多碱光电阴极膜厚对阴极灵敏度的影响研究

叙述了多碱光电阴极光谱反射的特点,测量了超二代微光像增强器多碱光电阴极的光谱反射曲线,分析了光谱响应曲线产生干涉加强峰和干涉减弱峰的原因,比较了不同膜层厚度多碱阴极光谱反射曲线的区别。根据能量守恒定律,利用实测的多碱光电阴极光谱反射率和光谱透过率,计算出多碱光电阴极的光谱吸收曲线,通过研究不同厚度多碱阴极的光谱吸收,发现多碱光电阴极膜层厚度加厚并不会提高其对所有波段光吸收率的特点。厚度增加只会增加短波和长波的光吸收率,但中波的光吸收率不会增加反而下降,这是由于受到光谱反射的影响。阴极膜层的厚度既影响光谱反射和光谱透过,又会影响光谱吸收,因此也影响多碱阴极的光谱响应,所以多碱光电阴极的膜层厚度是影响多碱光电阴极灵敏度的一个关键参数。实践证明,转移式技术制作的多碱光电阴极膜层厚度也存在一个最佳值,超过这一最佳厚度,阴极的灵敏度不增反降,这是因为红外光谱响应增加不多,但中波光谱响应下降很多。所以对转移式多碱光电阴极而言,实践证明当膜层厚度达到最佳厚度时,膜层呈现淡红色,在制作过程中要控制好阴极膜层的厚度,这样才可能获得较高的阴极灵敏度。     

Cs、O激活对GaAsP光阴极光谱响应特性的影响

为了探究Cs、O激活电流对透射式GaAsP光阴极光谱响应特性的影响,通过光谱响应测试仪测试不同Cs、O电流激活后的透射式GaAsP光阴极光谱响应曲线,结果表明,随着铯氧蒸发电流比的减小,GaAsP光阴极光谱曲线的形状会发生一定的改变,长波响应能力逐渐降低、短波响应能力逐渐提高。利用双偶极层模型理论,分析认为铯氧蒸发电流比的改变影响了GaAsP光阴极表面势垒的形状,使得不同激发能量的光电子通过隧道效应穿越表面势垒宽度发生变化,从而影响GaAsP光阴极光谱响应特性。根据此现象对进一步提高GaAsP光阴极在530 nm特征波长的量子效率具有积极的意义。     

4H-SiC金属-半导体-金属结构紫外探测器的模拟与分析

用MEDICI软件对金属-半导体-金属(MSM)结构4H-SiC紫外(UV)探测器的I-V特性以及光谱响应等特性进行了模拟与分析,并探讨了金属电极的宽度、电极间距以及外延层厚度对探测器响应度的影响.结果表明,室温下该探测器的暗电流线性密度达到10-13A/μm,且在不同电压下光电流至少比暗电流大两个数量级;探测器的光谱响应范围为200~400 nm,在347 nm处响应度达到极大值;增大指宽或者减小指间距可以提高探测器的响应度;当波长小于峰值波长时外延层厚度对探测器的响应度基本没影响,而当波长大于峰值波长时随着外延层厚度的增大探测器的响应度有所增大.     

梯度Si1-cGec混晶太阳电池长波光谱响应及其短路电流的理论计算与分析

提出了一种新型Si/Si1-cGec太阳电池结构.对长波波段的响应区域-Si基区Si1-cGec梯度区光生少子分布进行了求解.根据电流连续性原理计算了光谱响应SR,讨论了电池结构和梯度区最大锗浓度c对光生电流J1的影响.结果表明:在一定条件下梯度区的引入使得SR明显提高,但c和梯度区厚度同时增加,窄能隙的复合效应显现出来.电池结构对器件性能的影响更为显著.当梯度区厚度L2远小于基区厚度L1时,复合及电场的抽运使得SR低于相同厚度Si基区之值.     

梯度Si_(1-c)Ge_c混晶太阳电池长波光谱响应及其短路电流的理论计算与分析

提出了一种新型 Si/Si1- c Gec太阳电池结构 .对长波波段的响应区域—Si基区 Si1- c Gec梯度区光生少子分布进行了求解 .根据电流连续性原理计算了光谱响应 SR,讨论了电池结构和梯度区最大锗浓度 c对光生电流 JI的影响 .结果表明 :在一定条件下梯度区的引入使得 SR明显提高 ,但 c和梯度区厚度同时增加 ,窄能隙的复合效应显现出来 .电池结构对器件性能的影响更为显著 .当梯度区厚度 L2 远小于基区厚度 L1时 ,复合及电场的抽运使得 SR低于相同厚度 Si基区之值 .     

