Raman谱研究不同缓冲层结构对Si_(1-x)Ge_x应力弛豫的影响

应用 Raman散射谱研究超高真空化学气相淀积 ( UHV/CVD)生长的不同结构缓冲层对恒定组分上表层 Si1- x Gex 层应力弛豫的影响 .Raman散射的峰位不仅与 Ge组分有关 ,而且与其中的应力状态有关 .在完全应变和完全弛豫的情况下 ,Si1- x Gex 层中的 Si- Si振动模式相对于衬底的偏移都与 Ge组分成线性关系 .根据实测的 Raman峰位 ,估算了应力弛豫 .结果表明 :对组分渐变缓冲层结构而言 ,超晶格缓冲层中界面间应力更大 ,把位错弯曲成一个封闭的环 ,既减少了表面位错密度 ,很大程度上又释放了应力     

代位杂质局域振动的键轨道方法

本文在通常价力场模型之下根据弹性常数C_(11)和成键能量E_b之间的一个经验关系得到由键轨道参数计算径向力常数的简单方法,并由采用原子波函数的局域计算得到描写杂质-主晶格原子之间键轨道的参数,从而得到代位杂质-主晶格原子间的力常数和局域振动的频率.本方法适用于必须考虑力常数变化的情况.对GaAs中硼和碳的不同代位及荷电状态的局域振动进行了计算和讨论,得到的频率随杂质种类和荷电状态变化的趋势与实验结果是一致的.此外,结果表明晶格弛豫对力常数的变化有重要的影响.     

GaP_(1-x)N_x混晶的光致发光谱

通过Ga P1 - x Nx( x=0 .0 5 %～3.1%)混晶的低温光致发光( PL )谱,探讨了N在不同组分Ga Nx P1 - x混晶的发光特性中所起的作用.在低组分( x =0 .0 5 %～0 .81%)下,Ga Nx P1 - x的PL谱由NNi 对及其声子伴线的发光组成;在高组分( x≥1.3%)下,NNi 对之间相互作用形成的与N有关的杂质带导致了Ga Nx P1 - x混晶的带隙降低.同时,在x=0 .12 %的Ga Nx P1 - x中,得到了清晰的NN3 零声子线及其声子伴线,从而直接证实了NN3具有与孤立N中心完全相似的声子伴线.     

用喇曼光谱表征锗硅应变层超晶格

对Ge_xSi_(1-x)/Si超晶格的喇曼光谱研究表明,这类样品中各层间的应力分配取决于缓冲层组分。合金层中的Ge—Si峰峰移δω随组分x或应变ε作线性变化。对Ge_n/Si_n(n为原子层数)超晶格的喇曼光谱研究表明,在n=4的超薄层超晶格中,锗硅界面互混程度较小,并发现样品的生长温度对其质量有决定性影响。     

Raman谱研究不同缓冲层结构对Si1-xGex 应力弛豫的影响

应用Raman散射谱研究超高真空化学气相淀积(UHV/CVD)生长的不同结构缓冲层对恒定组分上表层Si1-xGex层应力弛豫的影响.Raman散射的峰位不仅与Ge组分有关,而且与其中的应力状态有关.在完全应变和完全弛豫的情况下,Si1-xGex层中的Si-Si振动模式相对于衬底的偏移都与Ge组分成线性关系.根据实测的Raman峰位,估算了应力弛豫,结果表明:对组分渐变缓冲层结构而言,超品格缓冲层中界面间应力更大,把位错弯曲成一个封闭的环,既减少了表面位错密度,很大程度上又释放了应力.     

