陷阱电荷对GMLM工作电压的影响

光栅平动式光调制器(GMLM)依靠可动光栅在静电力作用下向下反射镜移动,从而改变光程差,实现光调制.结构中siO2绝缘层在外加电场作用下产生陷阱电荷,对器件的驱动特性产生影响.作者依据高斯定理,建立GMLM存在陷阱电荷情况下的电力学模型,分析了外加电场作用下,GMLM极板电荷的分布,以及外加电压与可动光栅位移的关系;比较了两种情况下(考虑与不考虑绝缘层陷阱电荷影响)工作电压变化情况.设计了实验方案,进行了实验研究.结果表明:由于陷阱电荷产生陷阱电压,使得产生相同位移需要的工作电压增加;充电时间越长,陷阱电荷产生的陷阱电压越大;实验结果与理论分析吻合.     

电场偏置对MOS器件电离辐射效应的影响

研究了外加电场对MOS器件电离辐射效应的影响.采用10 keV X射线对MOS器件在正/反电场偏置条件下进行总剂量辐射,分析了MOS器件辐射前后阈值电压的漂移量.实验结果表明,正偏情况下MOS器件的阈值电压漂移量远大于反偏情况下MOS器件的阈值电压漂移量.基于一维连续性方程,在考虑电子-空穴对的复合/逃逸率、电子及空穴的捕获横截面与外加电场关系的基础上,模拟了辐射诱生栅氧化层内陷阱电荷与辐射总剂量之间的关系,分析了陷阱电荷对MOS器件阈值电压的影响,仿真结果与实验数据吻合良好.     

FLOTOXEEPROM擦写过程中隧道氧化层陷阱俘获电荷的研究

本文首先从理论上分析FLOTOX EEPROM隧道氧化层中陷阱俘获电荷对注入电场和存储管阈值电压的影响,然后给出了在不同擦写条件下FLOTOX EEPROM存储管的阈值电压与擦写周期关系的实验结果,接着分析了在反复擦写过程中陷阱俘获电荷的产生现象.对于低的擦写电压,擦除阈值减少,在隧道氧化层中产生了负的陷阱俘获电荷;对于高的擦写电压,擦除阈值增加,产生了正陷阱俘获电荷.这一结果与SiO₂中电荷的俘获——解俘获动态模型相吻合.     

低能X射线对NMOST的辐照损伤及退火特性

本文研究了NMOS晶体管低能X射线辐照后氧化物陷阱电荷的产生、界面态的性质及空穴陷阱的退火特性等问题。实验结果表明,电离辐照产生的界面态具有施主性和受主性,而氧化物陷阱电荷引起的电压变化在退火过程中,随外加偏置电场极性的不同,表现出可逆性,它对晶体管阈值电压的变化起着决定性的作用。     

栅氧化层及界面电荷对SiC MOSFET阈值电压稳定性的影响

阈值电压不稳定是SiC MOSFET的一个主要问题，而栅氧化层及界面电荷是引起器件阈值电压不稳定的关键因素。结合三角波电压扫描法和中带电压法提取了SiC MOSFET中的栅氧化层陷阱电荷面密度、界面陷阱电荷面密度和可动电荷面密度随应力时间的变化量，总结了三种电荷面密度变化量在不同应力时间下的变化规律，分析了其对器件阈值电压不稳定性的影响，同时推测了长时间偏压作用下SiC MOSFET阈值电压稳定性的劣化机制。测试结果表明，栅氧化层陷阱电荷面密度、界面陷阱电荷面密度和可动电荷面密度在不同偏压温度下随应力时间的变化规律不同，常温应力下器件阈值电压稳定性劣化主要与栅氧化层陷阱电荷有关，而高温下，则主要与界面陷阱电荷有关。     

热载流子应力下超薄栅pMOS器件氧化层陷阱电荷的表征

利用电荷泵技术研究了4nm pMOSFET的热载流子应力下氧化层陷阱电荷的产生行为.首先,对于不同沟道长度下的热载流子退化,通过直接的实验证据,发现空穴陷阱俘获特性与应力时间呈对数关系.然后对不同应力电压、不同沟道长度下氧化层陷阱电荷(包括空穴和电子陷阱俘获)的产生做了进一步的分析.发现对于pMOSFET的热载流子退化,氧化层陷阱电荷产生分两步过程:在较短的应力初期,电子陷阱俘获是主要机制;而随着应力时间增加,空穴陷阱俘获作用逐渐显著,最后主导了氧化层陷阱电荷的产生.     

