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 fundamental advantages of carbon-based graphene material,such as its high tunnelling probability,symmetric band structure(linear dependence of the energy band on the wave direction),low effective mass,and characte...The fundamental advantages of carbon-based graphene material,such as its high tunnelling probability,symmetric band structure(linear dependence of the energy band on the wave direction),low effective mass,and characteristics of its 2D atomic layers,are the main focus of this research work.The impact of channel thickness,gate under-lap,asymmetric source/drain doping method,workfunction of gate contact,and High-K material on Graphene-based Tunnel Field Effect Transistor(TFET)is analyzed with 20 nm technology.Physical modelling and electrical characteristic performance have been simulated using the Atlas device simulator of SILVACO TCAD with user-defined material syntax for the newly included graphene material in comparison to silicon carbide(SiC).The simulation results in significant suppression of ambipolar current to voltage characteristics of TFET and modelled device exhibits a significant improvement in subthreshold swing(0.0159 V/decade),the ratio of Ion/Ioff(1000),and threshold voltage(-0.2 V with highly doped p-type source and 0.2 V with highly doped n-type drain)with power supply of 0.5 V,which make it useful for low power digital applications.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
In this work, a double-gate-all-around tunneling field-effect transistor is proposed. The performance of the novel device is studied by numerical simulation. The results show that with a thinner body and an additional...In this work, a double-gate-all-around tunneling field-effect transistor is proposed. The performance of the novel device is studied by numerical simulation. The results show that with a thinner body and an additional core gate, the novel device achieves a steeper subthreshold slope, less susceptibility to the short channel effect, higher on-state current, and larger on/off current ratio than the traditional gate-all-around tunneling field-effect transistor. The excellent performance makes the proposed structure more attractive to further dimension scaling.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
A new T-shaped tunnel field-effect transistor(TTFET) with gate dielectric spacer(GDS) structure is proposed in this paper. To further studied the effects of GDS structure on the TTFET, detailed device characteristics ...A new T-shaped tunnel field-effect transistor(TTFET) with gate dielectric spacer(GDS) structure is proposed in this paper. To further studied the effects of GDS structure on the TTFET, detailed device characteristics such as current-voltage relationships, energy band diagrams, band-to-band tunneling(BTBT) rate and the magnitude of the electric field are investigated by using TCAD simulation. It is found that compared with conventional TTFET and TTFET with gate-drain overlap(GDO) structure, GDS-TTFET not only has the minimum ambipolar current but also can suppress the ambipolar current under a more extensive bias range. Furthermore, the analog/RF performances of GDS-TTFET are also investigated in terms of transconductance, gate-source capacitance, gate-drain capacitance, cutoff frequency, and gain bandwidth production. By inserting a low-κ spacer layer between the gate electrode and the gate dielectric, the GDS structure can effectively reduce parasitic capacitances between the gate and the source/drain, which leads to better performance in term of cutoff frequency and gain bandwidth production. Finally, the thickness of the gate dielectric spacer is optimized for better ambipolar current suppression and improved analog/RF performance.展开更多
An analytical model of gate-all-around (GAA) silicon nanowire tunneling field effect transistors (NW-TFETs) is developted based on the surface potential solutions in the channel direction and considering the band ...An analytical model of gate-all-around (GAA) silicon nanowire tunneling field effect transistors (NW-TFETs) is developted based on the surface potential solutions in the channel direction and considering the band to band tunneling (BTBT) efficiency. The three-dimensional Poisson equation is solved to obtain the surface potential distributions in the partition regions along the channel direction for the NW-TFET, and a tunneling current model using Kane's expression is developed. The validity of the developed model is shown by the good agreement between the model predictions and the TCAD simulation results.展开更多
