SiGe/Ge/SiGe异质结构中自旋极化输运特性的模拟

利用蒙特卡罗方法对SiGe/Ge/SiGe异质结构的自旋极化输运特性进行了模拟研究.在Ge沟道调制掺杂异质结构形成的二维空穴气中,空穴的自旋进动主要受Rashba自旋轨道相互作用控制.在77～300K的温度范围内,对自旋散射长度、自旋极化率等自旋极化输运特性进行了研究.模拟结果显示,低温和窄宽度沟道有利于减小散射对自旋极化输运的影响,避免自旋极化率衰减,增大自旋散射长度.栅控的漏端电流自旋相关效应使器件跨导增大,并产生负跨导效应.     

SiGe/Ge/SiGe异质结构中自旋极化输运特性的模拟

利用蒙特卡罗方法对SiGe/Ge/SiGe异质结构的自旋极化输运特性进行了模拟研究．在Ge沟道调制掺杂异质结构形成的二维空穴气中,空穴的自旋进动主要受Rashba自旋轨道相互作用控制．在77～300K的温度范围内,对自旋散射长度、自旋极化率等自旋极化输运特性进行了研究．模拟结果显示,低温和窄宽度沟道有利于减小散射对自旋极化输运的影响,避免自旋极化率衰减,增大自旋散射长度．栅控的漏端电流自旋相关效应使器件跨导增大,并产生负跨导效应．     

掺硼金刚石薄膜热敏电阻器性能

用微波等离子体ＣＶＤ方法制作了掺硼金刚石薄膜热敏电阻器。该器件的结构由Ｓｉ３Ｎ４基底和２μｍ厚的掺硼金刚石薄膜组成，并采用了经退火处理的钛／金双金属层制作欧姆接触，结果在室温到６００℃范围内获得了欧姆接触，温度响应以及电阻温度系数优良的热敏电阻器。     

SiGe microsystems: world's first merchant SiGe epiwafer supplier

Merchant epiwafer companies are a classic example of spotting an unfulfilled need and then setting about satisfying it. Such companies are peculiar to III-Vs but as far as I am aware have no precedent in mainstream silicon. However, a new Canadian company called SiGe Microsystems looks set to change that. As the name suggests, this start-up is offering custom SiGe epiwafers and it is growing them on the revolutionary Leybold UHV-CVD system which was initially developed for IBM. I spoke to one of the founding members of the company, Derek Houghton, someone well-known for his contributions to both III-Vs and Si with some unique perspectives on the future of SiGe and GaAs.     

B掺ZnO薄膜的制备及其光学性能研究

利用溶胶-凝胶法(sol-gel)在玻璃和硅衬底上生长了B掺杂量分别为0 at％、0.5at％、1.0 at％、2.0 at％、3.0 at％、4.0 at％的ZnO薄膜.采用X射线衍射仪(X-ray diffraction,XRD)、扫描电子显微镜(scanning electron microscope,SEM)、紫外-可见(ultraviolet-visible,UV-Vis)分光光度计等测试手段对薄膜的结构、形貌和光学性能进行了表征.结果 表明:所制备的样品在2θ=34.4°左右出现了ZnO晶体的(002)衍射峰,说明制得的样品具有六方纤锌矿结构.并且(002)衍射峰的半高宽先变小后变大,这说明衍射峰的强度是先加强后减弱,证明其晶粒尺寸是先增大后减小.当B掺杂量为3.0 at％时,样品沿(002)方向择优取向生长最为明显,薄膜上的晶粒生长均匀、致密.B掺氧化锌(BZO)薄膜在可见光区的透过率随B3+的掺杂量的增加先增加后减小,并出现轻微蓝移的现象.当掺入B3+的量为3.0 at％时,薄膜结晶质量最好,表面最为均匀、致密,透过率达到90％.     

FCVD制作重掺硼光纤预制件

使用改进的化学气相沉积（MCVD）工艺制作光纤预制件已经几十年了,使用的热源是氢氧焰,电磁感应石墨加热FCVD是近年来出现的一种新的加热方式,如只从理论上分析,FCVD具有降低光纤中的氢杂质,易于制作大直径的芯棒等特点,但我们的试验结果表明,其致命的缺点是加热速度反应过慢,和反应管内堆积的疏松团聚颗粒易于挥发,造成光纤预制件锥度过大,同时局部出现不容易玻璃化的现象,造成成品率明显低。     

Self-heating in multi-emitter SiGe HBTs

High power bipolar transistors often have multiple emitters, to achieve high currents, and efficient use of the whole emitter area. The emitters experience high current densities and are self-heated above the ambient temperature, leading to concerns about thermal run-away and damage to the device. Here we use a multi-emitter SiGe HBT, with multiple emitter contacts, to examine the temperature distribution in the emitters in such devices. We have measured the temperature increase in different emitters by biasing one emitter at a time and using the other base–emitter junctions as thermometers. We show that use of a selectively implanted collector does not alter the temperature increase or thermal coupling between the emitters.     

