多孔硅的电荷存贮现象

Uhlir[1]和Tunner[2]发现多孔硅(PS)以来,对其形成机制,电化学特性等进行了深入细致的研究.特别是近年Canham[3]观察到PS的可见光致发光现象后,PS的光电特性成为人们研究的焦点.在我们的研究中,首次观察到PS具有存贮电荷的能力.     

集成型硅光电负阻器件及应用研究

本文报道了对集成型硅光电负阻器件及其应用的初步研究结果。文中介绍了硅光电负阻器件(PLBT)的特性并对用该器件所构成的光控正弦波振荡器进行了实验研究。根据实验结果,文中还探讨了该类型振荡器在光调制方面所具有的功能.     

一种光电混合集成有源光双稳器件

本文报道一种光电混合集成的有源双稳态器件,它仅由一只半导体激光器,两只PIN光电探测器及几只电子元器件构成.实验上得到了光学迟滞回线,显示了光开关、光存储、光脉冲整形等功能.文中简述了器件工作原理,光电混合集成制作工艺技术及性能指标.     

具有混合结构的三基色有机光电探测器的光电特性

采用溶液旋涂和高真空蒸镀工艺制备了平面和体异质结混合型器件结构的三基色有机光电探测器,利用实验分步探究其不同组分的活性层厚度、混合度以及前置吸收层对器件光电特性的影响.在此基础上,对三基色有机光电探测器进行样品制备及测试.结果表明,混合型结构的光电探测器件对光的吸收几乎覆盖整个可见光区域,对350~700nm范围的光呈现出类似于平台式的宽光谱响应.该器件在-1V偏置电压下,对红、绿、蓝光的比探测率分别为2.89×10~(11) Jones、3.22×10~(11) Jones、1.97×10~(11)Jones,表明该器件对红、绿、蓝光有较好探测效果,尤其对红光的探测率有3~4倍提升.     

基于过渡金属硫族化合物同质结的光电探测器

近年来,二维过渡金属硫族化合物(transition metal dichalcogenides, TMDCs)由于其出色的电学和光学特性在光电探测领域被广泛研究.相比于报道较多的场效应晶体管型以及异质结型器件,同质结器件在光电探测方面具有独特优势.本文将聚焦基于TMDCs同质结的光电探测器的研究,首先介绍同质结光电器件的主要工作原理,然后以载流子调控方式为分类依据总结TMDCs同质结的几种制备方法及其获得的电学和光电性能.此外,本文还对同质结器件中光生载流子的输运过程进行具体分析,阐述横向p-i-n结构具有超快光电响应速度的原因.最后对基于TMDCs同质结的光电探测器的研究进行总结与前景展望.     

石墨烯/二氧化钛异质结场效应探测器光电特性

利用二氧化钛薄膜光吸收及表面钝化特性,在硅晶圆基底表面制备石墨烯/二氧化钛异质结场效应管光电探测器,并研究其光电响应特性.结果表明,二氧化钛钝化后的探测器可以有效抑制沟道表面的气体小分子吸附,降低器件的暗电流漂移;同时,探测器利用石墨烯的电荷敏感和复合薄膜的光谱吸收特性,显著提高了石墨烯场效应管的响应度.紫外波段,顶层二氧化钛吸光产生的光生电子将注入到石墨烯沟道中,对石墨烯沟道产生n型掺杂,器件最大响应度可达3.5×10~5A/W.在可见光波段,因为二氧化钛层与石墨烯薄膜间存在杂质能级,界面间的电荷转移使沟道载流子寿命显著提高.相对于传统的二氧化钛阵列探测器,该探测器在响应波段与响应度性能上都具有明显优势.     

量子光通信中偏振光空间姿态传递

通过设计正交偏振光信标器,实现了空间信标姿态的单光路传递,为星地量子光链路的建立提供了条件.通过分析光学器件,尤其是镀膜器件中偏振信标光的传递特性,仿真分析不同入射角、旋转角条件下,出射信标光的偏振模式.分析了由光学器件引入的位相差和不同反射率、透射率对偏振模式的影响.利用琼斯矩阵推导了马吕斯定律在椭圆偏振光入射时的表达形式,建立起测量椭圆偏振光主偏振方位角模型.利用光电位置传感器接收正交信标光,结合光电位置传感器的光点位置检测能力解耦信标光的俯仰角和方位角,利用光电位置传感器的光强探测能力解耦信标光的偏振基矢角,实现了单器件三维信标姿态测量.实验表明,所述系统具有完成信标光三维姿态检测的能力,可用于星地量子光通信、空间信标姿态检测.     

