The instability of plasma waves in the channel of field-effect transistors will cause the electromagnetic waves with THz frequency.Based on a self-consistent quantum hydrodynamic model,the instability of THz plasmas w...The instability of plasma waves in the channel of field-effect transistors will cause the electromagnetic waves with THz frequency.Based on a self-consistent quantum hydrodynamic model,the instability of THz plasmas waves in the channel of graphene field-effect transistors has been investigated with external magnetic field and quantum effects.We analyzed the influence of weak magnetic fields,quantum effects,device size,and temperature on the instability of plasma waves under asymmetric boundary conditions numerically.The results show that the magnetic fields,quantum effects,and the thickness of the dielectric layer between the gate and the channel can increase the radiation frequency.Additionally,we observed that increase in temperature leads to a decrease in both oscillation frequency and instability increment.The numerical results and accompanying images obtained from our simulations provide support for the above conclusions.展开更多
The exploration and research of low-cost,environmentally friendly,and sustainable organic semiconductor materials are of immense significance in various fields,including electronics,optoelectronics,and energy conversi...The exploration and research of low-cost,environmentally friendly,and sustainable organic semiconductor materials are of immense significance in various fields,including electronics,optoelectronics,and energy conversion.Unfortunately,these semiconductors have almost poor charge transport properties,which range from∼10^(−4) cm^(2)·V^(−1)·s^(−1) to∼10^(−2) cm^(2)·V^(−1)·s^(−1).Vat orange 3,as one of these organic semiconductors,has great potential due to its highly conjugated structure.We obtain high-quality multilayered Vat orange 3 crystals with two-dimensional(2D)growth on h-BN surfaces with thickness of 10–100 nm using physical vapor transport.Raman’s results confirm the stability of the chemical structure of Vat orange 3 during growth.Furthermore,by leveraging the structural advantages of 2D materials,an organic field-effect transistor with a 2D vdW vertical heterostructure is further realized with h-BN encapsulation and multilayered graphene contact electrodes,resulting in an excellent transistor performance with On/Off ratio of 104 and high field-effect mobility of 0.14 cm^(2)·V^(−1)·s^(−1).Our results show the great potential of Vat orange 3 with 2D structures in future nano-electronic applications.Furthermore,we showcase an approach that integrates organic semiconductors with 2D materials,aiming to offer new insights into the study of organic semiconductors.展开更多
GaN-based p-channel heterostructure field-effect transistors(p-HFETs)face significant constraints on on-state currents compared with n-channel high electron mobility transistors.In this work,we propose a novel double ...GaN-based p-channel heterostructure field-effect transistors(p-HFETs)face significant constraints on on-state currents compared with n-channel high electron mobility transistors.In this work,we propose a novel double heterostructure which introduces an additional p-GaN insertion layer into traditional p-HFETs.The impact of the device structure on the hole densities and valence band energies of both the upper and lower channels is analyzed by using Silvaco TACD simulations,including the thickness of the upper AlGaN layer and the doping impurities and concentration in the GaN buffer layer,as well as the thickness and Mg-doping concentration in the p-GaN insertion layer.With the help of the p-GaN insertion layer,the C-doping concentration in the GaN buffer layer can be reduced,while the density of the two-dimensional hole gas in the lower channel is enhanced at the same time.This work suggests that a double heterostructure with a p-GaN insertion layer is a better approach to improve p-HFETs compared with those devices with C-doped buffer layer alone.展开更多
Terahertz(THz) radiation can be generated due to the instability of THz plasma waves in field-effect transistors(FETs). In this work, we discuss the instability of THz plasma waves in the channel of FETs with spin and...Terahertz(THz) radiation can be generated due to the instability of THz plasma waves in field-effect transistors(FETs). In this work, we discuss the instability of THz plasma waves in the channel of FETs with spin and quantum effects under non-ideal boundary conditions. We obtain a linear dispersion relation by using the hydrodynamic equation, Maxwell equation and spin equation. The influence of source capacitance, drain capacitance, spin effects, quantum effects and channel width on the instability of THz plasma waves under the non-ideal boundary conditions is investigated in great detail. The results of numerical simulation show that the THz plasma wave is unstable when the drain capacitance is smaller than the source capacitance;the oscillation frequency with asymmetric boundary conditions is smaller than that under non-ideal boundary conditions;the instability gain of THz plasma waves becomes lower under non-ideal boundary conditions. This finding provides a new idea for finding efficient THz radiation sources and opens up a new mechanism for the development of THz technology.展开更多
Cold-source field-effect transistors(CS-FETs)have been developed to overcome the major challenge of power dissipation in modern integrated circuits.Cold metals suitable for n-type CS-FETs have been proposed as the ide...Cold-source field-effect transistors(CS-FETs)have been developed to overcome the major challenge of power dissipation in modern integrated circuits.Cold metals suitable for n-type CS-FETs have been proposed as the ideal electrode to filter the high-energy electrons and break the thermal limit on subthreshold swing(SS).In this work,regarding the p-type CS-FETs,we propose TcX_(2) and ReX_(2)(X=S,Se)as the injection source to realize the sub-thermal switching for holes.First-principles calculations unveils the cold-metal characteristics of monolayer TcX_(2) and ReX_(2),possessing a sub-gap below the Fermi level and a decreasing DOS with energy.Quantum device simulations demonstrate that TcX_(2) and ReX_(2) can enable the cold source effects in WSe_(2) p-type FETs,achieving steep SS of 29-38 mV/dec and high on/off ratios of(2.3-5.6)×10^(7).Moreover,multilayer Re S2retains the cold metal characteristic,thus ensuring similar CS-FET performances to that of the monolayer source.This work underlines the significance of cold metals for the design of p-type CS-FETs.展开更多
