硼掺杂对μc-Si:H薄膜微结构和光电性能的影响

采用射频等离子增强化学气相沉积(RF-PECVD)法制备了掺硼氢化微晶硅(μc-Si:H)薄膜,研究了硼掺杂对薄膜的结晶状况、沉积速率、暗电导率和光学带隙的影响.拉曼光谱、扫描电子显微镜、分光光度计和电导率测试结果表明:当掺硼比(B2H6/SiH4)由0.1;增加到0.75;时,硅膜的晶化率逐渐降低,并由微晶向非晶过渡;沉积速率随掺硼比的增加线性增大;暗电导率先升高后下降,当掺硼比为0.5;时,暗电导率最大;光学带隙随掺硼比的增加逐渐减小.     

P型微晶硅薄膜材料性能的研究

本文讨论了P型微晶硅薄膜性能随硅烷浓度(SC)的变化.采用X射线衍射仪(XRD),拉曼光谱仪和傅立叶变换红外吸收光谱仪(FTIR)对薄膜的结构进行了表征.随硅烷浓度的增加,微晶硅薄膜材料的生长速率和暗电导率(σd)逐渐增大,光学带隙逐渐降低.当硅烷浓度为2.0;时,硅基薄膜材料是以非晶硅为主并有散落的微晶硅颗粒的非晶硅结构.当硅烷浓度为1.5;时,硼的掺杂效率最大,同时可观察到硼抑制薄膜晶化的现象.     

从P-a-SiC:H到P-μc-Si:H过程中材料特性的变化

采用RF-PECVD方法,在P-a-SiC:H薄膜沉积技术基础上,通过逐步减小碳、硼的掺杂浓度,增大氢稀释率,使材料从非晶态向微晶态转变,在获得本征微晶材料之后,再逐步增大硼掺杂浓度,得到P型微晶硅薄膜材料(暗电导率为5.22×10-3S/cm,光学带隙大于2.0eV).在这个过程中可以明显观察到碳、硼抑制材料晶化的作用.     

硼掺杂对用于SHJ太阳电池的nc-Si∶H薄膜微结构的影响

采用RF-PECVD法在低温低功率密度下制备了p型nc-Si∶H薄膜,并系统地研究了硼掺杂对薄膜微结构及光电性能的影响.结果表明:由于“硼掺杂效应”,随着掺硼比的增大,nc-Si∶H薄膜的晶化率逐渐降低,晶粒尺寸减小,薄膜的择优取向由[111]变为[220];光学带隙逐渐减小,电导率则先升后降;本实验中薄膜的最优掺杂比为0.3;.以优化后的p型nc-Si∶H薄膜做窗口层,SHJ太阳电池的性能得到明显改善,获得了效率为14.1;的电池.     

HWCVD低温制备超薄硼掺杂纳米晶硅薄膜

采用热丝化学气相沉积(HWCVD)技术在低温条件下(100℃)制备超薄(～30 nm)的硼掺杂硅薄膜.系统研究了氢稀释比例RH对薄膜的微结构和电学性能的影响.当RH由55增加至115,薄膜的有序度增加,晶化率升高,载流子浓度增加,暗电导率增加;同时,薄膜的缺陷密度增加、霍尔迁移率降低.实验证实,当RH=55～70时,超薄硅薄膜开始晶化,这是薄膜由非晶到纳米晶的转化区.快速热退火工艺进一步提高了薄膜导电率.在RH=115、衬底温度为100℃沉积条件下,经过420℃、80 s退火,获得电导率为6.88 S/cm的超薄硼掺杂纳米晶硅薄膜.     

P型非晶硅薄膜制备及其在HIT太阳电池中应用

采用RF-PECVD沉积技术制备P型非晶硅薄膜材料,研究硼烷浓度和加热温度对薄膜性能的影响.通过对两者优化,制备出了宽光学带隙、高电导率和致密性较好的P型非晶硅材料.作为窗口层应用到HIT太阳电池中,对其厚度进行优化,在N型单晶硅衬底上制备出了效率为14.28;的HIT太阳电池.     