Anodic passivation of SiGe

We have investigated the oxide composition and the electronic behavior of the interface of anodically and thermally oxidized SiGe single crystals and epitaxial layers. X-ray photoelectron spectroscopies show the existence of SiO₂, GeO₂ and possibly mixed oxide compounds such as SiOGe only in the anodic oxide, whereas the thermally grown oxide layers on SiGe samples consist of pure SiO₂. In addition, the Ge enrichment at the interface and relaxation phenomena of the strained SiGe lattice of epitaxial layers, which occurs during thermal treatments, are completely reduced using the anodic treatment. Further, the defect concentration at the interface is reduced after the anodic oxidation as obtained from capacitance–voltage and photoluminescence measurements.     

B掺杂ZnO纳米薄膜的结构和光学特性研究

采用脉冲磁控溅射法制备了B掺杂ZnO(ZnO:B)纳米薄膜,并用X射线衍射(XRD)、扫描电子显微镜(SEM)和紫外-可见-近红外分光光度计分别研究了薄膜的结构和光学特性。结果表明:ZnO:B为多晶纳米薄膜,具有六方钎锌矿结构,且薄膜沿着c轴取向择优生长;在可见光和近红外光谱区的透光性能良好,其中在可见光区的平均透光率大于84%,而在近红外区的透光率随着波长增加而逐渐降低至45%。运用逐点无约束最优化法分析计算了薄膜的光学常数,在可见光区,ZnO:B纳米薄膜的光学常数随波长的变化很小且数值基本恒定,折射率约为2.0,而在紫外区,光学常数随波长的变化显著。     

Germanium-Rich SiGe Nanowires Formed Through Oxidation of Patterned SiGe FINs on Insulator

In this study, the authors report on the fabrication of Ge-rich SiGe nanowires (SGNWs) by oxidation of SiGe fins on insulator. Nanowires of different shapes and size are obtained by varying the initial fin shape, Ge content, oxidation process temperature, and oxidation time. Transmission electron microscopy observations revealed nanowires with rectangular, square, elliptical, circular, octagonal, and hexagonal cross-sections, with different Ge content. The elliptical, octagonal, and hexagonal facets are unique shapes formed with low-index faces belonging to (110) groups. These possess very high Ge content up to 95%, and were obtained in the samples oxidized from 850°C to 875°C. In␣addition, the in-plane strain in the fabricated SGNWs is evaluated using micro-Raman spectroscopy. The possible mechanism behind the formation and transformation of different nanowire shapes is discussed.     

Surface treatment effects on atomic diffusion in Si explained without self interstitials

Many recent discussions of surface treatment effects on atomic diffusion in Si have explained these largely in terms of effects attributed to Si self interstitials. However, we have shown by our straight forward Monte Carlo (VIDSIM) simulation of diffusion of Au into Si according to the “kick-out” mechanism of Seeger that this mechanism is in fact completely incapable of explaining the two-sided, “U shaped” profile of substitutional Au which results from a one sided in-diffusion of Au. We have shown that if Auinterstitials can displace Si at any appreciable rate, then the Au substitutional profile must decrease monotonically from source side to far side. We noted that this is strong evidence that Si self interstitials play no role in thermal processes in Si. Here we show that the surface treatment effects often attributed to Si self interstitials can be naturally explained without them. Supported in part by U.S. AFOSR-89-0309.     

165-GHz Transceiver in SiGe Technology

Two D-band transceivers, with and without amplifiers and static frequency divider, transmitting simultaneously in the 80-GHz and 160-GHz bands, are fabricated in SiGe HBT technology. The transceivers feature an 80-GHz quadrature Colpitts oscillator with differential outputs at 160 GHz, a double-balanced Gilbert-cell mixer, 170-GHz amplifiers and broadband 70-GHz to 180-GHz vertically stacked transformers for single-ended to differential conversion. For the transceiver with amplifiers and static frequency divider, which marks the highest level of integration above 100 GHz in silicon, the peak differential down-conversion gain is -3 dB for RF inputs at 165 GHz. The single-ended, 165-GHz transmitter output generates -3.5 dBm, while the 82.5-GHz differential output power is +2.5 dBm. This transceiver occupies 840 mum times 1365 mum, is biased from 3.3 V, and consumes 0.9 W. Two stand-alone 5-stage amplifiers, centered at 140 GHz and 170 GHz, were also fabricated showing 17 dB and 15 dB gain at 140 GHz and 170 GHz, respectively. The saturated output power of the amplifiers is +1 dBm at 130 GHz and 0 dBm at 165 GHz. All circuits were characterized over temperature up to 125degC. These results demonstrate for the first time the feasibility of SiGe BiCMOS technology for circuits in the 100-180-GHz range.     