A vertical GaN field-effect transistor with an integrated self-adapted channel diode(CD-FET)is proposed to improve the reverse conduction performance.It features a channel diode(CD)formed between a trench source on th...A vertical GaN field-effect transistor with an integrated self-adapted channel diode(CD-FET)is proposed to improve the reverse conduction performance.It features a channel diode(CD)formed between a trench source on the insulator and a P-type barrier layer(PBL),together with a P-shield layer under the trench gate.At forward conduction,the CD is pinched off due to depletion effects caused by both the PBL and the metal-insulator-semiconductor structure from the trench source,without influencing the on-state characteristic of the CD-FET.At reverse conduction,the depletion region narrows and thus the CD turns on to achieve a very low turn-on voltage(V_(F)),preventing the inherent body diode from turning on.Meanwhile,the PBL and P-shield layer can modulate the electric field distribution to improve the off-state breakdown voltage(BV).Moreover,the P-shield not only shields the gate from a high electric field but also transforms part of C_(GD)to CGS so as to significantly reduce the gate charge(Q_(GD)),leading to a low switching loss(E_(switch)).Consequently,the proposed CD-FET achieves a low V_(F)of 1.65 V and a high BV of 1446 V,and V_(F),Q_(GD)and E_(switch)of the CD-FET are decreased by 49%,55%and 80%,respectively,compared with those of a conventional metal-oxide-semiconductor field-effect transistor(MOSFET).展开更多
Nanowires with gate-all-around(GAA) structures are widely considered as the most promising candidate for 3-nm technology with the best ability of suppressing the short channel effects,and tunneling field effect transi...Nanowires with gate-all-around(GAA) structures are widely considered as the most promising candidate for 3-nm technology with the best ability of suppressing the short channel effects,and tunneling field effect transistors(TFETs)based on GAA structures also present improved performance.In this paper,a non-quasi-static(NQS) device model is developed for nanowire GAA TFETs.The model can predict the transient current and capacitance varying with operation frequency,which is beyond the ability of the quasi-static(QS) model published before.Excellent agreements between the model results and numerical simulations are obtained.Moreover,the NQS model is derived from the published QS model including the current-voltage(I-V) and capacitance-voltage(C-V) characteristics.Therefore,the NQS model is compatible with the QS model for giving comprehensive understanding of GAA TFETs and would be helpful for further study of TFET circuits based on nanowire GAA structure.展开更多
A dielectric modulation strategy for gate oxide material that enhances the sensing performance of biosensors in junction-less vertical tunnel field effect transistors(TFETs)is reported.The junction-less technique,in w...A dielectric modulation strategy for gate oxide material that enhances the sensing performance of biosensors in junction-less vertical tunnel field effect transistors(TFETs)is reported.The junction-less technique,in which metals with specific work functions are deposited on the source region to modulate the channel conductivity,is used to provide the necessary doping for the proper functioning of the device.TCAD simulation studies of the proposed structure and junction structure have been compared,and showed an enhanced rectification of 10^(4) times.The proposed structure is designed to have a nanocavity of length 10 nm on the left-and right-hand sides of the fixed gate dielectric,which improves the biosensor capture area,and hence the sensitivity.By considering neutral and charged biomolecules with different dielectric constants,TCAD simulation studies were compared for their sensitivities.The off-state current IOFFcan be used as a suitable sensing parameter because it has been observed that the proposed sensor exhibits a significant variation in drain current.Additionally,it has been investigated how positively and negatively charged biomolecules affect the drain current and threshold voltage.To explore the device performance when the nanogaps are fully filled,half filled and unevenly filled,extensive TCAD simulations have been run.The proposed TFET structure is further benchmarked to other structures to show its better sensing capabilities.展开更多
The effects of low-κ and high-κ spacer were investigated on the novel tunnel dielectric based tunnel field-effect transistor(TD-FET) mainly based upon ultra-thin dielectric direct tunneling mechanism. Drive currents...The effects of low-κ and high-κ spacer were investigated on the novel tunnel dielectric based tunnel field-effect transistor(TD-FET) mainly based upon ultra-thin dielectric direct tunneling mechanism. Drive currents consist of direct tunneling current and band-to-band tunneling(BTBT) current. Meanwhile, tunneling position of the TD-FET differs from conventional tunnel-FET in which the electron and hole tunneling occur at intermediate rather than surface in channel(or source-channel junction under gate dielectric). The 2-D nature of TD-FET current flow is also discussed that the on-current is degraded with an increase in the spacer width. BTBT current will not begin to play part in tunneling current until gate voltage is 0.2 V. We clearly identify the influence of the tunneling dielectric layer and spacer electrostatic field on the device characteristics by numerical simulations. The inserted Si_3N_4 tunnel layer between P+ region and N+ region can significantly shorten the direct and band-to-band tunneling path, so a reduced subthreshold slope(Ss) and a high on-current can be achieved. Above all the ambipolar current is effectively suppressed, thus reducing off-current. TD-FET demonstrates excellent performance for low-power applications.展开更多
