差分SPV法测量a-Si:H材料少子扩散长度的数学模型

用差分SPV法测量a-Si:H材料的少子扩散长度,可以消除被测样品背面结的影响.本文讨论了这种测量方法的数学模型,导出了测量公式,分析了影响测量结果的各种因素.     

差分SPV法测量a—Si：H材料少子扩散长度的数学模型

用差分ＳＰＶ法测量ａ－Ｓｉ：Ｈ材料的少子扩散长度，可以消除被测样品背面结的影响。本文讨论了这种测量方法的数学模型，导出了测量公式，分析了影响测量结果的各种因素。     

扩散pn结扩散p区中平均少子扩散长度的测定

本文分析了用表面光压(SPV)法测量扩散pn结扩散p区中平均少子扩散长度的可行性,给出了有效少子扩散长度L_0与结深x_i、扩散区及衬底少子扩散长度L_1、L_2的关系曲线;提供了一种确定扩散区少子扩散长度的方法。     

量值恒定的表面光电压法测量半导体少子扩散长度的研究

为了在保持材料完整性的基础上,对单晶硅材料的质量进行评价,设计了一种利用表面光电压测量半导体少子扩散长度的系统.系统采用斩波器、单色仪和锁相放大器来获取半导体表面光电压信息,利用表面光电压与材料的光吸收系数的关系得出半导体少子扩散长度,重点阐述了系统的测量原理及各个模块的设计与实现方法.检测结果表明,量值恒定的表面光电压法用于测量半导体少子扩散长度能达到预期的效果.     

注入水平对测试少子扩散长度影响的计算机模拟

通过计算机数值求解半导体的基本方程，模拟了表面光伏（ＳＰＶ）法测量Ｎ型硅少子扩散长度时注入水平对测量值的影响。结果表明，当注入水平较高时，少子扩散长度的测量值变长。模拟结果与已公开发表的实验结果一致。     

一种测量硅中少子扩散长度和复合寿命的新方法

少子扩散长度和少子复合寿命是硅片的重要参量.本文介绍了在硅片上制造突变结的二极管来测量和计算硅片中的少子扩散长度和少子复合寿命的新方法,其基本原理就是依据肖克莱方程所显示的二极管伏安特性.该方法还适用于改变测试温度的条件,由此可获得不同温度下的少子扩散长度和少子复合寿命这二个参量的数值.     

一种测量硅中少子扩散长度和复合寿命的新方法

少子扩散长度和少子寿命是硅片的重要参量.本文介绍了在硅片上制造突变结的二极管来测量和计算硅片中的少子扩散长度和少子复合寿命的方法,其基本原理就是依据肖克莱方程所显示的二极管伏安特性.该方法还适用于改变测试温度的条件,由此可获得不同温度下的少子扩散长度和少子复合寿命这二个参量的数值.     

EBIC测定GaP LPE样片的少子扩散长度

少数载流子扩散长度(L)是半导体材料的一个重要参量,它反映了晶体的完整性,与晶体的结晶质量、掺杂及晶体缺陷等有关.扫描电子显微镜(SEM)的电子束感生电流(EBIC)被广泛地用于测定少子扩散长度,其优点是通过改变电子束的加速电压,就能精确地控制激发源的大小和深度,从获得的EBIC扫描曲线,拟合得到L值[1～3].GaP是目前商用绿色LED的主要材料,市场需求量很大,但对其重要参量少子扩散长度的测量却很少.本工作利用EBIC对一组GaP绿色LED用LPE样片进行少子扩散长度测量.     

同型外延材料表面光伏法测试的分析

本文应用数值计算方法研究了表面光电压是表面非平衡少子浓度的单调函数这一假设对于同型外延材料的可应用性。我们发现这一假设对该材料一般地说并不成立。因此在使用等光伏表面光伏法测试同型外延材料少子扩散长度时一般不应把表面非平衡少子浓度视为常数。在文中,我们也分析了可以把表面非平衡少子浓度作常数处理的条件。     

无接触法测量多晶硅材料的少子扩散长度

用微波光电导谱仪无接触、非破坏性地测量了多晶硅的微波光电导谱,推导了由光电导谱计算多晶硅样品的少子扩散长度和表面复合速度的计算方法,并由此算得了样品的少子扩散长度和表面复合速度。测试区域是一个直径为3mm的圆斑。这是一种简便而又准确的测试方法。这样的方法还适用于GaAs薄片材料少子扩散长度的测量和计算。     

Separation of local bulk and surface recombination in crystalline silicon from luminescence reabsorption

Spontaneous photoemission of crystalline silicon provides information on excess charge carrier density and thereby on electronic properties such as charge carrier recombination lifetime and series resistance. This paper is dedicated to separating bulk recombination from surface recombination in silicon solar cells and wafers by exploiting reabsorption of spontaneously emitted photons. The approach is based on a comparison between luminescence images acquired with different optical short pass filters and a comprehensive mathematical model. An algorithm to separate both front and back surface recombination velocities and minority carrier diffusion length from photoluminescence (PL) images on silicon wafers is introduced. This algorithm can likewise be used to simultaneously determine back surface recombination velocity and minority carrier diffusion length in the base of a standard crystalline silicon solar cell from electroluminescence (EL) images. The proposed method is successfully tested experimentally. Copyright © 2009 John Wiley & Sons, Ltd.     

