激光束感应电流法研究HgCdTe电活性缺陷和焦平面器件的光电特性

用高分辨率的、非破坏的光学表征技术的激光束感应电流研究碲镉汞(MCT)晶片中电活性缺陷和光伏型红外碲镉汞焦平面器件及光伏型硅光电器件P-N结光电特性,实验表明在MCT晶片中探测到激光束感应电流,在光伏型P-N结构的器件中,观察到周期结构的激光束感应电流分布.定性地观察激光束感应电流图谱以及定量地分析单个P-N结的感应电流分布形状可以判断器件的均匀性和器件的质量.     

变磁场I-V法对碲镉汞光伏器件少子扩散特性的研究

零偏压电阻-面积乘积(R0A)和反向饱和电流密度J0是决定光电二极管性能的重要参数．提出了一种对碲镉汞(Hg1-xCdxTe)光伏器件的少子扩散特性进行研究的有效方法．利用变磁场下的电流-电压(I-V)测试,得到了组分x在0．5与0．6之间的器件R0A和J0随磁场强度B变化的函数关系．由实验结果估算得到了室温工作的短波红外(SWIR)碲镉汞光伏器件的少子扩散长度．其数值与用激光诱导电流(LBIC)方法得到的相一致．     

激光束感应电流法研究HgCdTe电活性缺陷和焦平面器件的光电特性

用高分辨率的、非破坏的光学表征技术的激光束感应电流研究碲镉汞（MCT）晶片中电活性缺陷和光伏型红外碲镉汞焦平面器件及光伏型硅光电器件P－N结光电特性,实验表明在MCT晶片中探测到激光束感应电流,在光伏型P－N结构的器件中,观察到周期结构的激光束感应电流分布。定性地观察激光束感应电流图谱以及定量地分析单个P－N结的感应电流分布形状可以判断器件的均匀性和器件的质量。     

多阳极微通道阵列探测器件

多阳极微通道阵列（ＭＡＭＡ）探测器件是一种新型的真空光电成像器件,近年来获得了一些重要的应用。该器件在光子计数状态工作,因而具有很好的位置,时间分辨能力和很高的探测灵敏度。本文介绍我们所研制的３６０×１０２４像素ＭＡＭＡ探测器件的工作原理、结构,性能及应用。     

微纳光子学亚波长器件研究的重要进展——逆向干涉相消法提高波分复用器透射效率50%

据www.opt.ac.cn网站报道,微纳光子学主要研究在微纳尺度下光与物质相互作用的规律及其光的产生、传输、调控、探测和传感等方面的应用。微纳光子学亚波长器件能有效提高光子集成度,有望像电子芯片一样把光子器件集成到尺寸很小的单一光芯片上。纳米表面等离子体学是一块新兴微纳光子学领域,主要研究金属纳米结构中光与物质的相互作用。它具有尺寸小、速度快和克服传统衍射极限等特点,有望实现电子学和光子学在纳米尺度上的完美联姻,将为新一代的光电技术开创新的平台。金属-介质-金属F-P腔是最基本的纳米等离子体波导结构,具有良好的局域场增强和共振滤波特性,是制作纳     

基于CuPc…C60的混合层异质结光伏器件性能研究

制备了基于CuPc…C60混合层异质结有机光伏器件,将其与CuPc-C60双层结构光伏器件进行对比研究。结果表明混合层结构器件性能得到改善,其开路电压、短路电流密度、填充因子和光电转换效率都有提高,分别从CuPc-C60双层结构器件的0.39V、1.92mA/cm2、0.36%、0.48依次提高到CuPc…C60混合层结构器件的0.48V、2.21mA/cm2、0.54%、0.51。根据整数电荷转移模型来分析光伏器件D/A界面及有机材料-ITO衬底界面特性,认为混合层异质结有机光伏器件给体材料HOMO与受体材料LUMO的能级差增加使得器件开路电压提高。混合层异质结有机光伏器件D/A界面面积增加和给体材料HOMO与受体材料LUMO的能级差增加都提高了激子的分离效率,所以器件的短路电流密度增加。     

激光束诱导电流对HgCdTe器件的研究

HgCdTe红外探测器件是目前研究和使用的主要探测器件之一，pn结构是它的基本功能单元和提高性能的关键之一，由其列阵构成的焦平面是HgCdTe红外探测器件发展的重要方向。因此迫切需要一种方便可行的无损检测方法可以实现对焦平面列阵的在线信息反馈以及针对pn功能结构进行深入研究。激光束诱导电流(LBIC)即是一种以激光为     

