硅、锗和氩离子注入富硅二氧化硅的电致发光

将Si、Ge和Ar三种离子注入到磁控溅射制备的富硅二氧化硅和热生长的二氧化硅中,在N2气氛中,作550、650、750、850、950和1050℃退火后,进行电致发光研究.对比样品为退火条件相同的未经注入的上述两种二氧化硅.对于离子注入情况,只观察到Au/1050℃退火的离子注入的富硅二氧化硅/p-Si的电致发光.低于1050℃退火的离子注入富硅二氧化硅和上述各种温度下退火的热生长二氧化硅,无论离子注入与否,都未观察到电致发光.Au/未注入富硅二氧化硅/p-Si的电致发光光谱在1.8eV处出现主峰,在2.4eV处还有一肩峰.在Au/Si注入富硅二氧化硅/p-Si的电致发光谱中,上述两峰的     

Optimization and characterization of amorphous/crystalline silicon heterojunction solar cells

Amorphous hydrogenated silicon/crystalline silicon (a‐Si:H/c‐Si) heterojunction solar cells are investigated and optimized with regard to efficiency and simplicity of processing. Starting with a survey of a‐Si:H/c‐Si heterojunction solar cell results from the literature, we describe the fabrication steps of our a‐Si:H/c‐Si technology and analyze the electronic device properties by quantum efficiency, current–voltage, admittance, and capacitance–voltage measurements. The open‐circuit voltage and the fill factor of the a‐Si:H/c‐Si heterojunction solar cells under investigation are limited by recombination in the neutral zone of the crystalline Si absorber. Recombination at the a‐Si:H/c‐Si‐interface is subsidiary in respect of the limitation of the open‐circuit voltage. Our best n‐type a‐Si:H/p‐type c‐Si solar cell prepared without high‐efficiency features such as back‐surface field or surface texturing has an independently confirmed efficiency of 14.1% and an open‐circuit voltage of 655 mV. Copyright © 2001 John Wiley & Sons, Ltd.     

355nm激光作用下Si(CH3)4分子的MPI质谱研究

在 35 5nm的激光作用下 ,利用扩散分子束技术和四极质谱装置相结合研究了气相Si(CH3 ) 4分子多光子电离 (MPI)质谱分布。测量了Si(CH3 ) + 4,Si(CH3 ) + 3 ,Si(CH3 ) + 2 ,Si(CH3 ) + 及Si+ 离子的激光光强指数 ,检测了这 5种碎片离子的信号强度占总信号强度的分支比随光强的变化关系。据此 ,讨论了该分子MPI过程可能经历的通道 ,得到了Si+ 主要来自于母体分子的多光子解离—硅原子的电离 ,Si(CH3 ) + n(n =1,2 ,3)主要来自于中性碎片Si(CH3 ) n(n =1,2 ,3)的自电离 ,Si(CH3 ) + 4来自于母体分子的 (3+1)电离的结论     

UV/UHV/CVD生长应变Si1-xGex层

应用紫外光化学气相淀积技术在450和480℃超高真空的背景下在Si衬底上分别生长出应变Si1-xGx和Si材料.在此低温下,有效地控制了衬底中的杂质外扩以及界面的不清晰.X射线分析结果表明Si1-xGex材料结晶状况良好,二次离子质谱分析结果表明多层Si1-xGex/Si材料界面陡峭,说明该技术能够生长出高质量的应变Si1-x-Gex/Si材料.     

Si/Si直接键合界面的FTIR和XPS研究

通过新颖的键合方法实现了Si/Si直接键合.采用傅里叶红外透射谱(FTIR)对Si/Si键合界面进行了研究,结果表明,高温退火样品的界面组分为Si和O,无OH和H网络存在.X射线光电子谱(XPS)测试结果进一步表明,界面主要为单质Si和SiOx混合网络,且随着退火温度的升高,界面层Si-Si直接成键的密度也越高.     

