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A new field plate (FP) is proposed for gallium nitride high‐electron‐mobility transistors (HEMTs). It features an innovative arcuate end (AE), which allows the induced charges that originally gathered at the FP end to diffuse over a wider area. Hence, not only is the electric field in the channel at the gate edge alleviated due to the induced charges, but also that concentrated at the FP end is reduced by means of AE. The simulation results indicate that by upgrading a source FP with AE, HEMT gains a 99% increase in breakdown voltage while remaining unaltered in specific on‐resistance. It also gets a 43.41% decrease in power loss during one cycle while maintaining the same breakdown voltage, which greatly contributes to enhance the efficiency of power electronic circuits. [ABSTRACT FROM AUTHOR]

[Display omitted] Constructing semiconductor heterojunctions can enable novel schemes for highly efficient photocatalytic activity. However, introducing strong covalent bonding at the interface remains an open challenge. Herein, ZnIn 2 S 4 (ZIS) with abundant sulfur vacancies (Sv) is synthesized with the presence of PdSe 2 as an additional precursor. The sulfur vacancies of Sv-ZIS are filled by Se atoms of PdSe 2 , leading to the Zn–In–Se–Pd compound interface. Our density functional theory (DFT) calculations reveal the increased density of states at the interface, which will increase the local carrier concentration. Moreover, the length of the Se-H bond is longer than that of the S H bond, which is good for the evolution of H 2 from the interface. In addition, the charge redistribution at the interface results in a built-in field, providing the driving force for efficient separation of photogenerated electron-hole. Therefore, the PdSe 2 /Sv-ZIS heterojunction with strong covalent interface exhibits an excellent photocatalytic hydrogen evolution performance (4423 μmol g−1h−1) with an apparent quantum efficiency (λ > 420 nm) of 9.1 %. This work will provide new inspirations to improve photocatalytic activity by engineering the interfaces of semiconductor heterojunctions. [ABSTRACT FROM AUTHOR]

Abstract Green energy transition and climate change have gathered significant momentum in the world because of the rising population and increased clean energy demands. For this reason, renewable energy alternatives such as inexhaustible photo energy from the sun appear to be the ultimate solution to the world's energy needs. Formamidinium tin tri‐iodide (HC(NH2)2SnI3)‐based perovskites are found to be more efficient and stable than their methylammonium tin tri‐iodide (MASnI3) counterparts because of its wider bandgap and better temperature stability. A device simulation of FASnI3‐based solar cell is numerically performed using solar cell capacitance simulator (SCAPS‐1D). The focus is to investigate the effect of changing working temperature, metal back contact, absorber thickness, defect density, and doping concentration on the performance of the proposed solar cell device. The optimised solar cell parameters of the proposed solar cell were: short‐circuit current density (Jsc) of 28.45 mAcm−2, open‐circuit voltage (Voc) of 1.0042 V, fill factor of 63.73%, and power conversion efficiency of 18.21% at 300 K, thus, paving the way for novel perovskite solar cells which are environmentally benign because they are lead‐free, have better absorption efficiency, and can be injected into the production work flow for commercial applications.

Green energy transition and climate change have gathered significant momentum in the world because of the rising population and increased clean energy demands. For this reason, renewable energy alternatives such as inexhaustible photo energy from the sun appear to be the ultimate solution to the world's energy needs. Formamidinium tin tri‐iodide (HC(NH2)2SnI3)‐based perovskites are found to be more efficient and stable than their methylammonium tin tri‐iodide (MASnI3) counterparts because of its wider bandgap and better temperature stability. A device simulation of FASnI3‐based solar cell is numerically performed using solar cell capacitance simulator (SCAPS‐1D). The focus is to investigate the effect of changing working temperature, metal back contact, absorber thickness, defect density, and doping concentration on the performance of the proposed solar cell device. The optimised solar cell parameters of the proposed solar cell were: short‐circuit current density (Jsc) of 28.45 mAcm−2, open‐circuit voltage (Voc) of 1.0042 V, fill factor of 63.73%, and power conversion efficiency of 18.21% at 300 K, thus, paving the way for novel perovskite solar cells which are environmentally benign because they are lead‐free, have better absorption efficiency, and can be injected into the production work flow for commercial applications. [ABSTRACT FROM AUTHOR]

The fabrication of heterojunction-based photodetectors (PDs) is well known for the enhancement of PDs performances, tunable nature of photoconductivity, and broadband application. Herein, the PDs based on MoSe _2 and MoSe _2 /Bi _2 Se _3 heterojunction on sapphire (0001) substrates were deposited using a r.f. magnetron sputtering system. The high-resolution x-ray diffraction and Raman spectroscopy characterizations disclosed the growth of the 2-H phase of MoSe _2 and the rhombohedral phase of Bi _2 Se _3 thin films on sapphire (0001). The chemical and electronic states of deposited films were studied using x-ray photoelectron spectroscopy and revealed the stoichiometry growth of MoSe _2 . We have fabricated metal-semiconductor–metal type PD devices on MoSe _2 and MoSe _2 /Bi _2 Se _3 heterojunction and the photo-response measurements were performed at external voltages of 0.1–5 V under near-infrared (1064 nm) light illumination. The bare MoSe _2 PD device shows positive photoconductivity behavior whereas MoSe _2 /Bi _2 Se _3 heterojunction PD exhibits negative photoconductivity. It was found that the responsivity of MoSe _2 and MoSe _2 /Bi _2 Se _3 heterojunction PDs is ~ 1.39 A W ^−1 and ~ 5.7 A W ^−1 , respectively. The enhancement of photoresponse of MoSe _2 /Bi _2 Se _3 PD nearly four-fold compared to bare MoSe _2 PD shows the importance of heterojunction structures for futuristics optoelectronic applications.

