a-Si:H/a-SiN_x:H多层膜界面的研究

<正> 尽管过去几年对非晶半导体多层膜及其界面对多层膜传输性能影响的研究甚多,然而对于界面缺陷态的特性及其密度了解甚少。不同的测量方法得到的a-Si:H/a-SiNx:H界面缺陷态密度可从1010变到1012cm-2。这一实验结果反映了每一测试方法仅能探测某些能级的缺陷,在某些情况下可能是不同类的缺陷。非晶硅系材料都包含有氢。已发现,在多层膜的沉积过程中,由于组成多层膜的子层间应力释放的需要以及两子层材料的氢扩散系数不同而     

Pd/a-Si:H界面的光电子能谱研究

本文利用光电子能谱(XPS、UPS)技术研究了Pd淀积层与离子注入制备的a-Si∶H层组成的系统.本工作分析了Pd/a-Si∶H的界面键合状态及组分分布的变化对价带谱与芯能级谱的影响,并与Pd/C-Si系统的结果进行了比较.结果表明:Pd/a-Si∶H界面具有与Pd/C-Si界面相似的电子结构;但是,Pd原子在a-Si∶H中具有较大的扩散速率,因此,处于更富Si的环境中。     

Study of light-induced annealing effects in a-Si:H thin films

Light-induced metastability was examined in hydrogenated amorphous silicon thin films using a 500 W xenon lamp and a 10 mW HeCd laser. Positron beam annihilation spectroscopy (PAS) and fourier transform infrared spectroscopy (FTIR) were examined to investigate the effects of light on the structural properties of the films. The experimental results exhibited significant decrease in the S-parameter of the PAS, indicating marked reduction in the defect density of the films. The FTIR spectroscopy showed significant reduction in the transmission coefficient of IR radiation at frequencies corresponding to Si–H and Si–H₃ phonon modes, indicating that the observed annealing effects were due to light-induced formation of Si–H and Si–H₃ bonds. A second thermal annealing process conducted after the light exposure experiment resulted in a further substantial decrease in defect density for the sample exposed to HeCd laser. The experimental results are explained by a competing, light induced, dangling bond creation/annealing process, in which the incoming photons caused the annealing of dangling bonds, particularly those at around the voids. However, in the bulk region, the photons caused both the breaking of weak Si–Si bonds as well as the annealing of dangling bonds.     

Electrical and photoelectric properties of a-Si:H layered films: The influence of thermal annealing

The electrical and photoelectric properties of layered a-Si:H films obtained by cyclic plasmochemical deposition and the effect of thermal annealing on these properties have been studied. Unannealed films demonstrate high photosensitivity, with a photoconductivity to dark conductivity ratio of K=3.4×10⁶. Increasing the annealing temperature causes the film photosensitivity to fall because of a considerable decrease in the photoconductivity and increase in the dark conductivity. For films annealed at temperatures above 500°C, the conductivity is the sum of the band conductivity and the hopping conductivity via states at the Fermi level.     

a—Si：H TFT自对准工艺的研究

实验研究了自对准结构的ａ－Ｓｉ：Ｈ ＴＦＴ的制备工艺，对其中关键的底部曝光和顶胶工艺进行了详细的研究和分析，对制备工艺和结构参数进行了合理的优化，成功地制备出自对准结构的ａ－Ｓｉ：Ｈ ＴＦＴ。对影响自对准结构ａ－Ｓｉ：Ｈ ＴＦＴ特性的主要因素进行了详细的分析，提出了一种新颖的双有源层结构的ａ－Ｓｉ：Ｈ ＴＦＴ，可以有效地改善ａ－Ｓｉ：Ｈ ＴＦＴ的开态特性，其通断电流比ＩＯＮ／ＩＯＦＦ〉１０＾５。     

氢化非晶硅薄膜晶体管的静态特性研究

发展了一种研究a－Si：HTFT静态特性的新方法。从a－Si材料的带隙态密度适配参数分布函数出发，采用Shockley－Read-Hall统计描述，发展了一种局域态电行密度统一模型，该模型同时考虑了带尾局域态和缺陷局域态的作用。提出并分析了沟道区有效温度参数的概念，在此基础上，推导出了a－Si：HTFT电流—电压特性的解析表达式。其理论值与实验值符合很好。并详细分析了a－Si材料参数对TFTN态特性的影响。     

用计算机模拟研究a-Si:H的悬挂键(英文)

In order to investigate defects in a-Si:H films, many previous experimental works on ESR and ENDOR have been suggested. This paper reports our results of computer simulation for some dangling bond clusters. Using the molecular orbital method, the hyperfine interaction constant and Lande splitting factor are obtained. Compared these results with experimental data and analyzed electronic configuration of these clusters with the defects state, the effects of neighbor hydrogen and other atoms on the dangling bonds are discussed.     

准周期a-Si:H/a-SiN_x:H超晶格

本文首次报道成功地实现了非晶态半导体准周期(无平移对称性)超晶格结构.利用辉光放电汽相淀积技术,由两种超薄的a-Si:H层和a-SiN_x:H层按Fibonacci序列程序淀积而构成一维准周期超晶格.其中两种一维周期格子的调制波长比为黄金分割τ=(1+5~(1/2))/2.剖面电子显微像和相应的电子衍射花样揭示出这类新型非晶态半导体超晶格的奇异性质.简单的理论计算给予实验衍射图像以明确的物理解释.     

