低剂量率60Coγ辐线辐照下SOIMOS器件的退化机理

本文通过实验分析了O．8μm工艺H形栅SOIMOS器件在低剂量率下的1射线总剂量效应．实验结果表明,总剂量相同时,低剂量率的辐照效应更严重,关态偏置条件下的阈值电压漂移大于开态,辐照引起NMOS器件发生kink效应时的漏极电压％升高．研究结果表明：界面态对PMOS器件亚阈值斜率和跨导退化的影响作用不同,主要原因是栅极偏置不同使起作用的界面态数量不同．     

绝缘体上硅金属氧化物半导体场效应晶体管中辐射导致的寄生效应研究

基于⁶⁰Co γ射线源研究了总剂量辐射对绝缘体上硅（silicon on insulator,SOI）金属氧化物半导体场效应晶体管器件的影响.通过对比不同尺寸器件的辐射响应,分析了导致辐照后器件性能退化的不同机制.实验表明：器件的性能退化来源于辐射增强的寄生效应;浅沟槽隔离（shallow trench isolation,STI）寄生晶体管的开启导致了关态漏电流随总剂量呈指数增加,直到达到饱和;STI氧化层的陷阱电荷共享导致了窄沟道器件的阈值电压漂移,而短沟道器件的阈值电压漂移则来自于背栅阈值耦合;在同一工艺下,尺寸较小的器件对总剂量效应更敏感.探讨了背栅和体区加负偏压对总剂量效应的影响,SOI器件背栅或体区的负偏压可以在一定程度上抑制辐射增强的寄生效应,从而改善辐照后器件的电学特性.     

深亚微米器件沟道长度对总剂量辐照效应的影响

研究了180 nm 互补金属氧化物半导体技术下的器件沟道长度对总剂量辐照效应的影响. 在其他条件如辐照偏置、器件结构等不变的情况下, 氧化层中的陷阱电荷决定了辐照响应. 浅沟槽隔离氧化层中的陷阱电荷使得寄生的侧壁沟道反型, 从而形成大的关态泄漏电流. 这个电流与沟道长度存在一定的关系, 沟道长度越短, 泄漏电流越大. 首次发现辐照会增强这个电流的沟道长度调制效应, 从而使得器件进一步退化.     

偏置条件对SOINMOS器件总剂量辐照效应的影响

本文研究了0．8μmSOINMOS晶体管，经剂量率为50rad（Si）／s的60Coγ射线辐照之后的总剂量效应，分析了器件在不同辐照条件和测量偏置下的辐照响应特性．研究结果表明：器件辐照时的栅偏置电压越高，辐照后栅氧化层中积累的空穴陷阱电荷越多，引起的漏极泄漏电流越大．对于漏偏置为5V的器件，当栅电压大于阈值电压时，前栅ID-VG特性曲线中的漏极电流因碰撞电离而突然增大，体电极的电流曲线呈现倒立的钟形．     

辐照下背栅偏置对部分耗尽型绝缘层上硅器件背栅效应影响及机理分析

基于部分耗尽型绝缘层上硅（SOI）器件的能带结构,从电荷堆积机理的电场因素入手,为改善辐照条件下背栅Si/SiO₂界面的电场分布,将半导体金属氧化物（MOS）器件和平板电容模型相结合,建立了背栅偏置模型.为验证模型,利用合金烧结法将背栅引出加负偏置,对NMOS和PMOS进行辐照试验,得出:NMOS背栅接负压,可消除背栅效应对器件性能的影响,改善器件的前栅I-V特性;而PMOS背栅接负压,则会使器件的前栅I-V性能恶化.因此,在利用背栅偏置技术改善SOI/NMOS器件性能的同时,也需要考虑背栅偏置对PMOS的影响,折中选取偏置电压.该研究结果为辐照条件下部分耗尽型SOI/MOS器件背栅效应的改善提供了设计加固方案,也为宇航级集成电路设计和制造提供了理论支持.     