Energy shortage and escalating pollution are major challenges globally. Heterogeneous photocatalysis is one of the most cost-effective methods for producing renewable energy and removing pollutants. In particular, ZnO nanostructures are promising photocatalysts that are economic, stable, and biologically safe. ZnO-based nanoheterostructures have been used for heavy metal reduction, organic pollutants degradation, photocatalytic hydrogen production, and drug mineralization. Here, we review ZnO-based nanoheterojunctions as photocatalysts for hydrogen production and pollutant degradation. Hydrogen production has reached 1200 mol g−1 h−1 using Ce-doped ZnO/ZnS heterojunction, with a 8.5-fold higher efficiency than bare ZnO. Nearly complete removal of a dye pollutant was achieved in 15 min using hybrid ethyl cellulose-modified g-C3N4/ZnO. Moreover, ZnO/Ag2WO4/Fe3O4 showed a 152% and 143% higher antibiotic degradation rate than bare Ag2WO4 and ZnO, respectively. We present methods to modify ZnO, including coupling with other semiconductors, metal/non-metal doping, and carbon-based materials coupling; and methods for charge divergence in binary and ternary ZnO-based nanocomposites. [ABSTRACT FROM AUTHOR]

Using a tight-binding mode-space NEGF technique, we explore the essential physics, design and performance potential of the III-V core-shell (CS) nanowire (NW) heterojunction tunneling field-effect transistor (TFET). The CS TFET “line-tunneling” current increases significantly with the core diameter dC and outperforms the best III-V axial “point-tunneling” NW heterojunction TFET ION by up to 6× for dC = 6.6 nm. Reaching such a high level of current at low supply voltage, however, requires and involves specific and sometime unanticipated optimizations and physics that are thoroughly investigated here. In spite of the commonly accepted view, we also show and explain the weak gate-length dependency observed for the line-tunneling current in a III-V TFET. We further investigate the effect of electron-phonon scattering and discrete dopant impurity band tails on optimized CS NW TFETs. Including those non-idealities, the CS-TFET inverter performance significantly outperforms that of the axial TFETs. The low-power (LP) VDD = 0.35V CS-inverter delay is comparable to that of the high-performance (HP) Si CMOS using VDD = 0.55, which shows promise for an LP TFET technology with HP speed.

Functional materials with attractive electronic and photoelectronic properties show great promise in various fields. In recent decades, tremendous research efforts have been devoted to the design of photoactive and electroactive materials for qualitative and quantitative analysis of environmental pollutants. This review gives a concise overview on the fundamentals and recent research progress of functional material‐based electrochemical and photoelectrochemical technology for environmental pollutant monitoring. The rational design of functional photoactive and electroactive materials with promoted electrochemical properties and basic signaling strategies for electrochemical and photoelectrochemical sensors are presented. Based on these insights, very recent achievements for electrochemical and photoelectrochemical environmental pollutant sensors are summarized from the viewpoint of various functional materials. At last, critical challenges and future research perspectives in this field are proposed and discussed to provide a backdrop for future research. [ABSTRACT FROM AUTHOR]

Photocatalysts are part of key strategies to enable green fuel. Photocatalysis and water splitting could be a promising solution to challenges associated with the intermittent nature of sunlight as a huge energy source on Earth. In this study, photo-electrochemical performance and behavior of mixed-phase titanium oxide and iron oxide heterojunction (Ti-TiO x (High-voltage)-FeO x electrode) are compared to the photo-electrochemical performance and behavior of titanium oxide nanotubes with the rutile phase and iron oxide heterojunction (TiO x -nanotubes (H 2 SO 4 /KF)-FeO x electrode). The results of photo-electrochemical experiments show that the application of stabilization potential and the presence/absence of dissolved oxygen could not be considered as significant factors affecting the photo-electrochemical properties of the Ti-TiO x (High-voltage)-FeO x and TiO x -nanotubes (H 2 SO 4 /KF)-FeO x electrodes. The Ti-TiO x (High-voltage)-FeO x electrode shows an anodic photo-electrochemical response in wavelengths shorter than 530 nm and cathodic photo-electrochemical response in wavelengths longer than 530 nm. However, the Ti-nanotubes (H 2 SO 4 /KF)-FeO x electrode consistently exhibits the anodic photo-electrochemical response. Both of the prepared heterojunctions are further characterized through Scanning Electron Microscopy, Energy-dispersive X-ray Spectroscopy, Diffuse Reflectance UV–Vis Spectroscopy, X-ray Diffraction, and Attenuated Total Reflectance Spectroscopy methods. These experiments show that despite different morphologies observed in SEM imaging data, the deposited iron oxide layers on both mixed-phase titanium oxide and titanium oxide nanotubes share the same hematite phase structure. However, only iron oxide electro-deposited on the surface of the mixed-phase titanium oxide, which contains both anatase and rutile phases, with vacant sites of oxygen, exhibits un-expected anodic and cathodic photo-electrochemical responses. Furthermore, according to the results of the characterization and photo-electrochemical investigations, the different chemical environment of mixed-phase titanium oxide, and the possible formation of different types of heterojunction structures in mixed-phase titanium oxide and iron oxide, in contrast to the titanium oxide nanotubes and iron oxide, might be considered the possible discernible reasons for the observed different photo-electrochemical responses. This paper sheds new light on photo-electrochemistry of iron oxide/mixed-phase titanium oxide heterojunction for possible solar energy conversion. In this study, photo-electrochemical performance and behavior of mixed-phase titanium oxide and iron oxide heterojunction were investigated. Image 1 • Photo-electrochemical studies conducted on mixed-phase titanium oxide and iron oxide. • The photocatalysts showed a cathodic response contrary to n-type nature of hematite. • Mixed-phase TiO 2 imposes different chemical conditions on iron oxide photocatalyst. • Photo-electrochemistry of the compound confirms the energy band level. [ABSTRACT FROM AUTHOR]

