Ge/SiGe异质结构肖特基源漏MOSFET

制备了氧化铪(HfO2)高k介质栅Si基Ge/SiGe异质结构肖特基源漏场效应晶体管(SB-MOSFET)器件,研究了n型掺杂Si0.16Ge0.84层对器件特性的影响,分析了n型掺杂SiGe层降低器件关态电流的机理。使用UHV CVD沉积系统,采用低温Ge缓冲层技术进行了材料生长,首先在Si衬底上外延Ge缓冲层,随后生长32 nm Si0.16Ge0.84和12 nm Ge,并生长1 nm Si作为钝化层。使用原子力显微镜和X射线衍射对材料形貌和晶体质量进行表征,在源漏区沉积Ni薄膜并退火形成NiGe/Ge肖特基结,制备的p型沟道肖特基源漏MOSFET,其未掺杂Ge/SiGe异质结构MOSFET器件的空穴有效迁移率比相同工艺条件制备的硅器件的高1.5倍,比传统硅器件空穴有效迁移率提高了80%,掺杂器件的空穴有效迁移率与传统硅器件的相当。     

在薄硅外延片上制备高频肖特基势垒二极管

采用超高真空化学气相沉积技术,在n型重掺Si衬底上生长了轻掺的薄硅外延层,利用扩展电阻和原子力显微分析对外延层进行了检验.结果表明,重掺Si衬底与薄硅外延层之间的界面过渡区陡峭,外延层厚度在亚微米级,掺杂浓度为10 1 7cm- 3.在此外延片上制备了高频肖特基二极管的原型器件,与传统的硅基肖特基二极管相比截止频率有了大幅提高     

Si1-xGex:C缓冲层上Ge薄膜的CVD外延生长

用化学气相沉积方法,在Si(100)衬底上生长Si1xGex:C合金作为缓冲层,继而外延生长了Ge晶体薄膜.根据AES测量结果可以认为,缓冲层包括由衬底中的Si原子扩散至表面与GeH4,C2H4反应而生成的Si1-xGex:C外延层和由Si1-xGex:C外延层中Ge原子向衬底方向扩散而形成的Si1-xGex层.缓冲层上外延所得Ge晶体薄膜晶体取向较为单一,其厚度超过在Si上直接外延Ge薄膜的临界厚度,且薄膜中的电子迁移率与同等掺杂浓度(1.0×1019 cm-3)的体Ge材料的电子迁移率相当.     

在SixGe1-xC0.02衬底上直接生长石墨烯

基于锗衬底在石墨烯生长方面的自限制生长和表面催化特性,以甲烷(CH4)和氢气(H2)为前驱体,采用化学气相沉积(CVD)法分别在锗硅碳(SixGe1-xC0.02)(x=0.15,0.25,0.73)衬底和外延锗上直接生长石墨烯.研究了不同Si组分、H2与CH4体积流量比和生长温度对石墨烯质量的影响.利用光学显微镜(OM)、扫描电子显微镜(SEM)以及喇曼光谱对衬底和生长的石墨烯进行了表征分析.喇曼光谱结果表明,Si0.5Ge0.85C0.02衬底在750℃下可以生长出石墨烯,调节气体H2与CH4的体积流量比为50∶0.5时,生长出的石墨烯是双层的.OM和SEM结果表明,锗硅碳衬底具有比锗更好的热稳定性,高温下不会升华.     

Si1-xGex:C缓冲层上Ge薄膜的CVD外延生长

用化学气相沉积方法,在Si(100)衬底上生长Si1xGex:C合金作为缓冲层,继而外延生长了Ge晶体薄膜.根据AES测量结果可以认为,缓冲层包括由衬底中的Si原子扩散至表面与GeH4,C2H4反应而生成的Si1-xGex:C外延层和由Si1-xGex:C外延层中Ge原子向衬底方向扩散而形成的Si1-xGex层.缓冲层上外延所得Ge晶体薄膜晶体取向较为单一,其厚度超过在Si上直接外延Ge薄膜的临界厚度,且薄膜中的电子迁移率与同等掺杂浓度(1.0×1019 cm-3)的体Ge材料的电子迁移率相当.     