The tunneling current in a graphene nanoribbon tunnel field effect transistor(GNR-TFET) has been quantum mechanically modeled. The tunneling current in the GNR-TFET was compared based on calculations of the Dirac-like...The tunneling current in a graphene nanoribbon tunnel field effect transistor(GNR-TFET) has been quantum mechanically modeled. The tunneling current in the GNR-TFET was compared based on calculations of the Dirac-like equation and Schrodinger’s equation. To calculate the electron transmittance, a numerical approach-namely the transfer matrix method(TMM)-was employed and the Launder formula was used to compute the tunneling current. The results suggest that the tunneling currents that were calculated using both equations have similar characteristics for the same parameters, even though they have different values. The tunneling currents that were calculated by applying the Dirac-like equation were lower than those calculated using Schrodinger’s equation.展开更多
Tunneling field effect transistors(TFETs) based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low...Tunneling field effect transistors(TFETs) based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low power devices. Here,we investigate the TFETs based on two different integration types: in-plane and vertical heterostructures composed of two kinds of layered phosphorous(β-P and δ-P) by ab initio quantum transport simulations. NDR effects have been observed in both in-plane and vertical heterostructures, and the effects become significant with the highest peak-to-valley ratio(PVR)when the intrinsic region length is near zero. Compared with the in-plane TFET based on β-P and δ-P, better performance with a higher on/off current ratio of - 10-6 and a steeper subthreshold swing(SS) of - 23 mV/dec is achieved in the vertical TFET. Such differences in the NDR effects, on/off current ratio and SS are attributed to the distinct interaction nature of theβ-P and δ-P layers in the in-plane and vertical heterostructures.展开更多
A Ⅲ-Ⅴ heterojunction tunneling field-effect transistor(TFET) can enhance the on-state current effectively,and GaAsSb/InGaAs heterojunction exhibits better performance with the adjustable band alignment by modulating...A Ⅲ-Ⅴ heterojunction tunneling field-effect transistor(TFET) can enhance the on-state current effectively,and GaAsSb/InGaAs heterojunction exhibits better performance with the adjustable band alignment by modulating the alloy composition.In this paper,the performance of the cylindrical surrounding-gate GaAsSb/InGaAs heterojunction TFET with gate-drain underlap is investigated by numerical simulation.We validate that reducing drain doping concentration and increasing gate-drain underlap could be effective ways to reduce the off-state current and subthreshold swing(SS),while increasing source doping concentration and adjusting the composition of GaAsSbInGaAs can improve the on-state current.In addition,the resonant TFET based on GaAsSb/InGaAs is also studied,and the result shows that the minimum and average of SS reach 11 mV/decade and 20 mV/decade for five decades of drain current,respectively,and is much superior to the conventional TFET.展开更多
The tunnel field-effect transistor(TFET) is a potential candidate for the post-CMOS era.As one of the most important electrical parameters of a device,double gate TFET(DG-TFET) gate threshold voltage was studied.First...The tunnel field-effect transistor(TFET) is a potential candidate for the post-CMOS era.As one of the most important electrical parameters of a device,double gate TFET(DG-TFET) gate threshold voltage was studied.First,a numerical simulation study of transfer characteristic and gate threshold voltage in DG-TFET was reported.Then,a simple analytical model for DG-TFET gate threshold voltage VTG was built by solving quasi-two-dimensional Poisson equation in Si film.The model as a function of the drain voltage,the Si layer thickness,the gate length and the gate dielectric was discussed.It is shown that the proposed model is consistent with the simulation results.This model should be useful for further investigation of performance of circuits containing TFETs.展开更多
A Si/Ge heterojunction line tunnel field-effect transistor (LTFET) with a symmetric heteromaterial gate is proposed. Compared to single-material-gate LTFETs, the heteromaterial gate LTFET shows an off-state leakage ...A Si/Ge heterojunction line tunnel field-effect transistor (LTFET) with a symmetric heteromaterial gate is proposed. Compared to single-material-gate LTFETs, the heteromaterial gate LTFET shows an off-state leakage current that is three orders of magnitude lower, and steeper subthreshold characteristics, without degradation in the on-state current. We reveal that these improvements are due to the induced local potential barrier, which arises from the energy-band profile modulation effect. Based on this novel structure, the impacts of the physical parameters of the gap region between the pocket and the drain, including the work-function mismatch between the pocket gate and the gap gate, the type of dopant, and the doping concentration, on the device performance are investigated. Simulation and theoretical calculation results indicate that the gap gate material and n-type doping level in the gap region should be optimized simultaneously to make this region fully depleted for further suppression of the off-state leakage current.展开更多