50周期的In_(0.3)Ga_(0.7)As/GaAs应变超晶格的生长

在本文，我们用一个低组分的InxGa(1-x)As缓冲层（x～0．01），有效地限制了50周期的In0.3Ga0．7As／GaAs应变超晶格本身弛豫所产生的位错，X射线双晶衍射测量结果表明使用这样缓冲层的超晶格质量明显改善，可以观察到12级卫星峰，而在没有这个缓冲层的样品上只能观察到3个衍射卫星峰．透射电子显微镜上观察到产生的位错被限制在这个缓冲层中或弯曲进入了衬底而没有进入所需要的外延层。     

用减压化学气相沉积技术制备应变硅材料

利用减压化学气相沉积技术，制备出应变Si/弛豫Si0.9Ge0.1/渐变组分弛豫SiGe/Si衬底. 通过控制组分渐变SiGe过渡层的组分梯度和适当优化弛豫SiGe层的外延生长工艺，有效地降低了表面粗糙度和位错密度.与Ge组分突变相比，采用线性渐变组分后，应变硅材料表面粗糙度从3.07nm减小到0.75nm，位错密度约为5E4cm-2，表面应变硅层应变度约为0.45%.     

Si(111)衬底无微裂GaN的MOCVD生长

采用Al N插入层技术在Si(1 1 1 )衬底上实现无微裂Ga N MOCVD生长.通过对Ga N外延层的a,c轴晶格常数的测量,得到了Ga N所受张应力与Al N插入层厚度的变化关系.当Al N厚度在7～1 3nm范围内,Ga N所受张应力最小,甚至变为压应力.因此,Ga N微裂得以消除.同时研究了Al N插入层对Ga N晶体质量的影响,结果表明,许多性能相比于没有Al N插入层的Ga N样品有明显提高     

InP/Si键合界面热应力分析

从理论上分析了键合热应力产生的原因,在此基础上,采用双层条状金属热应力模型讨论InP/Si键合过程中应力的大小及分布情况.结果表明, 由剪切应力和晶片弯矩决定的界面正应力是晶片中心区域大面积键合失败的主要原因,同时InP/Si键合合适的退火温度应该在250～300 ℃.最后在300 ℃退火条件下很好地实现了InP/Si键合,界面几乎没有气泡,有效键合面积超过90%.     

用X射线衍射研究缓冲层对GaInAs材料的影响

用分子束外延方法制备了具有GaInAs组分渐变缓冲层和不具有GaInAs组分渐变缓冲层的Ga0.9In0.1As/GaAs结构的外延材料。利用高分辨率X射线衍射法(HRXRD)对制备的两种样品分别进行了测试分析。实验结果表明,GaInAs组分渐变缓冲层对外延生长在GaAs衬底上的Ga0.9In0.1As外延材料的晶体质量具有显著的改善作用,极大降低了由于外延层与衬底晶格不匹配所带来的影响。从X射线倒易空间衍射(RSM)二维图谱结果来看,具有GaInAs组分渐变缓冲层结构的样品,其Ga0.9In0.1As外延层与GaInAs组分渐变缓冲层接近完全弛豫,Ga0.9In0.1As外延层的应变降低,表面残留应力小于0.06%,同时,GaAs衬底与Ga0.9In0.1As外延层之间的偏移夹角明显变小。     

注F栅介质抗电离辐射损伤机理

对含 F MOS结构的抗电离辐射特性和机理进行了系统研究。其结果表明 :F减少工艺过程引入栅介质的 E’中心缺陷和补偿 Si/ Si O2 界面 Si悬挂键的作用 ,将导致初始氧化物电荷和界面态密度的下降 ;栅 Si O2 中的 F主要以 F离子和 Si- F结键的方式存在 ;含 F栅介质中部分 Si- F键替换 Si- O应力键而使 Si/ Si O2 界面应力得到释放 ,以及用较高键能的 Si- F键替换 Si- H弱键的有益作用是栅介质辐射敏感性降低的根本原因 ;含 F CMOS电路辐射感生漏电流得到抑制的主要原因是场氧介质中氧化物电荷的增长受到了明显抑制。     

First-principles study on electronic properties and lattice structures of WZ-ZnO/CdS interface

We theoretically investigated the lattice structure, interface bonding energy, optical absorption properties and electronic properties of WZ-ZnO (1 1 2)/CdS (1 1 0) interface from first-principles calculations. The interface lattice mismatch is less than 4.3%. The atomic bond lengths and atomic positions change slightly on the interface after relaxation. The WZ-ZnO (1 1 2)/CdS (1 1 0) interface has bonding energy about −0.61 J/m², suggesting that this interface can exist stably. Through analysis of the density of states, no interface state is found near the Fermi level. In addition, there are orbital hybridizations between different interfacial atoms, and these orbital hybridizations effectively enhance the bonding of Zn and S atoms, Cd and O atoms on the interface. By analysis of difference density charge and Bader charge, we find that electrons on the interface are largely redistributed and charges transport near the Fermi level which strengthen the adhesion of the interface.     