Two-dimensional(2D) materials have attracted extensive interest due to their excellent electrical, thermal,mechanical, and optical properties. Graphene has been one of the most explored 2D materials. However, its zero...Two-dimensional(2D) materials have attracted extensive interest due to their excellent electrical, thermal,mechanical, and optical properties. Graphene has been one of the most explored 2D materials. However, its zero band gap has limited its applications in electronic devices. Transition metal dichalcogenide(TMDC), another kind of 2D material,has a nonzero direct band gap(same charge carrier momentum in valence and conduction band) at monolayer state,promising for the efficient switching devices(e.g., field-effect transistors). This review mainly focuses on the recent advances in charge carrier mobility and the challenges to achieve high mobility in the electronic devices based on 2DTMDC materials and also includes an introduction of 2D materials along with the synthesis techniques. Finally, this review describes the possible methodology and future prospective to enhance the charge carrier mobility for electronic devices.展开更多
Various biaxial compressive strained GaSb p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) are experimentally and theoretically investigated, The biaxial compressive strained GaSb MOSFETs show ...Various biaxial compressive strained GaSb p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) are experimentally and theoretically investigated, The biaxial compressive strained GaSb MOSFETs show a high peak mobility of 638 cm2/V.s, which is 3.86 times of the extracted mobility of the fabricated GaSb MOSFETs without strain. Meanwhile, first principles calculations show that the hole effective mass of GaSb depends on the biaxial compressive strain. The biaxiai compressive strain brings a remarkable enhancement of the hole mobility caused by a significant reduction in the hole effective mass due to the modulation of the valence bands.展开更多
Field-effect transistors (FETs) for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional (2D) materials, drastically different properties and requi...Field-effect transistors (FETs) for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional (2D) materials, drastically different properties and require different consider- ations. The unique band structure of graphene necessitates engineering of the Dirac point, including the opening of the bandgap, the doping and the interface, before the graphene can be used in logic applications. On the other hand, MoS2 is a semiconductor, and its electron transport depends heavily on the surface properties, the number of layers, and the carrier density. Finally, we discuss the prospects for the future developments in 2D material transistors.展开更多
We present the design consideration and fabrication of 4H-SiC trenched-and-implanted vertical junction field-effect transistors (TI-VJFETs). Different design factors, including channel width, channel doping, and mes...We present the design consideration and fabrication of 4H-SiC trenched-and-implanted vertical junction field-effect transistors (TI-VJFETs). Different design factors, including channel width, channel doping, and mesa height, are con- sidered and evaluated by numerical simulations. Based on the simulation result, normally-on and normally-off devices are fabricated. The fabricated device has a 12 μm thick drift layer with 8 × 10^15 cm^-3 N-type doping and 2.6 μm channel length. The normally-on device shows a 1.2 kV blocking capability with a minimum on-state resistance of 2.33 mΩ.cm2, while the normally-off device shows an on-state resistance of 3.85 mΩ.cm2. Both the on-state and the blocking performances of the device are close to the state-of-the-art values in this voltage range.展开更多
Black phosphorous(BP),an excellent two-dimensional(2D)monoelemental layered p-type semiconductor material with high carrier mobility and thickness-dependent tunable direct bandgap structure,has been widely applied in ...Black phosphorous(BP),an excellent two-dimensional(2D)monoelemental layered p-type semiconductor material with high carrier mobility and thickness-dependent tunable direct bandgap structure,has been widely applied in various devices.As the essential building blocks for modern electronic and optoelectronic devices,high quality PN junctions based on semiconductors have attracted widespread attention.Herein,we report a junction field-effect transistor(JFET)by integrating narrow-gap p-type BP and ultra-wide gap n-typeβ-Ga2O3 nanoflakes for the first time.BP andβ-Ga2O3 form a vertical van der Waals(vdW)heterostructure by mechanically exfoliated method.The BP/β-Ga2O3 vdW heterostructure exhibits remarkable PN diode rectifying characteristics with a high rectifying ratio about 107 and a low reverse current around pA.More interestingly,by using the BP as the gate andβ-Ga2O3 as the channel,the BP/β-Ga2O3 JFET devices demonstrate excellent n-channel JFET characteristics with the on/off ratio as high as 107,gate leakage current around as low as pA,maximum transconductance(gm)up to 25.3μS and saturation drain current(IDSS)of 16.5μA/μm.Moreover,it has a pinch-off voltage of–20 V and a minimum subthreshold swing of 260 mV/dec.These excellent n-channel JFET characteristics will expand the application of BP in future nanoelectronic devices.展开更多
Field-effect transistors(FETs)present highly sensitive,rapid,and in situ detection capability in chemical and biological analysis.Recently,two-dimensional(2D)transition-metal dichalcogenides(TMDCs)attract significant ...Field-effect transistors(FETs)present highly sensitive,rapid,and in situ detection capability in chemical and biological analysis.Recently,two-dimensional(2D)transition-metal dichalcogenides(TMDCs)attract significant attention as FET channel due to their unique structures and outstanding properties.With the booming of studies on TMDC FETs,we aim to give a timely review on TMDCbased FET sensors for environmental analysis in different media.First,theoretical basics on TMDC and FET sensor are introduced.Then,recent advances of TMDC FET sensor for pollutant detection in gaseous and aqueous media are,respectively,discussed.At last,future perspectives and challenges in practical application and commercialization are given for TMDC FET sensors.This article provides an overview on TMDC sensors for a wide variety of analytes with an emphasize on the increasing demand of advanced sensing technologies in environmental analysis.展开更多
