A novel graphene nanoribbon field effect transistor with two different gate insulators

In this paper, a novel structure for a dual-gated graphene nanoribbon field-effect transistor (GNRFET) is offered, which combines the advantages of high and low dielectric constants. In the proposed Two Different Insulators GNRFET (TDI-GNRFET), the gate dielectric at the drain side is a material with low dielectric constant to form smaller capacitances, while in the source side, there is a material with high dielectric constant to improve On-current and reduce the leakage current. Simulations are performed based on self-consistent solutions of the Poisson equation coupled with Non-Equilibrium Green's Function (NEGF) formalism in the ballistic regime. We assume a tight-binding Hamiltonian in the mode space representation. The results demonstrate that TDI-GNRFET has lower Off-current, higher On-current and higher transconductance in comparison with conventional low-K GNRFET. Furthermore, using a top-of-the-barrier two-dimensional circuit model, some important circuit parameters are studied. It is found that TDI-GNRFET has smaller capacitances, lower intrinsic delay time and shorter power delay product (PDP) in comparison with high-K GNRFET. Moreover, mobile charge and average velocity are improved in comparison with low dielectric constant GNRFET. The results show that the TDI-GNRFET can provide Drain Induced Barrier Lowering (DIBL) and Subthreshold Swing near their theoretical limits.     

离子凝胶薄膜栅介石墨烯场效应管

在石墨烯场效应晶体管栅介结构中引入具有良好电容特性或极化特性的材料可改善晶体管性能.本文采用化学气相沉积制备的石墨烯并以PVDF-[EMIM]TF2N离子凝胶薄膜(ion-gel film)作为介质层制备底栅型石墨烯场效应管(graphene-based field effect transistor, GFET),研究其电学特性以及真空环境和温度对GFET性能的影响.结果表明离子凝胶薄膜栅介石墨烯场效应晶体管表现出良好的电学特性,室温空气环境中,与SiO_2栅介GFET相比, ion-gel膜栅介GFET开关比(J_(on)/J_(off))和跨导(g_m)分别提高至6.95和3.68×10~(–2) mS,而狄拉克电压(V_(Dirac))低至1.3 V;真空环境下ion-gel膜栅介GFET狄拉克电压最低可降至0.4 V;随着温度的升高, GFET的跨导最高可提升至6.11×10~(–2) mS.     

A-Z-A型石墨烯场效应晶体管吸附 效应的第一性原理研究

利用第一性原理的计算方法, 研究了A-Z-A型GNR-FET的电子结构和输运性质及其分子吸附效应. 得到了以下结论: 纯净的A-Z-A型GNR-FET具有典型的双极型晶体管特性, 吸附分子的存在会使纳米带能隙变小. 对于吸附H, H₂, H₂O, N₂, NO, NO₂, O₂, CO₂和SO₂分子的情况, A-Z-A型GNR-FET仍然保持着场效应晶体管的基本特征, 但吸附不同类型的分子会使GNR-FET的输运特性发生不同程度的改变; 对于吸附OH分子的情况, 输运特性发生了本质的改变, 完全不具有场效应晶体管的特性. 这些研究结果将有助于石墨烯气体探测器的工程实现, 并对应用于不同环境中GNR-FET的设计具有重要指导意义.     

A novel 10-nm physical gate length double-gate junction field effect transisto

A novel double-gate （DG） junction field effect transistor （JFET） with depletion operation mode is proposed in this paper. Compared with the conventional DG MOSFET, the novel DG JFET can achieve excellent performance with square body design, which relaxes the requirement on silicon film thickness of DG devices. Moreover, due to the structural symmetry, both p-type and n-type devices can be realized on exactly the same structure, which greatly simplifies integration. It can reduce the delay by about 60% in comparison with the conventional DG MOSFETs.     

HfO2基铁电场效应晶体管读写电路的单粒子翻转效应模拟

使用器件-电路仿真方法搭建了氧化铪基铁电场效应晶体管读写电路,研究了单粒子入射铁电场效应晶体管存储单元和外围灵敏放大器敏感节点后读写数据的变化情况,分析了读写数据波动的内在机制.结果表明:高能粒子入射该读写电路中的铁电存储单元漏极时,处于"0"状态的存储单元产生的电子空穴对在器件内部堆积,使得栅极的电场强度和铁电极化增大,而处于"1"状态的存储单元由于源极的电荷注入作用使得输出的瞬态脉冲电压信号有较大波动;高能粒子入射放大器灵敏节点时,产生的收集电流使处于读"0"状态的放大器开启,导致输出数据波动,但是其波动时间仅为0.4 ns,数据没有发生单粒子翻转能正常读出.两束高能粒子时间间隔0.5 ns先后作用铁电存储单元漏极,比单束高能粒子产生更大的输出数据信号波动,读写"1"状态的最终输出电压差变小.     

