硼掺杂硅薄膜及其在叠层电池隧道结中的应用

Boron-doped hydrogenated silicon films with different gaseous doping ratios（B2H6/SiH4） were deposited in a plasma-enhanced chemical vapor deposition（PECVD） system.The microstructure of the films was investigated by atomic force microscopy（AFM） and Raman scattering spectroscopy.The electrical properties of the films were characterized by their room temperature electrical conductivity（σ） and the activation energy（Ea）.The results show that with an increasing gaseous doping ratio,the silicon films transfer from a microcrystalline to an amorphous phase,and corresponding changes in the electrical properties were observed.The thin boron-doped silicon layers were fabricated as recombination layers in tunnel junctions.The measurements of the I-V characteristics and the transparency spectra of the junctions indicate that the best gaseous doping ratio of the recombination layer is 0.04,and the film deposited under that condition is amorphous silicon with a small amount of crystallites embedded in it.The junction with such a recombination layer has a small resistance,a nearly ohmic contact,and a negligible optical absorption.     

Effect of Film Thickness on Properties of a-Si∶H Films

The a-Si∶H films with different thickness smaller than 1 μm were deposited by plasma enhanced chemical vapor deposition (PECVD) under the optimum deposition conditions. The effect of different thickness on film properties is analyzed.The results show that,with the increase of the film thickness,the dark conductivity, photoconductivity and threshold voltage increase, the optical gap and peak ratio of TA to TO in the Raman spectra decrease, the refractive index keeps almost constant, and the optical absorption coefficient and current ratio of on/off state first maximize and then reduce.     

非晶碲镉汞薄膜的暗电导与光电导

This paper reports the dark conductivity and photoconductivity of amorphous Hg_(0.78)Cd_(0.22)Te thin films deposited on an Al_2O_3 substrate by RF magnetron sputtering.It is determined that dark conduction activation energy is 0.417 eV for the as-grown sample.Thermal quenching is absent for the as-grown sample during the testing temperature zone,but the reverse is true for the polycrystalline sample.Photosensitivity shows the maximum at 240 K for amorphous thin films,while it is higher for the as-grown ...     

Development of aluminum-doped ZnO films for a-Si:H/μc-Si:H solar cell applications

This study deals with the optimization of direct current(DC) sputtered aluminum-doped zinc oxide (AZO) thin films and their incorporation into a-Si:H/μc-Si:H tandem junction thin film solar cells aiming for high conversion efficiency.Electrical and optical properties of AZO films,i.e.mobility,carrier density,resistivity, and transmittance,were comprehensively characterized and analyzed by varying sputtering deposition conditions, including chamber pressure,substrate temperature,and sputtering power.The correlations between sputtering processes and AZO thin film properties were first investigated.Then,the AZO films were textured by diluted hydrochloric acid wet etching.Through optimization of deposition and texturing processes,AZO films yield excellent electrical and optical properties with a high transmittance above 81%over the 380-1100 nm wavelength range,lowsheet resistance of 11Ω/□and high haze ratio of 41.3%.In preliminary experiments,the AZO films were applied to a-Si:H/μc-Si:H tandem thin film solar cells as front contact electrodes,resulting in an initial conversion efficiency of 12.5%with good current matching between subcells.     

Investigation of Induced Distortions in a-Si∶H/a-SiNx∶H Multilayers by Raman Scattering Technique

The a-Si∶H/SiNx∶H sample series are investigated by means of Raman scattering technique(RST). The result shows that due to the structural mismatch between a-Si∶H and a-SiNx∶H, severe induced distortions are produced in the interface of the heterojunction, and these induced distortions tend towards a certain energy state. The ordering of the interface structure depends on the periodic number of multilayer thin films.     

酞菁锌/氢化非晶硅复合薄膜光电性质的研究

Composites consisting of hydrogenated amorphous silicon （a-Si： H, inorganic） and zinc phthalocyanine （ZnPc, organic） were prepared by vacuum evaporation of ZnPc and sequential deposition amorphous silicon via plasma enhanced chemical vapor deposition （PECVD）. The optical and electrical properties of the composite film have been investigated. The results demonstrate that ZnPc can endure the temperature and bombardment of the PECVD plasma and photoconductivity of the composite film was improved by 89.9% compared to pure a-Si： H film. Electron mobility-lifetime products/lr of the composite film were increased by nearly one order of magnitude from 6.96 × 10^-7 to 5.08 × 10^-6 cm2/V. Combined with photoconductivity spectra of the composites and pure a-Si： H, we tentatively elucidate the improvement in photoconductivity of the composite film.     