WSe2光电性质的第一性原理研究

本文采用基于非平衡态格林函数-密度泛函理论的第一性原理方法,计算了单层WSe₂的光电性质.计算结果表明：在小偏压下,几乎整个可见光范围内都能产生较强的光响应,且光响应与偏振角θ呈现完美的余弦关系,与唯象理论相符合.锯齿型和扶手椅型WSe₂纳米器件均在光子能量为2.8 eV(443 nm,对应于可见光)时,能产生较大的光响应;利用能带结构和态密度分析了产生较大光响应的原因,其主要来自第一布里渊区高对称点X处的电子受激跃迁.此外,WSe₂纳米器件还具有较强的各向异性和较高的偏振灵敏度;这些结果可为WSe₂在光电子器件中的应用提供重要的理论参考.     

GaAs薄膜电池光电转换特性研究

微纳减反层结构及微纳金属等离激元结构能有效提高砷化镓(GaAs)薄膜光伏器件在可见到近红外波段的吸收效率。本文采用有限元法(FEM)分析了微纳减反层对GaAs光伏器件的光谱吸收率的影响,并获得相应结构的光电转换特性。进一步探究了在器件内部布置金纳米线对相应结构的光电特性的影响。对应的计算结果显示,微纳减反层结构及金属纳米线结构能有效增强器件的电学输出特性,并提高器件光电转换能力到19.6%。掌握微结构对光伏器件内部光电特性的影响规律可为器件设计和制备提供有益指导。     

In, Al共掺杂ZnO纳米串光电探测器的组装与研究

用化学气相沉积法合成了高密度的In, Al共掺杂ZnO纳米串, 用合成出的纳米串组装成了光电探测器. 纳米串为六角纤锌矿结构, 平均长度大约为5 μ m. 研究了光电导的机制以及光电探测器的光电特性, 包括在暗环境及紫外照射下的伏安特性、光电响应率和光电响应时间. 结果表明, 器件存在内部增益机制, 光响应时间小于0.5 s, 衰减时间约为23 s, 可用于光电探测.     

Infrared-induced temperature distributions of solid D2 ices

A specific-wavelength infrared (IR) light (λ=3140 nm) was irradiated into a solid D₂ ice prepared in a cylinder target cell. The temperature in the solid D₂ ice oscillated periodically with a high amplitude when irradiated by the IR light. The temperature oscillation has been well explained based on the two-dimensional heat transfer theory plus the IR-irradiation effect. The transmission optical imaging reveals that such a temperature oscillation is favorable to recrystallize the solid D₂ ice from multicrystal to quasi single crystal. This suggests an efficient method to layer the solid hydrogen-isotope ice for the inertial-confinement-fusion (ICF) experiments.     

The light-enhanced NO2 sensing properties of porous silicon gas sensors at room temperature

The NO2 gas sensing behavior of porous silicon（PS） is studied at room temperature with and without ultraviolet（UV） light radiation.The PS layer is fabricated by electrochemical etching in an HF-based solution on a p ＋-type silicon substrate.Then,Pt electrodes are deposited on the surface of the PS to obtain the PS gas sensor.The NO2 sensing properties of the PS with different porosities are investigated under UV light radiation at room temperature.The measurement results show that the PS gas sensor has a much higher response sensitivity and faster response-recovery characteristics than NO2 under the illumination.The sensitivity of the PS sample with the largest porosity to 1 ppm NO2 is 9.9 with UV light radiation,while it is 2.4 without UV light radiation.We find that the ability to absorb UV light is enhanced with the increase in porosity.The PS sample with the highest porosity has a larger change than the other samples.Therefore,the effect of UV radiation on the NO2 sensing properties of PS is closely related to the porosity.     

Partial crystallization of silicon by high intensity laser irradiation

Commercial single crystal silicon wafers and amorphous silicon films piled on single crystal silicon wafers were irradiated with a femtosecond pulsed laser and a nanosecond pulsed laser at irradiation intensities between 10¹⁷ W/cm² and 10⁹ W/cm². In the single crystal silicon substrate, the irradiated area was changed to polycrystalline silicon and the piled silicon around the irradiated area has spindly column structures constructed of polycrystalline and amorphous silicon. In particular, in the case of the higher irradiation intensity of 10¹⁶ W/cm², the irradiated area was oriented to the same crystal direction as the substrate. In the case of the lower irradiation intensity of 10⁸ W/cm², only amorphous silicon was observed around the irradiated area, even when the target was single crystal silicon. In contrast, only amorphous silicon particles were found to be piled on the amorphous silicon film, irrespective of the intensity and pulse duration.Three-dimensional thermal diffusion equation for the piled particles on the substrate was solved by using the finite difference methods. The results of our heat-flow simulation of the piled particles almost agree with the experimental results.     

Athermal effects in ion implanted layers

Abstract

Defect structure and electrical characterization of boron and arsenic implanted layers has been investigated for implantation under athermal (light) excitation. This Photon Assisted (PA) implantation owes its specific properties to an additional electric field acting on charged particles including carriers and charged defects. It was shown that in case of n-type silicon this extra field draws charged vacancies and self-interstitials towards each other and, thus, diminishes transient diffusion of boron. This effect resulted in junctions which are about 20% shallower compared to conventionally processed reference wafers. Experiments using light of an Ar-ion laser and white light of a high pressure Xe arc lamp were compared. Some deactivation of carriers in the deeper laying parts of the p-region was always a by-product.     