基于锆钛酸铅的低电压驱动MEMS电场传感器研究

该文提出一种基于锆钛酸铅(PZT)的低电压驱动微机电系统(MEMS)电场传感器。该传感器基于电荷感应原理,其敏感单元由固定电极和可动电极构成。固定电极与可动电极均为感应电极,同时两者又是屏蔽电极。在PZT压电材料的驱动下,可动电极产生垂直于敏感芯片基底的振动并且与固定电极形成交互屏蔽,当存在待测电场时,分别在可动电极和固定电极上产生相位差为180°的感应电流信号。该文进行了传感器的设计和有限元仿真,提出敏感微结构的加工工艺流程,突破了基于PZT压电材料的可动电极MEMS工艺兼容制备技术,完成了敏感芯片制备,对传感器进行了性能测试。该传感器具有工作电压低的突出优点。实验测试表明,在0～50 kV/m电场强度范围内,采用1 V交流驱动电压,电场传感器的灵敏度为0.292 mV/(kV/m),线性度为2.89%。     

热载流子应力下超薄栅p MOS器件氧化层陷阱电荷的表征

利用电荷泵技术研究了 4nmpMOSFET的热载流子应力下氧化层陷阱电荷的产生行为 .首先 ,对于不同沟道长度下的热载流子退化 ,通过直接的实验证据 ,发现空穴陷阱俘获特性与应力时间呈对数关系 .然后对不同应力电压、不同沟道长度下氧化层陷阱电荷 (包括空穴和电子陷阱俘获 )的产生做了进一步的分析 .发现对于 pMOSFET的热载流子退化 ,氧化层陷阱电荷产生分两步过程 :在较短的应力初期 ,电子陷阱俘获是主要机制 ;而随着应力时间增加 ,空穴陷阱俘获作用逐渐显著 ,最后主导了氧化层陷阱电荷的产生.     

氧化锌基TFT稳定性研究进展

总结了氧化锌基TFT稳定性的最新研究进展,分析了栅偏压、栅绝缘层和背沟道影响TFT稳定性,尤其是阈值电压稳定性的主导机制.结果表明,氧化锌基TFT的不稳定性主要取决于陷阱缺陷态对可动载流子的俘获作用,以及新陷阱态的产生.总结了提高氧化锌基TFT稳定性的三种途径:降低栅偏压;提高沟道/栅绝缘层界面质量,降低缺陷态密度;钝化保护背沟道.     

为VLSI器件用热生长氮化物作栅的场效应管工艺

讨论绝缘栅采用热生长的氮化硅厚为70A°的可靠的亚微米沟道1千兆场效应管。这种场效应管显示出十分高的跨导,很好的稳定性,并削除了短沟道效应。 在短沟道的一千兆场效应管理,当采用大的介电常的十分薄的栅绝缘层时,具有下列优点:随着场效应管的绝缘层厚度减薄,跨导将增加微定绝缘层中电荷,可动离子和固定电荷的分布是均匀的,则对开启电压的变化影响很小,因为载流子俘获截面很小,所以绝缘层里的热电子陷入引起开启电压的漂移很小,由于垂直于沟道的电场变大,各种沟道效应减至最小。     

Tenfold Enhancement in Light Emission from Low-Temperature Operational Doped OLEDs by Detrapping Super-Long-Lived Trapped Charges

