基于高电阻率衬底的Si/SiGe HBT

介绍了一种基于电阻率高达1000Ω·cm的硅衬底的锗硅异质结晶体管的研制.首先根据衬底寄生参数模型分析了衬底对器件高频性能的影响,然后设计了器件的材料与横向结构尺寸,该器件采用掩埋金属自对准技术在3μm工艺线上制备而成,测得其典型直流电流增益为120,BVCEO为9.0V,fT为10.2GHz,fmax为5.3GHz,比同结构尺寸的常规N 衬底Si/SiGe HBT的fT和fmax分别高出3.9GHz和1.5GHz.     

Effects of neutron irradiation on SiGe HBT and Si BJT devices

The change of electrical performance of SiGc HBT and Si BJT is studied after irradiation with 1.3×10¹³ and 1.0×10¹⁴ reactor fast neutrons cm^–2. I _c and decrease, while I _b increases generally with an increasing neutron irradiation fluence for SiGe HBT. For Si BJT, I _c increases at low V _be bias, decreases at high V _be bias; I _b increases; and decreases much more than a SiGe HBT at the same fluence. It is shown that a SiGe HBT has much better anti-radiation performance than a Si BJT. The mechanism of performance changes induced by irradiation is discussed.     

改善多指功率SiGe HBTs热稳定性的版图设计

提出非均匀指间距结构功率SiGe HBTs的版图设计用以改善热稳定性。模拟和实验结果均表明,与传统的均匀指间距结构相比,非均匀指间距结构HBT的峰值结温和温度分布非均匀性均得到显著改善。上述改善归功于非均匀指间距结构HBT中心指间距的增加,从而有效阻止热流由外侧指流向中心指处。此外,与均匀指间距结构器件相比,其热阻改善13.71%,热退化功率水平提高22.8%。因此,模拟和实验均证明采用非均匀指间距结构HBT的版图设计可有效改善功率HBTs热稳定性。     

SiGe/Si异质结光电器件

SiGe/Si异质结光电器件及其光电集成(OEIC)是硅基光电研究的一个非常引人注目的领域.综述了SiGe/Si异质结材料的基本性质,SiGe/Si异质结光电器件的结构、性能、应用及其光电集成.重点介绍了SiGe/Si光电探测器及其与其他相关器件的集成.     

Effects of electron irradiation on SiGe devices

The degradation and the recovery behavior of the device performance for SiGe diodes and p-MOSFETs irradiated by 2-MeV electrons are reported. For diodes, it is noted that both the reverse and forward current increase by irradiation. An interesting observation is that the forward current decreases after irradiation for a forward voltage larger than ~ 0.7 V. This reduction can be explained by an increased resistivity of the Si substrate. The degradation recovers by thermal annealing after irradiation. For a fluence of 1 × 10¹⁵ e/cm², the diode performance almost recovers to the initial condition after 250 °C annealing. For the transistors, after irradiation, a slight negative shift of the threshold voltage and a decrease of the drain current for input and output characteristics have been observed together with a decrease of hole mobility. This is mainly due to the increase of the threshold voltage induced by positive charge trapping in the gate oxide.     

Si/SiGe异质结双极晶体管的研制

通过理论分析计算，计算机模拟和工艺实验，对Si/SiGe异质结双极晶体管（HBT）的结构参数进行了精细的优化设计，特别是采用了本征间隔层和新颖的Ge分布曲线，有效地削弱了基区杂质外扩散，基区复合和异质结势垒效应的不利影响。开发了兼容于硅工艺的锗硅HBT工艺，并据此试制出了Si/SiGeHBT，测量结果表明，器件的直流和交流特性均较好，电流放大系数为50，截止频率fT为5.1GHz。     

横向尺寸的变化对SiGe HBT高频噪声的影响

从发射极条宽、发射极条长、基极条数、发射极与基极间距四个方面分析了横向尺寸变化对SiGe HBT高频噪声的影响.结果表明增加发射极条长、基极条数和减小发射极与基极间距可以较为有效地减小晶体管噪声,而减小发射极与基极间距对噪声的改善效果比较显著.发射极与基极间距从1μm减小到0.5μm,2GHz工作频率下最小噪声系数可减小9dB,在0.5GHz工作频率下最小噪声系数可降至1.5dB,2GHz工作频率下最小噪声系数为3dB.     