A Ge/Si heterojunction L-shaped tunnel field-effect transistor combined with hetero-gate-dielectric (GHL-TFET) is proposed and investigated by TCAD simulation. Current-voltage characteristics, energy-band diagrams, ...A Ge/Si heterojunction L-shaped tunnel field-effect transistor combined with hetero-gate-dielectric (GHL-TFET) is proposed and investigated by TCAD simulation. Current-voltage characteristics, energy-band diagrams, and the distri- bution of the band-to-band tunneling (BTBT) generation rate of GHL-TFET are analyzed. In addition, the effect of the vertical channel width on the ON-current is studied and the thickness of the gate dielectric is optimized for better suppression of ambipolar current. Moreover, analog/RF figure-of-merits of GHL-TFET are also investigated in terms of the cut-off frequency and gain bandwidth production. Simulation results indicate that the ON-current of GHL-TFET is increased by about three orders of magnitude compared with that of the conventional L-shaped TFET. Besides, the introduction of the hetero-gate-dielectric not only suppresses the ambipolar current effectively but also improves the analog/RF performance drastically. It is demonstrated that the maximum cut-off frequency of GHL-TFET is about 160 GHz, which is 20 times higher than that of the conventional L-shaped TFET.展开更多
The tunneling field-effect transistor(TFET) is a potential candidate for the post-CMOS era.In this paper,a threshold voltage model is developed for this new kind of device.First,two-dimensional(2D) models are used...The tunneling field-effect transistor(TFET) is a potential candidate for the post-CMOS era.In this paper,a threshold voltage model is developed for this new kind of device.First,two-dimensional(2D) models are used to describe the distributions of potential and electric field in the channel and two depletion regions.Then based on the physical definition of threshold voltage for the nanoscale TFET,the threshold voltage model is developed.The accuracy of the proposed model is verified by comparing the calculated results with the 2D device simulation data.It has been demonstrated that the effects of varying the device parameters can easily be investigated using the model presented in this paper.This threshold voltage model provides a valuable reference to TFET device design,simulation,and fabrication.展开更多
The tunnel field-effect transistor (TFET) is proposed by using the advantages of dopingless and line-tunneling technology. The line tunneling is created due to the fact that the gate electric field is aligned with the...The tunnel field-effect transistor (TFET) is proposed by using the advantages of dopingless and line-tunneling technology. The line tunneling is created due to the fact that the gate electric field is aligned with the tunneling direction, which dramatically enhances tunneling area and tunneling current. Moreover, the effects of the structure parameters such as the length between top gate and source electrode, the length between top gate and drain electrode, the distance between bottom gate and drain electrode, and the metal position on the on-state current, electric field and energy band are investigated and optimized. In addition, analog/radio-frequency performance and linearity characteristics are studied. All results demonstrate that the proposed device not only enhances the on/of current ratio and reduces the subthreshold swing, but also offers eight times improvement in cut-off frequency and gain band product as compared with the conventional point tunneling dopingless TFET, at the same time;it shows better linearity and small distortions. This proposed device greatly enhances the potential of applications in dopingless TFET.展开更多
By using the linear combination of bulk band (LCBB) method incorporated with the top of the barrier splitting (TBS) model, we present a comprehensive study on the quantum confinement effects and the source-to-drai...By using the linear combination of bulk band (LCBB) method incorporated with the top of the barrier splitting (TBS) model, we present a comprehensive study on the quantum confinement effects and the source-to-drain tunneling in the ultra-scaled double-gate (DG) metal-oxide semiconductor field-effect transistors (MOSFETs). A critical body thickness value of 5 nm is found, below which severe valley splittings among different X valleys for the occupied charge density and the current contributions occur in ultra-thin silicon body structures. It is also found that the tunneling current could be nearly 100% with an ultra-scaled channel length. Different from the previous simulation results, it is found that the source-to-drain tunneling could be effectively suppressed in the ultra-thin body thickness (2.0 nm and below) by the quantum confinement and the tunneling could be suppressed down to below 5% when the channel length approaches 16 nm regardless of the body thickness.展开更多