半导体光电阴极的研究进展

半导体光电阴极具有量子效率高、暗电流小的优点,被广泛应用于光电倍增管、像增强器等各类真空光电探测和成像器件,促进了极弱光的超快探测和成像技术的发展。另外作为能够产生高品质电子束的真空电子源,用于加速器光注入器、电子显微镜等科学装置。本文首先介绍了目前常用半导体光电阴极的分类以及在真空光电探测成像、真空电子源领域的具体应用。然后对碱金属碲化物光电阴极、碱金属锑化物光电阴极、GaAs光电阴极三类典型半导体光电阴极的制备技术进行了总结,并介绍了微纳结构、低维材料、单晶外延等新技术在半导体光电阴极研制中的应用。最后对半导体光电阴极的技术发展进行了展望。     

G-APD阵列——一种具有单光子灵敏度的三维成像探测器

介绍了一种利用盖革模式雪崩二极管(G-APD)作为成像单元的新型阵列光电探测器,重点介绍了该新型成像光电探测器的关键技术、器件研发和系统应用的发展状况。G-APD阵列探测器兼具单光子探测灵敏度和皮秒级时间分辨率两大特点,适用于对极微弱光目标的三维成像探测。同时,G-APD阵列探测器又是一种全固态的光电探测器件,不仅体积小、重量轻、可靠性高,而且还可用现有的微光电子工艺进行规模化生产。因此,G-APD阵列是目前阵列光电探测器件的一个重大发展,必将在各种高端光电成像领域获得广泛的应用。     

硅基雪崩光电二极管技术及应用

硅基雪崩光电二极管是一种可用于对微弱光甚至单光子进行探测的光电器件,被广泛应用于激光测距、激光成像、量子通信和生物医疗等领域。从工作原理、常见结构和分类3个方面对硅基雪崩光电二极管的技术进行分析,并对其性能发展趋势进行阐述,最后介绍了硅基雪崩光电二极管的应用。     

A discrete element model of laser beam induced current (LBIC) due to the lateral photovoltaic effect in open-circuit HgCdTe photodiodes

The non-destructive optical characterization technique of Laser-Beam-Induced-Current (LBIC) imaging has proven useful in qualitatively assessing electrically active defects and localized non-uniformities in HgCdTe materials and devices used for infrared photovoltaic arrays. To further the development of a quantitative working model for LBIC, this paper focuses on the application of the technique to photovoltaic structures that are represented by a discrete element equivalent circuit. For this particular case the LBIC signal arises due to the lateral photovoltaic effect in non-uniformly illuminated open-circuit photodiodes. The outcomes of the model predict all of the experimentally observed geometrical features of the LBIC image and signal. Furthermore, the model indicates that the LBIC signal has an extremely weak dependence on the p-n junction reverse saturation current, and shows a linear dependence with laser power. This latter feature map be useful for non-contact measurement of the quantum efficiency of individual photodiodes within a large two-dimensional focal plane array. The decay of the LBIC signal outside the physical boundary of the p-n junction is of the same form as the roll-off in the short circuit photoresponse and, therefore, can be used to extract the diffusion length of minority carriers. Experimental data is obtained from an arsenic implanted p-on-n junction fabricated on MBE grown Hg/sub 1-x/Cd/sub x/Te material with an x-value of 0.3. The p-on-n diode is shown to be uniform and of high quality with an R/sub 0/A product of 1/spl times/10/sup 8/ /spl Omega//spl middot/cm/sup 2/ at 77 K. The validity of the simple model developed in this paper, is confirmed by the excellent agreement with experimental results. Consequently, the LBIC technique is shown to be an appropriate diagnostic tool for non-contact quantitative analysis of semiconductor materials and devices.<>     

Correlation of laser-beam-induced current with current-voltage measurements in HgCdTe photodiodes