Growth of Si and Ge nanostructures on Si substrates using ultrathin SiO/sub 2/ technology

Using scanning reflection electron microscopy and a high-temperature scanning tunneling microscopy (STM), we study the growth processes of Si and Ge nanostructures on Si substrates covered with ultrathin SiO/sub 2/ films. Si windows are formed in the ultrathin SiO/sub 2/ films by irradiating focused electron beams used for SREM or field emission electron beams from STM tips before or during heating samples. Ge nanoislands are grown only at the Si window positions by depositing Ge on the samples and by subsequent annealing of them. Moreover, Ge nanoislands about 7 nm in size and ultrahigh density (>10/sup 12//cm/sup 2/) are grown on the ultrathin SiO/sub 2/ films. These nanoislands can be manipulated by STM when they are separated from Si substrates by the ultrathin SiO/sub 2/ films. Si, Ge, Ge/Si and Si/Ge/Si nanoislands can also be grown on the Si windows by selective growth using Si/sub 2/H/sub 6/ and GeH/sub 4/ gases. These nanoislands are found to be stable on the Si windows during high-temperature annealing. These results indicate that ultrathin SiO/sub 2/ technology is useful for growing Si and Ge nanostructures on given areas.     

Environmental life cycle assessment of roof‐integrated flexible amorphous silicon/nanocrystalline silicon solar cell laminate

This paper presents an environmental life cycle assessment of a roof‐integrated flexible solar cell laminate with tandem solar cells composed of amorphous silicon/nanocrystalline silicon (a‐Si/nc‐Si). The a‐Si/nc‐Si cells are considered to have 10% conversion efficiency. Their expected service life is 20 years. The production scale considered is 100 MW_p per year. A comparison of the a‐Si/nc‐Si photovoltaic (PV) system with the roof‐mounted multicrystalline silicon (multi‐Si) PV system is also presented. For both PV systems, application in the Netherlands with an annual insolation of 1000 kWh/m² is considered. We found that the overall damage scores of the a‐Si/nc‐Si PV system and the multi‐Si PV system are 0.012 and 0.010 Ecopoints/kWh, respectively. For both PV systems, the impacts due to climate change, human toxicity, particulate matter formation, and fossil resources depletion together contribute to 96% of the overall damage scores. Each of both PV systems has a cumulative primary energy demand of 1.4 MJ/kWh. The cumulative primary energy demand of the a‐Si/nc‐Si PV system has an uncertainty of up to 41%. For the a‐Si/nc‐Si PV system, an energy payback time of 2.3 years is derived. The construction for roof integration, the silicon deposition, and etching are found to be the largest contributors to the primary energy demand of the a‐Si/nc‐Si PV system, whereas encapsulation and the construction for roof integration are the largest contributors to its impact on climate change. Copyright © 2012 John Wiley & Sons, Ltd.     

Diffusion and trapping of implanted hydrogen in a Si/Si:B/Si structure

H implantation in Si/Si:B/Si structures is a promising route to improve the Smart Cut™ process and transfer thin Si layers of reduced roughness and controlled thickness onto regular Si wafers. However, the mechanisms driving this process are unknown and thus difficult to model or optimize. For this reason, we have experimentally studied the redistribution of H which takes place in such structures after implantation and during annealing using SIMS and TEM. We show that the Si:B layer already traps H during implantation and form platelets parallel to the wafer surface. During annealing, the H atoms implanted in the Si regions are slowly transferred toward the Si:B layer where they are trapped on large platelets which grow further during annealing. Routes to optimize this process go through the minimization of H precipitation in the pure Si regions. This can probably be achieved by optimizing the implantation conditions.     

Effect of band alignment and density of states on the collector current in p-Si/n-Si/sub 1-y/C/sub y//p-Si HBTs

p-Si/n-Si/sub 1-y/C/sub y//p-Si heterojunction bipolar transistors with varying carbon fractions in the base were grown by rapid thermal chemical vapor deposition (RTCVD), to better understand the potential of Si/sub 1-y/C/sub y/ in enhancing the performance of Si-based bipolar technology. The band line-up issues which make Si/sub 1-y/C/sub y/ a desirable choice for forming the base region in a p-n-p HBT are discussed. Electrical measurements performed on the p-Si/n-Si/sub 1-y/C/sub y//p-Si HBTs (y=0.6, 0.8 at.%) are used to extract important information regarding the electronic properties of the Si/Si/sub 1-y/C/sub y/ material system, e.g., the bandgap reduction in Si/sub 1-y/C/sub y/ compared to Si and minority carrier recombination lifetime in Si/sub 1-y/C/sub y/. Temperature dependent measurements of the collector current were performed to extract the bandgap narrowing at the Si/Si/sub 1-y/C/sub y/ heterojunction. This paper includes a detailed analysis of the impact of heavy doping and reduced density of states in Si/sub 1-y/C/sub y/ compared to Si on the extraction of the energy bandgap offset, and on the collector current of p-n-p HBTs. The impact of the reduced density of states on the design of p-n-p Si/Si/sub 1-y/C/sub y/ HBTs is discussed. The measured value of the energy band offset is (65 meV/at.% C) very close to previously measured values of the conduction band offset at the Si/Si/sub 1-y/C/sub y/ heterojunction. The results are thus consistent with a band line-up at the Si/Si/sub 1-y/C/sub y/ interface that is dominated by a conduction band offset with little if any valence band offset.     