栅极电势对强光场下石墨烯场效应管中电子隧穿的影响

利用时域有限差分方法研究了强光场下石墨烯场效应管中栅极电势对电子隧穿的影响. 在强光场下由于光学stark效应,石墨烯场效应管的完美手征透射被抑制.这种抑制除了 可以利用光场来调控外,也可以通过改变栅极电势的宽度、势垒高度等来调控. 研究了非方势垒中电子的隧穿. 研究发现,当电势的倾斜较小时,电子隧穿概率变化不大.而当电势倾斜很大时,电子隧穿概率急剧改变.     

A multi-scale model linking microstructure and macro electric behaviors of ferroelectric field effect transistor

A multi-scale model linking microstructure and macro electric properties of ferroelectric field effect transistor (FeFET) is established based on the phase field method and Maxwell's total current law. The simulation results confirm that the channel current of FeFET is modulated by local interface ferroelectric domains which are easily affected by the microstructure. Using the developed transistor model, we investigate the effects of location of dislocation sites on hysteresis behavior of ferroelectric film and electric behavior of FeFET. Interfacial dislocations have strong effects on hysteresis behavior than internal dislocations since the former can induce imprint behavior while the latter only reduce the coercive field. However, due to the c-domains at the interface, the effects of interfacial and internal dislocations on FeFET electrical properties are the exact opposite. The interfacial dislocations just increase the voltage required to toggle the channel while the internal dislocations can induce disappearance of the FeFET memory window.     

Fabrication of a graphene field effect transistor array on microchannels for ethanol sensing

A new approach to the fabrication of back-gated graphene FET (field effect transistor) arrays on microchannels was investigated. Narrow walls fabricated on a substrate with SU-8 (a negative photoresist), with top metal electrodes were pressed onto another silicon/SiO₂ substrate with predeposited graphene pieces such that the electrodes came into contact with graphene pieces and formed the source and drain contact. The SU-8 narrow walls with the top metal layer were fabricated by the conventional lift-off process. The graphene pieces were reduced chemically from graphite oxide. The I_DS changed immediately by more than 17% when the device was exposed to an ethanol atmosphere. The current recovered very well after the ethanol gas was pumped out. The SU-8 microchannels served as gas flow passages that helped the ethanol vapor reach the sensitive region of the device: the graphene channel. This work provides a convenient way of constructing back-gated graphene FETs for sensing applications. This method could potentially be scaled up for mass production.     

Reduced graphene oxide field-effect transistor with indium tin oxide extended gate for proton sensing

In this study, the reduced graphene oxide field-effect transistor (rGO FET) with indium tin oxide (ITO) extended gate electrode was demonstrated as a transducer for proton sensing application. In this structure, the proton sensing area of the ITO extended gate electrode is isolated from the active area of the rGO FET. The proton sensing properties based on the rGO FET transducer were analyzed. The rGO FET device with encapsulation by a tetratetracontane (TTC) layer showed good stability in electrolytic solutions. The device showed an ambipolar behavior with shifts in Dirac point as the pH of the electrolyte is varied. The pH sensitivity based on the Dirac point shift as a sensing parameter was about 43–50 mV/pH for a wide range of pH values from 2 to 12. The ITO extended gate rGO FET may be considered a potential transducer for sensing of H⁺ in electrolytes. Its sensing area can be modified further for various ions sensing applications.     

Electrical properties and memory effect in the field effect transistor based on organic ferroelectric insulator and pentacene

We have fabricated a field effect transistor (FET) based on an organic ferroelectric insulator and molecular conductor, and investigated the electrical properties and memory effects on the PEN-FET. We have observed a drastic change in the drain current at around the coercive electric fieldE _c of the organic ferroelectric insulator in not only a FET (PEN-FET) based on a pentacene (PEN) film but also a FET (IPEN-FET) based on an iodine doped PEN film. The magnitude of the change of the drain current for the IPEN-FET is 200 times larger than that for the PEN-FET. It is expected from these results that the PEN-FET (especially the IPEN-FET) is an improvement in such devices, since it operates at a low gate electric field accompanied by the appearance of the spontaneous polarization in the organic ferroelectric insulator. In addition, we have found that the drain current for the PEN-FET does not return to the initial drain current ofE _G =0 V/cm for more than one week, even if the gate electric field is changed to 0 V/cm from 500 V/cm(>E _c ). From these results, it is suggested that the PEN-FET becomes a memory device.     

铟镓锌氧薄膜晶体管的悬浮栅效应研究

为了避免光照对铟镓锌氧薄膜晶体管(InGaZnO thin film transistors,IGZO TFTs)电学特性的影响,IGZO TFT要增加遮光金属层.本文研究了遮光金属栅极悬浮时,IGZO TFT的输出特性.采用器件数值计算工具TCAD(technology computer-aided design)分析了IGZO层与栅介质层界面处电势分布,证实了悬浮栅(floating gate,FG)IGZO TFT输出曲线的不饱和现象是由悬浮栅与TFT漏端的电容耦合造成.基于等效电容的电压分配方法,提出了悬浮栅IGZO TFT电流的一阶模型.TCAD数值分析及一阶物理模型结果与测试具有较高程度的符合,较完整地解释了悬浮栅IGZO TFT的电学特性.     