Laser-beam-induced current (LBIC) is being investigated as an alternative to electrical measurements of individual photodiodes in a two-dimensional array. This is possible because LBIC only requires two electrical contacts to an array and the two-dimensional scanning of a focused laser beam across the array to image the entire array. The measured LBIC profiles, obtained from linear arrays of HgCdTe photodiodes, will be used to study the uniformity of photodiodes in the array and to extract the R₀A of the photodiodes. It will be shown that the shape of the LBIC signal is correlated to the electrical performance of the photodiode, with R₀A related to the spreading length of the photodiodes. Linear arrays of n-on-p, mid-wavelength infrared (MWIR) and long wave-length infrared (LWIR) devices were formed in liquid-phase epitaxy HgCdTe epilayers using a plasma junction-formation technique. The LBIC profiles were measured on each of the devices at various temperatures. For the MWIR devices, the extracted spreading length shows no correlation with R₀A. However, the LBIC signal does detect nonuniform devices within the array. For the case of the LWIR devices, the spreading length is extracted as a function of temperature, with the R₀A subsequently calculated from the spreading length. The calculated R₀A, obtained without requiring contact to each photodiode in the array, agrees well with electrical measurements. Asymmetry of the LBIC signals for certain devices in the arrays is shown to be a result of localized leakage at the photodiode junction or from the contact pads through the passivation layers. These results are confirmed by numerical modeling of the device structures.     

Solar photovoltaics in Sri Lanka: A short history

With a significant unelectrified rural population, Sri Lanka has followed the evolution of solar photovoltaic (PV) technology in the West very closely since the 1970s as terrestrial applications for photovoltaics were developed. It was not until 1980 that the Sri Lankan government embarked on the promotion of solar photovoltaics for rural domestic use when the Ceylon Electricity Board formed the Energy Unit. Since then, solar photovoltaics has attracted the private sector, where several companies have been operating at different levels with varying degrees of success-Vidya Silpa, agents for Arco and now Showa, selling solar photovoltaic systems on a small scale; Power & Sun (now S.P.&L. Co. Ltd) with its solar photovoltaic module assembling facility and a marketing operation; Sunpower Systems, agents for BP Solar Australia, focusing on institutional systems; and BP Solar Australia working on government-funded projects-so that private solar photovoltaic promoters have now gained valuable experience in a variety of dissemination methodologies. In addition, Australian and Sri Lankan government-funded pilot projects such as the Pansiyagama 1000 home programme and the Uva Infrastructure Project with 74 large-scale solar photovoltaic systems for rural hospitals and water pumping schemes- both administered by the National Housing Development Authority (NHDA) -have given all the local promoters further valuable insight into how and how not to promote solar photovoltaics. The establishment of community-based solar photovoltaic programmes by non-governmental organizations, such as the Sarvodaya Shramadana Society and the newly formed Solanka Associates, has developed a novel approach to bridge the gap between this state-of-the-art technology and the remotely located end-users. The developments in the Sri Lankan solar photovoltaic scene have attracted the attention of the World Bank. to quote from a paper presented by Loretta Schaeffer, Program Manager of the Bank's Asia Alternative Energy Unit in Washington at the Solar Energy Forum-SOLTECH'93-held on 28th April 1993 in Washington, DC: ‘The Bank may get involved in providing PV-powered household systems throughout the country as there is a strong private sector involvement and use of proven local experience in systems design, development, installation, operation and maintenance’. Even though 70% of the 3.3 million homes are unelectrified, acceptance of solar photovoltaics as a viable alternative by policy makers is yet to be fully realized in Sri Lanka. the main obstacle has been the relatively high cost of photovoltaics. In spite of this, the private sector companies, certain government agencies (such as the NHDA) and the non-government organizations view photovoltaics as a technology that could meet the basic needs for electricity of the rural people who, otherwise, would be left in the dark.     

Interpretation of current flow in photodiode structures using laser beam-induced current for characterization and diagnostics

This paper presents an interpretation of the physical mechanisms involved in the generation of laser beam-induced current (LBIC) in semiconductor p-n junction diodes. LBIC is a nondestructive semiconductor characterization technique that has been used in a qualitative manner for a number of years and is especially useful for examining individual photodiodes within large two-dimensional arrays of devices. The main thrust of this work is the analysis of LBIC in terms of nonzero steady-state circulatory current flow within the device and, hence, the interpretation of LBIC line profiles to diagnose the patterns of current flow within the structure. This provides an important basis for future studies seeking to relate LBIC to indicators of p-n junction performance and integrity such as dark current components and reverse bias saturation current. In particular, this paper examines the ideal cases of a single isolated p-n junction diode structure, and also considers an array of such devices in close proximity to each other. Modifications to the idealized theory that are required to account for localized junction leakage and surface recombination are presented, and the effect of Schottky contacts is discussed. Numerical simulations based on the HgCdTe family of semiconductors are presented to support the theory.     