总剂量效应致0.13μm部分耗尽绝缘体上硅N型金属氧化物半导体场效应晶体管热载流子增强效应

空间科学的进步对航天用电子器件提出了更高的性能需求, 绝缘体上硅(SOI)技术由此进入空间科学领域, 这使得器件的应用面临深空辐射环境与地面常规可靠性的双重挑战. 进行SOI N型金属氧化物半导体场效应晶体管电离辐射损伤对热载流子可靠性的影响研究, 有助于对SOI器件空间应用的综合可靠性进行评估. 通过预辐照和未辐照、不同沟道宽长比的器件热载流子试验结果对比, 发现总剂量损伤导致热载流子损伤增强效应, 机理分析表明该效应是STI辐射感生电场增强沟道电子空穴碰撞电离率所引起. 与未辐照器件相比, 预辐照器件在热载流子试验中的衬底电流明显增大, 器件的转移特性曲线、输出特性曲线、跨导特性曲线以及关键电学参数V_T, GM_max, ID_SAT退化较多. 本文还对宽沟道器件测试中衬底电流减小以及不连续这一特殊现象进行了讨论.     

金属-氧化物-半导体器件γ辐照温度效应

研究了金属-氧化物-半导体(MOS)器件在γ射线辐照条件下的温度效应.采用加固的CC4007进 行辐照实验,在不同温度、不同偏压,以及不同退火条件下对MOS器件的辐照效应进行了比 较,发现温度对辐照效应的影响主要是决定界面态建立的快慢.高温下辐照的器件,界面态 建立的时间缩短.根据实验结果对器件阈值电压漂移的机理进行了探讨. 关键词： 金属-氧化物-半导体场效应 辐射效应 阈值电压漂移     

总剂量辐照下沟道长度对部分耗尽绝缘体上硅p型场效应晶体管电特性的影响

本文通过实验研究了0.8μm PD(Partially Depleted)SOI(Silicon-On-Insulator)p型Metal-oxidesemiconductor-feld-efect-Transistor(MOSFET)经过剂量率为50 rad(Si)/s的60Coγ射线辐照后的总剂量效应,分析了沟道长度对器件辐照效应的影响.研究结果表明:辐照总剂量相同时,短沟道器件的阈值电压负向漂移量比长沟道器件大,最大跨导退化的更加明显.通过亚阈值分离技术分析得到,氧化物陷阱电荷是引起阈值电压漂移的主要因素.与长沟道器件相比,短沟道器件辐照感生的界面陷阱电荷更多.     

高场应力及栅应力下AlGaN/GaN HEMT器件退化研究

采用不同的高场应力和栅应力对AlGaN/GaN HEMT器件进行直流应力测试,实验发现：应力后器件主要参数如饱和漏电流,跨导峰值和阈值电压等均发生了明显退化,而且这些退化还是可以完全恢复的;高场应力下,器件特性的退化随高场应力偏置电压的增加和应力时间的累积而增大;对于不同的栅应力,相对来说,脉冲栅应力和开态栅应力下器件特性的退化比关态栅应力下的退化大.对不同应力前后器件饱和漏电流,跨导峰值和阈值电压的分析表明,AlGaN势垒层陷阱俘获沟道热电子以及栅极电子在栅漏间电场的作用下填充虚栅中的表面态是这些不同应 关键词： AlGaN/GaN HEMT器件 表面态(虚栅) 势垒层陷阱 应力     

MOS器件辐照过程和辐照后效应模拟

模拟MOS器件脉冲电离辐射响应和长时间恢复效应.假设隧道电子从硅进入氧化层和界面态的建立是辐射效应的恢复机理.在整个退火恢复期,采用卷积模型并考虑了栅偏置压的效应.模拟结果表明:退火过程所加栅偏压的大小以及隧道电子效应与建立的界面态所占比例的不同影响器件的恢复率.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.