Heterojunctions of amorphous (a‐Si) and crystalline (c‐Si) silicon combine the favorable absorption characteristics of a‐Si for the solar spectrum, high energy conversion efficiencies, low processing temperatures, potential for low production costs, and a reduced amount of silicon used due to thin a‐Si films. To investigate a‐Si/c‐Si heterojunctions, amorphous p‐type silicon (a‐Si) with a thickness of 5 nm is deposited via radio frequency‐pulsed magnetron sputtering on p‐doped, (100)‐oriented, crystalline silicon (c‐Si) wafers. During deposition, the crystalline silicon wafers are kept at 430 °C and the hydrogen flow rate is varied from 0 to 50 sccm (standard cubic centimeters per minute). Temperature‐dependent current–voltage measurements are carried out to investigate the dominant transport mechanisms of electrical conduction. Moreover, the influence of hydrogen on physical properties such as barrier height, activation energy, and electrical conductivity is analyzed. A current–voltage dependence as predicted by the thermionic emission model for the low forward‐bias region below 0.25 V is observed. Temperature regimes for nearest neighbor hopping and band conduction are revealed by the Arrhenius plot and are found to depend on the hydrogen flow rate. [ABSTRACT FROM AUTHOR]

A novel material of Ag3PO4–Ag–Bi2WO6 Z‐scheme heterojunction has been successfully synthesised using a simple deposition–precipitation method. In this work, the authors used diverse techniques to characterise the structure, catalytic performance, and morphology of the prepared materials. Meanwhile, the catalytic performance of prepared materials was evaluated by degrading organic pigment. The excellent catalytic performance of the material is according to the collaboration of Ag nanoparticles in the Ag3PO4–Ag–Bi2WO6 heterojunction. Ag nanoparticles enhance the stableness and activeness of the catalyst by acting as a charge transfer bridge between Ag3PO4 and Bi2WO6, which results in improving electron–hole pairs' separation. Compared with pure Bi2WO6 and Ag3PO4–Bi2WO6 materials, Ag3PO4–Ag–Bi2WO6 has higher decomposition effectiveness of methylene blue under the same conditions. The photocatalytic mechanism was put forward and the process of the hole–electron pair's separation is discussed in detail, which is due to the formation of the Z‐scheme heterojunction with Ag nanoparticles acted as a charge transfer bridge. [ABSTRACT FROM AUTHOR]

A novel double‐trench superjunction SiC metal–oxide–semiconductor field‐effect transistor (MOSFET) with an integrated Schottky contact at the drain side is proposed in this study. Results indicate an improvement of 58% in reverse recovery current Irrm/charge Qrr and 22% in the trench corner electric field Eox−m compared to the device without Schottky and without superjunction, respectively. This comparison became possible using mixed mode simulations in Sentaurus TCAD. While the improvement in electric field is due to incorporation of superjunction concept along the drift region, the improvement of reverse recovery is due to Schottky contact forming a barrier for the charge carriers. Using calibrated two‐dimensional numerical simulations, the authors were able to demonstrate the influence of Schottky contact on reverse recovery current of the device. The superiority of the proposed device is presented by plotting the switching energy loss with respect to external gate resistance and temperature through non‐isothermal simulations. [ABSTRACT FROM AUTHOR]

Tunnel field effect transistors (TFETs) have been exhibiting an enticing performance to succeed in metal–oxide–semiconductor technology. However, TFET also possesses several challenges such as low drive current, ambipolarity, and requirement of abrupt doping profiles for the occurrence of band‐to‐band tunnelling (BTBT) conduction mechanism at the junction. To overcome these challenges, the authors propose a heterojunction doping less tunnel field‐effect transistor with an asymmetric double gate (HJ ADG DLTFET). This device employs a low bandgap material at the source region, which increases the BTBT rate at the channel–source interface leading to enhanced drive current while maintaining low off‐current. Consequently, an increment of one order for ION (∼1.5 × 10−5 A/µm) compared to the conventional ADG DLTFET has been provided by this device. Additionally, the comparative analysis of the proposed device and conventional one has been performed to reveal the advantages of the proposed structure in terms of transfer characteristics, transconductance, gate‐to‐drain capacitance, cut‐off frequency, gain–bandwidth product, device efficiency, and transconductance frequency product. Moreover, the effect of gate length and drain voltage variations has been analysed for HJ ADG DLTFET concerning the aforementioned characteristics. [ABSTRACT FROM AUTHOR]

In the recent years, zinc oxide has emerged as one of the promising alternate materials to titania for photocatalytic applications due to its several advantages properties. This review recapitulates the ongoing advancement in the field of ZnO-based heterojunctions as visible light responsive photocatalysts for energy conversion (hydrogen evolution) and environmental remediation (pollutants degradation) applications. After a short introduction about zinc oxide materials, the various approaches utilized in the design and development of efficient ZnO-based nanoheterostructures has been discussed in detail. Specifically, strategies such as coupling ZnO with other semiconductors, supporting on carbonaceous materials, decorating with noble metal nanoparticles, doping with heteroatoms and engineering defects in the semiconductor material have been elaborated with a particular emphasis on hydrogen energy and organic pollutants removal. Finally, the future perspective of this material has been highlighted. This comprehensive review not only summarizes the recent literature in this topic, but also provides a detailed insight on the scope of this material for hydrogen energy and environmental remediation applications. [ABSTRACT FROM AUTHOR]