Fabrication of GaAs/Si Heterostructures and Their Photoelectric Properties

Fabrication of GaAs/Si heterostructures and their photoelectric properties are investigated by Raman, photoluminescence and Hall-effect measurements. The crystallinity of GaAs epilayers grown on Si substrate is significantly affected by the substrate orientation and the growth method. The photoelectric properties of GaAs epilayers grown on Si （211） substrates deposited by using a two-step growth method are improved. These results indicate that GaAs epilayersgrownonSi （100） andSi （211） substrates by using two step growth method are promising for potential applications in high-speed and high-frequency photoelectric devices.     

Evaluation of Surface Cleaning of Si(211) for Molecular-Beam Epitaxy Deposition of Infrared Detectors

We report an assessment of the reproducibility of the HF cleaning process and As passivation prior to the nucleation of ZnTe on the Si(211) surface using temperature desorption spectroscopy, ion scattering spectroscopy, and electron spectroscopy. Observations suggest full H coverage of the Si(211) surface with mostly monohydride and small amounts of dihydride states, and that F is uniformly distributed across the top layer as a physisorbed species. Variations in major contaminants are observed across the Si surface and at the CdTe-ZnTe/Si interface. Defects act as getters for impurities present on the Si surface, and some are buried under the CdTe/ZnTe heterostructure. Overall, the data show evidence of localized concentration of major impurities around defects, supporting the hypothesis of a physical model explaining the electrical activation of defects in long-wave infrared (LWIR) HgCdTe/CdTe/Si devices.     

与Si 工艺兼容的Si/ SiGe/ Si HBT 研究

我们对Si/SiGe/Si HBT及其Si兼容工艺进行了研究,在研究了一些关键的单项工艺的基础上,提出了五个高速Si/SiGe/Si HBT结构和一个低噪声Si/SiGe/Si HBT结构,并已研制成功台面结构Si/SiGe/Si HBT和低噪声Si/SiGe/Si HBT,为进一步高指标的Si/SiGe/Si HBT的研究建立了基础。     

基于几何相位分析的Nb/Si{111}界面应变研究

本文使用高分辨透射电镜(HRTEM)成像和几何相位分析,研究不同溅射气压制备的铌薄膜/硅基体的界面微观结构和应变状态.研究结果表明:铌薄膜表面由花瓣状层片组织构成,层片组织随机分布,没有明显的特征取向;随着溅射气压的增大,层片尺寸随之增大,致密度减小,出现了大量孔隙,铌薄膜和硅基体之间产生铌、硅元素的混合层;随着溅射气压的增大,硅基体中应变的大小和方向均不相同,溅射气压对硅基体的应变状态具有很大影响;硅基体的应变主要来自于界面混合层和铌薄膜的作用,混合层中铌原子和硅原子相互混杂,存在大量结构缺陷,产生本征应力,从而导致硅基体中产生应变.     

大面积高效率高稳定非晶硅太阳电池的研究

根据电流连续性原则和光伏材料选择原则，对叠层电池的电流匹配进行了研究，结果表明，电流匹配是影响叠层电池短路电流和转换效率的重要因素之一，电流匹配可以通过调整单元电池厚度来实现，在此基础上，获得了面积为４００ｃｍ＾２，转移效率分别为８．２８％，７．５２％和６．７４％的ａ－Ｓｉ／ａ－Ｓｉ，ａ－Ｓｉ／ａ－ＳｉＧｅ和ａ－Ｓｉ／Ａ－Ｓｉ／ａ－ＳｉＧｅ高效率叠层电池。     

Interaction of self-assembled Ge islands and adjacent Si layers grown on unpatterned and patterned Si(001) substrates

For use in electronic devices, self-assembled Ge islands formed on Si(001) must be covered with an additional Si layer. Chemically vapor deposited Si layers initially grow very rapidly over Ge islands because of the catalytic effect of Ge on the reaction of the Si-containing gas. The edges of the Si features covering Ge “pyramids” are rotated by 45° with respect to the edges of the Ge pyramids because of the different mechanisms orienting the Ge islands and the Si features. When multiple layers of islands are formed, the in-plane ordering of the Ge islands depends on the thickness of the Si interlayer separating the island layers. When selective Si is grown on a patterned Si wafer to form the underlying structure for the Ge islands, the position of the islands is influenced by the detailed shape of the Si near the edges, which in turn depends on the thickness of the selectively deposited Si, the pattern size, and the amount of surrounding oxide.     