热丝化学气相沉积微晶硅薄膜结构及性质研究

采用热丝化学气相沉积(HWCVD)技术,以钨丝作为热丝,在不同热丝温度和氢稀释度下,分别在玻璃和单晶硅片衬底上沉积微晶硅(μc-Si∶H)薄膜材料.对所制备的微晶硅薄膜材料使用XRD、傅里叶变换红外吸收光谱、透射谱等进行结构与性能的表征分析.结果表明,随着热丝温度升高,氢稀释度变大,薄膜呈现明显的(220)择优生长取向,晶粒尺寸逐渐增大,光学吸收边出现红移,光学带隙逐渐变小.通过优化沉积参数,在热丝温度为1577℃、氢稀释浓度为95.2;、衬底温度为350℃,沉积速率为0.6 nm/s和沉积气压8 Pa条件下,制备的微晶硅薄膜呈现出了(220)方向的高度择优生长取向,平均晶粒尺寸为146 nm,光学带隙约为1.5 eV,光电导率σ.为3.2×10-6Ω-1·cm-1,暗电导率σrd为8.6×10-7 Ω-1·cm-1,表明制备的材料是优质微晶硅薄膜材料.     

P／I界面处理对a-Si：H柔性太阳能电池性能的影响

采用等离子体辅助化学汽相沉积(PECVD)技术制备本征非晶硅薄膜,对p/i界面进行处理.在此基础上,制备P型微晶硅(μc-Si:H)薄膜与柔性太阳能电池.对P型硅薄膜及太阳能电池的性能进行研究.结果表明:对p/i界面采用H等离子体处理,再引入一定厚度的成核层,可以成功得到高电导率的P型微晶硅窗口层,提高柔性太阳能电池的光伏特性.其中的成核层,不仅促进微晶相P层的生长,还可以起到界面缓冲层的作用.     

溅射气压对碳硅氧薄膜透过率及光学带隙的影响

采用射频磁控溅射技术在玻璃基底和单晶硅片(100)上制备了碳硅氧(SiOC)薄膜,通过扫描电镜、X射线衍射、拉曼光谱、X射线光电子能谱及紫外可见透射光谱等技术手段对其进行了分析,研究了在不同溅射气压下所制备薄膜的组分、透过率及光学带隙.结果表明:随着溅射气压的增大,薄膜内部sp3键含量、透过率及光学带隙均随之增大,sp3键及其形成的宽带隙σ键对薄膜光学带隙有着较大影响.在溅射气压为3.0 Pa的条件下,薄膜光学带隙为2.67 eV.     

掺磷nc-Si:H薄膜的微结构与光电特性

采用常规射频等离子体增强化学气相沉积方法,以高氢稀释的SiH4为源气体和以PH3为掺杂剂,制备了磷掺杂的氢化纳米晶硅薄膜.结果表明,薄膜的生长速率随PH3/SiH4流量比(Cp)增加而显著减小.Raman谱的研究证实,随CP增加,薄膜的晶化率经历了先增大后减小的过程,当C,=1.0;,晶化率达到最大值45.9;.傅里叶变换红外吸收谱测量结果显示,薄膜中的H含量在CP=2.0;时达到最低值9.5;.光学测量结果表明,本征和掺P的氢化纳米晶硅薄膜在可见光谱范围呈现出良好的光吸收特性,在0.8 ～3.0 eV范围内,nc-Si (P):H薄膜的吸收系数显著大于c-Si.和α-Si:H薄膜相比,虽然短波范围的吸收系数较低,但是在hv＜1.7 eV区域,nc-Si(P):H薄膜的吸收系数要高两到三个量级,显示出优良的红光响应.电学测量表明,适当掺P会显著提高氢化纳米晶硅薄膜的暗电导率,当CP=0.5;时,薄膜的暗电导率可达5.4S·cm-1.     

Crystallization of n-doped amorphous silicon PECVD films: comparison between SPC and RTA methods

Amorphous silicon films are deposited by radio-frequency plasma-enhanced chemical-vapor deposition (RF-PECVD) with different n-doping rates. The amorphous films are subsequently crystallized using either solid phase crystallization (SPC) or rapid thermal annealing (RTA). We compare the effect of the n-doping rate on some properties of the microcrystalline silicon films obtained with both techniques. In the SPC process, the time required for the beginning of the crystallization decreases with increasing phosphorus doping. Moreover, doped films present slightly higher crystal size than intrinsic films but the doping rate does not significantly influence the grain size. For RTA, the doping rate decreases the crystallization temperature and increases significantly the crystal size. Whatever the doping rate, the average grain sizes obtained by RTA are larger than those obtained by SPC. The electrical resistance of the crystallized films also depends on the crystallization process: RTA films present a lower dark conductivity than SPC films. These results are discussed taking into account the different kinetics of both crystallization techniques and the role played by the silicon dangling bonds and their charge states on the crystal growth.     