NH3等离子体钝化对Al2O3/SiGe界面的影响

研究了不同条件的非原位NH_3等离子体钝化对Al_2O_3/SiGe/Si结构界面组分的影响。在p型Si(100)衬底上外延一层30 nm厚的应变Si_0.7Ge_0.3,采用双层Al_2O_3结构,第一层1 nm厚的Al_2O_3薄膜为保护层,之后使用非原位NH_3等离子体分别在300和400℃下对Al_2O_3/SiGe界面进行不同时间和功率的钝化处理,形成硅氮化物(SiN_xO_y)和锗氮化物(GeN_xO_y)的界面层。通过X射线光电子能谱(XPS)分析表面的物质成分,结果表明NH_3等离子体钝化在界面处存在选择性氮化,更倾向于与Si结合从而抑制Ge形成高价态,这种选择性会随着时间的增加、功率的增高和温度的升高变得更加明显。     

在薄硅外延片上制备高频肖特基势垒二极管

采用超高真空化学气相沉积技术,在n型重掺Si衬底上生长了轻掺的薄硅外延层,利用扩展电阻和原子力显微分析对外延层进行了检验.结果表明,重掺Si衬底与薄硅外延层之间的界面过渡区陡峭,外延层厚度在亚微米级,掺杂浓度为1017cm-3.在此外延片上制备了高频肖特基二极管的原型器件,与传统的硅基肖特基二极管相比截止频率有了大幅提高.     

低温注入硅片中的锗在快速热处理后的再分布

大剂量(4×1016cm-2)的Ge离子在77K低温下被注入于(100)硅片中,并结合随后的1080℃快速热处理(RTP)以形成Si/SiGe异质结构.用卢瑟福背散射技术和二次离子质谱技术研究注锗硅片退火前后Ge的分布.结果表明,快速热处理退火不仅能使注锗硅片发生固相外延生长,表层形成合金层,而且导致Ge向表面的质量运输.最终出现平台式的Ge分布形态.快速热处理后Ge这种再分布被认为有利于提高HBT的增益和获得表面应变沟道     

Si1-xGex∶C缓冲层上Ge薄膜的CVD外延生长

用化学气相沉积方法，在Si(100)衬底上生长Si1-xGex∶C合金作为缓冲层，继而外延生长了Ge晶体薄膜. 根据AES测量结果可以认为，缓冲层包括由衬底中的Si原子扩散至表面与GeH4, C2H4反应而生成的Si1-xGex∶C外延层和由Si1-xGex∶C外延层中Ge原子向衬底方向扩散而形成的Si1-xGex层. 缓冲层上外延所得Ge晶体薄膜晶体取向较为单一，其厚度超过在Si上直接外延Ge薄膜的临界厚度，且薄膜中的电子迁移率与同等掺杂浓度(1.0E19cm-3)的体Ge材料的电子迁移率相当.     

新型紧凑硅基电光调制器研究

设计了一种应用于微波光子学的硅基锗硅电吸收调制器。调制器基于Franz-Keldysh电吸收调制效应,通过硅基锗硅的选择外延形貌控制实现了调制器有源区单模传输和较大的限制因子。形貌控制同时可形成三维渐变耦合结构,减小了硅脊形波导与Ge Si有源区波导的输入输出损耗。为了优化电学结构,调制器采用了硅和锗硅并联。设计表明,对于70μm长有源区,调制器消光比为8.4 d B,3 d B带宽50 GHz,同时具有较低的插损3.6 d B。     

AFM observation of OMVPE grown ErP on InP (0 0 1), (1 1 1)A and (1 1 1)B substrates

ErP has been grown on InP (0 0 1), (1 1 1)A and (1 1 1)B substrates by low-pressure organometallic vapor-phase epitaxy. The morphological change with growth temperature has been explored by atomic force microscope. On all the substrates, ErP is grown in island structure. Height and area size of the ErP islands on (1 1 1)A substrate exhibit an obvious dependence on growth temperature. ErP islands grown at 540°C, that is the suitable temperature for ErP formation, gather to step edges to make wires.     

Reliability of a consecutivek-out-of-r-from-n:F system

The reliability of the consecutive k-out-of-r-from-n:F system is studied. For k=2 an explicit solution is given for n components in line or in cycle in the i.i.d. case. For k⩾3 sharp lower and upper bounds are given for the reliability of the system and demonstrated for different values of n, k, r, p. These bounds are exact for r=n, n-1, n-2, n-3, and for these values the exact analytic solution is also given     