非晶硅中的缺陷态光吸收谱

<正> 非晶硅薄膜的光学及电学性质与共电子局域态分布紧密相关。为了改进非晶硅薄膜器件的性质,如太阳能电池、薄膜晶体管等,需要低局域态密度的材料,因而测量并了解局域态的性质十分重要。局域态包括带尾态、缺陷态及亚稳缺陷态。本文着重讨论缺陷态及亚稳缺陷态。     

a-Si:H薄膜的磷-碳二元复合掺杂改性研究

以SiH4,PH3,CH4为源气体,采用射频等离子增强化学气相沉积(RF-PECVD)方法,通过改变CH4流量制备了磷、碳二元掺杂非晶硅薄膜,研究了磷、碳二元掺杂对薄膜微观结构和光学性能的影响.用X射线光电子能谱仪(XPS)观察到了C-Si峰的存在,同时发现随着CH4流量的增加,薄膜中C元素含量逐渐增大.傅里叶转换红外光谱(FTIR)测试表明,掺杂薄膜中的H含量随着CH4流量的增加逐渐增大,由11.5%增大到24.6%.光学性能测试表明,随着CH4流量的增加,掺杂薄膜的折射率逐渐降低,而光学带隙逐渐增加.     

Flexible a-Si:H Position-Sensitive Detectors

Flexible and large area (5 mm /spl times/80 mm with an active length of 70 mm) position-sensitive detectors (PSDs) deposited onto polymeric substrates (polyimide-Kapton VN) have been fabricated. The optimized structure presented is based on a heterojunction of amorphous silicon (a-Si:H)/ZnO:Al. The sensors were characterized by spectral response, photocurrent dependence as a function of light intensity, and position detection measurements. The set of data obtained on one-dimensional PSDs based on the heterojunction show excellent performances with a maximum spectral response of 0.12 A/W at 500 nm and a nonlinearity of /spl plusmn/10% over 70-mm length. The produced sensors present a nonlinearity higher than those ones produced on glass substrates, due to the different thermal coefficients exhibited by the polymer and the a-Si:H film. In order to prove this behavior, it was measured the defect density obtained by the constant photocurrent method on a-Si:H thin films deposited on polymeric substrates and bent with different radii of curvature.     

Large-area low-frequency discharge-produced a-Si:H

Using a capacitive glow discharge process at 380 kHz, very-large-area uniform films of a a-Si:H (60 cm diameter) have been deposited. The thickness uniformity, activated conductivity, photoconductivity and photoinduced effects in these films are discussed.     

a-Si:C:H and a-Si:N:H Thin Films Obtained by PECVD for Applications in Silicon Solar Cells

Hydrogenated amorphous silicon-carbon (a-Si:C:H) and hydrogenated silicon-nitrogen (a-Si:N:H) antireflective films were deposited by plasma-enhanced chemical vapor deposition (PECVD) at 13.56 MHz in SiH₄ + CH₄ and SiH₄ + NH₃ gaseous mixtures of various compositions. The silicon and glass samples were investigated by optical spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). A correlation between film properties and process parameters was found. The refractive index decreased and the energy gap increased with an increase of carbon and nitrogen in the films. For some process parameters, it was possible to obtain smooth, hydrogen rich, and homogeneous films of low reflectivity. The silicon solar cells with antireflective coatings revealed an increase in efficiency.     

Effect of thermal treatment on structure and properties of a-Si:H films obtained by cyclic deposition

The effect of thermal treatment in a vacuum on the structure and properties of amorphous hydrogenated silicon (a-Si:H) films obtained by cyclic deposition with intermediate annealing in hydrogen plasma was studied. a-Si:H films deposited under optimal conditions are characterized by the nonuniform distribution of the nanocrystalline phase (<1 vol %) across the film thickness and have the optical gap E _g=1.85 eV, the activation energy of conductivity E _a =0.91 eV, and a high photosensitivity (σ_ph/σ_d≈10⁷ under illumination of 100 mW/cm² in the visible spectral range). Transmission electron microscopy studies demonstrated that thermal treatment in a vacuum leads to blurring of the initial layered structure of a-Si:H films and to a somewhat higher amount of nanocrystalline inclusions in the amorphous phase matrix. Thermal treatment above 350°C causes a dramatic increase in the dark conductivity, as well as the resulting decrease in the photosensitivity, of a-Si:H films.     

Gated-four-probe a-Si:H TFT structure: a new technique to measurethe intrinsic performance of a-Si:H TFT

In this letter, a new technique based on gated-four-probe hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) structure is proposed. This new technique allows the determination of the intrinsic performance of a-Si:H TFT without any influence from source/drain series resistances. In this method, two probes within a conventional a-Si:H TFT are used to measure the voltage difference within a channel. By correlating this voltage difference with the drain-source current induced by applied gate bias, the a-Si:H TFT intrinsic performance, such as mobility, threshold voltage, and field-effect conductance activation energy, can be accurately determined without any influence from source/drain series resistances     

等离子刻蚀a-Si:H/a-C:H超晶格

本文介绍了 C_yF_(14)+ O_2等离子刻蚀 a=Si:H/a-C:H 超晶格的工艺原理及方法,简便可行.     

a—Si：H TFT有源矩阵制造技术的研究

对ａ：Ｓｉ：Ｈ ＴＦＴ有源矩阵的一些关键制造工艺进行研究。研究了Ｔａ２Ｏ５／ａ－ＳｉＮｘ双绝缘层的制备技术，提出了一种新的双有源层结构ａ－Ｓｉ：Ｈ ＴＦＴ来降低背光源对器件特性的影响，研制的ａ－Ｓｉ：Ｈ ＴＦＴ有源矩阵实现了彩色视频信号的动态显示。     

Anodic oxidation of a-Si:H films

It is shown that thick native oxide layers (up to 2500 ?) can be grown on a-Si:H films at room temperature by anodic oxidation. Ellipsometric measurements indicate uniformity of the oxide layer with a refractive index of 1.46. The voltage growth rate is found to be 5.3 ?/V.