A comprehensive review of recent progress on enhancement-modeβ-Ga_(2)O_(3)FETs:Growth,devices and properties

Power electronic devices are of great importance in modern society.After decades of development,Si power devices have approached their material limits with only incremental improvements and large conversion losses.As the demand for electronic components with high efficiency dramatically increasing,new materials are needed for power device fabrication.Betaphase gallium oxide,an ultra-wide bandgap semiconductor,has been considered as a promising candidate,and variousβ-Ga_(2)O_(3)power devices with high breakdown voltages have been demonstrated.However,the realization of enhancement-mode(E-mode)β-Ga_(2)O_(3)field-effect transistors(FETs)is still challenging,which is a critical problem for a myriad of power electronic applications.Recently,researchers have made some progress on E-modeβ-Ga_(2)O_(3)FETs via various methods,and several novel structures have been fabricated.This article gives a review of the material growth,devices and properties of these E-modeβ-Ga_(2)O_(3)FETs.The key challenges and future directions in E-modeβ-Ga_(2)O_(3)FETs are also discussed.

Experimental investigation on the instability for NiO/β-Ga_(2)O_(3) heterojunction-gate FETs under negative bias stress

A NiO/β-Ga_(2)O_(3) heterojunction-gate field effect transistor(HJ-FET)is fabricated and it_(s)instability mechanisms are exper-imentally investigated under different gate stress voltage(V_(G,s))and stress times(t_(s)).Two different degradation mechanisms of the devices under negative bias stress(NBS)are identified.At low V_(G,s)for a short t_(s),NiO bulk traps trapping/de-trapping elec-trons are responsible for decrease/recovery of the leakage current,respectively.At higher V_(G,s)or long t_(s),the device transfer char-acteristic curves and threshold voltage(V_(TH))are almost permanently negatively shifted.This is because the interface dipoles are almost permanently ionized and neutralize the ionized charges in the space charge region(SCR)across the heterojunction inter-face,resulting in a narrowing SCR.This provides an important theoretical guide to study the reliability of NiO/β-Ga_(2)O_(3) hetero-junction devices in power electronic applications.

基于GaN FETs的高频半桥谐振变换器分析与设计

随着Si材料半导体器件性能逐步达到瓶颈,宽禁带半导体器件(GaN、SiC)在诸多方面展现出了很好的性能,如低导通阻抗,小输入、输出电容等,这些特性使得GaN和SiC器件能够应用在更高的开关频率条件,从而提高系统的功率密度。针对基于GaN FETs构成的高频半桥谐振变换器进行设计,分析了高频条件下寄生电感参数对系统驱动电压及漏源极电压的影响,同时分析了高频条件下系统电压电流测量所需注意的事项及影响因素,为高频条件下GaN FETs的应用提供一定的帮助。

Advances in MoS_2-Based Field Effect Transistors(FETs)

This paper reviews the original achievements and advances regarding the field effect transistor(FET) fabricated from one of the most studied transition metal dichalcogenides: two-dimensional Mo S2. Not like graphene, which is highlighted by a gapless Dirac cone band structure, Monolayer Mo S2 is featured with a 1.9 e V gapped direct energy band thus facilitates convenient electronic and/or optoelectronic modulation of its physical properties in FET structure. Indeed,many Mo S2 devices based on FET architecture such as phototransistors, memory devices, and sensors have been studied and extraordinary properties such as excellent mobility, ON/OFF ratio, and sensitivity of these devices have been exhibited. However, further developments in FET device applications depend a lot on if novel physics would be involved in them. In this review, an overview on advances and developments in the Mo S2-based FETs are presented. Engineering of Mo S2-based FETs will be discussed in details for understanding contact physics, formation of gate dielectric, and doping strategies. Also reported are demonstrations of device behaviors such as low-frequency noise and photoresponse in Mo S2-based FETs, which is crucial for developing electronic and optoelectronic devices.

Design Consideration in the Development of Multi-Fin FETs for RF Applications

In this paper, we propose multi-fin FET design techniques targeted for RF applications. Overlap and underlap design configuration in a base FinFET are compared first and then multi-fin device (consisting of transistor unit up to 50) is studied to develop design limitations and to evaluate their effects on the device performance. We have also investigated the impact of the number of fins (up to 50) in multi-fin structure and resulting RF parameters. Our results show that as the number of fin increases, underlap design compromises RF performance and short channel effects. The results provide technical understanding that is necessary to realize new opportunities for RF and analog mixed-signal design with nanoscale FinFETs.