Epitaxial growth of zinc oxide by the method of atomic layer deposition on SiC/Si substrates

For the first time, zinc oxide epitaxial films on silicon were grown by the method of atomic layer deposition at a temperature T = 250°C. In order to avoid a chemical reaction between silicon and zinc oxide (at the growth temperature, the rate constant of the reaction is of the order of 10²²), a high-quality silicon carbide buffer layer with a thickness of ~50 nm was preliminarily synthesized by the chemical substitution of atoms on the silicon surface. The zinc oxide films were grown on n- and p-type Si(100) wafers. The ellipsometric, Raman, electron diffraction, and trace element analyses showed that the ZnO films are epitaxial.     

Electrochemical deposition of cerium on porous silicon to improve photoluminescence properties

In this work, we present results for Cerium (Ce) doping effects on photoluminescence (PL) properties of porous silicon (PS). Cerium was deposited using electrochemical deposition on porous silicon prepared by electrochemical anodization of P-type (100) Si. From the photoluminescence spectroscopy, it was shown that porous silicon treated with cerium can lead to an increase of photoluminescence when they are irradiated by light compared to the porous silicon layer without cerium. In order to understand the contribution of cerium to the enhanced photoluminescence, energy dispersive X-ray (EDX) spectroscopy, Fourier transmission infrared spectroscopy (FTIR), X-ray diffraction (XRD) and atomic force microscopy (AFM) were performed, and it was shown that the improved photoluminescence may be attributed to the change of Si–H bonds into Si–O–Ce bonds and to a newly formed PS layer during electrochemical Ce coating.     

Getter formation in silicon by implantation of antimony ions

A porous silicon layer as a getter of uncontrolled impurities has been prepared by implantation of Sb⁺ into silicon and subsequent thermal treatments. The lifetime of nonequilibrium charge carriers in n- and p-type silicon wafers with a getter layer is 3–4 times longer than that without a getter.     

Structural and phase changes in single-crystalline silicon treated with compression plasma flows

The structural-phase changes in p-type single-crystalline silicon treated with compression plasma flows (CPFs) with an energy density of 5–12 J/cm² are investigated by the X-ray diffraction method depending on the crystallographic orientation of the silicon and the plasma energy density. In addition, the conductivity type on the treated silicon surface is determined by means of measuring the sign of the thermopower.; the surface morphology, by scanning electron microscopy; and the open-circuit voltage, upon illumination of the treated silicon surface (AM1.5 spectrum). It is found that treatment with CPFs results in the occurrence of the photovoltaic effect conditioned by the formation of an n-type modified surface layer. Depending on the crystallographic orientation, the modified layer either remains single crystalline (for the initial orientation (111)) or is subjected to amorphization (for the initial orientation (100)). At an energy density of ～8–9 J/cm² the action of CPFs leads to texture formation on the silicon surface.     

Piezospectroscopic study (78°K) of radiation- produced absorption bands in Si†

Abstract

A detailed study has been made on two sharp sub-bands, 3.45 μ (2900 cm^?1) and 3.61 μ (2765 cm^?1) of the 3.3 μ broad defect absorption band in irradiated Si. Our results indicate that the 3.45 μ and 3.61 μ bands are observed in all types of Si (n-, p-type, and intrinsic) subjected to fast neutron reactor irradiation. Spectra were measured at 78 °K under the effect of a variable uniaxial compressive stress with polarized light. A relatively large dichroism is observed for all three stress directions ?100?, ?110?, and ?111?. We also confirm that both sharp bands exhibit splitting and energy shifts under the action of stress. The model of the divacancy defect given by Watkins and Corbett⁽⁵⁾ has been utilized to explain the data. The dichroism can be accounted for by the effects of Jahn-Teller alignment which arises from the strong bonding of nearest neighbor atoms of the divacancy. The splittings of the bands are small indicating that the Jahn-Teller distortion is little altered in the ground and excited states. The splittings appear to be most sensitive to stress along the vacancy-vacancy axis and a tentative model for the transitions is given.     

Features of atomic and electronic structure of oxides on porous silicon surface according to XANES data

Based on synchrotron research of the fine structure main parameters of SiL _{2, 3} X-ray absorption edges (X-ray absorption near edge structure (XANES)) in porous silicon on boron-doped Si(100) wafers, the thickness of the surface oxide layer and the degree of distortions of the silicon-oxygen tetrahedron in this layer were estimated. The thickness of the oxide layer formed on the amorphous layer coating nanocrystals of porous silicon exceeds the thickness of the native oxide on the surface of Si(100) : P and Si(100) : B single-crystal (100) silicon wafers by several times. Distortion of the silicon-oxygen tetrahedron, i.e., the basic unit of silicon oxide, is accompanied by Si-O bond stretching and an increase in the angle between Si-O-Si bonds.