An all‐GaN integrated cascode device with an output current of 5 A, threshold voltage of +0.65 V and breakdown voltage of 624 V is demonstrated. Compared with the commercial 600 V hybrid GaN plus Si cascode device (TPH3202), the integrated cascode exhibits a significantly reduced delay time when switched at 200 V and 2.7 A. This is attributed to the absence of a Si metal–oxide–semiconductor field‐effect transistor (MOSFET) driver, leading to a much smaller input capacitance as indicated by the high voltage capacitance measurements. In addition, the integrated cascode device shows a reduced ringing effect due to monolithic integration. When compared with commercial 600 V standalone GaN devices (GS66502B and GS‐065‐004), a reduced Miller effect is observed for the integrated cascode when switched under low gate‐driving current conditions. The results demonstrate the advantages of the cascode device to switch with low gate‐driving current using cheaper, faster, and more efficient gate drivers. [ABSTRACT FROM AUTHOR]

We report a novel hydrothermal in situ synthesis route for the CdS-sensitized TiO 2 nanorod array films and their photoelectrochemical (PEC) performance are investigated in this paper. Although heterojunctions have been well recognized for enhancing the PEC performance of TiO 2 nanostructures, the specific synthesis methodology of high production quality, low preparation cost, and high controllability over the heterojunction structures is still a hot and open topic. In this work, controllable nanoscale TiO 2 /CdS heterojunctions have been successfully realized through hydrothermal synthesis. The absorption spectrum is shown to be broadened from ~350 nm to ~570 nm, and the photocurrent density increases from 0.35 to 2.03 mA/cm2, corresponding to photo-conversion efficiency of ~0.88%. The method is considered as an efficient and facile choice in the fabrication of TiO 2 -based PEC hydrogen production functional materials. • The TiO 2 /CdS semiconductor heterojunction is successfully prepared by a novel in situ synthesis method. • The CdS-sensitized TiO 2 nanorod arrays can broaden the absorption spectrum region from 250 nm to 570 nm. • The deposited CdS properties can be effectively controlled through reaction duration. • The novel deposited CdS-sensitized TiO 2 nanorod films are shown to exhibit excellent photoelectrochemical performances. [ABSTRACT FROM AUTHOR]

Different source field plate (FP) connections are compared for the all-GaN integrated cascode device to address the capacitance matching and turn-off controllability issues reported in the conventional GaN plus Si cascode. The experimental results suggest that the cascode device with an FP connected to the source terminal can significantly suppress the off-state internode voltage, leading to minimized capacitive energy loss and reduced overvoltage stress at the internode. This is attributed to the reduced ratio of the drain–source capacitance of the depletion mode cascode part to the total capacitance at the cascode internode. An additional FP on the E-mode cascode part is proposed to further suppress the off-state internode voltage and benefit the device. Cascode devices with the source FP connecting to the enhancement mode gate have an improved switching controllability via gate resistance during turn-off and hence enhanced dv/dt immunity in the drain loop. [ABSTRACT FROM AUTHOR]

A novel ultrathin barrier AlGaN/GaN hybrid-anode-diode (UTB-HAD) with in-situ Si3N4-cap passivation is experimentally demonstrated. The forward turn-on voltage (Von) of the UTB-HAD is determined by the intrinsic threshold voltage of the two-dimension electron gas (2DEG) channel, which can be precisely controlled by tailoring the as-grown AlGaN-barrier thickness. The typical Von as low as 0.48 V is obtained by using the UTB AlGaN/GaN with a barrier thickness of 4.9 nm. The MOCVD has grown in-situ Si3N4-cap and the LPCVD-Si3N4 bilayer passivation stack is developed to effectively restore the 2DEG in the UTB AlGaN/GaN heterostructure and simultaneously improve the dynamic characteristics of the diode. The UTB-HAD and the novel passivation scheme are of great potential for power applications. [ABSTRACT FROM AUTHOR]

High-frequency performance of vertical InAs/InGaAs heterostructure nanowire MOSFETs on Si is demonstrated for the first time for a gate-last configuration. The device architecture allows highly asymmetric capacitances, which increases the power gain. A device with Lg = 120 nm demonstrates fT = 120 GHz, fmax = 130 GHz and maximum stable gain (MSG) = 14.4 dB at 20 GHz. These metrics demonstrate the state-of-the-art performance of vertical nanowire MOSFETs. [ABSTRACT FROM AUTHOR]

The vacuum pocket retaining molecular beam epitaxial regrowth of the nano‐patterned GaSb surface was demonstrated. The high contrast 2D photonic crystal layer was incorporated into the test 2 µm emitting laser heterostructure. The photonic dispersion determined from angle‐resolved electroluminescence experiment showed four well‐resolved bands corresponding to the model predictions for the square lattice. The single‐mode lasing near 2 µm has been observed at the temperature corresponding to the alignment of the photonic crystal band‐edge states and the quantum well gain peak. The reference devices without the photonic crystal layer emitted trivial spectra and did not lase at any temperature. [ABSTRACT FROM AUTHOR]