Atomic scale effects of zirconium and hafnium incorporation at amodel silicon/silicate interface by first principles calculations

First principles calculations aimed at quantifying the effects of zirconium and hafnium incorporation at a model silicon/silicate interface have been performed. The tetrahedral bonding character of silicates allows useful comparisons as well as important new distinctions to be drawn with the familiar Si/SiO₂ system. The calculated energy cost of forming (Zr,Hf)-Si bonds suggests that SiO ₂-like bonding is energetically favored over silicide-like bonding at the Si interface. The calculations also suggest that the volume strain associated with Zr or Hf incorporation may lead to increased stress, both in the bulk oxide and in the interfacial transition region     

Effect of physical stress on the degradation of thinSiO2 films under electrical stress

In this work, we demonstrate that for ultrathin MOS gate oxides, the reliability is closely related to the SiO₂/Si interfacial physical stress for constant current gate injection (V_g^- ) in the Fowler-Nordheim tunneling regime. A physical stress-enhanced bond-breaking model is proposed to explain this. The oxide breakdown mechanism is very closely related to the Si-Si bond formation from the breakage of Si-O-Si bond, and that is influenced by the physical stress in the film. The interfacial stress is generated due to the volume expansion from Si to SiO₂ during the thermal oxidation, and it is a strong function of growth conditions, such as temperature, growth rate, and growth ambient. Higher temperatures, lower oxidation rates, and higher steam concentrations allow faster stress relaxation through viscous flow. Reduced disorder at the interface results in better reliability. Fourier transform infrared spectroscopy (FTIR) technique has been used to characterize stress in thin oxide films grown by both furnace and rapid thermal process (RTP). In conjunction with the Gibbs free energy theory, this model successfully predicts the trends of time-to-breakdown (t_bd) as a function of oxide thickness and growth conditions. The trends of predicted t_bd values agree well with the experimental data from the electrical measurement     

Improved interfacial properties of GaAs MOS capacitor with NH3-plasma-treated ZnON as interfacial passivation layer

The GaAs MOS capacitor was fabricated with HfTiON as high-k gate dielectric and NH₃-plasma-treated ZnON as interfacial passivation layer (IPL), and its interfacial and electrical properties are investigated compared to its counterparts with ZnON IPL but no NH₃-plasma treatment and without ZnON IPL and no plasma treatment. Experimental results show that low interface-state density near midgap (1.17×10¹² cm^-2eV^-1) and small gate leakage current density have been achieved for the GaAs MOS device with the stacked gate dielectric of HfTiON/ZnON plus NH₃-plasma treatment. These improvements could be ascribed to the fact that the ZnON IPL can effectively block in-diffusion of oxygen atoms and out-diffusion of Ga and As atoms, and the NH₃-plasma treatment can provide not only N atoms but also H atoms and NH radicals, which is greatly beneficial to removal of defective Ga/As oxides and As-As band, giving a high-quality ZnON/GaAs interface.     

CaF_2/Si(111)界面的电子结构和化学键(英文)

CaF_2/Si(111) interfaces formed at 700℃ as well as at room temperature have been studied with XPS, UPS and LEED. The experimental results show that the substrate temperature has a significant influence on the interface in respect of ifs electronic structure and chemical bond. When the substrate temperature was at 700℃, the interface is found to be consisted of predominate Si-Ca bonds which correspond to an interface state located at 1.2eV below Fermi level. There is depletion of fluorine atoms due to the dissociation of the CaF2 molecule at the interface. When the substrate was at room temperature, there are no chemical bonds between substrate and adatoms nor depletion of fluorine atoms at the interface. Annealing of this interface at 700℃ results in preferential evaporation of F, and the surface undergoes a number of reconstructions until a 3×1 reconstruction is obtained. The bonding at this interface is similar to that of CaF2/Si(111) interface when the substrate temperature was at 700℃.     