氧等离子处理的二硫化钼场效应晶体管表面掺杂和湿度传感研究

二维半导体过渡金属二硫属化物(transition metal dichalcogenide,TMD)具有独特的电学、光学和力学性能,在数字电路、光伏器件和能量存储等多个领域中具有巨大的应用潜力。通过表面掺杂控制TMD的电学性能为实现灵敏传感提供了有效的方法。本文开展了氧等离子体对二硫化钼(MoS_(2))掺杂特性的研究。首先,测试了MoS_(2)场效应晶体管(field-effect transistor,FET)的输运特性,发现氧等离子体处理对FET具有p型掺杂作用。随后,通过拉曼光谱研究了掺杂机制的成因,并证实了沟道表面类MoO_(3)缺陷的形成。最后,研究了经等离子体处理的晶体管的湿度传感特性,由于氧等离子体处理使得沟道对水分子的吸收中心增加,在潮湿环境下晶体管具有十分灵敏的响应特性,源漏电流值变化了约54%。这项工作不仅提供了一种调控TMD电学性能的简单方法,也展示了低维材料化学传感器的发展潜力。

螺旋断层放疗设备中千伏级X射线信号自动检测方法的探究

本文主要探讨了在螺旋管断层放疗设备中使用非物理连接方式同步X射线平板探测器、球管和高压发生器的可能性,提出了利用平板探测器内置传感器自动检测X射线信号的方法。通过简单的测试验证了平板探测器面板FET关断模式与跳跃式扫描读出模式相结合下X射线自动检测的可实现性。这种方法可以利用X射线信号的上升沿和下降沿判断X射线的发生以及计算曝光的时长。

Modeling of cylindrical surrounding gate MOSFETs including the fringing field effects

A physically based analytical model for surface potential and threshold voltage including the fringing gate capacitances in cylindrical surround gate（CSG） MOSFETs has been developed.Based on this a subthreshold drain current model has also been derived.This model first computes the charge induced in the drain/source region due to the fringing capacitances and considers an effective charge distribution in the cylindrically extended source/drain region for the development of a simple and compact model.The fringing gate capacitances taken into account are outer fringe capacitance,inner fringe capacitance,overlap capacitance,and sidewall capacitance.The model has been verified with the data extracted from 3D TCAD simulations of CSG MOSFETs and was found to be working satisfactorily.

Investigation and statistical modeling of InAs-based double gate tunnel FETs for RF performance enhancement

In this paper,RF performance analysis of In As-based double gate（DG）tunnel field effect transistors（TFETs）is investigated in both qualitative and quantitative fashion.This investigation is carried out by varying the geometrical and doping parameters of TFETs to extract various RF parameters,unity gain cut-off frequency（f_t）,maximum oscillation frequency（f_（max））,intrinsic gain and admittance（Y）parameters.An asymmetric gate oxide is introduced in the gate-drain overlap and compared with that of DG TFETs.Higher ON-current（ION）of about 0.2 mA and less leakage current（IOFF）of 29 f A is achieved for DG TFET with gate-drain overlap.Due to increase in transconductance（g_m）,higher ft and intrinsic gain is attained for DG TFET with gate-drain overlap.Higher f_（max） of 985 GHz is obtained for drain doping of 5×10^（17）cm^（-3） because of the reduced gate-drain capacitance（C_（gd））with DG TFET with gate-drain overlap.In terms of Y-parameters,gate oxide thickness variation offers better performance due to the reduced values of Cgd.A second order numerical polynomial model is generated for all the RF responses as a function of geometrical and doping parameters.The simulation results are compared with this numerical model where the predicted values match with the simulated values.

Line-edge roughness induced single event transient variation in SOI Fin FETs

The impact of process induced variation on the response of SOI Fin FET to heavy ion irradiation is studied through 3-D TCAD simulation for the first time. When Fin FET biased at OFF state configuration（Vgs D0, Vds DVdd/ is struck by a heavy ion, the drain collects ionizing charges under the electric field and a current pulse（single event transient, SET） is consequently formed. The results reveal that with the presence of line-edge roughness（LER）, which is one of the major variation sources in nano-scale Fin FETs, the device-to-device variation in terms of SET is observed. In this study, three types of LER are considered： type A has symmetric fin edges, type B has irrelevant fin edges and type C has parallel fin edges. The results show that type A devices have the largest SET variation while type C devices have the smallest variation. Further, the impact of the two main LER parameters,correlation length and root mean square amplitude, on SET variation is discussed as well. The results indicate that variation may be a concern in radiation effects with the down scaling of feature size.