A carrier‐storage‐enhanced superjunction (SJ) insulated gate bipolar transistor (IGBT) with n‐Si and p‐3C‐SiC pillars (Si/SiC SJ IGBT) is studied. At the on‐state, the n‐Si/p‐SiC heterojunction acts as a barrier for holes in the n‐Si pillar, which helps to enhance the carrier‐storage effect in the n‐Si pillar and improves the tradeoff between turn‐off loss (Eoff) and on‐state voltage drop (VCE(sat)). It is found by simulations that VCE(sat) of the Si/SiC SJ IGBT can be 0.35 V lower than that of the conventional SJ IGBT with the same breakdown voltage (VB = 1450 V). Under Eoff = 5 mJ/cm2, VCE(sat) of the Si/SiC SJ IGBT is 1.22 V, which is 0.30 and 0.81 V lower than VCE(sat) of the conventional SJ IGBT and the field stop IGBT, respectively. [ABSTRACT FROM AUTHOR]

A novel technology based on aluminium gallium nitride (AlGaN)/GaN hybrid‐anode diode (HAD) for precise modulation of turn‐on voltage is proposed and experimentally demonstrated. By delicately tailoring the as‐grown barrier thickness, the turn‐on voltage of the HAD and yet the non‐linearity at zero bias (i.e. 0 V) for efficient microwave detection can be flexibly modulated. An AlGaN/GaN ultra‐thin‐barrier HAD (UTB‐HAD) was designed and fabricated for zero‐bias microwave detection. The AlGaN‐barrier thickness was optimised to be 5 nm by TCAD simulation, which yields a strong non‐linearity at zero bias featuring a high‐curvature coefficient (γ) of 27 V−1 in the fabricated UTB‐HAD. The first‐order voltage sensitivity βV is projected to be as high as 2.7 mV/μW. The proposed approach of precise sensitivity modulation is of great interests for high‐efficient zero‐bias microwave detection applications. [ABSTRACT FROM AUTHOR]

We analyze the influence of dimensionality on optoelectronic properties of heterojunction core–shell nanowires (CSNWs) as subwavelength optical cavities. We discuss how the transition rates change with respect to electron distribution and identify three factors explicitly contributed to the transition rates with strong dependence on dimensionality. These results explain the great increase in optical gain and quantum efficiency of CSNWs and enable new classes of submicrometer-scale optoelectronic devices. [ABSTRACT FROM AUTHOR]

Introduction of multiple quantum wells (MQWs) is an efficient way to enhance the light absorption capability in phototransistors. Direct band gap Ge1−x Snx alloy (x > 0.08) having large absorption coefficient is an attractive material for heterojunction phototransistors (HPTs) compatible with CMOS platform. In this work, simulations are employed to obtain current gain, responsivity and collector current characteristics of Ge/GeSn/Ge HPTs with incorporation of MQWs (Ge0.87 Sn0.13 /Ge0.83 Sn0.17) in the base region. The performances of bulk, single quantum well and MQW HPT structures are examined and compared. Best performance is shown by HPTs having MQW structure over a wide range of base emitter voltage. [ABSTRACT FROM AUTHOR]

All-GaN-integrated cascode heterojunction field effect transistors were designed and fabricated for power switching applications. A threshold voltage of +2 V was achieved using a fluorine treatment and a metal–insulator–semiconductor gate structure on the enhancement mode part. The cascode device exhibited an output current of 300 mA/mm by matching the current drivability of both enhancement and depletion mode parts. The optimization was achieved by shifting the threshold voltage of the depletion mode section to a more negative value with the addition of a dielectric layer under the gate. The switching performance of the cascode was compared to the equivalent GaN enhancement-mode-only device by measuring the hard switching speed at 200 V under an inductive load in a double pulse tester. For the first time, we demonstrate the switching speed advantage of the cascode over equivalent GaN enhancement-mode-only devices, due to the reduced Miller-effect and the unique switching mechanisms. These observations suggest that practical power switches at high power and high switching frequency will benefit as part of an integrated cascode configuration. [ABSTRACT FROM AUTHOR]

Semiconductor heterostructures are suitable for the design and fabrication of terahertz (THz) plasmonic devices, due to their matching carrier densities. The classical dispersion relations in the current literature are derived for metal plasmonic materials, such as gold and silver, for which a homogeneous dielectric function is valid. Penetration of the electric fields into semiconductors induces locally varying charge densities and a spatially varying dielectric function is expected. While such an occurrence renders tunable THz plasmonics a possibility, it is crucial to understand the conditions under which propagating resonant conditions for the carriers occur, upon incidence of an electromagnetic radiation. In this manuscript, we derive a dispersion relation for a p−n heterojunction and apply the methodology to a GaAs p−n junction, a material of interest for optoelectronic devices. Considering symmetrically doped p- and n-type regions with equal width, the effect of certain parameters (such as doping and voltage bias) on the dispersion curve of the p−n heterojunction were investigated. Keeping in sight the different effective masses and mobilities of the carriers, we were able to obtain the conditions that yield identical dielectric functions for the p- and n-regions. Our results indicated that the p−n GaAs system can sustain propagating resonances and can be used as a layered plasmonic waveguide. The conditions under which this is feasible fall in the frequency region between the transverse optical phonon resonance of GaAs and the traditional cut-off frequency of the diode waveguide. In addition, our results indicated when the excitation was slightly above the phonon resonance frequency, the plasmon propagation attained low-loss characteristics. We also showed that the existence or nonexistence of the depletion zone between the p- and n- interfaces allowed certain plasmon modes to propagate, while others decayed rapidly, pointing out the possibility for a design of selective filters.