Measurement of minority carrier lifetime and diffusion length in silicon epitaxial layers by means of the photocurrent technique

A new method for the determination of minority carrier lifetime and diffusion length in thin silicon epitaxial layers was developed. Using a transparent MIS structure the surface recombination velocity was reduced below 25 cm/s. This method makes possible to determine minority carrier lifetime and also diffusion length much greater than the thickness of the epitaxial layer.     

Determination of material parameters from regions close to the collector using electron beam-induced current

The conventional method of extracting the minority carrier diffusion length using the electron beam-induced current (EBIC) technique requires that the electron beam be placed at region more than two diffusion lengths away from the collector. The EBIC signals obtained under this condition usually has low signal to noise ratio. In addition, the true diffusion length of the sample is initially unknown and hence it is difficult to estimate how close the beam can be placed from the collector. To overcome all these difficulties, a new method of extracting minority carrier diffusion length from the EBIC signal is proposed. It is shown that this method can be applied to EBIC signals obtained from regions close to the collector. It is also shown that the surface recombination velocity of the sample can also be obtained using this method. This theory is verified using EBIC data generated from a device simulation software.     

Evaluation of the surface photovoltage method of minority-carrier diffusion-length measurement

The surface photovoltage (SPV) method of semiconductor minority carrier diffusion length measurement is simulated numerically by solving the semiconductor equations under monochromatic illumination. It is shown that the extracted diffusion length is dependent on the SPV level and the initial surface potential. This dependence arises because of carrier generation in the surface space charge region. For the p-type silicon investigated, the extracted diffusion length is found to be within 10% of the actual value even when the assumption of low level injection is violated.     

Minority Carrier Diffusion Lengths in Silicon Slices and Shallow Junction Devices

Measurements of surface photovoltage as a function of the wavelength of incident light provide a convenient method for the determination of minority carrier diffusion length in semiconductors. The diffusion length in silicon slices with a thickness greater than twice the diffusion length has been measured by the steady-state surface photovoltage method with a single laboratory reproducibility of ± 10% over a long period of time. Radial variations in diffusion length in silicon slices as well as the effects of heat treatment have been studied. The diffusion length in the base region of shallow junction devices has been measured by the collection of short-circuit current as a function of the wavelength of incident light. The single laboratory reproducibility of this method for the determination of diffusion length in single crystalline and polycrystalline silicon solar cells is also about ± 10%. Prepared for the Division of Solar Energy of the U. S. Energy Research and Development Administration under Con-tract No. E(04-3)1285.     

中子辐照的单晶硅参数研究

在不同温度和红外光照下，测量了经中子辐照的单晶硅表面光电压，确定了其深能级的位置和少子扩散长度；由双能级复合理论，推导了中子辐照单晶硅的深能级复合中心和寿命的计算公式；计算了热中子辐照和高能中子辐照单晶硅后的深能级密度、费米能级和其他有关重要参数。     

PC1D方法对铝背场钝化技术的分析

降低单晶硅原材料成本,采用更薄的硅片作为太阳电池的原料是晶体硅太阳电池产业发展的趋势之一。对薄片化的太阳电池,铝背场的背表面钝化工艺显得愈加重要。采用PC1D太阳电池软件模拟的方法,对以商业用p型硅为衬底的单晶硅125×125太阳电池的铝背场的背表面钝化技术进行了模拟,分析得出,对一定厚度的电池片来说,尤其是当少数载流...     

Influence of wafer thickness on the performance of multicrystalline Si solar cells: an experimental study

The influence of the thickness of silicon solar cells has been investigated using neighbouring multicrystalline silicon wafers with thickness ranging from 150 to 325 μm. For silicon solar cell structures with a high minority‐carrier diffusion length one expects that J_sc would decrease as the wafer becomes thinner due to a shorter optical path length. It was found experimentally that J_sc is nearly independent of the thickness of the solar cell, even when the minority‐carrier diffusion length is about 300 μm. This indicates that the Al rear metallisation acts as a good back surface reflector. A decrease in J_sc is observed only if the wafer thickness becomes less than about 200 μm. The observed trend in V_oc as a function of the wafer thickness has been explained with PC1D modelling by a minority‐carrier diffusion length in the Al‐oped BSF which is small in relation to the thickness of the BSF. This effectively increases the recombination velocity at the rear of the cell. We have shown that the efficiency of solar cells made with standard industrial processing is hardly reduced by reducing the wafer thickness. Solar cell efficiencies might be increased by better rear surface passivation. Copyright © 2002 John Wiley & Sons, Ltd.