堆叠栅介质对称双栅单Halo应变Si金属氧化物半导体场效应管二维模型

提出了一种堆叠栅介质对称双栅单Halo应变Si金属氧化物半导体场效应管(metal-oxide semiconductor field effect transistor,MOSFET)新器件结构.采用分区的抛物线电势近似法和通用边界条件求解二维泊松方程,建立了全耗尽条件下的表面势和阈值电压的解析模型.该结构的应变硅沟道有两个掺杂区域,和常规双栅器件(均匀掺杂沟道)比较,沟道表面势呈阶梯电势分布,能进一步提高载流子迁移率;探讨了漏源电压对短沟道效应的影响;分析得到阈值电压随缓冲层Ge组分的提高而降低,随堆叠栅介质高k层介电常数的增大而增大,随源端应变硅沟道掺杂浓度的升高而增大,并解释了其物理机理.分析结果表明:该新结构器件能够更好地减小阈值电压漂移,抑制短沟道效应,为纳米领域MOSFET器件设计提供了指导.     

Performance analysis of indium phosphide channel based sub-10 nm double gate spin field effect transistor

In this paper, a novel double gate Spin-Field Effect Transistor (DG spin-FET) with indium phosphide (InP) as channel material is evaluated. The proposed spin-FET device is well suited for CMOS technology, as both n and p-type devices can be formed by using parallel and anti-parallel combinations of spin-FET respectively. The proposed device feature size is in sub 10 nm range and therefore is compatible with state of the art integrated circuit technology. The leakage currents have been reduced by employing high-k dielectric (HfO₂). A comparative analysis of the proposed device with the devices reported in the literature confirm that the proposed device has improved on-off ratio and ON current. Besides the device has low transit time and less parasitic capacitances required for high frequency and low power applications respectively.     

Free-standing tetracene single crystal field effect transistor

We have fabricated and studied field effect transistors (FETs) on the optically transparent free-standing organic single crystals of tetracene. These FETs exhibit effective hole channel mobility μ_eff up to 0.15 cm²/Vs and on-off ratios up to 2×10⁷. Using measured values of μ_eff, thermal activation energy, and a simple model, we deduce an intrinsic free carrier mobility in the range of tens of cm²/Vs, similar to that found in pentacene crystals. These values should be considered only as a rough indication of achievable mobilities in samples much purer than those presently studied. The obtained results show the possibility of FET behavior in transparent crystals with low intrinsic carrier density.     

GaN基异质结构效应晶体管功率器件

文章从晶体结构和微电子学理论出发，介绍了GaN基异质结构效应晶体管(HFET)的极化效应，二维电子气(2DEG)的源、产生，极化对2DEG的影响以及提高2DEG浓度的方法；列举了三种典型的电流崩塌效应，介绍了其成因和抑制的方法，并对各种方法进行了比较；阐述了栅极场调控电极对GaN基器件电参数的影响，解释了提高器件击穿电压的原理，并对场调控电极对器件功率特性的影响进行了说明，从而指出利用场调控电极的GaN基HFET将会在微波高功率方面有很大的发展前途．     

Self-connected horizontal silicon nanowire field effect transistor

We propose a technique to fabricate self-connected horizontal Si nanowire (NW) field effect transistors (FETs) by a self-assembly mechanism. We show direct growth of Si NWs between two predefined metallic electrodes along the SiO₂ gate oxide using the vapour–liquid–solid (VLS) growth mode. In our approach, the gold catalyst layer is covered by the contact metal, giving rise to selective and localized catalytic activity and growth of NWs from the gold edges. The diameter of the NWs can be adjusted by the thickness of the catalyst layer. Using such a process, we demonstrate field effect operation on the conductivity of a non-intentionally doped 20 nm diameter Si NW. This technique can be implemented in three dimensions, paving the way to three-dimensionalD integration using vertical stacks of self-connected FETs.     

声子散射下碳纳米管场效应管建模方法研究

声子散射对碳纳米管场效应管(carbon nanotube field effect transistor, CNTFET)的特性有着不可忽略的影响. 传统研究方法基于弹道输运模型来分析发生声子散射时各参数对器件特性的影响, 进而建立CNTFET声子散射模型.为了降低模型复杂度, 提高仿真计算的速度, 本文深入研究了CNTFET的声子散射影响, 对手性、温度和能量三个参数的变化进行了仿真, 分析了参数对器件特性的影响. 采用线性近似拟合的方式建立了一种新的CNTFET声子散射模型.通过分析散射下电流的变化, 验证了该模型的正确性和有效性.与半经典散射模型相比, 该模型由于不需要进行积分计算, 计算过程较为简单, 降低了运算量. 关键词： 碳纳米管场效应管 声子散射模型 线性近似拟合