A vertical carbon nanotube field-effect transistor(CNTFET) based on silicon(Si) substrate has been proposed and simulated using a semi-classical theory. A single-walled carbon nanotube(SWNT) and an n-type Si nanowire ...A vertical carbon nanotube field-effect transistor(CNTFET) based on silicon(Si) substrate has been proposed and simulated using a semi-classical theory. A single-walled carbon nanotube(SWNT) and an n-type Si nanowire in series construct the channel of the transistor. The CNTFET presents ambipolar characteristics at positive drain voltage(Vd) and n-type characteristics at negative Vd. The current is significantly influenced by the doping level of n-Si and the SWNT band gap. The n-branch current of the ambipolar characteristics increases with increasing doping level of the n-Si while the p-branch current decreases. The SWNT band gap has the same influence on the p-branch current at a positive Vd and n-type characteristics at negative Vd. The lower the SWNT band gap, the higher the current. However, it has no impact on the n-branch current in the ambipolar characteristics. Thick oxide is found to significantly degrade the current and the subthreshold slope of the CNTFETs.展开更多
Graphene has attracted enormous interests due to its unique physical, mechanical, and electrical properties. Specially, graphene-based field-effect transistors (FETs) have evolved rapidly and are now considered as a...Graphene has attracted enormous interests due to its unique physical, mechanical, and electrical properties. Specially, graphene-based field-effect transistors (FETs) have evolved rapidly and are now considered as an option for conventional silicon devices. As a critical step in the design cycle of modem IC products, compact model refers to the development of models for integrated semiconductor devices for use in circuit simulations. The purpose of this review is to provide a theoretical description of current compact model of graphene field-effect transistors. Special attention is devoted to the charge sheet model, drift-diffusion model, Boltzmann equation, density of states (DOS), and surface-potential-based compact model. Finally, an outlook of this field is briefly discussed.展开更多
The influence of total dose irradiation on hot-carrier reliability of 65 nm n-type metal-oxide-semiconductor field- effect transistors (nMOSFETs) is investigated. Experimental results show that hot-carrier degradati...The influence of total dose irradiation on hot-carrier reliability of 65 nm n-type metal-oxide-semiconductor field- effect transistors (nMOSFETs) is investigated. Experimental results show that hot-carrier degradations on ir- radiated narrow channel nMOSFETs are greater than those without irradiation. The reason is attributed to radiation-induced charge trapping in shallow trench isolation (STI). The electric field in the pinch-off region of the nMOSFET is enhanced by radiation-induced charge trapping in STI, resulting in a more severe hot-carrier effect.展开更多
C60 field-effect transistor (OFET) with a mobility as high as 5.17 cm2/V.s is fabricated. In our experiment, an ultrathin pentacene passivation layer on poly-(methyl methacrylate) (PMMA) insulator and a bathophe...C60 field-effect transistor (OFET) with a mobility as high as 5.17 cm2/V.s is fabricated. In our experiment, an ultrathin pentacene passivation layer on poly-(methyl methacrylate) (PMMA) insulator and a bathophenanthroline (Bphen)/Ag bilayer electrode are prepared. The OFET shows a significant enhancement of electron mobility compared with the corresponding device with a single PMMA insultor and an Ag electrode. By analysing the C60 film with atomic force microscopy and X-ray diffraction techniques, it is shown that the pentacene passivation layer can contribute to C60 film growth with the large grain size and significantly improve crystallinity. Moreover, the Bphen buffer layer can reduce the electron contact barrier from Ag electrodes to C60 film efficiently.展开更多
Trap-assisted tunneling(TAT) has attracted more and more attention, because it seriously affects the sub-threshold characteristic of tunnel field-effect transistor(TFET). In this paper, we assess subthreshold perf...Trap-assisted tunneling(TAT) has attracted more and more attention, because it seriously affects the sub-threshold characteristic of tunnel field-effect transistor(TFET). In this paper, we assess subthreshold performance of double gate TFET(DG-TFET) through a band-to-band tunneling(BTBT) model, including phonon-assisted scattering and acoustic surface phonons scattering. Interface state density profile(D_(it)) and the trap level are included in the simulation to analyze their effects on TAT current and the mechanism of gate leakage current.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.12065015)the Hongliu Firstlevel Discipline Construction Project of Lanzhou University of Technology。
文摘The instability of plasma waves in the channel of field-effect transistors will cause the electromagnetic waves with THz frequency.Based on a self-consistent quantum hydrodynamic model,the instability of THz plasmas waves in the channel of graphene field-effect transistors has been investigated with external magnetic field and quantum effects.We analyzed the influence of weak magnetic fields,quantum effects,device size,and temperature on the instability of plasma waves under asymmetric boundary conditions numerically.The results show that the magnetic fields,quantum effects,and the thickness of the dielectric layer between the gate and the channel can increase the radiation frequency.Additionally,we observed that increase in temperature leads to a decrease in both oscillation frequency and instability increment.The numerical results and accompanying images obtained from our simulations provide support for the above conclusions.