Dual-metal gate and gate–drain underlap designs are introduced to reduce the ambipolar current of the device based on the C-shaped pocket TFET(CSP-TFET).The effects of gate work function and gate–drain underlap leng...Dual-metal gate and gate–drain underlap designs are introduced to reduce the ambipolar current of the device based on the C-shaped pocket TFET(CSP-TFET).The effects of gate work function and gate–drain underlap length on the DC characteristics and analog/RF performance of CSP-TFET devices,such as the on-state current(I_(on)),ambipolar current(I_(amb)),transconductance(g_(m)),cut-off frequency(f_(T))and gain–bandwidth product(GBP),are analyzed and compared in this work.Also,a combination of both the dual-metal gate and gate–drain underlap designs has been proposed for the C-shaped pocket dual metal underlap TFET(CSP-DMUN-TFET),which contains a C-shaped pocket area that significantly increases the on-state current of the device;this combination design substantially reduces the ambipolar current.The results show that the CSP-DMUN-TFET demonstrates an excellent performance,including high I_(on)(9.03×10^(-4)A/μm),high I_(on)/I_(off)(~10^(11)),low SS_(avg)(~13 mV/dec),and low I_(amb)(2.15×10^(-17)A/μm).The CSP-DMUN-TFET has the capability to fully suppress ambipolar currents while maintaining high on-state currents,making it a potential replacement in the next generation of semiconductor devices.展开更多
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.
文摘The fundamental advantages of carbon-based graphene material,such as its high tunnelling probability,symmetric band structure(linear dependence of the energy band on the wave direction),low effective mass,and characteristics of its 2D atomic layers,are the main focus of this research work.The impact of channel thickness,gate under-lap,asymmetric source/drain doping method,workfunction of gate contact,and High-K material on Graphene-based Tunnel Field Effect Transistor(TFET)is analyzed with 20 nm technology.Physical modelling and electrical characteristic performance have been simulated using the Atlas device simulator of SILVACO TCAD with user-defined material syntax for the newly included graphene material in comparison to silicon carbide(SiC).The simulation results in significant suppression of ambipolar current to voltage characteristics of TFET and modelled device exhibits a significant improvement in subthreshold swing(0.0159 V/decade),the ratio of Ion/Ioff(1000),and threshold voltage(-0.2 V with highly doped p-type source and 0.2 V with highly doped n-type drain)with power supply of 0.5 V,which make it useful for low power digital applications.
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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61176038 and 61474093)the Science and Technology Planning Project of Guangdong Province,China(Grant No.2015A010103002)the Technology Development Program of Shanxi Province,China(Grant No.2016GY075)
文摘In this work, a double-gate-all-around tunneling field-effect transistor is proposed. The performance of the novel device is studied by numerical simulation. The results show that with a thinner body and an additional core gate, the novel device achieves a steeper subthreshold slope, less susceptibility to the short channel effect, higher on-state current, and larger on/off current ratio than the traditional gate-all-around tunneling field-effect transistor. The excellent performance makes the proposed structure more attractive to further dimension scaling.
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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61306116 and 61472322)
文摘A new T-shaped tunnel field-effect transistor(TTFET) with gate dielectric spacer(GDS) structure is proposed in this paper. To further studied the effects of GDS structure on the TTFET, detailed device characteristics such as current-voltage relationships, energy band diagrams, band-to-band tunneling(BTBT) rate and the magnitude of the electric field are investigated by using TCAD simulation. It is found that compared with conventional TTFET and TTFET with gate-drain overlap(GDO) structure, GDS-TTFET not only has the minimum ambipolar current but also can suppress the ambipolar current under a more extensive bias range. Furthermore, the analog/RF performances of GDS-TTFET are also investigated in terms of transconductance, gate-source capacitance, gate-drain capacitance, cutoff frequency, and gain bandwidth production. By inserting a low-κ spacer layer between the gate electrode and the gate dielectric, the GDS structure can effectively reduce parasitic capacitances between the gate and the source/drain, which leads to better performance in term of cutoff frequency and gain bandwidth production. Finally, the thickness of the gate dielectric spacer is optimized for better ambipolar current suppression and improved analog/RF performance.