Although doping organic fluorophores into host matrix is a common way to obtain high-efficiency organic light-emitting diodes (OLEDs), trapped charges are often observed on dopant molecules that are considered to be detrimental to the further enhancement of their photoelectric performances. Surprisingly, trapped charges with a super-long lifetime of >2 h are detected in doped OLEDs operated at 20 K, which has never been discovered previously in the literature. However, the observations demonstrate that the longer lifetimes of these trapped charges are primarily governed by the larger spacing distances between trapped electrons and holes, rather than being solely determined by the well-accepted energy-level depth of trap states. More amazingly, compared with the device driven only by a conventional constant voltage source, a tenfold enhancement in light emission is achieved in low-temperature operational doped OLEDs powered by an alternating positive and negative pulse voltage, because the applied negative pulse voltage can assist these super-long-lived trapped electrons and holes to detrap and then recombine with each other for producing enhanced light-emission. Therefore, this study clarifies the dynamic behaviors of trapped charges and paves the pathway for obtaining high-performance OLEDs working in low-temperature circumstances such as outer-space or aerospace fields.     

一种用于微型光谱仪的光栅光调制器件

提出了一种改进型的可应用于微型光谱仪的光栅光调制器(GLM),器件由可动光栅和底层反射层组成。通过静电驱动由多个GLM组成的线阵单元,下拉栅条至不同高度可实现对不同波长光进行开关选通调制。介绍了该器件的工作原理、结构和工艺流程,利用Coventor软件对器件进行建模。通过有限元分析了器件的机电耦合特性,得到了器件的吸合电压和响应频率,并得出不同结构参数对器件栅条平坦度的影响关系。仿真结果表明:通过增加栅条厚度,改进底电极结构,且采用减薄的折叠型支撑梁,能够有效改善光栅面平坦度,使其较好地实现对光的开关选通。     

一种新颖的宽带可调光纤光栅滤波器

分析了光纤光栅（FBG）调谐的基本原理,进而采用新颖的调谐结构,设计并实现了一种宽带可调谐的FBG滤波器。该滤波器仅用1支FBG制做而成,其波长调谐范围最高可达40nm。实验结果表明,该FBG滤波器的调谐波长与调谐步进位移量之间具有良好的二次曲线关系。     

Vertical coupled-cavity microinterferometer on GaAs withdeformable-membrane top mirror

Fabry-Perot microinterferometer is demonstrated that combines a GaAs-AlAs vertical cavity with a suspended movable membrane. Electrostatic displacement of the gold/silicon nitride membrane allows for broad and continuous wavelength tuning of the cavity resonance formed by the combination of the GaAs cavity and the air gap below the membrane. The device exhibits a 32-nm tuning range around the 920-nm center wavelength for 0-14 V applied bias and FWHM linewidths near 3 nm; this corresponds to membrane deflections of up to 0.27 μm. Such structures provide the foundation for wavelength selective photodiodes, light emitters, and lasers in which the active wavelength is under voltage control     

基于陷落电荷效应的非晶硅TFT的开态电流模型

对非晶硅薄膜晶体管,提出基于陷落电荷和自由电荷分析的新方法。考虑到带隙中指数分布的深能态和带尾态,给出了基于阈值电压的开启区电流模型。定义阈值电压为栅氧/半导体界面处陷落于深能级陷阱态的电荷与陷落于带尾态的电荷相等时所对应的栅压。电流模型中,引入一陷落电荷参数β,此参数建立了电子的带迁移率与有效迁移率之间的关系。最后,将电流模型同时与Pao-Sah模型和实验数据进行比较和验证,结果表现出很好的一致性。     

基于重复测试和栅压应力测试的石墨烯晶体管回滞特性的研究

The current transport characteristic is studied systematically based on a back-gate graphene field effect transistor, under repeated test and gate voltage stress. The interface trapped charges caused by the gate voltage sweep process screens the gate electric field, and results in the neutral point voltage shift between the forth and back sweep direction. In the repeated test process, the neutral point voltage keeps increasing with test times in both forth and back sweeps, which indicates the existence of interface trapped electrons residual and accumulation. In gate voltage stress experiment, the relative neutral point voltage significantly decreases with the reducing of stress voltage, especially in -40 V, which illustrates the driven-out phenomenon of trapped electrons under negative voltage stress.     