微波功率SiGe HBT研究进展

Si的热导率比大部分化合物半导体(如GaAs)的热导率高,SiGe HBT在一个较宽的温度范围内稳定,SiGe HBT的发射结电压VBE的温度系数dVBE/dT比Si的小,双异质结SiGe HBT本身具有热-电耦合自调能力,所加镇流电阻可以较小,所有这些使SiGe HBT比GaAs HBT和SiBJT在功率处理能力上占一定优势。文章对微波功率SiGe HBT一些重要方面的国内外研究进展进行评述,希望对从事微波功率SiGe HBT的研究者有所帮助。     

高电子迁移率Si/SiGe异质结构:缓解性SiGe缓冲层的影响

在不同类型的部分缓解性SiGe缓冲层上生长了n型调制掺杂Si/SiGe异质结构,采用这一材料系统是为了得到足够大的导带突变。对样品进行了各种测试分析,如二次离子质谱,x光摆动像分析,透射电子显微镜分析,卢瑟福背散射分析和变温霍尔测量。在750℃生长的厚的线性渐变SiGe缓冲层样品中得到了最高的霍尔迁移率为1.5K下173000cm~2V~(-1)s~(-1)。这一层序达到的室温迁移率约为1800cm~2V~(-1)s~(-1)。发现不管是用没有Ge组分渐变的一般缓冲层,还是直接用有源层是调制掺杂SiGe势垒开始以缓解应变了的Si阱层,主要是在低温下霍尔迁移率严重地下降。     

Applications and processing of SiGe and SiGe:C for high-speed HBT devices

The continued growth of high-speed-digital data transmission and wireless communications technology has motivated increased integration levels for ICs serving these markets. Further, the increasing use of portable wireless communications tools requiring long battery lifetimes necessitates low power consumption by the semiconductor devices within these tools. The SiGe and SiGe:C materials systems provide solutions to both of these market needs in that they are fully monolithically integratible with Si BiCMOS technology. Also, the use of SiGe or SiGe:C HBTs for the high-frequency bipolar elements in the BiCMOS circuits results in greatly decreased power consumption when compared to Si BJT devices.Either a DFT (graded Ge content across the base) or a true HBT (constant Ge content across the base) bipolar transistor can be fabricated using SiGe or SiGe:C. Historically, the graded profile has been favored in the industry since the average Ge content in the pseudomorphic base is less than that of a true HBT and, therefore, the DFT is tolerant of higher thermal budget processing after deposition of the base. The inclusion of small amounts of C (e.g. <0.5%) in SiGe is effective in suppressing the diffusion of B such that very narrow extremely heavily doped base regions can be built. Thus the f_T and f_max of a SiGe:C HBT/DFT are capable of being much higher than that of a SiGe HBT/DFT.The growth of the base region can be accomplished by either nonselective mixed deposition or by selective epitaxy. The nonselective process has the advantage of reduced complexity, higher deposition rate and, therefore, higher productivity than the selective epitaxy process. The selective epi process, however, requires fewer changes to an existing fabrication sequence in order to accommodate SiGe or SiGe:C HBT/DFT devices into the BiCMOS circuit.     

SiGe器件及其在蓝牙系统中的应用

SiGe是目前RF半导体领域中一项非常引人关注的半 导体生产工艺。继IBM公司之后,TI公司、ST公司和Conexant Systems公司等主要的芯片供应商纷纷加入了使 用者的行列。与此同时,随着蓝牙技术在个人无线设备（尤 其是手机、头戴式耳机、笔记本个人电脑和PDA等）领域 中应用的迅猛发展,迫切需要开发包含无线及基带电路的 超低功耗芯片组。SiGe技术不仅可满足这种低功耗要求,而且还能满足 蓝牙技术应用的诸多其他要求,本文将对有关情况做简要     

Parasitic energy barriers in SiGe HBTs

Parasitic energy barriers can easily be introduced during processing. Measurements and calculations of experimental n-p-n HBTs (heterojunction bipolar transistors) are presented, showing that a parasitic conduction-band barrier at the base-collector junction reduces the collector current and the cutoff frequency. A simple analytical model explains the f_T degradation, caused by the reduction of the collector current and a pileup of minority carriers in the base. With the model the effective height and width of the barrier can also be derived from the measured collector current enhancement factor I_C(SiGe)/I_C(Si)     

调制掺杂层在SiGe PMOSFET中的应用

在普通Si器件性能模拟的基础上，详细研完了长沟应变SiGe器件的模拟，并进一步探讨了调制掺杂层的引入对器件性能(主要是跨导)的影响。在器件模拟过程中，采用隐含的SiGe材料和Si材料模型会得到与实际情况差别较大的结果。根据前人的材料研完工作，引入了插值所得的近似因子，以修正Silvaco中隐含的SiGe能带模型和迁移率参数。然后，依据修正后的模型对SiGe PMOS进行了更为精确的二维模拟，并验证了调制掺杂层的作用。