Investigations on Sn-doped Ni oxide thin films and their use as optical sensor devices

Tin-doped NiO thin films (5.0, 7.4, and 9.3 at.% Sn) have been prepared by thermal oxidation of vacuum deposited films of pure Ni and Sn elements on glass and silicon substrates. The prepared films were comprehensively characterised by X-ray fluorescence, X-ray diffraction, UV–VIS-NIR absorption spectroscopy, and electrical (ac and dc) measurements. Experimental data indicate that Sn⁴⁺ doping slightly stress the host NiO crystalline structure and change the optical and electrical properties. The electrical and optical behaviours of the Sn-doped NiO films show that they are wide-band semiconductors with band gap 3.69–3.76 eV and have insulating properties. The ac and dc electrical measurements show that it is possible to use Sn-doped NiO as an optical-sensitive oxide in metal-oxide-silicon configurations.     

β-Ga2O3薄膜掺杂工艺及性能研究进展

β-Ga2O3薄膜因其禁带宽度大,稳定性高,生产成本低等优势,被认为是在光电探测器、发光器件等领域非常有前景的材料之一.但β-Ga2O3较低的导电率限制了其在某些领域的应用,通过掺杂技术改进β-Ga2O3薄膜在光学和电学的性能吸引了大量科研者的目光.本文介绍了几种常用的掺杂手段及掺杂对β-Ga2O3薄膜结构和光电特性的影响,并对以后的研究工作进行了展望.     

高掺锌/镁铌酸锂薄膜的光电性质

室温下采用射频磁控溅射(RFMS)技术在玻璃与硅基板上分别沉积了纯铌酸锂LN薄膜、高掺锌(6%,摩尔分数,下同)LN∶ZnO薄膜和高掺镁(5%)LN∶MgO薄膜,并在575 ℃条件下退火进一步提高薄膜的结晶度。通过原子力显微镜(AFM)、X射线衍射(XRD)、紫外可见吸收(UV-Vis)和椭偏仪等测试研究了三种铌酸锂薄膜的形貌、结构和光学性质。XRD分析表明掺杂铌酸锂薄膜和纯铌酸锂薄膜具有相同的生长取向,AFM、XRD、UV-Vis测试结果表明,掺杂将增大铌酸锂薄膜的晶粒尺寸,光学带隙的红移现象与晶粒尺寸相关,且掺Mg的影响大于掺Zn。此外利用霍尔效应测试仪研究了LN、LN∶ZnO和LN∶MgO薄膜的电学性质,测试结果表明三种薄膜均为n型半导体,其中LN∶MgO薄膜电导率的变化趋势不同于LN∶ZnO和LN薄膜,且发现温度在18~50 ℃范围内,随着温度的升高,LN∶MgO薄膜的电导率变化微小,而LN∶ZnO和LN薄膜的电导率逐渐增大。     

Optical properties of hydrogenated amorphous silicon films doped with fluorinated gases

Doped amorphous silicon films were prepared by plasma-enhanced chemical vapour deposition of silane and hydrogen mixtures, using phosphorus pentafluoride (PF₅) and boron trifluoride (BF₃) as dopant precursors. The films were studied by UV-vis spectroscopy and their photo and dark conductivity were measured, the latter as a function of temperature. The optical gap of the n-type samples, doped with PF₅, diminished as the concentration of this gas in the plasma was increased. However, the optical gap of p-type samples, doped with BF₃, did not show any appreciable optical gap decrease as the concentration of BF₃ was varied from 0.04% to 4.7%. The dark conductivity of the p-type films at these extremes of the doping range were 7.6 × 10⁻¹⁰ and 3.5 × 10⁻¹ Ω⁻¹ cm⁻¹, respectively.     

