8.62 and −6.01 to 0.71 and 0.01, respectively, enlarged the ON/OFF ratio from 10.2 to 66.2, and increased the recognition accuracy from 24.5% to 82.1% simultaneously. With the implementation of the double-charge-trapping-layer gate-stack, we could further enlarge the ON/OFF ratio to 75.3 and increase the recognition accuracy to 86.5% simultaneously.

In this article, we introduce a new class of p-type transparent conductive oxide (TCO) CuCrO2 (150 nm) heterogeneously integrated onto fluorine doped tin oxide (FTO)/glass for forming-free memristor-based neuromorphic applications. The fabricated Al/CuCrO2/FTO memristors demonstrate a reliable bipolar resistive switching with an ON/ OFF ratio of 1000. The retention of the device was found to be steady even beyond 106 s, which demonstrates its nonvolatility. The current–voltage ( ${I}$ – ${V}$ ) characteristics were fit to evaluate its transport properties and a band diagram was projected to have a better insight of the device operational principles. To validate the experimental observations, a new model has been developed, and the simulated ${I}$ – ${V}$ behavior was analogous to the experimental one. Efforts were then devoted to observe long-term potentiation (LTP) and long-term depression (LTD) utilizing identical but opposite pulses to evaluate the device’s efficacy for synaptic applications. The synaptic behavior was well controlled by the pulse (pulse amplitude and width) variations. The conductance change was found to be symmetric and then saturated, which reflects the popular biological Hebbian rules. Finally, a long-term synaptic modulation has been implemented by establishing the spike rate dependent plasticity (SRDP) rule, which is a part of spiking neural networks and advantageous to mimic the brain’s capability at low power. All the obtained experimental results were systematically corroborated by neural network simulation. Overall, our approach provides a new road map toward the development of TCO-based alternative memristors, which can be employed to mimic the synaptic plasticity for energy-efficient bioinspired neuromorphic systems and non-von Neumann computer architectures.

In this paper, the proposed architecture of electrostatic doped based nanotube tunnel field-effect transistor (NT-TFET) has been discussed. The proposed architecture of NT-TFET structure showed improved performance as compared to nanowire TFET (NW-TFET) with the same physical parameters. To analyze the performance of electrostatic doped based NT-TFET, different parameters like device parameter, analog parameter and linearity parameter have been discussed. Electron/hole concentration, electric field, electric potential, energy band diagram and non-local band-to-band tunneling rate (BTBT) have been analyzed as several device parameters. The tunneling rate and tunneling area are greater in NT-TFET as compare to NW-TFET. Analog parameters include drain current, ON-current (ION), OFF-current (IOFF), ION/IOFF, intrinsic gain, output conductance, sub-threshold slope, and threshold voltage have been analyzed. The Drain current (IDS) of value 3*10−5 A/μm, OFF-current is of the order of ~ 10−19 and higher ION/IOFF current ratio of 2*1012 are obtained. The proposed architecture of electrostatic doped based nanotube TFET (NT-TFET) has improved the drain current, steep sub-threshold, OFF-current, and ION/IOFF current ratio.

This paper presents the band gap design and J-V characteristic curve of Zinc Oxide (ZnO) based on Junction Field Effect Transistor (JFET). The physical properties for analysis of semiconductor field effect transistor play a vital role in semiconductor measurements to obtain the high-performance devices. The main objective of this research is to design and analyse the band diagram design of semiconductor materials which are used for high performance junction field effect transistor. In this paper, the fundamental theory of semiconductors, the electrical properties analysis and bandgap design of materials for junction field effect transistor are described. Firstly, the energy bandgaps are performed based on the existing mathematical equations and the required parameters depending on the specified semiconductor material. Secondly, the J-V characteristic curves of semiconductor material are discussed in this paper. In order to achieve the current-voltage characteristic for specific junction field effect transistor, numerical values of each parameter which are included in analysis are defined and then these resultant values are predicted for the performance of junction field effect transistors. The computerized analyses have also mentioned in this paper.