Al-ZnO/Si heterojunction-based large area, self-powered, low reverse leakage current, and broadband photodetectors with high responsivity are fabricated using the simple and low temperature process. Different from widely applied (p)Si-based heterojunctions, these devices are (n)Si-based and offer superior performance. With optimized Al–ZnO thickness, excellent light confinement is achieved. An interfacial passivation layer that improves the hetero-interface helps achieved a reverse current density as low as 4.5 \times 10^-7 A/cm ^-2 at −0.5 V for a 4.84 cm2 device, with rectification ratio of 2.7 \times 10^3 at ±0.5 V. In self-powered mode, the photodetector achieved responsivities of 0.292, 0.426, and 0.486 A/W (external quantum efficiency, EQE of 78.7%, 96.1%, and 98.8%) for primary blue (460 nm), green (550 nm), and red (610 nm) light, respectively. The operation of self-powered Al–ZnO/(n)Si photodetectors is demonstrated for the first time with modulated optical signal at circuit level. [ABSTRACT FROM PUBLISHER]

Al–ZnO/(n)Si and Al–ZnO/(p)Si heterojunction structures were fabricated by RF-sputtering of Al–ZnO thin film on Si substrates and their electrical and photoresponse properties were comparatively analyzed. The Al–ZnO/(n)Si heterojunction exhibited excellent diode behavior with an equivalent barrier height of 0.72 eV and an rectification ratio of 6.7 \times 10^3 at ±0.5 V, while no rectifying behavior was observed for Al–ZnO/(p)Si device. Illuminated I–V analysis performed with different light intensities revealed excellent photoresponse properties and the strong dependence of the photocurrent on external bias for both Al–ZnO/(n)Si and Al–ZnO/(p)Si structures. The Al–ZnO/(n)Si structure requires smaller reverse bias than Al–ZnO/(p)Si for similar photoresponse. Based on dark I–V, illuminated I–V, and the energy band diagrams, photoresponse mechanisms were explained. In order to further understand the photoresponse mechanisms, quantum efficiency measurements were carried out, with applied external voltage bias. A general descriptive model was presented for the first time for the photogenerated current density in both Al–ZnO/(n)Si and Al–ZnO/(p)Si heterojunctions at different voltage bias. [ABSTRACT FROM AUTHOR]

Confirming the photocatalytic inactivity of Cu2O nanocubes through the formation of Au-decorated-Cu2O heterostructures, spiky ZnO nanostructures are grown on Cu2O cubes, octahedra, and rhombic dodecahedra to demonstrate that charge transfer across semiconductor heterojunctions is also strongly facet dependent. Unintended CuO formation in the growth of ZnO on perfect Cu2O cubes makes them slightly active toward methyl orange photodegradation. Under optimal ZnO growth conditions without CuO presence, Cu2O cubes remain inactive, while rhombic dodecahedra show an enhanced photocatalytic activity due to better charge transfer according to normal Cu2O-ZnO band alignment. Surprisingly, photocatalytically active Cu2O octahedra become inactive after ZnO deposition. An extensive interfacial microscopic examination reveals preferential formation of the ZnO (101) planes on the {111} surfaces of Cu2O octahedra, while different ZnO lattice planes are observed to deposit on Cu2O cubes and rhombic dodecahedra. The photocatalytic inactivity of ZnO-decorated Cu2O octahedra is explained in terms of an unfavorable band alignment arising from an unusual degree of band bending for the ZnO {101} face relative to the band energy of the Cu2O {111} surface. The efficiency of charge transfer across semiconductor heterojunctions strongly depends on the band edge energies of the contacting planes. [ABSTRACT FROM AUTHOR]

Metal nanoparticle (NP) co-catalysts on metal oxide semiconductor supports are attracting attention as photocatalysts for a variety of chemical reactions. Related efforts seek to make and use Pt-free catalysts. In this regard, we report here enhanced CH formation rates of 25 and 60 μmol·g·h by photocatalytic CO reduction using hitherto unused ZnPd NPs as well as Au and Ru NPs. The NPs are formed by colloidal synthesis and grafted onto short n-type anatase TiO nanotube arrays (TNAs), grown anodically on transparent glass substrates. The interfacial electric fields in the NP-grafted TiO nanotubes were probed by ultraviolet photoelectron spectroscopy (UPS). Au NP-grafted TiO nanotubes (Au-TNAs) showed no band bending, but a depletion region was detected in Ru NP-grafted TNAs (Ru-TNAs) and an accumulation layer was observed in ZnPd NP-grafted TNAs (ZnPd-TNAs). Temperature programmed desorption (TPD) experiments showed significantly greater CO adsorption on NP-grafted TNAs. TNAs with grafted NPs exhibit broader and more intense UV-visible absorption bands than bare TNAs. We found that CO photoreduction by nanoparticle-grafted TNAs was driven not only by ultraviolet photons with energies greater than the TiO band gap, but also by blue photons close to and below the anatase band edge. The enhanced rate of CO reduction is attributed to superior use of blue photons in the solar spectrum, excellent reactant adsorption, efficient charge transfer to adsorbates, and low recombination losses. [ABSTRACT FROM AUTHOR]

New high‐quality thermoelectric devices with amorphous silicon/magnesium silicide (a‐Si/Mg2Si)‐stacked hetero‐structure thin film layers have been fabricated using both radio frequency sputtering and rapid thermal annealing techniques. The thermoelectric properties of the a‐Si/Mg2Si hetero‐structure layers were found to be much superior to those of the a‐Si layer. [ABSTRACT FROM AUTHOR]

