一种带隙基准电压源的设计与仿真

设计了一款带隙基准电压源,基于0.18μm的CMOS工艺,在Hspice下仿真,仿真结果表明,温度在-25~80℃内变化时,温度系数为9.14×10-6℃;电源电压在3~5 V之间变化时,基准电压在1 250±43 mV内变化,满足设计要求。     

Investigation of donor–acceptor copolymer films and their blends with fullerene in the active layers of bulk heterojunction solar cells by Raman microspectroscopy

Thin films made of three low-band gap donor–acceptor copolymers (CDTF, CDTDP and CDTDOP) composed of 4,6-bis(3′-dodecylthiophen-2′-yl)thieno[3,4-c][1,2,5]thiadiazole-5′,5′-diyl as an electron-acceptor structural unit and various electron-donor structural units, such as 9,9-bis(2-ethylhexyl)fluorene-2,7-diyl, 2,5-didodecyl-1,4-phenylene and 2,5-didodecyloxy-1,4-phenylene, respectively, and thin films of their blends with various ratios of a soluble fullerene derivative [6,6]-phenyl C₆₁-butyric acid methyl ester ([60]PCBM) as an active layer for bulk heterojunction solar cells were studied by means of UV–vis absorption spectroscopy and Raman microspectroscopy. The molecules of CDTDP and CDTDOP possess the same main chains; they differ in the side-chain oxygen only, which changes the donor strength of the donor units. UV–vis and Raman studies allow us to show differences in the hindering of molecule planarization and aggregation in the blends. Absorption of the polymer films covered the whole visible spectral region and extended up to near infrared for CDTDOP. The absorption behavior of the CDTDP blend films qualitatively differed from the absorption behavior of the blend films of CDTF or CDTDOP. The Raman measurements were performed at two different laser excitation wavelengths (633 and 785 nm), which enabled the photoluminescence of both components in the Raman spectra to be distinguished. The Raman study was performed in different parts of the films, including the separated areas. It was proven that the separated areas in the blend films had higher contents of [60]PCBM than the rest of the films.     

Annealing temperature dependent structural and optical properties of electrodeposited CdSe thin films

Cadmium selenide films were synthesized using simple electrodeposition method on indium tin oxide coated glass substrates. The synthesized films were post annealed at 200 °C, 300 °C and 400 °C. X-ray diffraction of the films showed the hexagonal structure with crystallite size <3 nm for as deposited films and 3–25 nm for annealed films. The surface morphology of films using field emission scanning electron microscopy showed granular surface. The high resolution transmission electron microscopy of a crystallite of the film revealed lattice fringes which measured lattice spacing of 3.13 Å corresponding to (002) plane, indicating the lattice contraction effect, due to small size of CdSe nanocrystallite. The calculation of optical band gap using UV–visible absorption spectrum showed strong red-shift with increase in crystallite size, indicating to the charge confinement in CdSe nanocrystallite.     

The effect of Fe3+-doped on structure and optical properties of mesoporous Al2O3/SiO2 composite

The composition of 98.0(Al_1.9Fe_0.1O₃)/2.0SiO₂ was synthesized by modifying auto-combustion method and the effect of calcination temperature on structure and optical properties were studied. The prepared powders were characterized by X-ray diffraction (XRD) patterns, X-ray fluorescence (XRF) spectrometry, Ultraviolet-visible (UV–vis) spectra and Fourier transform infrared (FTIR) spectroscopy. The particle size distribution and the specific surface area of nanoparticles were studied using Transmission electron microscopy (TEM) and BET analysis technique. Adopting Kramers–Kronig relation, FTIR and UV–vis spectra, the optical constants of nano-alumina, including optical band gap (E_g), refractive index (n), extinction coefficients (k), real (ε₁) and imaginary parts (ε₂) of dielectric function were obtained. The results of optical band gap values indicate quantum confinement effect. The energy loss functions were determined to show loss of energy that transmit through a solid.     