基金supported by the National Natural Science Foundation of China(Grant Nos.61274096,61204043,61306042,61306045,and 61306132)the Guangdong Natural Science Foundation,China(Grant Nos.S2012010010533 and S2013040016878)+2 种基金the Shenzhen Science&Technology Foundation,China(Grant No.ZDSY20120618161735041)the Fundamental Research Project of the Shenzhen Science&Technology Foundation,China(Grant Nos.JCYJ20120618162600041,JCYJ20120618162526384,JCYJ20130402164725025,and JCYJ20120618162946025)the International Collaboration Project of the Shenzhen Science&Technology Foundation,China(Grant Nos.GJHZ20120618162120759,GJHZ20130417170946221,GJHZ20130417170908049,and GJHZ20120615142829482)
文摘An analytical model of gate-all-around (GAA) silicon nanowire tunneling field effect transistors (NW-TFETs) is developted based on the surface potential solutions in the channel direction and considering the band to band tunneling (BTBT) efficiency. The three-dimensional Poisson equation is solved to obtain the surface potential distributions in the partition regions along the channel direction for the NW-TFET, and a tunneling current model using Kane's expression is developed. The validity of the developed model is shown by the good agreement between the model predictions and the TCAD simulation results.
基金supported by Hibah Penelitian Berbasi Kompetensi 2018 RISTEKDIKTI Republic of Indonesia
文摘The tunneling current in a graphene nanoribbon tunnel field effect transistor(GNR-TFET) has been quantum mechanically modeled. The tunneling current in the GNR-TFET was compared based on calculations of the Dirac-like equation and Schrodinger’s equation. To calculate the electron transmittance, a numerical approach-namely the transfer matrix method(TMM)-was employed and the Launder formula was used to compute the tunneling current. The results suggest that the tunneling currents that were calculated using both equations have similar characteristics for the same parameters, even though they have different values. The tunneling currents that were calculated by applying the Dirac-like equation were lower than those calculated using Schrodinger’s equation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11604019,61574020,and 61376018)the Ministry of Science and Technology of China(Grant No.2016YFA0301300)+1 种基金the Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications),Chinathe Fundamental Research Funds for the Central Universities,China(Grant No.2016RCGD22)
文摘Tunneling field effect transistors(TFETs) based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low power devices. Here,we investigate the TFETs based on two different integration types: in-plane and vertical heterostructures composed of two kinds of layered phosphorous(β-P and δ-P) by ab initio quantum transport simulations. NDR effects have been observed in both in-plane and vertical heterostructures, and the effects become significant with the highest peak-to-valley ratio(PVR)when the intrinsic region length is near zero. Compared with the in-plane TFET based on β-P and δ-P, better performance with a higher on/off current ratio of - 10-6 and a steeper subthreshold swing(SS) of - 23 mV/dec is achieved in the vertical TFET. Such differences in the NDR effects, on/off current ratio and SS are attributed to the distinct interaction nature of theβ-P and δ-P layers in the in-plane and vertical heterostructures.