In this study, flower-like Bi2MoO6/BiOI heterostructure photocatalysts were synthesized via an anion exchange method using BiOI as precursor. The composition of Bi2MoO6/BiOI can be easily controlled by adjusting the MoO/I molar ratio. Photocatalytic activity studies based on the degradation of Rhodamine B (RhB) show that Bi2MoO6/BiOI50% photocatalyst exhibited the best performance under visible light excitation. The radical scavengers test demonstrated that holes was the main reactive species for the degradation of RhB, andO also took part in the photodecomposition process. Photoelectrochemical measurement reveals that the Bi2MoO6/BiOI50% exhibit enhanced carrier densities, charge separation and photocurrent compared with the original Bi2MoO6 and BiOI. Our results show that bismuth-based heterojunctions fabricated through the anion exchange method could be a cost-effective approach to improve the photocatalytic activity and photoelectrochemical performance of BiOI. Flower-like Bi2MoO6/BiOI heterostructures were synthesized via an anion exchange method. The photocatalytic test confirmed that the activity of Bi2MoO6/BiOI heterojunctions is greatly improved by degrading RhB solution under visible light irradiation, and Bi2MoO6/BiOI=50% photocatalyst exhibited best photocatalytic activity and photoelectrochemical performance. [ABSTRACT FROM AUTHOR]

Ultra‐thin InAlN/GaN heterostructure field‐effect transistors (HFETs) having high maximum oscillation frequency (fmax) are fabricated by scaling lateral dimensions. A 3 nm GaN cap layer is adopted to reduce the electron density and suppress the short‐channel effects. Non‐alloyed regrown n+‐GaN ohmic contacts with total ohmic resistance (Rtot) of 0.13 Ω.mm is also introduced into the device, in which the virtual source‐to‐drain distance is 600 nm. T‐shaped gate with 40 nm length is formed in the centre of the source‐to‐drain region by self‐aligned e‐beam lithography. The peak extrinsic transconductance (gm) reaches 956 mS/mm. Most of all, a high fmax of 405 GHz is obtained, which is the highest value among the reported InAlN/GaN HFETs. These obtained results mean that the InAlN/GaN HFETs having reliability should be still suitable for G‐band (140–220 GHz) power‐amplifier application with further optimisation. [ABSTRACT FROM AUTHOR]

A p-n heterojunction made of MgO and Ga4Se3S single crystal has been successfully produced. The current–voltage curve analysis has shown that the current conduction mechanism is mostly governed by the Richardson–Schottky mechanism. The width of the effective interface region of the p-n junction was found to be 3.72\times 10^-5 cm. The work function and the electron affinity of the Ga4Se3S crystals were also determined as 4.32 and 3.96 eV, respectively. On the other hand, the capacitance–voltage curve analysis, which was carried out in the power range that extends from Bluetooth to WLAN power outputs, reflected a built-in voltage of 0.48 eV and density of noncompensated carriers of 8.2\times 10^16 \mathrmcm^-3 . The device is observed to exhibit a wide range of negative resistance associated with the tunneling of charged particles at reverse biasing down to $\sim 1.28$ V. At that voltage, when exposed to a He–Ne laser beam of $\sim 3$ mW, the device reflected a responsivity of $\sim 80.$ The charge storability increased and the $I$ – $V$ characteristics are significantly shifted. These properties are promising because it indicates the applicability of these tunneling devices in optoelectronics. [ABSTRACT FROM PUBLISHER]

A Pd‐functionalised hydrogen gas sensor based on an AlGaN/GaN heterostruture platform was investigated. The optimum bias voltage and reaction temperature were 0.1 V and 200°C, respectively, with which a wide range of hydrogen concentration from 0.1–4% in the air (i.e. 1000–40,000 ppm) was detectable. Not only low‐power consumption but also high sensitivity with fast response was achieved due to the excellent properties of the AlGaN/GaN heterostructure platform. The sensitivity was 72.8% with a response time of ∼3 s in 4% hydrogen concentration. [ABSTRACT FROM AUTHOR]

Nonlinearity in p-i-n photodetectors leads to power generation at harmonics of the input frequency, limiting the performance of RF-photonic systems. We use one-dimensional and two-dimensional simulations of the drift-diffusion equations to determine the physical origin of the saturation in a simple heterojunction p-i-n photodetector at room temperature. Incomplete ionization, external loading, impact ionization, and the Franz-Keldysh effect are all included in the model. Impact ionization is the main source of nonlinearity at large reverse bias (>10 V in the device that we simulated). The electron and hole current contributions to the second harmonic power were calculated. We find that impact ionization has a greater effect on the electrons than it does on the holes. We also find that the hole velocity saturates slowly with increasing reverse bias, and the hole current makes a large contribution to the harmonic power at 10 V. This result implies that decreasing the hole injection will decrease the harmonic power. [ABSTRACT FROM PUBLISHER]

High electric conductivity is observed in multilayer stack of m-MTDATA/F16CuPc. Impedance data shows that the circuit resistance is significantly dropped by three orders of magnitude from ∼0.2 MΩ to ∼0.4 kΩ when the number of alternating units is increased from one to six, keeping a total thickness of 300 nm. Impedance results show that as the number of alternating units increases, the organic stack shows an increasing capacitance and a decreasing resistance. This result suggests the increasing charges accumulate at the heterojunctions, leading to reduction in overall film resistance. The application of the high conductive units in OLED device results in stability enhancement. [ABSTRACT FROM AUTHOR]