The Solarex approach to expanding the PV business

Solarex was founded in 1973 to develop photovoltaic products for terrestrial applications. Over the last 24 years, the company has moved from single-crystal silicon technology to polycrystalline silicon and has also developed both single-junction and multi-junction amorphous silicon solar cell technology. Solarex is now starting to produce 8-ft² amorphous silicon tandem modules in a new plant in Virginia and has initiated new programs to develop the grid-connected markets in the USA and overseas. However, the current USA lead in photovoltaics is in jeopardy as government programs in both Japan and Germany are aggressively supporting the development of building integrated photovoltaic systems in those countries. In order to maintain its leadership in photovoltaics, the USA needs to implement a new national initiative to support the development of building integrated photovoltaics. © 1997 John Wiley & Sons, Ltd.     

Light Management with Patterned Micro‐ and Nanostructure Arrays for Photocatalysis,Photovoltaics, and Optoelectronic and Optical Devices

The design and fabrication of patterned micro‐ and nanostructure arrays have been demonstrated to be a powerful strategy toward efficient light management, which is of vital importance to a variety of photon‐related applications such as photocatalysis, photovoltaics, optoelectronic devices, and optical devices. Tunable optical reflectance, scattering, transmittance, and absorption can be readily achieved by adjusting the characteristics of the primary units in the micro‐/nanoarrays and the spatial patterns of the aligned units, thus realizing controllable light–matter interactions. This review describes various light management strategies based on patterned micro‐/nanoarrays, such as scattering enhancement, antireflection, resonances, photonic crystals, and plasmonic structures. Furthermore, recent advances in the applications of patterned micro‐/nanoarrays in photoelectrochemical water splitting, solar cells, photodetectors, light emitting diodes, lasers, color display, microlens arrays, and photonic crystal sensors are summarized, with particular attention paid to the light management mechanisms and the relationship between the structure and device performance. Lastly, the prospects and existing challenges facing the development of the photon‐related applications based on patterned micro‐/nanoarrays are discussed.     

SiGe: a key to unlocking the potential of solar cells

Research and development of silicon germanium (SiGe) has been under way for well over a decade. A surprising number of research institutes have been developing photovoltaic devices based on the SiGe alloy system for almost as long. While the technology is still some way off making a full-scale commercial impact, its capability remains as impressive as ever. SiGe stands as a highly promising means to unlock the fullest potential of thin-film silicon photovoltaics.     

Probing the Photovoltage and Photocurrent in Perovskite Solar Cells with Nanoscale Resolution

In this work, by coupling scanning Kelvin probe force microscopy (SKPM) and photoconductive atomic force microscopy (pcAFM), the variation of the surface potential, photogenerated voltage, and photocurrent networks of the perovskite solar cells (PSCs) with different film topography is studied. The nanoscale photovoltaic reaction of different perovskite capping layers with three different perovskite crystalline sizes is first studied by using the SKPM technique. The performance of the overall device is correlated with the local nanostructure of the perovskite film. Photocurrent maps under various applied voltages are also presented. The pcAFM measurements on three different morphology positions determine that the defect region on the capping layer can induce the charge recombination process in the complete PSCs and thus suppress the V_oc in the complete device. These results suggest that the performance of PSCs can still be improved through better control of morphology. Henceforth, SKPM coupled with pcAFM techniques has the potential to become a routine characterization tool for perovskite organic and hybrid photovoltaics.     

Nanoscale mapping by electron energy-loss spectroscopy reveals evolution of organic solar cell contact selectivity

Organic photovoltaic (OPV) devices are on the verge of commercialization being long-term stability a key challenge. Morphology evolution during lifetime has been suggested to be one of the main pathways accounting for performance degradation. There is however a lack of certainty on how specifically the morphology evolution relates to individual electrical parameters on operating devices. In this work a case study is created based on a thermodynamically unstable organic active layer which is monitored over a period of one year under non-accelerated degradation conditions. The morphology evolution is revealed by compositional analysis of ultrathin cross-sections using nanoscale imaging in scanning transmission electron microscopy (STEM) coupled with electron energy-loss spectroscopy (EELS). Additionally, devices are electrically monitored in real-time using the non-destructive electrical techniques capacitance–voltage (C–V) and Impedance Spectroscopy (IS). By comparison of imaging and electrical techniques the relationship between nanoscale morphology and individual electrical parameters of device operation can be conclusively discerned. It is ultimately observed how the change in the cathode contact properties occurring after the migration of fullerene molecules explains the improvement in the overall device performance.