First-principles study of near surface point defects stability in Si (100) and SiGe(100)

Calculations based on Density Functional Theory are carried out to study interstitial generation close to the Si(100) surface with further consideration of effects related to the presence of substitutional Ge atoms on the surface. Defect structures, vacancy and Si interstitial, and associated energies are calculated. We observe that germanium atoms tend to increase the stability of created defects, promote the generation of interstitials through drastic structural changes and blocks the climb of Si interstitials towards the surface.     

Terahertz emission of SiGe/Si quantum wells

THz emission of stimulated character was observed in Si/SiGe/Si quantum well (QW) structures doped with boron. The resonance cavity formed by extremely parallel-structure planes due to total internal reflection, is necessary for the emission. The mechanism for the possible population inversion of strain-split acceptor levels is proposed.     

SiGe／Si和SGOI材料的Li离子束RBS分析

SiGe合金薄膜中的Ge含量度分布对材料的禁带宽度和制作器件的性能有十分重要的影响。本文用Li离子束卢瑟福背散射分析法对SiGe／Si和SiGe-OI材料样品进行了分析。与TEM，SEM、Raman等分析结果进行比较表明，Li离子束RBS分析可同时测量SiGe层厚度，Ge含量度其深度分布，Si过渡层和SiO2层厚度，并有较好的测量精度。     

Physics and applications of Si/SiGe/Si resonant interband tunneling diodes

Room temperature (RT) current–voltage characteristics of Si/Si_1−xGe_x/Si p⁺-i-n⁺ interband tunneling diodes are presented. The variation of the structural properties results in a more detailed picture of the tunneling process in these diodes, which allows further improvement of the relevant parameter. Special attention is paid to the peak current density (PCD) and the peak-to-valley current ratio (PVCR) of the devices. For an optimized structure with a 3-nm thick Si_0.54Ge_0.46 layer in the intrinsic zone a record PVCR of 6.0 at a PCD of approximately 1.5 kA/cm² was achieved. By reducing the layer thickness to 2.6 nm and simultaneously increasing the Ge content to 54%, the PCD increases to 30 kA/cm² at a high PVCR of 4.8.     

Si/SiGe hetero-junction solar cell with optimization design and theoretical analysis

Performances of solar cells, such as short circuit current density, open-circuit voltage, fill factor, and efficiency of solar cells on the multi-crystalline (mc)-SiGe on the Si with different Ge contents, are compared and investigated in this paper. The average Ge concentration was varied from 0% to ~ 20%. Appropriate addition of Ge in crystal Si is a very effective method to enhance the short circuit current density without degrading the open-circuit voltage owing to the modulation of the SiGe band-gap. The band-gap of the SiGe can be extracted by electron-hole plasma (EHP) model. With an optimization of Ge content and clean process condition, the overall efficiency of a Si/SiGe hetero-junction solar cell with Ge content of 8% is found to be ~ 16% and ~ 4% improvement achieved, as compared to the control multi-crystalline (mc)-Si solar cell. The theoretical simulations and analyses can help design the high efficiency Si/SiGe hetero-junction solar cell.     

样品辐照电子源的研发

为了研究地球早期环境和生命演化过程,设计制作了样品辐照电子源。电子通过热灯丝发射,能量通过阴极电压来调节,电子束斑尺寸通过静电透镜来调节。灯丝缠绕方式提高了发射电子的均匀性。根据理论分析和电磁软件仿真,确定了电子源阴极与控制极距离的参数。仿真结果显示,在能量为3.5 keV时聚焦电压越大束斑越小,在工作距离为150 mm时束斑直径可实现30-50 mm之间可调。实验结果显示,该装置发射的电子束能量在1-5 keV之间连续可调;在工作距离为150 mm时,3.5 keV电子束的束斑直径可调,与仿真结果变化趋势一致,可产生20.8μA电子束流。     

i基区渐变掺杂SiGe/Si异质结开关功率二极管的特性模拟

提出了在SiGe／Si异质结开关功率二极管的本征i区中采用掺杂浓度三层渐变式结构。由Medici模拟所得的特性曲线表明，该结构在正向I—V特性基本不发生改变的前提下，与i区固定掺杂结构相比具有更好的反向恢复电流与反向恢复电压特性，尤其软恢复特性更加明显，反向恢复过程加快。还对渐变掺杂所得到的优越性能进行了分析，从理论上给出了较好的解释。     