In this Paper, Dielectric Modulated Dopingless Double Gate Transistor (DM-DLDGTFET) device is proposed for the free label detection of the charged and neutral biomolecules. A charge-plasma principle is used for label-free detection of biosensors to reduce the processing complexity and cost of nanoscale products. Firstly, the simulations for the proposed device are carried using Atlas and different electrical parameters are analyzed using the same. It is observed that the dielectric constant and different biomolecule charges for example, protein, DNA, enzyme, cell and many more molecules affects the electrical characteristic of the device. The deposition of different workfunction materials over silicon body will do the formation of p+ source and n+ drain region in the DM-DLDGTFET. In addition, by etching the segment of the gate oxide layer to the source end for sensing biomolecules, a nano gap cavity is embedded within the dielectric gate. When biomolecule get immobilized at cavity region, the electrostatic properties of device for example, drain current, Ion/Ioff, subthreshold slope, average subthreshold slope, sensitivity get influenced. The energy band diagram and the device’s surface potential for both neutral and charged biomolecules are also discussed. For the validation of the proposed DL-TFET structure, the simulation results are calibrated with reported results and significant improvement are observed in the proposed structure.

A well-crystalline two-dimensional (2D) perovskite material, Ca2Nan–3NbnO3n+1– (CNNO–) nanosheets, derived from the Dion–Jacobson phase has the potential to generate hydrogen through photoelectroch...

Ge-based metal-oxide semiconductor structures exhibiting thin ALD-grown high-k dielectric HfO2 films were fabricated and characterized chemically, structurally, and electrically. X-ray photoelectron (XP) spectroscopy confirms the good stoichiometry of the ALD-grown HfO2 films. Furthermore, through the analysis of the XP spectra, the conduction and valence band offsets of HfO2|p-Ge were calculated to be equal to 1.8 ± 0.2 eV and 2.8 ± 0.2 eV, respectively. C(V) and G(V) analysis reveals structures with a well-defined MOS behavior with Dit values in the range of 1011 eV–1 cm–2 and a dielectric constant of HfO2 films of 20. The dominant carrier transport conduction mechanisms were studied through J(V) analysis, performed at both substrate and gate electron injection. Specifically, in the low voltage region (V 3.0 V) and high temperatures (>450 K). Applying Schottky’s emission model the energy barrier heights of HfO2|p-Ge and Al|HfO2 interfaces were evaluated equal to 1.7 ± 0.2 eV and 1.3 ± 0.2 eV, respectively. Combining the XPS and J(V) analysis results, the energy band diagram of Al|HfO2|p-Ge structures is constructed. The calculated values of conduction and valence band offsets via XPS and J(V) measurements are in very good agreement.

Incident photon-to-current conversion efficiency (IPCE) of CdS based quantum dot sensitized solar cells (QDSCs) is a major drawback in their low efficiency. Here we report a new trend in fabrication of QDSC with enhanced IPCE with application of as prepared Ag2S and Ag2S@ZnS QDs as a co sensitizer. Ag2S and Ag2S@ZnS QDs were synthesized first using a microwave method and were examined by means of XRD, TEM and UV–Vis spectroscopy. Then the prepared QDs were applied for the fabrication of QDSCs using a novel drop casting method. The results revealed a significant enhancement of IPCE as well as short current density (12.5 mA·cm−2) and cell efficiency (3%). The enhancement is directly related to well absorption of Ag2S with low band gap in the visible range and effective injection of photo-excited electrons to CdS compact layer according to suggested band diagram. Ag2S@ZnS co-sensitizer showed an enhancement in photocurrent density due to successful passivation of Ag2S QDs and suppressing recombination on their surface.

The realization of high-responsivity, self-powered and low-cost ultraviolet ( UV ) photodetector ( PD ) based on eco-friendly and earth-abundant compounds, remains far from satisfactory for future optoelectronic applications. In this paper, we demonstrated a new high-performance UV - PD based on planar ZnO thin-film, efficiently operating without any power supply. The proposed device was elaborated by evaporating an engineered back metallic layer onto the glass substrate and then depositing ZnO thin layer through RF sputtering technique. The sensor structural and optical properties were systematically analyzed by the techniques of X -ray diffraction ( XRD ) and UV – Vis absorbance spectrometry. The resulted ZnO UV-PD showcased a clear and distinctive photovoltaic behavior. Interestingly, it also demonstrated a high responsivity of 0.38A/W and a giant detectivity exceeding 10 14 Jones at zero bias, which is much higher than other reported self-powered UV-PD despite the use of an All-ZnO structure. The device photodetecting mechanism in self-driven mode was discussed using the energy band diagram, where the key role of the engineered back metallic layer in modulating the electric field distribution within the ZnO active region to effectively achieve an asymmetric behavior is emphasized. Therefore, the presented work offers a novel pathway to design high-responsivity self-powered UV-PDs based on a simple All-ZnO structure.