Normal and anti Meyer–Neldel rule in conductivity of highly crystallized undoped microcrystalline silicon films

We have studied the electrical conductivity behavior of highly crystallized undoped hydrogenated microcrystalline silicon (μc-Si:H) films having different microstructures. The dark conductivity is seen to follow Meyer–Neldel rule (MNR) in some films and anti-MNR in others, which has been explained on the basis of variation in the film microstructure and the corresponding changes in the effective density of states distributions. A band tail transport and statistical shift of Fermi level are used to explain the origin of MNR as well as anti-MNR in our samples. The observation of MNR and anti-MNR in electrical transport behavior of μc-Si:H is discussed in terms of the basic underlying physics of their origin and the significance of these relationships.     

Modification of amorphous hydrogenated silicon by co-sputtered aluminum

The electronic and optical properties of a-Si_1?xH_x have been modified by the incorporation of aluminum. Samples were prepared by rf sputtering in a hydrogenated atmosphere from a composite silicon-aluminum target. This paper reports on several modified material parameters including the optical band gap, electrical conductivity, and thermal activation energy. Aluminum concentrations up to 10.6% in the target have been investigated. It is observed that the optical band gap remains constant at 1.83 eV for Al concentrations up to 2.7%. For higher concentrations there is a marked decrease in optical gap. The conductivity initially decreases with small Al concentration and the activation energy increases, characteristic of compensation of the inherently n-type material. For higher Al concentrations the conductivity increases by seven orders of magnitude and the activation energy decreases to a minimum of about 0.2 eV. The increase in conductivity can be explained by both the movement of the Fermi level and the shrinking band gap. Microprobe analyses have also been performed to determine the amount of Al actually incorporated into the films. Finally, implications of these results are discussed and compared to previously reported results on gas phase doping and ion implantation.     

Microcrystalline silicon oxide (μc-SiOx:H) alloys: A versatile material for application in thin film silicon single and tandem junction solar cells

We report on the development and application of n-type hydrogenated microcrystalline silicon oxide (μc-SiO_x:H) alloys in single and tandem junction thin film silicon solar cells. Single junction microcrystalline silicon (μc-Si:H) solar cells are prepared in n-i-p deposition sequence where n-type μc-SiO_x:H films serve as window layers. In tandem solar cells, μc-SiO_x:H layers are placed between amorphous (a-Si:H) and μc-Si:H component cells, serving as an intermediate reflector. The requirements for μc-SiO_x:H layer depending on its application are discussed. Our results show that the optical, electrical and structural properties of μc-SiO_x:H can be conveniently tuned over a wide range to fulfil various requirements for applications in both types of cells. Additionally, the properties of μc-SiO_x:H layers appear to be substrate dependent, which should be taken into account when layers are utilized in cells. The advantages of low refractive index and high optical band gap allow to achieve high efficiencies of 9.2% and 12.6% for single junction and tandem solar cells, respectively.     

Effect of gallium incorporation on the physical properties of ZnO films grown by spray pyrolysis

Gallium-doped zinc oxide thin films were deposited by the spray pyrolysis technique onto Corning 7059 glass substrates at a temperature of 350°C using a precursor solution of zinc acetate in isopropyl alcohol. The films were prepared using different gallium concentrations keeping the other deposition parameters such as air and solution flow rates and solution concentration constant. The variations of the structural, electrical and optical properties with the doping concentration were investigated. X-ray diffraction data showed that the films were polycrystalline with the (0 0 2) preferred orientation. The texture coefficient and grain size were evaluated for different doping concentrations. The films with 5.0 at% gallium had a resistivity of 1.5×10⁻³ Ω cm and a transmittance of 85% with an energy band gap of 3.35 eV.     

A comparison of structures and properties of SiNx and SiOx films prepared by PECVD

In this paper, amorphous silicon nitride (SiNx) and silicon oxide (SiOx) films were prepared by plasma-enhanced chemical vapor deposition (PECVD). The chemical structures and physical properties of the resulting materials were investigated and compared. Results reveal that SiOx films match better with Si substrate, whereas SiNx films exhibit larger refractive index, moderate optical band gap, and higher Young's modulus and film hardness. In overall, SiNx films are more suitable to serve as supporting and insulating materials for VOx-based infrared microbolometers. The difference in the physical properties is attributed to various bonding configurations for the resulting materials. Finally, several methods for evaluating the residual stresses in amorphous thin films were discussed.