基金supported by the National Natural Science Foundation of China(Grant Nos.U21A6004,62375160,62274180,and 12004389).
文摘The exploration and research of low-cost,environmentally friendly,and sustainable organic semiconductor materials are of immense significance in various fields,including electronics,optoelectronics,and energy conversion.Unfortunately,these semiconductors have almost poor charge transport properties,which range from∼10^(−4) cm^(2)·V^(−1)·s^(−1) to∼10^(−2) cm^(2)·V^(−1)·s^(−1).Vat orange 3,as one of these organic semiconductors,has great potential due to its highly conjugated structure.We obtain high-quality multilayered Vat orange 3 crystals with two-dimensional(2D)growth on h-BN surfaces with thickness of 10–100 nm using physical vapor transport.Raman’s results confirm the stability of the chemical structure of Vat orange 3 during growth.Furthermore,by leveraging the structural advantages of 2D materials,an organic field-effect transistor with a 2D vdW vertical heterostructure is further realized with h-BN encapsulation and multilayered graphene contact electrodes,resulting in an excellent transistor performance with On/Off ratio of 104 and high field-effect mobility of 0.14 cm^(2)·V^(−1)·s^(−1).Our results show the great potential of Vat orange 3 with 2D structures in future nano-electronic applications.Furthermore,we showcase an approach that integrates organic semiconductors with 2D materials,aiming to offer new insights into the study of organic semiconductors.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62104184,62234009,62090014,62188102,62104178,and 62104179)the Fundamental Research Funds for the Central Universities of China(Grant Nos.YJSJ23019,XJSJ23047,and ZDRC2002)+1 种基金the China National Postdoctoral Program for Innovative Talents(Grant No.BX20200262)the China Postdoctoral Science Foundation(Grant No.2021M692499)。
文摘GaN-based p-channel heterostructure field-effect transistors(p-HFETs)face significant constraints on on-state currents compared with n-channel high electron mobility transistors.In this work,we propose a novel double heterostructure which introduces an additional p-GaN insertion layer into traditional p-HFETs.The impact of the device structure on the hole densities and valence band energies of both the upper and lower channels is analyzed by using Silvaco TACD simulations,including the thickness of the upper AlGaN layer and the doping impurities and concentration in the GaN buffer layer,as well as the thickness and Mg-doping concentration in the p-GaN insertion layer.With the help of the p-GaN insertion layer,the C-doping concentration in the GaN buffer layer can be reduced,while the density of the two-dimensional hole gas in the lower channel is enhanced at the same time.This work suggests that a double heterostructure with a p-GaN insertion layer is a better approach to improve p-HFETs compared with those devices with C-doped buffer layer alone.
基金funded by National Natural Science Foundation of China (No. 12065015)the Hongliu First-level Discipline Construction Project of Lanzhou University of Technology。
文摘Terahertz(THz) radiation can be generated due to the instability of THz plasma waves in field-effect transistors(FETs). In this work, we discuss the instability of THz plasma waves in the channel of FETs with spin and quantum effects under non-ideal boundary conditions. We obtain a linear dispersion relation by using the hydrodynamic equation, Maxwell equation and spin equation. The influence of source capacitance, drain capacitance, spin effects, quantum effects and channel width on the instability of THz plasma waves under the non-ideal boundary conditions is investigated in great detail. The results of numerical simulation show that the THz plasma wave is unstable when the drain capacitance is smaller than the source capacitance;the oscillation frequency with asymmetric boundary conditions is smaller than that under non-ideal boundary conditions;the instability gain of THz plasma waves becomes lower under non-ideal boundary conditions. This finding provides a new idea for finding efficient THz radiation sources and opens up a new mechanism for the development of THz technology.