Microcrystalline Silicon Materials and Solar Cells Prepared by VHF-PECVD

A series of samples deposited by VHF - PECVD at different pressures were studied. The measurement results of photosensitivity (photo conductivity/dark conductivity) and activation energy indicaten ear the same rule with the change of the pressure. The results measured by Raman scattering spectra, X-ray diffraction and FTIR all proved the evident crystallization of the materials. Treating the p/i interface by hydrogen has a great improving effect on the performance of the microcrystalline silicon (μc-Si) p-i-n solar cells if the treatment time was appropriate. An efficiency of 4.24% for μc-Si p-i-n solar cells deposited by VHF-PECVD was firstly obtained.     

The effect of the film thickness and doping content of SnO2:F thin films prepared by the ultrasonic spray method

This paper reports on the effects of film thickness and doping content on the optical and electrical properties of fluorine-doped tin oxide. Tin(II) chloride dehydrate, ammonium fluoride dehydrate, ethanol and HCl were used as the starting materials, dopant source, solvent and stabilizer, respectively. The doped films were deposited on a glass substrate at different concentrations varying between 0 and 5 wt% using an ultrasonic spray technique. The SnO2 :F thin films were deposited at a 350 C pending time(5, 15, 60 and 90 s). The average transmission was about 80%, and the films were thus transparent in the visible region. The optical energy gap of the doped films with 2.5 wt% F was found to increase from 3.47 to 3.89 eV with increasing film thickness, and increased after doping at 5 wt%. The decrease in the Urbach energy of the SnO2:F thin films indicated a decrease in the defects. The increase in the electrical conductivity of the films reached maximum values of 278.9 and 281.9( cm)1for 2.5 and 5 wt% F, respectively, indicating that the films exhibited an n-type semiconducting nature. A systematic study on the influence of film thickness and doping content on the properties of SnO2:F thin films deposited by ultrasonic spray was reported.     

快速光热退火法制备多晶硅薄膜的研究

为了制备应用于太阳电池的优质多晶硅薄膜,研究了非晶硅薄膜的快速光热退火技术。先利用 PECVD 设备沉积非晶硅薄膜,然后放入快速光热退火炉中进行退火。退火前后的薄膜利用 X 射线衍射仪(XRD)和扫描电子显微镜(SEM)测试其晶体结构及表面形貌,用电导率设备测试其暗电导率。研究表明退火温度、退火时间对非晶硅薄膜的晶化都有很大的影响,光热退火前先用常规高温炉预热有助于增大多晶硅薄膜的晶粒尺寸和暗电导率。     

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.     

Study of thermal equilibration in selenium- and sulphur-doped a-Si:H

The present paper reports the thermal equilibration in selenium- and sulphur-doped hydrogenated amorphous silicon thin films deposited by plasma-enhanced chemical vapour deposition. The conductivity of Se- and S-doped a-Si:H is observed to be very sensitive to the rate at which the samples are cooled following the high temperature anneal. Arrhenius plots of conductivity for various doped films revealed thermal equilibration above the equilibration temperature, T _E, thus accounting for larger activation energies. The barrier energy is lower for a-Si,Se:H than for a-Si,S:H, due to a higher defect density in S-doped films.     

Low temperature crystallization of amorphous silicon using an excimer laser

Low temperature processing is a prerequisite for compatible technologies involving combined a-Si and poly-silicon devices or for fabricating these devices on glass substrates. This paper describes excimer-laser-induced crystallization of thin amorphous silicon films deposited by plasma CVD (a-Si:H) and LPCVD (a-Si). The intense, pulsed UV produced by the laser is highly absorbed by the thin amorphous material, but the average temperature is compatible with low temperature processing. The process produces crystallites whose structure and electrical characteristics vary according to starting material and laser scan parameters. The crystallized films have been principally characterized using x-ray diffraction, TEM, and transport measurements. The results indicate that crystallites nucleate in the surface region and are randomly oriented. The degree of crystallization near the surface increases as the doping level and/or deposited laser energy density is increased. The crystallite size increases with a power law dependence on deposited energy, while the conductivity increases exponentially above threshold for unintentionally doped PECVD films. The magnitude of the Hall mobility of the highly crystallized samples is increased by two orders of magnitude over that of the amorphous starting material.     