脉冲光照射下一维PSD响应特性的研究

研究一维位置敏感探测器(PSD)的脉冲响应特性及脉冲光照射下光生电流输出的规律,对准确计算光的入射位置有着十分重要的意义。给出脉冲光函数的表达式,讨论了4种脉冲光模式照射下的PSD脉冲响应特性,并详细研究了“脉冲堆积”现象。结果表明,如果脉冲光照射时间远远大于PSD的响应时间时,光的入射位置满足一维PSD的转化公式;如果光照射时间小于PSD的响应时间时,只要满足照射时间大于2.5倍的时间响应常数,则停止照射的时间越短,光入射位置与PSD输出电流之间越接近线性关系。     

LCoS芯片p-n结光生电流理论分析

LCoS中像素有源驱动电路受到光照后会在p-n结上产生光生漏电流,而光生漏电流的产生会引起LCoS的图像对比度退化,直接影响其成像质量。从光学和半导体器件物理两方面出发,分析了光生漏电流的产生机理,指出了影响漏电流大小的主要因素是入射光功率和挡光层的厚度。以Al膜作为挡光层材料,实际测量了不同厚度Al膜在可见光范围内的反射率,并在测量数据的基础上分别计算了不同情况下的光生电流的大小。当Al膜厚度为50nm时,光生电流最大仅为5.15×10-10A,可以抑制光生漏电流的产生,满足了LCoS的实际使用时的要求。     

吸收层与倍增层分离的4H-SiC雪崩光电探测器

设计和制备了吸收层和倍增层分开的4H-SiC穿通型雪崩紫外光电探测器.设计器件的倍增层和吸收层厚度分别为0.25和1μm.采用multiple junction termination extension(MJTE)方法减少器件的电流集边效应和器件表面电场.对器件的暗电流、光电流和光谱响应进行了测量.器件在55V的低击穿电压下获得了一个高的增益(＞104);穿通前器件暗电流约为10pA数量级;0V偏压下器件光谱响应的紫外可见比大于103.光谱响应的峰值波长随反向偏压的增大而向短波方向移动,在击穿电压附近光谱响应的峰值波长移到210nm,此波长远远小于在0V时的响应峰值.结果显示器件在紫外光探测中具有优良的性能.     

吸收层与倍增层分离的4H-SiC雪崩光电探测器

设计和制备了吸收层和倍增层分开的4H-SiC穿通型雪崩紫外光电探测器.设计器件的倍增层和吸收层厚度分别为0.25和1μm.采用multiple junction termination extension(MJTE)方法减少器件的电流集边效应和器件表面电场.对器件的暗电流、光电流和光谱响应进行了测量.器件在55V的低击穿电压下获得了一个高的增益(＞104);穿通前器件暗电流约为10pA数量级;0V偏压下器件光谱响应的紫外可见比大于103.光谱响应的峰值波长随反向偏压的增大而向短波方向移动,在击穿电压附近光谱响应的峰值波长移到210nm,此波长远远小于在0V时的响应峰值.结果显示器件在紫外光探测中具有优良的性能.     

重结硅光电二极管

本文提出了一种重结光电二极管结构.这种结构由一个接近表面的浅结和一个较深的结组成,这两个结可以分别有效地收集产生在接近表面的和产生在体内的光生载流子,这对于提高光电二极管从短波长到长波长光的响应都是有利的.通过对所作实验样品的光谱响应灵敏度的测量,说明重结光电二极管结构对改善光电器件的光谱响应是有效的.     

Study of 2-D photon crystal Fano slab filters for biological sensing

A new compact optical Fano filter suitable for biological sensing is proposed, which patterns photon crystal in single crystalline silicon nanomembranes （SiNMs） and transferring onto transparent glass substrates. The effects of air hole size and silicon thickness on the transmission characteristics of new filter are numerically investigated by using three-dimensional finite-difference time-domain （FDTD） technique, the spectral response is also studied by back-filling bio-liquid. The results show that the dip wavelength wil shift toward longer wavelength by either reducing air hole radius or filling bioliquid. The number of dips will inereasc with the increase of silicon thickness. The size of proposed filter can be less than I mm^2.     

Thickness estimation of silicon-on-lnsulator by means of the fourier transform of bilinearly transformed infrared reflectance data

Knowledge of film thickness is essential for device design in silicon-on-insulator technology. A new thickness estimation technique, based on the calculation of the spatial frequencies of bilinearly transformed infrared reflectance data in a spectral window, is introduced. The assignment of dominant spectral peaks in the power spectral density curve to the optical thickness of the silicon, silicon dioxide and the combined layer, is also presented. Examples for silicon-on-silicon dioxide with the silicon layer ranging in thickness between 1000 nm and 50 nm, with fixed oxide thickness, are presented. Thickness values of both layers to better than a few percent accuracy, were obtained for silicon layers down to 100 nm and with reduced accuracy for layers as thin as 50 nm.     