SiGe/Si光电探测器研究进展

本文综述了目前国内外在工作波长１．３～１．５μｍ的ＳｉＧｅ／Ｓｉ超晶格探测器和工作波长为８～１２μｍ的ＳｉＧｅ／Ｓｉ异质结长波长红外探测器方面的研究进展，并分析了存在的问题和材料的各种生长方法。     

SiGe超快速软恢复功率开关二极管

SiGe材料由于禁带带隙较窄和与Si工艺相兼容的优点,被广泛用于高频双极晶体管的制造中.实验把SiGe/Si异质结应用于功率器件方面,制造出了超快速软恢复SiGe/Si异质结功率开关二极管.与同结构的传统Si二极管相比,该功率二极管可以获得更短的反向恢复时间,低的正向压降,低的反向峰值电流,较软的恢复特性.30%Ge含量的SiGe二极管反向恢复时间比同结构的Si二极管缩了短四分之三,软度因子接近于1.这些性能的改进无需采用少子寿命控制技术,因而很容易集成于功率集成电路中.     

Faceting and nanostructure effects in Si and SiGe epitaxy

Epitaxy in Si technologies has to be integrated in the flow of fabrication; in most cases, it has to be selective and deposition takes place in extremely small patterns.In a first part, Si or SiGe epitaxy faceting is presented and discussed. Today, the global view is that, at first order, faceting is a kinetic phenomenon, controlled by deposition kinetic anisotropies. On the contrary, in a second part we show that highly faceted structures tend to decrease their surface energy by thermal rounding and that this phenomenon is very important when considering very small (20-40 nm) patterns.The main part reports on the combination of faceting with small size effects. Experiments consist in depositing Si_0.72Ge_0.28 selectively in very narrow (35-80 nm) lines oriented either along < 110 > or < 100 > crystal axis on (100) Si wafers. Preliminary observations clearly demonstrate an important {100} faceting that is often not observed or reported in literature. Our results also evaluate the lateral overgrowth of selective epitaxies. < 110 >-oriented lines lead to a certain lateral epitaxial overgrowth that is limited by {111} facets whereas epitaxies in < 100 > lines present a much larger (> 2 times) overgrowth bordered by {100} facets.Finally, we demonstrate that the edge effects have to be taken into account. Firstly, the amount of epitaxial material deposited in narrow lines depends on the line orientation, and then we propose the concept of “anisotropic loading effect”. Secondly, we found that deposition rates in small patterns are not constant with time. This corresponds to “time-nonlinear loading effects” that were never conceptualized in literature.     

Synthesis of amorphous Si nanowires from solid Si sources using microwave irradiation

Si nanowires were synthesized from Si wafers and from thin Si films deposited on various substrates by microwave irradiation. The power and time were key determinants of the diameter and morphology of the synthesized Si nanowires. The nanowires had an amorphous structure due to the extremely high heating rate. Carbon coating of the Si nanowires was easily achieved by introducing acetylene after synthesizing the nanowires. Carbon-coated Si nanowires are potential candidates for use as the anode material in next generation Li-ion batteries.     

一种新型Si电子束蒸发器的研制及其应用研究

我们成功地设计出一种新型的Si电子束蒸发器,并将它应用于Ge/Si(111)量子点的生长.由于采用悬臂式设计,它完全克服了高压短路的问题.电子束蒸发器的性能试验表明,稳定输出功率可以控制输出稳定的Si束流.应用这种电子束蒸发器可以在700 ℃,成功沉积出平整的单晶Si薄膜.进一步的试验表明,在这种缓冲层表面可以自组装生长出Ge量子点.