Investigations on the influence of surfactant in morphology and optical properties of zinc oxide nanopowders for dye-sensitized solar cells applications

We studied the influence of the synthesis route on the morphology and optical properties of zinc oxide (ZnO), with applications in dye-sensitized solar cells (DSSCs). For this purpose, we obtained surfactant capped ZnO nanopowders, in the presence of non-ionic surfactants with different structures, and demonstrated their behavior as semiconductors in DSSCs. The ZnO nanopowders and films (obtained from nanopowders using the doctor blading method) were analyzed by transmission electron microscopy (TEM), high resolution TEM (HRTEM), and selected area electron diffraction (SAED). The optical properties were examined by UV, visible spectroscopy, and the band gap energies were calculated using the Tauc equation. The values obtained for DSSCs efficiencies were in good agreement with the characteristics of ZnO, both powders and films, and can be correlated with the synthesis route. The highest efficiency (1.19%) was achieved using ZnO nanopowder capped with Triton X-100, having a mean diameter of ～19 nm. We find that the use of capped ZnO nanoparticles is favorable for DSSCs, possibly because of the good porosity of the film and better dye adsorption. Moreover, the efficiency of the cells is influenced by the surfactant structure, due to the particle morphology.     

Investigation of structural,optical and morphological properties of copper doped zinc sulphide nanoparticles

Semiconductor nanoparticles doped with transition metal ions can influence the transition probabilities and electronic structure. The undoped and copper doped zinc sulphide nanoparticles with various concentrations are synthesized by wet chemical co-precipitation method. These nanoparticles are characterized by using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), UV–visible (UV–vis) absorption spectroscopy, Fourier Transform Infrared (FT-IR) Spectroscopy, conductivity measurement and time-resolved photoluminescence studies. X-ray powder diffraction analysis reveals that the synthesized samples have cubic zinc blende structure. The Scanning Electron Microscope shows the synthesized nanoparticles are agglomerated. The UV–visible spectra reveal the absorption edge is red shifted. The FT-IR spectra show vibrational peaks around 617 cm⁻¹ which indicate the presence of Cu–S stretching modes. The AC conductivity measurement confirms the semiconducting nature and shows a marked increase in conductivity as the doping concentration of copper increases. The photoluminescence shows that the emission at 426 nm may be due to transition from the conduction band to the zinc vacancies. These transition metal ions doped semiconductor nanoparticles have important applications in solid state lighting, imaging, and other photonic devices.     

Rapid epitaxy of 2-inch and high-quality α-Ga2O3 films by mist-CVD method

High thickness uniformity and large-scale films of α-Ga₂O₃ are crucial factors for the development of power devices. In this work, a high-quality 2-inch α-Ga₂O₃ epitaxial film on c-plane sapphire substrates was prepared by the mist-CVD method. The growth rate and phase control mechanisms were systematically investigated. The growth rate of the α-Ga₂O₃ films was limited by the evaporation of the microdroplets containing gallium acetylacetonate. By adjusting the substrate position (z) from 80 to 50 mm, the growth rate was increased from 307 nm/h to 1.45 μm/h when the growth temperature was fixed at 520 °C. When the growth temperature exceeded 560 °C, ε-Ga₂O₃ was observed to form at the edges of 2-inch sapphire substrate. Phase control was achieved by adjusting the growth temperature. When the growth temperature was 540 °C and the substrate position was 50 mm, the full-width at half maximum (FWHM) of the rocking curves for the (0006) and (10-14) planes were 0.023° and 1.17°. The screw and edge dislocations were 2.3 × 10⁶ and 3.9 × 10¹⁰ cm^-2, respectively. Furthermore, the bandgaps and optical transmittance of α-Ga₂O₃ films grown under different conditions were characterized utilizing UV-visible and near-IR scanning spectra.     

21世纪初微电子技术发展展望

综述了微电子领域中纳米技术、ＭＥＭＳ、Ｓｉ和ＧａＡｓ集成电路、微波／毫米波器件及宽禁带半导体技术目前的发展状况。在此基础上,对其在２１世纪初期的发展做了展望。     

一种阵列式版图布局的低温度系数CMOS带隙基准电压源

设计了一款低温度系数的自偏置CMOS带隙基准电压源电路,分析了输出基准电压与关键器件的温度依存关系,实现了低温度系数的电压输出。后端物理设计采用多指栅晶体管阵列结构进行对称式版图布局,以压缩版图面积。基于65 nm/3.3 V CMOS RF器件模型,在Cadence IC设计平台进行原理图和电路版图设计,并对输出参考电压的精度、温度系数、电源抑制比(PSRR)和功耗特性进行了仿真分析和对比。结果表明,在3.3 V电源和27℃室温条件下,输出基准电压的平均值为765.7 mV,功耗为0.75μW;在温度为-55~125℃时,温度系数为6.85×10~(-6)/℃。此外,输出基准电压受电源纹波的影响较小,1 kHz时的PSRR为-65.3 dB。     