Interfacial Chemistry of InP/GaAs Bonded Pairs

The interfacial chemistry of InP/GaAs direct bonding with either 5% HF in water or HF:ethanol (1:9) chemical pretreatments was investigated. Multiple internal transmission-Fourier transform infrared spectroscopy (MIT-FTIR) and atomic force microscopy (AFM) were used to probe the bonding interface. The bond strength was measured as a function of annealing conditions and prebonding chemical treatment. The HF-based pretreatments remove the initial native oxide, leaving an interfacial layer of either water or ethanol. The initial room-temperature bond strength is primarily determined by the strength of hydrogen bonding, which, in turn, is a function of the prebonding treatment. The removal of interfacial water and ethanol, and with the subsequent formation of the oxide layer, leads to an increased bond strength. For ethanol-based HF treatments, ethanol appears to react with the underlying interfacial oxide layer through a complex interaction with the absorbed water. After annealing, the bond strength for all prebonding preparations can reach a high value, comparable to the fracture strength of the InP. The oxide composition after thermal annealing shifts from In₂O₃ to the eventual thermodynamic equilibrium product, InPO₄.     

Effect of Misorientation and Preliminary Etching of the Substrate on the Structural and Optical Properties of Integrated GaAs/Si(100) Heterostructures Produced by Vapor Phase Epitaxy

It is shown for the first time that the structural and optical functional characteristics of integrated GaAs/Si(100) heterostructures can be controlled by using misoriented Si(100) substrates and their preliminary etching. The growth of an epitaxial GaAs layer on a Si substrate without the formation of antiphase domains can be carried out on a substrate deviated from the (100) singular plane by an angle smaller than 4°–6° or without a transition layer of GaAs nanocolumns. Preliminary treatment of the silicon substrate by etching makes it possible to use it for the vapor-phase epitaxial growth of a single-crystal GaAs film with a considerably smaller relaxation coefficient, which has a positive effect on the structural quality of the film. These data are in good agreement with the results of IR reflectance spectroscopy and photoluminescence and ultraviolet spectroscopy. The features of the optical properties of integrated GaAs/Si(100) heterostructures in the infrared and ultraviolet spectral regions are also defined by the relaxation coefficient.     

Interface structure of ultrathin oxide prepared by N/sub 2/O oxidation

With X-ray photoelectron spectroscopy (XPS) measurements, we found in the N/sub 2/O-grown oxide that the nitrogen incorporation should involve the NO or N reaction with the Si-Si bond and P/sub b/ centers at the interface. Consequently, nitrogen content is very low and accumulated mainly at the interface. In addition, we found that the nitrogen atoms at the interface exist in the form of Si-N bonding and the interface oxynitride layer is a mixture of SiO/sub 2/ and Si/sub 3/N/sub 4/ clusters. This structure will result in several undesirable effects. It will give rise to the permittivity and bandgap fluctuations at the interface and hence induced gigantic surface potential fluctuation and mobility degradation in the channel of MOS devices. This bonding structure also explains the interface trap generation during the electrical stressing. The sources of trap generation are attributed to the Si-Si bonds, P/sub b/ centers, and nitride-related defects due to the over-constrained silicon atoms in the Si/sub 3/N/sub 4/ clusters at the interface.     

Protons at the Si-SiO2 interface: a first principle investigation

We studied protons attached to bridging O atoms in the vicinity of the Si(1 0 0)-SiO₂ interface through density-functional calculations for realistic interface models. These protons do not disrupt the bonding network except in the case of strained Si-O bonds for which they lead to the formation of positively charged threefold coordinated Si(3)⁺. Defect energies mainly fall within a band of ∼0.5 eV, which is stabilized by ∼0.3 eV at the interface, the energies of the Si(3)⁺ defects lying at the bottom of this band. Hence, this work indicates that bridging O atoms in the vicinity of the interface can act as shallow proton traps and describes a mechanism for bond-rearrangements leading to Si(3)⁺. These results are consistent with experimental observations.