基于GaN-FET大功率、超低功耗移相器设计

提出了一种基于支节加载GaN-FET的大功率、低插损、超低功耗移相器。该移相器的核心电路由多节高阻抗微带支节线以及支节末端加载的GaN-FET管芯构成。通过对单支节加载GaN-FET移相器电路模型的详细分析,得到了移相器的插损和相移表达式,并将其作为基本单元进行拓展可得到满足所需工作带宽的多支节加载GaN-FET移相器。由于采用了高阻抗微带线支节,该移相器具有大功率处理能力。结合理论分析,对多支节加载GaN-FET移相器进行了设计、加工和测试。测试结果表明,所加工的移相器在9.2~9.8 GHz范围内,通过控制GaN FET的关断实现了30°和60°两种相移状态。同时,移相器功率承受能力大于10 W,插损优于1 dB,控制电流小于6μA。

不同FET方案对子宫内膜结核患者内膜厚度、内膜血流及妊娠结局的影响

目的对比分析自然周期(natural cycle,NC)、激素替代周期(hormone replacement treatment cycle,HRT)与促性腺激素释放激素激动剂-激素替代周期(gonadotropin releasing hormone agonist-hormone replacement treatment cycle,GnRH-a-HRT)3种不同冻融胚胎移植(frozen-thawed embryo transfer,FET)方案对子宫内膜结核患者内膜转化日子宫内膜厚度、内膜血流及FET妊娠结局的影响。方法收集2017年01月01日至2021年01月01日在昆明医科大学第二附属医院生殖医学科行FET助孕的子宫内膜结核患者,根据患者FET内膜准备方案分为NC组、HRT组及GnRH-a-HRT组。比较3组患者子宫内膜厚度、内膜血流及胚胎移植结局。结果对3组患者的妊娠结局进行比较分析后发现,GnRH-a-HRT组患者胚胎种植率、临床妊娠率、继续妊娠率及活产率均高于HRT组与NC组患者,差异均具有统计学意义(P<0.05);HRT组患者胚胎种植率、临床妊娠率、继续妊娠率及活产率均高于NC组患者,差异均具有统计学意义(P<0.05)。对3组患者子宫内膜厚度及内膜血流进行比较分析后发现,GnRH-a-HRT组患者子宫内膜厚度、内膜血流PSV值均高于HRT组与NC组患者,而内膜血流RI值与PI值均低于HRT组与NC组,差异具有统计学意义(P<0.05);HRT组患者子宫内膜厚度及内膜血流PSV值高于NC组,而内膜血流RI值与PI值均低于NC组,差异具有统计学意义(P<0.05)。结论子宫内膜结核患者采用GnRH-a-HRT进行内膜准备后,可改善提高患者内膜转化日内膜厚度及内膜血流PSV值,降低内膜血流RI及PI值,并最终改善子宫内膜结核FET妊娠结局。

基于MoS_(2)场效应晶体管的生物传感器用于无标记检测

场效应晶体管(FET)由于其响应快、灵敏度高、成本低等优点而受到广泛关注。在本文中我们制备了一种基于MoS_(2)纳米片的高灵敏度FET生物传感器,并探讨了其在牛血清白蛋白(BSA)检测中的应用。BSA与MoS_(2)通过疏水相互作用直接结合。该器件对BSA的检测极限为5 nM,并且对5nM至5μM范围内的BSA溶液均有较大的电流响应。通过对器件转移特性曲线和MoS_(2)拉曼光谱的分析,我们将源漏电流(I ds)的增加归因于BSA对MoS_(2)的n型掺杂。此外,MoS_(2) FETs可以扩展为一个通用的生物传感器平台,用于各种生物分子的灵敏检测,并有望应用于高度集成和多路复用的FET传感器结构。

Effect of temperature on heavy ion-induced single event transient on 16-nm FinFET inverter chains

The variations of single event transient(SET)pulse width of high-LET heavy ion irradiation in 16-nm-thick bulk silicon fin field-effect transistor(Fin FET)inverter chains with different driven strengths are measured at different temperatures.Three-dimensional(3D)technology computer-aided design simulations are carried out to study the SET pulse width and saturation current varying with temperature.Experimental and simulation results indicate that the increase in temperature will enhance the parasitic bipolar effect of bulk Fin FET technology,resulting in the increase of SET pulse width.On the other hand,the increase of inverter driven strength will change the layout topology,which has a complex influence on the SET temperature effects of Fin FET inverter chains.The experimental and simulation results show that the device with the strongest driven strength has the least dependence on temperature.

Innovative Teaching Approach Based on Finite Element Technique in Material Mechanics for Vocational Education

This paper proposed an innovative teaching approach based on finite element technique(FET)to improve the understanding of material mechanics.A teaching experiment was conducted using pure bending deformation of a beam as an example,and the deformation and stress distribution of the beam were analyzed using FET.The results showed that using color stress nephograms and color U nephograms can improve students’learning outcomes in mechanics classroom.The high levels of satisfaction and interest in incorporating new techniques into the classroom suggest that there is a need to explore and develop innovative teaching methods in mechanics and related fields.This approach may inspire educators to develop more effective ways of teaching material mechanics,and our research can contribute to the advancement of mechanics education.