确定CCD相机标定点个数的方法

针对带有径向畸变的单摄像机针孔成像数学模型,提出了确定标定点个数的方法.利用忽略切向畸变的径向一致约束推出线性方程式,应用最小二乘法求得线性方程式的系数.通过不断增加标定点的个数,得到系数的一系列解;观察系数解的变化是否稳定,从而判断所用标定点个数是否足够.     

Investigation on UV photodetector behavior of RF-sputtered ZnO by impedance spectroscopy

Ag/ZnO/Ag thin films representing metal/semiconductor/metal ultraviolet (UV) photodetectors were successfully prepared by RF magnetron sputtering. A UV light emitting diode was used as an illuminating source at 365 nm. The current-voltage characteristics of the device under UV illumination showed an enhancement in the forward current. Device modeling was carried out using impedance spectroscopy. The resistance of the device decreased as the light was switched from dark to UV. Moreover, the device showed further decrease in resistance at a bias voltage of up to 2 V.     

Preparation,structural and optical investigations of ITO nanopowder and ITO/epoxy nanocomposites

Indium Tin Oxide (ITO) nanopowder was synthesized by a sol–gel method. It was characterized by X-ray diffraction (XRD) and transmission electron microscopy. ITO/epoxy nanocomposites (ITO–EP-NCs) were prepared by mechanically dispersing the as-prepared ITO nanopowder into epoxy matrix. The XRD patterns show structural changes depending on ITO content. The interdependence of structural, morphological, optical properties and the dispersed concentration of ITO nanoparticles were investigated. The UV–visible absorption spectra revealed that the ITO–EP-NCs exhibit enhanced UV light absorption properties and wide absorption bandwidth ranging up to 400 nm from 2 wt% ITO loading. Thus, it indicated that UV and IR-shielding properties have been improved with the incorporation of ITO nanoparticles into the epoxy matrix.The gap energy of epoxy matrix was reduced by adding the ITO-NPs, leading to the improvement of its electrical conductivity. Indeed, the AC electrical conductivity of ITO–EP-NCs showed a critical percolation threshold p_c=0.21 wt% ITO. For low loading (<2 wt% ITO), the ITO–EP-NCs have combined good transparency in the visible range and enhanced electrical conductivity, which are required for optoelectronics devices.     

Properties of phosphorus-doped (Zn,Mg)O thin films and device structures

The properties of phosphorus-doped (Zn,Mg)O polycrystalline and epitaxial thin films are described. The as-deposited (Zn,Mg)O:P films are n type with high electron carrier density. High resistivity is induced in the films with moderate temperature annealing, which is consistent with suppression of the donor state and activation of the deep acceptor. The resistivity of the as-deposited and annealed film is an order of magnitude higher than similar samples with no Mg, consistent with a shift in the conduction band edge relative to the defect-related donor state. The capacitance-voltage characteristics of annealed metal/insulator/P-doped (Zn,Mg)O structures in which the (Zn,Mg)O is polycrystalline exhibit p-type polarity. In addition, multiple polycrystalline devices comprising n-type ZnO/P-doped (Zn,Mg)O thin-film junctions display asymmetric I–V characteristics that are consistent with the formation of a p-n junction at the interface, although the ideality factor is anomalously high.     

Effects of Channel Electron In‐Plane Velocity on the Capacitance‐Voltage Curve of MOS Devices

The coupling between the transverse and longitudinal components of the channel electron motion in NMOS devices leads to a reduction in the barrier height. Therefore, this study theoretically investigates the effects of the in‐plane velocity of channel electrons on the capacitance‐voltage characteristics of nano NMOS devices under inversion bias. Numerical calculation via a self‐consistent solution to the coupled Schrödinger equation and Poisson equation is used in the investigation. The results demonstrate that such a coupling largely affects capacitance‐voltage characteristic when the in‐plane velocity of channel electrons is high. The ballistic transport ensures a high in‐plane momentum. It suggests that such a coupling should be considered in the quantum capacitance‐voltage modeling in ballistic transport devices.     