Synergistic effects of NPN transistors caused by combined proton irradiations with different energies

There are a large number of protons with different energies from the dozens of keV to hundreds of MeV in space environment, which simultaneously act on the bipolar junction transistors (BJTs), and induce different irradiation effect and damage defects. Moreover, interaction between displacement defects and ionization defects occurs. In the paper, the interaction mechanisms between oxide charge and displacement defects in 3DG112 NPN BJTs caused by the combined 70 keV and 170 keV protons with 5 MeV proton irradiation are studied. Experimental results show the degradation of current gain increases linearly with increasing the irradiation fluence of the 170 keV and 5 MeV protons, but increases nonlinearly for the 70 keV protons, implying that the 170 keV and 5 MeV protons mainly induce displacement damage on the NPN BJTs, while the 70 keV protons cause ionization damage. It can be seen from the Geant4 calculation that 70 keV and 170 keV protons cause almost the same ionization damage on the 3DG112 transistors, while have significant difference in displacement damage ability, which is favorable to analyze the effect of displacement damage in oxide layer of NPN BJTs induced by 170 keV and 70 keV protons on ionization damage caused by the subsequent 5 MeV protons. DLTS analyses show that 5 MeV protons produce mainly displacement defect centers in based-collector junction of 3DG112 transistors, and 170 keV and 70 keV protons only induce almost the same number of the oxide trapped charges. While the combined irradiation can produce the more oxide trapped charges, except displacement defects, showing that displacement damage in oxide layer caused by 170 keV and 70 keV protons can increase the oxide trapped charges during the subsequent 5 MeV exposures. Moreover, the more displacement defects in oxide layer will induce more oxide trapped charges, and give more enhanced synergistic effects. These results will help to assess the reliability of BJTs in the space radiation environment.     

高场应力下FLOTOXMOS管的性能退化研究

利用氧化层动态电流弛豫谱分析方法,测试分析了在周期性电场应力下ＦＬＯＴＯＸＭＯＳ管隧道氧化层中陷阱电荷的特性,为研究陷阱电荷对ＦＬＯＴＯＸ ＥＥＰＲＯＭ 阈值电压的影响提供了实验依据。在＋ １１ Ｖ、－ １１ Ｖ 周期性老化电压下所产生的氧化层陷阱电荷饱和密度分别为－ １．８×１０１１ ｃｍ － ２和－ １．４×１０１１ ｃｍ － ２,平均俘获截面分别为５．８×１０－ ２０ ｃｍ ２ 和７．２×１０－ ２０ ｃｍ ２,有效电荷中心距分别为３．８ ｎｍ 和４．３ ｎｍ ,界面陷阱电荷饱和密度分别为６．５４×１０９ ｃｍ － ２ｅＶ－ １和－ ３．８×１０９ ｃｍ － ２ｅＶ－ １,平均俘获截面分别为１．１２×１０－ １９ ｃｍ ２ 和４．９×１０－ １９ ｃｍ ２。     

Magnetic field release of trapped charges in poly(fluorenylenevinylene)s

We have measured the effect of an applied magnetic field on the current through thin films of two different organic conjugated polymers that have previously shown to exhibit magnetoresistance, poly(9,9-dioctyl-1,4-fluorenylenevinylene) and poly(9,9-dioctyl-2,7-fluorenylenevinylene). The results show that the magnetic field releases trapped charges from inside the material and enhances the current. We have also performed optical absorption experiments on these polymer films under applied voltage and magnetic field. The results show that the magnetic field produces a change in the optical absorption in the low-energy range associated with deep traps and only under conditions when these traps are likely charged. These two results provide a strong case for the release of trapped charges caused by the magnetic field as being the cause of the magnetoresistance in these polymers and possibly in other organic materials where magnetoresistance was recently observed.