基金supported by the National Natural Science Foundation of China (Grant Nos.62034006,92264201,and 62104134)the Natural Science Foundation of Shandong Province of China (Grant Nos.ZR2023QF076 and ZR2023QF054)。
文摘Cold-source field-effect transistors(CS-FETs)have been developed to overcome the major challenge of power dissipation in modern integrated circuits.Cold metals suitable for n-type CS-FETs have been proposed as the ideal electrode to filter the high-energy electrons and break the thermal limit on subthreshold swing(SS).In this work,regarding the p-type CS-FETs,we propose TcX_(2) and ReX_(2)(X=S,Se)as the injection source to realize the sub-thermal switching for holes.First-principles calculations unveils the cold-metal characteristics of monolayer TcX_(2) and ReX_(2),possessing a sub-gap below the Fermi level and a decreasing DOS with energy.Quantum device simulations demonstrate that TcX_(2) and ReX_(2) can enable the cold source effects in WSe_(2) p-type FETs,achieving steep SS of 29-38 mV/dec and high on/off ratios of(2.3-5.6)×10^(7).Moreover,multilayer Re S2retains the cold metal characteristic,thus ensuring similar CS-FET performances to that of the monolayer source.This work underlines the significance of cold metals for the design of p-type CS-FETs.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61874149 and U20A20208)the Outstanding Youth Science and Technology Foundation of China(Grant No.2018-JCJQ-ZQ-060).
文摘A vertical GaN field-effect transistor with an integrated self-adapted channel diode(CD-FET)is proposed to improve the reverse conduction performance.It features a channel diode(CD)formed between a trench source on the insulator and a P-type barrier layer(PBL),together with a P-shield layer under the trench gate.At forward conduction,the CD is pinched off due to depletion effects caused by both the PBL and the metal-insulator-semiconductor structure from the trench source,without influencing the on-state characteristic of the CD-FET.At reverse conduction,the depletion region narrows and thus the CD turns on to achieve a very low turn-on voltage(V_(F)),preventing the inherent body diode from turning on.Meanwhile,the PBL and P-shield layer can modulate the electric field distribution to improve the off-state breakdown voltage(BV).Moreover,the P-shield not only shields the gate from a high electric field but also transforms part of C_(GD)to CGS so as to significantly reduce the gate charge(Q_(GD)),leading to a low switching loss(E_(switch)).Consequently,the proposed CD-FET achieves a low V_(F)of 1.65 V and a high BV of 1446 V,and V_(F),Q_(GD)and E_(switch)of the CD-FET are decreased by 49%,55%and 80%,respectively,compared with those of a conventional metal-oxide-semiconductor field-effect transistor(MOSFET).
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 62004119 and 62201332)the Applied Basic Research Plan of Shanxi Province, China (Grant Nos. 20210302124647 and 20210302124028)。
文摘Nanowires with gate-all-around(GAA) structures are widely considered as the most promising candidate for 3-nm technology with the best ability of suppressing the short channel effects,and tunneling field effect transistors(TFETs)based on GAA structures also present improved performance.In this paper,a non-quasi-static(NQS) device model is developed for nanowire GAA TFETs.The model can predict the transient current and capacitance varying with operation frequency,which is beyond the ability of the quasi-static(QS) model published before.Excellent agreements between the model results and numerical simulations are obtained.Moreover,the NQS model is derived from the published QS model including the current-voltage(I-V) and capacitance-voltage(C-V) characteristics.Therefore,the NQS model is compatible with the QS model for giving comprehensive understanding of GAA TFETs and would be helpful for further study of TFET circuits based on nanowire GAA structure.
文摘A dielectric modulation strategy for gate oxide material that enhances the sensing performance of biosensors in junction-less vertical tunnel field effect transistors(TFETs)is reported.The junction-less technique,in which metals with specific work functions are deposited on the source region to modulate the channel conductivity,is used to provide the necessary doping for the proper functioning of the device.TCAD simulation studies of the proposed structure and junction structure have been compared,and showed an enhanced rectification of 10^(4) times.The proposed structure is designed to have a nanocavity of length 10 nm on the left-and right-hand sides of the fixed gate dielectric,which improves the biosensor capture area,and hence the sensitivity.By considering neutral and charged biomolecules with different dielectric constants,TCAD simulation studies were compared for their sensitivities.The off-state current IOFFcan be used as a suitable sensing parameter because it has been observed that the proposed sensor exhibits a significant variation in drain current.Additionally,it has been investigated how positively and negatively charged biomolecules affect the drain current and threshold voltage.To explore the device performance when the nanogaps are fully filled,half filled and unevenly filled,extensive TCAD simulations have been run.The proposed TFET structure is further benchmarked to other structures to show its better sensing capabilities.
基金Projects(61574109,61204092)supported by the National Natural Science Foundation of China
文摘The effects of low-κ and high-κ spacer were investigated on the novel tunnel dielectric based tunnel field-effect transistor(TD-FET) mainly based upon ultra-thin dielectric direct tunneling mechanism. Drive currents consist of direct tunneling current and band-to-band tunneling(BTBT) current. Meanwhile, tunneling position of the TD-FET differs from conventional tunnel-FET in which the electron and hole tunneling occur at intermediate rather than surface in channel(or source-channel junction under gate dielectric). The 2-D nature of TD-FET current flow is also discussed that the on-current is degraded with an increase in the spacer width. BTBT current will not begin to play part in tunneling current until gate voltage is 0.2 V. We clearly identify the influence of the tunneling dielectric layer and spacer electrostatic field on the device characteristics by numerical simulations. The inserted Si_3N_4 tunnel layer between P+ region and N+ region can significantly shorten the direct and band-to-band tunneling path, so a reduced subthreshold slope(Ss) and a high on-current can be achieved. Above all the ambipolar current is effectively suppressed, thus reducing off-current. TD-FET demonstrates excellent performance for low-power applications.