The characteristics of tunnel oxides grown on textured siliconsurface with a simple and reliable process

In this work, a simple and reliable method to fabricate a textured Si surface and the characteristics of oxides grown on the textured Si surface are proposed. The concept of different oxidation rates in poly-Si grain and grain boundaries has been used to form textured Si surface which does not need to etch the surface of Si wafer and is without the constraint of stopping the oxidation process on the poly Si/Si-substrate interface to get better electrical characteristics. Tunnel oxide grown on the textured single crystalline Si exhibits much better electrical characteristics and reliabilities than those of oxides grown on poly-Si substrate (thin poly-Si film on Si substrate) and on untextured single crystalline Si substrate     

Molecular dynamics study on compressive strength of monocrystalline, nanocrystalline and amorphous Si mold for nanoimprint lithography

Molecular dynamics studies are carried out to investigate the compressive strengths and the failure mechanisms of monocrystalline, nanocrystalline and amorphous Si molds for nanoimprint lithography. The stress-strain characteristics and the stress distributions are analyzed for the three types of Si molds. The stress-strain characteristics show that the strength of the monocrystalline Si mold is the greatest among the three types of Si molds. The strength of the nanocrystalline Si mold decreases as the grain size decreases. This shows the Hall-Petch effect does not hold true in the grain size of nanometer order. The visualization of the stress distribution shows that the monocrystalline, nanocrystalline and amorphous Si mold fail due to the slipping of the specific atomic plane, the sliding in the grain boundaries and the nonlocal plastic deformation, respectively. As a result, the monocrystalline Si mold is the most suitable for nanoimprint lithography among the three types of Si molds in the nanoscale regime.     

A simulation study of high-speed silicon heteroemitter bipolartransistors

Using a two-dimensional numerical simulator, the upper limit of Si homotransistor cutoff frequency is estimated within the assumed conditions of punchthrough voltage. The potential speed advantages of silicon heteroemitter bipolar transistors (Si HBTs) (such as low emitter storage time, low emitter-base junction capacity, and possibility for large base width reduction) are shown by comparing Si HBTs with a Si homotransistor. It is confirmed that the cutoff frequency is enhanced from 48 to 127 GHz by the Si HBT structure. The optimum values of heteromaterial properties for high-speed HBT operation including energy gap, band discontinuity, and heterointerface recombination are discussed     

复合量子阱Ge_(0.3)Si_(0.7)/(Ge_(0.3)Si_(0.7))_m-(Si)_m/Ge_(0.3)Si_(0.7)的电子能带结构

采用建立在经验赝历势基础上的推广k·P方法计算了复合量子阱Ge0.3Si0.7／（Ge0.3Si0.7）m-（Si）m／Ge0.3Si0.7的电子束缚能组及其活界面方向的色激关系,并与通常的单带模型下的包络函数方法的计算结果进行了比较。结果表明由于超晶格中子能带的形成,邻近能带间的互作用使通常单带模型下的包络函数方法不再能适用于复合量子阱的计算。计算结果也表明复合量子阱的电子束缚能级沿界面方向在kx＜0.1（2π/a）范围内基本上不随kx变化。     

掺铒Al_2O_3/Si多层薄膜中纳米晶Si的形成和敏化效应

采用脉冲激光沉积制备了掺铒Al2O3/Si多层薄膜,在淀积过程中脉冲激光溅射产生的高能量Er原子渗透进入非晶硅层,并引入了额外的应力,在低退火温度下诱导形成纳米晶Si。利用纳米晶Si作为敏化剂有效地增强了Er3+在Al2O3中的光致发光。样品微观结构和发光强度的关系表明,获得高密度和小尺寸的纳米晶Si和Er3+处于良好的发光环境是实现优化发光的关键,最优化的Er3+发光强度在退火温度为600℃的条件下得到。