中国科学院微电子所在新型纳米环栅CMOS工艺与器件技术方面取得重要进展

近日,中国科学院微电子所先导中心殷华湘研究员团队基于主流GAA晶体管的制造工艺,在体硅衬底上通过调整SiGe/Si叠层外延中底部SiGe层的Ge含量,并在后栅沟道中采用纳米级高选择比SiGe层刻蚀技术,首次设计并制备出沟道结构类似鱼骨状的GAA器件(FishboneFET)。

GaAs FET/pHEMT器件小信号模型电路的确定

提出了一种精确、高效的FET/pHEMT器件模型参数提取的改进方法。首先利用FET器件漏端零偏置的简化模型,测出寄生元件值,再利用正常配置时FET/pHEMT器件网络S参数,使用“剥离”技术将寄生部分全部剔除。最后利用网络导纳参数的表达式,确定了本征电路元件参数。采用了该方法的提取过程物理意义清晰,优化处理容易。对NEC器件的测试结果显示,该改进方法效率高,测试精度小于3%。

GaAs MESFET可靠性及快速评价新方法的研究

提出了一种快速评价GaAsFET可靠性寿命的新方法 .利用GaAsFET失效敏感参数的温度特性和在一定电应力下的退化特性 ,及温度斜坡法在线快速提取器件失效敏感参数的退化量与温度的关系 ,从而进一步求出器件的失效激活能等相关的可靠性物理参数 .

西峰剖面午城黄土古风化强度变化与早更新世季风环境演化

游离铁(FeD)/全铁(FeT)比值被土壤学界用来反映土壤化学风化强度,并已在风尘堆积的古环境研究中得到较好应用。然而,迄今对第四纪黄土古风化强度的研究多集中于中更新世以来的序列,只有少数剖面的分析包含午城黄土。文章基于西峰剖面661个样品的FeD和FeT分析,建立了该剖面午城黄土的古风化强度序列,并与剖面原有1·2Ma以来的序列进行对比。结果表明,早更新世古土壤的风化强度与后期相比总体较低,而黄土层的风化强度总体偏高,反映了较小的冰期-间冰期反差;古风化强度的波动总体上与深海氧同位素有较好的一致性,体现了全球冰量变化对我国北方季风环境的控制。2·6～1·6Ma期间,古土壤的平均风化强度在整个第四纪最低,指示了较弱的夏季风环境效应。从约1·6Ma开始到1·2Ma,古土壤和黄土层的风化强度均增加,并开始有较显著的约100ka周期。这些特征在深海氧同位素记录中没有表现,而与热带地区一些环境特征相吻合,从而指示了低纬过程对我国北方早更新世季风环境的显著影响。

卵裂球的完整性和生长与否对冻融胚胎移植妊娠结局的影响

目的:探讨冻融胚胎移植(FET)周期卵裂球的完整性和生长与否对妊娠结局的影响。方法:375例FET周期,其中解冻当天移植周期242例,提前解冻周期133例,根据复苏后移植卵裂球的完整性分为3组:均完整(A组,n=235)、均有破损(B组,n=21)、完整与破损混合(C组,n=119);提前解冻者根据卵裂球的生长与否分为均有生长74例(Ⅰ组)、部分有生长45例(Ⅱ组)和均无生长14例(Ⅲ组)3组。结果:375例FET周期共解冻胚胎1284个,复苏率为61.2%,每移植周期临床妊娠率30.1%,种植率18.3%;A组的继续妊娠率和种植率分别为27.7%和20.5%,明显高于B组的9.5%和8.3%(P<0.05),C组为22.7%和15.1%,低于A组,但差异无统计学意义(P>0.05)。随着移植胚胎中含完整存活胚胎数的增加(0个、1个、2个、3个),继续妊娠率呈增加趋势(9.5%、17.6%、22.3%和38.2%),移植胚胎中含3个完整胚胎的继续妊娠率明显高于含0、1个完整胚胎者(P<0.05);提前解冻的Ⅰ组继续妊娠率(37.8%)和种植率(26.1%)最高,Ⅲ组最低(7.1%和8.3%),Ⅱ组为24.4%和14.1%,组间差异均有统计学意义(P<0.05)。结论:卵裂球的完整性是影响冻融胚胎种植率的重要因素,移植前提早解冻观察复苏后胚胎有无进一步生长,有助于评价冻融胚胎的发育潜能。