基金funded by Australian Research Council discovery project DP140103041Future Fellowship FT160100205
文摘Two-dimensional(2D) materials have attracted extensive interest due to their excellent electrical, thermal,mechanical, and optical properties. Graphene has been one of the most explored 2D materials. However, its zero band gap has limited its applications in electronic devices. Transition metal dichalcogenide(TMDC), another kind of 2D material,has a nonzero direct band gap(same charge carrier momentum in valence and conduction band) at monolayer state,promising for the efficient switching devices(e.g., field-effect transistors). This review mainly focuses on the recent advances in charge carrier mobility and the challenges to achieve high mobility in the electronic devices based on 2DTMDC materials and also includes an introduction of 2D materials along with the synthesis techniques. Finally, this review describes the possible methodology and future prospective to enhance the charge carrier mobility for electronic devices.
基金Project supported by the National Basic Research Program of China(Grant No.2011CBA00602)the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011ZX02708-002)
文摘Various biaxial compressive strained GaSb p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) are experimentally and theoretically investigated, The biaxial compressive strained GaSb MOSFETs show a high peak mobility of 638 cm2/V.s, which is 3.86 times of the extracted mobility of the fabricated GaSb MOSFETs without strain. Meanwhile, first principles calculations show that the hole effective mass of GaSb depends on the biaxial compressive strain. The biaxiai compressive strain brings a remarkable enhancement of the hole mobility caused by a significant reduction in the hole effective mass due to the modulation of the valence bands.
基金supported by the National Basic Research Program of China (Grant No. 2013CBA01600)the National Natural Science Foundation of China (Grant Nos. 61261160499 and 11274154)+2 种基金the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. 2011ZX02707)the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2012302)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120091110028)
文摘Field-effect transistors (FETs) for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional (2D) materials, drastically different properties and require different consider- ations. The unique band structure of graphene necessitates engineering of the Dirac point, including the opening of the bandgap, the doping and the interface, before the graphene can be used in logic applications. On the other hand, MoS2 is a semiconductor, and its electron transport depends heavily on the surface properties, the number of layers, and the carrier density. Finally, we discuss the prospects for the future developments in 2D material transistors.
基金supported by the National High Technology Research and Development Program of China(Grant No.2011AA050401)the National Science Fundfor Distinguished Young Scholars,China(Grant No.51225701)
文摘We present the design consideration and fabrication of 4H-SiC trenched-and-implanted vertical junction field-effect transistors (TI-VJFETs). Different design factors, including channel width, channel doping, and mesa height, are con- sidered and evaluated by numerical simulations. Based on the simulation result, normally-on and normally-off devices are fabricated. The fabricated device has a 12 μm thick drift layer with 8 × 10^15 cm^-3 N-type doping and 2.6 μm channel length. The normally-on device shows a 1.2 kV blocking capability with a minimum on-state resistance of 2.33 mΩ.cm2, while the normally-off device shows an on-state resistance of 3.85 mΩ.cm2. Both the on-state and the blocking performances of the device are close to the state-of-the-art values in this voltage range.
基金supported by the National Natural Science Foundation of China(Grant No.61922082,61875223,61927813)the Natural Science Foundation of Jiangsu Province(Grant No.BK20191195)The support from the Vacuum Interconnected Nanotech Workstation(Nano-X)of Suzhou Institute of Nano-tech and Nano-bionics(SINANO),Chinese Academy of Sciences。
文摘Black phosphorous(BP),an excellent two-dimensional(2D)monoelemental layered p-type semiconductor material with high carrier mobility and thickness-dependent tunable direct bandgap structure,has been widely applied in various devices.As the essential building blocks for modern electronic and optoelectronic devices,high quality PN junctions based on semiconductors have attracted widespread attention.Herein,we report a junction field-effect transistor(JFET)by integrating narrow-gap p-type BP and ultra-wide gap n-typeβ-Ga2O3 nanoflakes for the first time.BP andβ-Ga2O3 form a vertical van der Waals(vdW)heterostructure by mechanically exfoliated method.The BP/β-Ga2O3 vdW heterostructure exhibits remarkable PN diode rectifying characteristics with a high rectifying ratio about 107 and a low reverse current around pA.More interestingly,by using the BP as the gate andβ-Ga2O3 as the channel,the BP/β-Ga2O3 JFET devices demonstrate excellent n-channel JFET characteristics with the on/off ratio as high as 107,gate leakage current around as low as pA,maximum transconductance(gm)up to 25.3μS and saturation drain current(IDSS)of 16.5μA/μm.Moreover,it has a pinch-off voltage of–20 V and a minimum subthreshold swing of 260 mV/dec.These excellent n-channel JFET characteristics will expand the application of BP in future nanoelectronic devices.