基金supported by the National Natural Science Foundation of China(Grant Nos.61176038 and 61474093)the Science and Technology Planning Project of Guangdong Province,China(Grant No.2015A010103002)the Technology Development Program of Shaanxi Province,China(Grant No.2016GY-075)
文摘A Ⅲ-Ⅴ heterojunction tunneling field-effect transistor(TFET) can enhance the on-state current effectively,and GaAsSb/InGaAs heterojunction exhibits better performance with the adjustable band alignment by modulating the alloy composition.In this paper,the performance of the cylindrical surrounding-gate GaAsSb/InGaAs heterojunction TFET with gate-drain underlap is investigated by numerical simulation.We validate that reducing drain doping concentration and increasing gate-drain underlap could be effective ways to reduce the off-state current and subthreshold swing(SS),while increasing source doping concentration and adjusting the composition of GaAsSbInGaAs can improve the on-state current.In addition,the resonant TFET based on GaAsSb/InGaAs is also studied,and the result shows that the minimum and average of SS reach 11 mV/decade and 20 mV/decade for five decades of drain current,respectively,and is much superior to the conventional TFET.
基金Project(P140c090303110c0904)supported by NLAIC Research Fund,ChinaProject(JY0300122503)supported by the Research Fund for the Doctoral Program of Higher Education of China+1 种基金Projects(K5051225014,K5051225004)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2010JQ8008)supported by the Natural Science Basic Research Plan in Shaanxi Province of China
文摘The tunnel field-effect transistor(TFET) is a potential candidate for the post-CMOS era.As one of the most important electrical parameters of a device,double gate TFET(DG-TFET) gate threshold voltage was studied.First,a numerical simulation study of transfer characteristic and gate threshold voltage in DG-TFET was reported.Then,a simple analytical model for DG-TFET gate threshold voltage VTG was built by solving quasi-two-dimensional Poisson equation in Si film.The model as a function of the drain voltage,the Si layer thickness,the gate length and the gate dielectric was discussed.It is shown that the proposed model is consistent with the simulation results.This model should be useful for further investigation of performance of circuits containing TFETs.
基金supported by the National Natural Science Foundation of China(Grant No.61306105)the National Science and Technology Major Project of China(Grant No.2011ZX02708-002)+1 种基金the Tsinghua University Initiative Scientific Research Programthe Tsinghua National Laboratory for Information Science and Technology(TNList)Cross-discipline Foundation of China
文摘A Si/Ge heterojunction line tunnel field-effect transistor (LTFET) with a symmetric heteromaterial gate is proposed. Compared to single-material-gate LTFETs, the heteromaterial gate LTFET shows an off-state leakage current that is three orders of magnitude lower, and steeper subthreshold characteristics, without degradation in the on-state current. We reveal that these improvements are due to the induced local potential barrier, which arises from the energy-band profile modulation effect. Based on this novel structure, the impacts of the physical parameters of the gap region between the pocket and the drain, including the work-function mismatch between the pocket gate and the gap gate, the type of dopant, and the doping concentration, on the device performance are investigated. Simulation and theoretical calculation results indicate that the gap gate material and n-type doping level in the gap region should be optimized simultaneously to make this region fully depleted for further suppression of the off-state leakage current.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61574109 and 61204092)
文摘A Ge/Si heterojunction L-shaped tunnel field-effect transistor combined with hetero-gate-dielectric (GHL-TFET) is proposed and investigated by TCAD simulation. Current-voltage characteristics, energy-band diagrams, and the distri- bution of the band-to-band tunneling (BTBT) generation rate of GHL-TFET are analyzed. In addition, the effect of the vertical channel width on the ON-current is studied and the thickness of the gate dielectric is optimized for better suppression of ambipolar current. Moreover, analog/RF figure-of-merits of GHL-TFET are also investigated in terms of the cut-off frequency and gain bandwidth production. Simulation results indicate that the ON-current of GHL-TFET is increased by about three orders of magnitude compared with that of the conventional L-shaped TFET. Besides, the introduction of the hetero-gate-dielectric not only suppresses the ambipolar current effectively but also improves the analog/RF performance drastically. It is demonstrated that the maximum cut-off frequency of GHL-TFET is about 160 GHz, which is 20 times higher than that of the conventional L-shaped TFET.