The strong absorption characteristics of ternary one-dimensional photonic crystals with silver layer

In order to achieve broadband and efficient optical absorption, the multiple silver nanolayer was introduced into the photonic crystals to form a one-dimensional ternary periodic symmetric structure. The effects of thickness of each layer on the band range, absorption bandwidth, absorbance and absorption energy field distribution of the solar spectrum high absorption band were studied by the transfer matrix method. The absorption band with wavelength range from 724 nm to 1 188 nm, spectral width of 464 nm, and average absorbance of 0.78 was obtained by structural adjustment. The absorbed energy is mainly distributed in the first half of the symmetrical structure of the photonic crystal. When the thickness of the silver layer decreased from 30 nm to 15 nm, the local energy in each period increased significantly. At the same time, the distribution and transfer of energy in silicon and MgF2 layers can be controlled. The results of this paper can be used to improve the absorption of solar radiation, and provide an important basis for the design of photonic crystal and their application in solar energy utilization.     

Microwave photonic filter with tunability, reconfigurability and bipolar taps

A new microwave photonic filter structure realising fully programmable RF filtering that can tune the filter centre frequency and also reconfigure the filter shape, while exhibiting multiple taps and bipolar taps, is presented. It is based on a new arbitrary spectrum slicing technique using a multi-port programmable wavelength processor, based on liquid crystal on silicon pixels, which offers programmable finite impulse response filtering using software control. Experimental results demonstrate a high-order microwave filter with tunability, reconfigurability, bipolar taps, and with high free spectral range.     

偏振不灵敏硅基二氧化硅阵列波导光栅设计

以深刻蚀和热氧化工艺为基础,提出了一种新的阵列波导光栅(AWG)制备技术.这一工艺可使AWG中的波导侧向留有一硅层.采用有限元法和有限差分束传播法分别计算了存在这一硅层时的波导应力分布和有效折射率.结果表明由于这一侧向硅层的存在,使AWG中波导在水平和垂直方向的应力趋于一致,AWG的偏振相关波长明显减小.     

PSD233型位置敏感元件的特性及其在AFM中的应用

给出了自制的 3mm× 3mm位置敏感元件 (PSD)的光谱响应特性 ,覆盖从紫外光、可见光到红外光 (32 0～115 0nm)的广阔区域 .采用光束偏转法对其时间响应特性和位置敏感特性进行测定 .阐述了PSD在卧式原子力显微镜 (AFM)系统中的应用 ,介绍了卧式AFM的工作原理和控制系统 ,提供了部分样品的AFM扫描图像 .结果表明 ,该AFM系统具有较高的成像效率以及良好的工作稳定性、图像重复性和对比度 ,系统的最大扫描范围为 5 μm× 5 μm ,分辨率达到 1nm量级 ,表明PSD在光谱响应、时间响应和位置敏感特性等方面具有优良性能     

Modeling improvement of spectral response of solar cells by deployment of spectral converters containing semiconductor nanocrystals

A planar converter containing quantum dots as wavelength-shifting moieties on top of a solar cell was studied. The highly efficient quantum dots are to shift the wavelengths where the spectral response of the solar cell is low to wavelengths where the spectral response is high in order to improve the conversion efficiency of the solar cell. It was calculated that quantum dots with an emission at 603 nm increase the multicrystalline solar cell short-circuit current by nearly 10%. Simulation results for planar converters on hydrogenated amorphous silicon solar cells show no beneficial effects, due to the high spectral response at low wavelength.     

Photodetectors monolithically integrated on SOI substrate foroptical pickup using blue or near-infrared semiconductor laser

We made photodetectors on a silicon-on-insulator (SOI) substrate by a 0.35-μm BiCMOS fabrication process to detect the signal light used in an optical disk system. Investigating their characteristics at two wavelengths, 410 and 780 nm, for different structures, we found that the thickness of the silicon crystalline layer on the insulator strongly affected the frequency response at the longer wavelength, while the cutoff frequency was over 500 MHz for the shorter wavelength. We also simulated the frequency response     

缺陷为增益介质的光子晶体光放大特性的研究

为了研究含缺陷层为增益介质的三元1维光子晶体的光学特性,采用光学传输矩阵的方法进行了理论分析。结果表明,增益缺陷层厚度及光学常数的变化对于红外区的禁带结构影响不大,增益介质层主要对中心波长为1.8μm所处的透射带带边波长的放大效应特别明显。还研究了增益介质缺陷层的厚度、光学常数的变化对于红外区透射带边(2.1869μm)波长的光放大效应;当增益介质厚度为0.0101μm,n=5.03+0.124i时,可以获得在波长2.1869μm处透射系数为428的光放大。在红外区,光放大波长随着中心波长的变化而变化,但该波长都是在中心波长所处透射带的带边处。该结果可为以光子晶体作为激光增益介质的研究提供理论指导。