In this paper, the practical viability of an organic bulk heterojunction (BHJ)based photodiode is studied, including the analysis of dark current density (Jd in A/cm2), external quantum efficiency (EQE in percent), responsivity (R in A/W), noise-equivalent power (in W/Hz1/2), and specific detectivity (Jones in cmHz1/2/W). The dark current was minimized down to 90 pA/cm2 in P3HT : PC60BM BHJ photodiodes by increasing the thickness, whereas the EQE maintained high values. The measured noise current was 2:20 χ 10-13, 1:13 χ 10-13, and 1:94 χ 10-14 A/Hz1/2 for 45-, 55-, and 65-nm BHJ photodiodes, respectively. With those values, the calculated detectivity obtained, given light of a 550 nm wavelength, was 2:55 χ 1011, 5:93 χ 1011, and 4:16 χ 1012 Jones, respectively. The results demonstrated a performance of polymer:fullerence photodiode near equivalent to that of Si-based photodiodes. [ABSTRACT FROM PUBLISHER]

We have investigated the impact of surface recombination on the effective carrier injection efficiency and the Joule heating of axial InGaN/GaN nanowire light-emitting diodes (LEDs). The results reveal that the carrier injection efficiency of such devices is extremely low (<;10%), due to the severe carrier loss through nonradiative surface recombination. It is further observed that the thermal resistance of typical nanowire LEDs is comparable with, or lower than that of their planar counterparts, in spite of the reduced thermal conductivity of nanowires. The poor carrier injection efficiency, however, leads to significantly elevated junction temperatures for nanowire LEDs. We have further demonstrated, both theoretically and experimentally, that the carrier injection efficiency can be significantly improved in p-doped nanowires, due to the downward surface band bending, and in InGaN/GaN/AlGaN dot-in-a-wire core-shell nanoscale heterostructures, due to the superior carrier confinement offered by the large bandgap AlGaN shell. This paper offers important insight for the design and epitaxial growth of high-performance nanowire LEDs. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) response of p-Si/i-ZnO/n-ZnO (p-i-n) heterojunction photodetectors (HPDs) was dramatically enhanced by inserting a thin SiOx layer to form a p-Si/SiOx/ i-ZnO/n-ZnO structure. It was found that the leakage current of p-i-n HPDs is largely reduced by about three orders compared with that of conventional p-n HPDs. Photocurrent measurements show that the UV-generated carriers are first accelerated by the electric field in i-ZnO and then tunnel through the thin SiOx layer instead of being trapped by the interface states at the p-Si/ i-ZnO interface. This increases the UV response and consequently, the UV-to-visible rejection ratio is enhanced from 7 for the p-i-n HPDs without SiOx layer to 112 for the HPDs with SiOx insertion. [ABSTRACT FROM PUBLISHER]

We have directly measured the valence-band offsets (VBOs) of wurtzite C-plane and A-plane AlN/GaN heterojunctions by X-ray photoelectron spectroscopy. The VBOs were determined to be 0.82 ± 0.15 and 0.63 ± 0.15 eV for the C-plane and A-plane AlN/GaN heterojunctions, respectively. The discrepancy in VBOs of heterojunctions with different orientations is mainly due to the spontaneous polarization effect. The VBO of the nonpolar heterojunction is closer to the intrinsic value since the A-plane samples show no polarization effects. [ABSTRACT FROM AUTHOR]

Sonosensitizers-assisted sonodynamic therapy (SDT) has been emerging as a promising treatment for cancers, and yet few specific regulations of band structure of sonosensitizers have been reported in relation to oxygen in tissues. Herein, by a gradient doping technique to modulate the band structure of hetero-semiconductor nanorods, it is found that the reduction potential of band-edge is very critical to reactive oxygen species (ROS) production under low-intensity ultrasound (US) irradiation and particularly, when aligned with the reduction of oxygen, ROS generation is found to be most significantly enhanced. Withal, US-generated oxidation holes are found to be effective in consuming overexpressed glutathione in tumor lesions, which amplifies cellular oxidative stress and finally induces tumor cell death. Moreover, the intrinsic fluorescence property of semiconductors provides imaging capability to illumine tumor area and guide the SDT process. This study demonstrates that the reduction potential state of sonosensitizers is of crucial importance in ROS generation and the proposed reduction potential-tailored hetero-semiconductor nanorods materialize low-intensity US irradiation yet highly effective SDT and synergetic hole therapy of tumors with imaging guidance and reduced radiation injury., (© 2022 Wiley-VCH GmbH.)

The semiconductor direct-current triboelectric nanogenerator (SDC-TENG) based on the tribovoltaic effect is promising for developing a new semiconductor energy technology with high power density. Here, the first SDC-TENG built using gallium nitride (GaN) and bismuth telluride (Bi 2 Te 3 ) for ultrahigh-power generation is reported. During the friction process, an additional interfacial electric field is formed by continuous contact electrification (CE), and abundant electron-hole pairs are excited and move directionally to form a junction current that is always internally from Bi 2 Te 3 to GaN, regardless of the semiconductor type. The peak open-circuit voltage can reach up to 40 V and the power density is 11.85 W m -2 (average value is 9.23 W m -2 ), which is approximately 200 times higher than that of previous centimeter-level SDC-TENGs. Moreover, compared to traditional polymer TENGs under the same conditions, the average power density is remarkably improved by over 40 times. This study provides the first evidence of CE on the tribovoltaic effect and sets the normalized power density record for TENGs, which demonstrates a great potential of the tribovoltaic effect for energy harvesting and sensing., (© 2022 Wiley-VCH GmbH.)