基金Project supported by the National Ministries and Commissions,China (Grant Nos. 51308040203 and 6139801)the Fundamental Research Funds for the Central Universities,China (Grant Nos. 72105499 and 72104089)the Natural Science Basic Research Plan in Shaanxi Province,China (Grant No. 2010JQ8008)
文摘The tunneling field-effect transistor(TFET) is a potential candidate for the post-CMOS era.In this paper,a threshold voltage model is developed for this new kind of device.First,two-dimensional(2D) models are used to describe the distributions of potential and electric field in the channel and two depletion regions.Then based on the physical definition of threshold voltage for the nanoscale TFET,the threshold voltage model is developed.The accuracy of the proposed model is verified by comparing the calculated results with the 2D device simulation data.It has been demonstrated that the effects of varying the device parameters can easily be investigated using the model presented in this paper.This threshold voltage model provides a valuable reference to TFET device design,simulation,and fabrication.
基金Project supported by the Natural Science Research Key Project of Universities of Anhui Province,China(Grant No.KJ2017A502)the Introduced Talent Project of Anhui Science and Technology University,China(Grant No.DQYJ201603)the Excellent Talents Supported Project of Colleges and Universities,China(Grant No.gxyq2018048)。
文摘The tunnel field-effect transistor (TFET) is proposed by using the advantages of dopingless and line-tunneling technology. The line tunneling is created due to the fact that the gate electric field is aligned with the tunneling direction, which dramatically enhances tunneling area and tunneling current. Moreover, the effects of the structure parameters such as the length between top gate and source electrode, the length between top gate and drain electrode, the distance between bottom gate and drain electrode, and the metal position on the on-state current, electric field and energy band are investigated and optimized. In addition, analog/radio-frequency performance and linearity characteristics are studied. All results demonstrate that the proposed device not only enhances the on/of current ratio and reduces the subthreshold swing, but also offers eight times improvement in cut-off frequency and gain band product as compared with the conventional point tunneling dopingless TFET, at the same time;it shows better linearity and small distortions. This proposed device greatly enhances the potential of applications in dopingless TFET.
基金supported by the National Basic Research Program of China (Grant No.G2009CB929300)the National Natural Science Foundation of China (Grant Nos.60821061 and 60776061)
文摘By using the linear combination of bulk band (LCBB) method incorporated with the top of the barrier splitting (TBS) model, we present a comprehensive study on the quantum confinement effects and the source-to-drain tunneling in the ultra-scaled double-gate (DG) metal-oxide semiconductor field-effect transistors (MOSFETs). A critical body thickness value of 5 nm is found, below which severe valley splittings among different X valleys for the occupied charge density and the current contributions occur in ultra-thin silicon body structures. It is also found that the tunneling current could be nearly 100% with an ultra-scaled channel length. Different from the previous simulation results, it is found that the source-to-drain tunneling could be effectively suppressed in the ultra-thin body thickness (2.0 nm and below) by the quantum confinement and the tunneling could be suppressed down to below 5% when the channel length approaches 16 nm regardless of the body thickness.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52177185 and 62174055)。
文摘Dual-metal gate and gate–drain underlap designs are introduced to reduce the ambipolar current of the device based on the C-shaped pocket TFET(CSP-TFET).The effects of gate work function and gate–drain underlap length on the DC characteristics and analog/RF performance of CSP-TFET devices,such as the on-state current(I_(on)),ambipolar current(I_(amb)),transconductance(g_(m)),cut-off frequency(f_(T))and gain–bandwidth product(GBP),are analyzed and compared in this work.Also,a combination of both the dual-metal gate and gate–drain underlap designs has been proposed for the C-shaped pocket dual metal underlap TFET(CSP-DMUN-TFET),which contains a C-shaped pocket area that significantly increases the on-state current of the device;this combination design substantially reduces the ambipolar current.The results show that the CSP-DMUN-TFET demonstrates an excellent performance,including high I_(on)(9.03×10^(-4)A/μm),high I_(on)/I_(off)(~10^(11)),low SS_(avg)(~13 mV/dec),and low I_(amb)(2.15×10^(-17)A/μm).The CSP-DMUN-TFET has the capability to fully suppress ambipolar currents while maintaining high on-state currents,making it a potential replacement in the next generation of semiconductor devices.