Si基OLED微显示器阳极图案化研究

在传统的Si基OLED微显示器像素阳极工艺流程基础上,提出利用互补金属氧化物半导体(CMOS)工艺制作像素阳极的一次图案化工艺,从而精简工艺流程,节省投资。分析了常规CMOS工艺中Al作为像素阳极表面材料对OLED微显示器光电性能的影响,开发了一种Si芯片作为微显示器基板,最小像素面积为12mm×4mm,在其表面制作有机发光材料,形成Si基OLED微显示器。实验结果表明,在5V驱动电压下,本文研制的OLED微显示器发光强度可达1 000cd/m2以上,电流密度0.1mA/mm2以上,光电响应速度280ns以下,表明利用常规CMOS工艺开发Si基微显示器的可行性。     

利用直接隧穿弛豫谱技术对超薄栅MOS结构中栅缺陷的研究

给出了超薄栅MOS结构中直接隧穿弛豫谱(DTRS)技术的细节描述,同时在超薄栅氧化层(＜3nm)中给出了该技术的具体应用.通过该技术,超薄栅氧化层中明显的双峰现象被发现,这意味着在栅氧化层退化过程中存在着两种陷阱.更进一步的研究发现,直接隧穿应力下超薄栅氧化层(＜3nm)中的界面/氧化层陷阱的密度以及俘获截面小于FN 应力下厚氧化层(＞4nm)中界面/氧化层陷阱的密度和俘获截面,同时发现超薄氧化层中氧化层陷阱的矩心更靠近阳极界面.     

CMOS反相器高功率微波脉宽扰乱效应的建模和分析

本文对受脉宽影响的过剩载流子浓度分布及高功率微波(HPM)扰乱易发性进行解析建模,并利用仿真结果和实验数据对模型进行验证。利用机理分析与模型推导,得到过剩载流子主导闩锁效应中电流放大过程的结论。结果表明,P型衬底中的过剩载流子浓度分布确与HPM脉宽有关,HPM扰乱电压阈值Vp随着脉宽增宽而减小,同时这一变化存在一个拐点,这是由于P型衬底中的过剩载流子累积效应将随着时间推移而受到抑制。文中首次提出HPM脉宽扰乱效应的物理本质是过剩载流子的累积效应。实验验证认为,Vp解析模型能够对CMOS反相器的HPM扰乱易发性进行可靠和准确的预测,并同时考虑工艺、环境温度及版图参数等因素。从模型中可以得到,版图参数LB对脉宽扰乱效应有显著影响：LB较小的CMOS反相器更容易受到HPM的扰乱,这一结论将有助于提出反相器免于HPM扰乱的加固措施。     

The effect of oxygen on the epitaxial growth of diamond

We studied the effect of oxygen on the growth quality of diamond epitaxial layers. After oxygen is added during the growth of the diamond epitaxial layer, as the thickness of the epitaxial layer increases, the full width at half maximum of the rocking curve of the (004) plane of diamond epitaxial layer increases continuously, and, in addition, the intensities of both the Raman peaks and the free exciton emission peaks of the diamond epitaxial layer decrease continuously. These experimental results demonstrate that as the thickness of the diamond epitaxial layer increases, the quality of the diamond epitaxial layer degrades. The strong etching effect of the OH radical groups in the plasma on the diamond epilayers leads to the degradation of their crystallinity.     

MSM光电探测器电磁场特性的 TLM方法模拟

介绍了利用传输线矩阵方法模拟和分析金属－半导体－金属光电探测器的指栅电容的频率响应。应用时域电磁场三维TLM方法模拟分析了指栅间距和指栅间的耦合长度与光电探测器截止频率的关系。文中报道了本项研究所开发的三维电磁场时域模拟器TLM Simulator2.0及其功能。数值实验结果说明模拟器对微波结构的电磁场模拟是精确、有效的,具有很好的应用价值。     

SiC整流器件发展现状及展望

阐述了碳化硅（SiC）材料的优异特性,并在此基础上,针对目前处于商业化热点的SiC整流器件,进行了重点介绍,分析了国内外发展现状,并对未来发展趋势做出展望。