用于TFT有源层的Ar~+激光结晶a-Si:H的性质(英文)

This paper demonstrates the technological approach to the high performance a-Si:H thin film transistor (TFT) fabricated by the Ar+ laser-crystallization technique on the fused quartz substrates. The a-Si:H films for the active layer of TFT were prepared in a capacitively coupled glow-discharge deposition system. The films were crystallized by CW Ar+ laser scanning at low speeds (3-5 cm/s). The laser power ranges from 2.5W to 5.0W. The TEM cross-section micrograph illustrates that a liquid phase laser crystallization region (LP-LCR) has defect-free of structure with a grain size of the order of handreds of micron. In the Raman spectrum of LP-LCR, 475 cm-1 peak of a-Si:H disappears and 520 cm-1 peak of c-Si becomes stronger and sharper. The value of conductivity in the layer of LP-LCR is five orders of magnitude larger than the one in asepositedd a-Si:H film. We also discussed some problems to be overcome in application of a-Si : H TFTs in LCD.     

Study of photoconductivity and persistent photoconductivity in sulphur-doped amorphous hydrogenated silicon

We report on the spectral response and intensity dependence of photoconductivity (PC) and persistent photoconductivity (PPC) in plasma-enhanced chemical vapour deposition grown sulphur-doped n-type a-Si:H films. From the intensity dependence of PC it is found that the addition of sulphur changes the recombination mechanism from monomolecular for intrinsic and low-doped films to bimolecular at a high sulphur doping level. The photo-induced metastable increase of dark conductivity in these films is found to be quite similar to that for compensated and doping-modulated a-Si:H films. The PPC effect is detectable up to an illumination temperature of at least 380 K the highest temperature used in this study. At 300 K the conduction persists at a level of one order higher than the equilibrium dark conductivity for over 10³ s after removing the excitation. The PPC in a-Si, S:H is explained in terms of the valence alternation pair model.     

Improving the Performance of SiGe Metal–Semiconductor–Metal Photodetectors by Using an Amorphous Silicon Passivation Layer

SiGe metal-semiconductor-metal photodetectors (MSM-PDs) with a thin amorphous silicon (a-Si:H) passivation layer have been fabricated by an ultrahigh-vacuum chemical vapor deposition (UHVCVD) system. It was found that the thin (30 nm) a-Si:H passivation layer could effectively suppress the dark current of SiGe MSM-PDs. As compared to the unpassivated devices, the dark current for devices with a-Si:H passivation layers was drastically reduced by 1.7 times 10⁵, and the photo-to-dark current ratio was enhanced by 1.33 times 10⁶. We attribute this result to the passivation effect of a-Si:H films on SiGe surfaces by hydrogen diffusion, which can compensate the dangling bonds on the SiGe surface.     

Observation of Meyer–Neldel rule in CdS thin films

A study of electrical transport in CdS thin films is reported. We have observed, for the first time, that CdS thin film conductivity obeys the Meyer–Neldel rule (MNR). This was deduced from linking the conductivity pre-exponential factor to the activation energy variation. CdS films were deposited by chemical bath deposition at different solution temperatures in order to vary the electrical activation energy of the films. A correlation between the MNR rule and the disorder in the film network is highlighted. The multi-trapping process in the band tail-localized states governs the conductivity in CdS films. This explains the MNR observation in CdS films. The variation of the electrical conductivity pre-exponential factor and activation energy are correlated to the disorder in the film network; this was explained in terms of polaron formation and phonon–electron coupling with disorder.     

利用等离子增强化学汽相沉积生长初期快速结晶的纳米晶硅

成功地利用传统的等离子增强化学汽相沉积技术制备了纳米晶硅。为了提高生长初期的结晶速度,在PECVD设备和干法刻蚀设备中,利用H2/SF6等离子体对Si Nx薄膜表面进行处理。在制备纳米/微米晶粒结晶硅时常用的氢气稀释条件下,沉积得到了纳米晶硅。利用XRD和TEM观察了氢化纳米晶硅(nc-Si∶H)的微结构,发现实验成功得到了小于10 nm的晶体硅。为了检测结构和电学特性,测试了纳米晶硅薄膜的亮态和暗态电导率。室温下,电导率从非晶硅的10-10S/cm增加到10-5S/cm。     

微量硼掺杂氢化非晶硅薄膜光电导性能研究

采用射频磁控溅射的方法制备了微量硼掺杂氢化非晶硅薄膜,对样品的光电导性能进行了研究.结果表明,不同的硼掺杂量下,氢化非晶硅薄膜透过率随掺杂量的增加而变大,透过率曲线截止边红移;吸收系数随着硼掺杂量的增加而增大;薄膜的折射率随着波长的增加而下降,同一波长下随着掺杂量的增加而增大,在500 nm波长处折射率达到4.2以上,最大到4.6;薄膜的交流电阻率在微量硼掺杂下随着硼掺杂量的增加先减小后增大.