Distribution of the lifetime of consecutive k-within-m-out-of-n:F systems

The distribution of the lifetime (MTTF) of any consecutive k -within-m-out-of-n:F system, with independent exponentially distributed component lifetimes, is shown to be a convex combination of the distributions (MTTFs) of several convolutions of independent random variables, where each convolution represents a distinct path in the evolution of the system's history, and where in each convolution all but the last random variable is exponential. The last random variable in each convolution is either a zero lifetime or the lifetime of several disjoint consecutive k_i within m_i-out-of-n:F systems in series with each k_i<k, each m_i<m, and each n_i<n. This enables the calculations to proceed recursively. Calculations are facilitated by the symmetric nature of the convex combination     

Bounds for reliability of consecutivek-within-m-out-of-n:F systems

Upper and lower bounds for the reliability of a (linear or circular) consecutive k-within-m-out-of-n:F system with unequal component-failure probabilities are provided. Numerical calculations indicate that, for systems with components of good enough reliability, these bounds quite adequately estimate system reliability. The estimate is easy to calculate, having computational complexity O(m²×n). For identically distributed components, a Weibull limit theorem for system time-to-failure is proved     

Analysis of coplanar E-H planeT-junction using dissimilar rectangular waveguides

An analysis of a T-junction that differs from conventional H -plane T-junctions in that the T arm is rotated by 90° and coupling takes place through an inclined slot is presented. Since use of standard X-band waveguides results in such a T-junction operating above 11.7 GHz, nonstandard waveguide dimensions have been considered to bring down the operating frequency to 9.375 GHz. The effect of a change of the broad dimension of the primary feed waveguide on the resonant conductance is evaluated. The variations of resonant length with the angle of inclination of the slot, and coupling with frequency, are presented     

A generalization of consecutive-k-out-of-n:Fsystems

A linear (m, n)-lattice system consists of m ·n elements arranged like the elements of a (m ,n)-matrix, i.e. each of the m rows includes m elements, and each of the n columns includes m elements. A circular (m,n)-lattice system consists of m circles (centered at the same point) and n rays. The intersections of the circle and the rays represent the elements, i.e. each of the circles includes n elements and each of the rays has m elements. A (linear or circular) (m, n)-lattice system is a (linear or circular) connected-X-out-of-(m,n):F lattice system if it fails whenever at least one subset of connected failed components occurs which includes failed components connected in the meaning of connected-X. The paper presents some practical examples and the reliability formulas of simple systems using results of consecutive-k-out-of-n:F systems     

Reliability of a k-out-of-n warm-standby system

A general closed-form equation is developed for system reliability of a k-out-of-n warm-standby system (dormant failures). The equation reduces to the hot and cold standby cases under the appropriate restrictions     

Input Impedance Analysis of 1:1 Balun

The 1:1 balun constructed of a bifilar delay line and an inverse 1:1 transformer is analyzed for its input characteristics. As a main result of the analyses, the following results were obtained about the balun in this paper. 1) Resonance occurs when the line length is equal to n (any positive integer) times half of a wavelength of the unbalanced transmission mode. 2) The lower cutoff frequency is determined by electromagnetic coupling coefficient "k/sub m/" when L/sub sigma/ and /spl iota/ are constant. 3) The upper cutoff frequency is also given by a combination of k/sub m/ and k/sub e/, etc. 4) Shortening of the distance between the balun and the ground makes the resonant frequency lower when the balun has a magnetic core or when the electrostatic coupling coefficient "k/sub e/" becomes smaller and k/sub m/ is kept constant. /spl omega//sub OI/ becomes lower. 5) In order to realize a wide-band balun, /spl beta//sub b/ / /spl beta//sub u/ shouId be larger and and /spl beta//sub b/ / /spl omega/ should be kept constant.     

A technique for real-time measurement of Nth-orderderivativesdNV/dIN

A technique for the measurement of device derivatives d ^NV/dI^N of arbitrary order N described. Measurement is accomplished by injecting a test current composed of the sum of N square waves into the rest device, and then multiplying the corresponding voltage change by the product of those same square waves, followed by low-pass filtering. The algorithm is implemented in real time using a mixture of analog and digital circuitry, and its application to semiconductor laser control in high-speed optical communications is described     

Electrochemical C-V profiling of heterojunctiondevice structures

Electrochemical capacitance-voltage profiles of multiple (In,Al) GaAs heterostructures have been measured and compared with the results of a numerical calculation of the apparent charge density based on a one-dimensional Poisson solver. The calculation, using layer thicknesses, dopings, and heterojunction band discontinuities obtained from MBE growth calibrations, is in overall agreement with the measured data. The largest discrepancy occurs between the expected and measured heterojunction band discontinuity. This difference is consistent with an electrolyte/semiconductor interface which is not planar on a scale comparable to the layer thickness