基金the National Natural Science Foundation of China(No.21707102)the Fundamental Research Funds for the Central Universities,China(No.22120180524).
文摘Field-effect transistors(FETs)present highly sensitive,rapid,and in situ detection capability in chemical and biological analysis.Recently,two-dimensional(2D)transition-metal dichalcogenides(TMDCs)attract significant attention as FET channel due to their unique structures and outstanding properties.With the booming of studies on TMDC FETs,we aim to give a timely review on TMDCbased FET sensors for environmental analysis in different media.First,theoretical basics on TMDC and FET sensor are introduced.Then,recent advances of TMDC FET sensor for pollutant detection in gaseous and aqueous media are,respectively,discussed.At last,future perspectives and challenges in practical application and commercialization are given for TMDC FET sensors.This article provides an overview on TMDC sensors for a wide variety of analytes with an emphasize on the increasing demand of advanced sensing technologies in environmental analysis.
基金support by National High Technology Research and Development Program of China (No. 2011AA050504)the analysis supports from Instrumental Analysis Center of SJTU
文摘A vertical carbon nanotube field-effect transistor(CNTFET) based on silicon(Si) substrate has been proposed and simulated using a semi-classical theory. A single-walled carbon nanotube(SWNT) and an n-type Si nanowire in series construct the channel of the transistor. The CNTFET presents ambipolar characteristics at positive drain voltage(Vd) and n-type characteristics at negative Vd. The current is significantly influenced by the doping level of n-Si and the SWNT band gap. The n-branch current of the ambipolar characteristics increases with increasing doping level of the n-Si while the p-branch current decreases. The SWNT band gap has the same influence on the p-branch current at a positive Vd and n-type characteristics at negative Vd. The lower the SWNT band gap, the higher the current. However, it has no impact on the n-branch current in the ambipolar characteristics. Thick oxide is found to significantly degrade the current and the subthreshold slope of the CNTFETs.
基金Project supported by the Opening Project of Key Laboratory of Microelectronics Devices and Integrated Technology,Institute of Microelectronics,Chinese Academy of Sciences,the National Natural Science Foundation of China(Grant No.61574166)the National Basic Research Program of China(Grant No.2013CBA01604)+1 种基金the National Key Research and Development Program of China(Grant No.2016YFA0201802)and the Beijing Training Project for the Leading Talents in S&T,China(Grant No.Z151100000315008)
文摘Graphene has attracted enormous interests due to its unique physical, mechanical, and electrical properties. Specially, graphene-based field-effect transistors (FETs) have evolved rapidly and are now considered as an option for conventional silicon devices. As a critical step in the design cycle of modem IC products, compact model refers to the development of models for integrated semiconductor devices for use in circuit simulations. The purpose of this review is to provide a theoretical description of current compact model of graphene field-effect transistors. Special attention is devoted to the charge sheet model, drift-diffusion model, Boltzmann equation, density of states (DOS), and surface-potential-based compact model. Finally, an outlook of this field is briefly discussed.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11475255,U1532261 and 11505282
文摘The influence of total dose irradiation on hot-carrier reliability of 65 nm n-type metal-oxide-semiconductor field- effect transistors (nMOSFETs) is investigated. Experimental results show that hot-carrier degradations on ir- radiated narrow channel nMOSFETs are greater than those without irradiation. The reason is attributed to radiation-induced charge trapping in shallow trench isolation (STI). The electric field in the pinch-off region of the nMOSFET is enhanced by radiation-induced charge trapping in STI, resulting in a more severe hot-carrier effect.
基金supported by the National Science Foundation for Post-Doctoral Scientists of China (Grant No.20100471667)the Natural Science Foundation of Chongqing Science and Technology Commission (CQ CSTC) (Grant No.2011jjA40020)+1 种基金the National Natural Science Foundation of China (Grant Nos.60736005 and 61021061)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education of China (Grant No.GGRYJJ08-05)
文摘C60 field-effect transistor (OFET) with a mobility as high as 5.17 cm2/V.s is fabricated. In our experiment, an ultrathin pentacene passivation layer on poly-(methyl methacrylate) (PMMA) insulator and a bathophenanthroline (Bphen)/Ag bilayer electrode are prepared. The OFET shows a significant enhancement of electron mobility compared with the corresponding device with a single PMMA insultor and an Ag electrode. By analysing the C60 film with atomic force microscopy and X-ray diffraction techniques, it is shown that the pentacene passivation layer can contribute to C60 film growth with the large grain size and significantly improve crystallinity. Moreover, the Bphen buffer layer can reduce the electron contact barrier from Ag electrodes to C60 film efficiently.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61574109 and 61204092)
文摘Trap-assisted tunneling(TAT) has attracted more and more attention, because it seriously affects the sub-threshold characteristic of tunnel field-effect transistor(TFET). In this paper, we assess subthreshold performance of double gate TFET(DG-TFET) through a band-to-band tunneling(BTBT) model, including phonon-assisted scattering and acoustic surface phonons scattering. Interface state density profile(D_(it)) and the trap level are included in the simulation to analyze their effects on TAT current and the mechanism of gate leakage current.