A quantum efficiency analytical model for complementary metal–oxide–semiconductor image pixels with a pinned photodiode structure

A quantum efficiency analytical model for complementary metal–oxide–semiconductor（CMOS） image pixels with a pinned photodiode structure is developed. The proposed model takes account of the non-uniform doping distribution in the N-type region due to the impurity compensation formed by the actual fabricating process. The characteristics of two boundary PN junctions located in the N-type region for the particular spectral response of a pinned photodiode, are quantitatively analyzed. By solving the minority carrier steady-state diffusion equations and the barrier region photocurrent density equations successively, the analytical relationship between the quantum efficiency and the corresponding parameters such as incident wavelength, N-type width, peak doping concentration, and impurity density gradient of the N-type region is established. The validity of the model is verified by the measurement results with a test chip of 160×160 pixels array,which provides the accurate process with a theoretical guidance for quantum efficiency design in pinned photodiode pixels.

A low-power high-quality CMOS image sensor using 1.5 V 4T pinned photodiode and dual-CDS column-parallel single-slope ADC

This paper presents a low-power high-quality CMOS image sensor(CIS)using 1.5 V 4T pinned photodiode(4T-PPD)and dual correlated double sampling(dual-CDS)column-parallel single-slope ADC.A five-finger shaped pixel layer is proposed to solve image lag caused by low-voltage 4T-PPD.Dual-CDS is used to reduce random noise and the nonuniformity between columns.Dual-mode counting method is proposed to improve circuit robustness.A prototype sensor was fabricated using a 0.11μm CMOS process.Measurement results show that the lag of the five-finger shaped pixel is reduced by 80%compared with the conventional rectangular pixel,the chip power consumption is only 36 mW,the dynamic range is 67.3 dB,the random noise is only 1.55 e^(-)_(rms),and the figure-of-merit is only 1.98 e^(-)·nJ,thus realizing low-power and high-quality imaging.

Analysis and simulation of lateral PIN photodiode gated by transparent electrode fabricated on fully-depleted SOI film

A novel device,lateral PIN photodiode gated by transparent electrode (LPIN PD-GTE) fabricated on fully-depleted SOI film was proposed.ITO film was adopted in the device as gate electrode to reduce the light absorption.Thin Si film was fully depleted under gate voltage to achieve low dark current and high photo-to-dark current ratio.The model of gate voltage was obtained and the numerical simulations were presented by ATLAS.Current-voltage characteristics of LPIN PD-GTE obtained in dark (dark current) and under 570 nm illumination (photo current) were studied to achieve the greatest photo-to-dark current ratio for active channel length from 2 to 12μm.The results show that the photo-to-dark current ratio is 2.0×107,with dark current of around 5×10-4 pA under VGK=0.6 V,PIN=5 mW/cm2,for a total area of 10μm×10μm in fully depleted SOI technology.Thus,the LPIN PD-GTE can be suitable for high-grade photoelectric systems such as blue DVD.

Scalability of dark current in silicon PIN photodiode

The mechanism for electrical conduction is investigated by the dark temperature-dependent current–voltage characteristics of Si PIN photodiodes with different photosensitive areas.The characteristic tunneling energy E（00） can be obtained to be 1.40 me V,1.53 me V,1.74 me V,1.87 me V,and 2.01 me V,respectively,for the photodiodes with L = 0.25 mm,0.5 mm,1 mm,1.5 mm,and 2 mm by fitting the ideality factor n versus temperature curves according to the tunneling-enhanced recombination mechanism.The trap-assisted tunneling-enhanced recombination in the i-layer plays an important role in our device,which is consistent with the experimental result that area-dependent leakage current is dominant with the side length larger than 1 mm of the photosensitive area.Our results reveal that the quality of the bulk material plays an important role in the electrical conduction mechanism of the devices with the side length larger than 1 mm of the photosensitive area.

Silicon PIN photodiode applied to acquire high-frequency sampling XAFS spectra

Experimental techniques based on SR facilities have emerged with the development of synchrotron radiation(SR)sources.Accordingly,detector miniaturization has become significant for the development of SR experimental techniques.In this study,the miniaturization of a detector was achieved by coupling a commercial silicon PIN photodiode(SPPD)into a beamstop,aiming for it not only to acquire X-ray absorption fine structure(XAFS)spectra,but also to protect the subsequent two-dimensional detector from high-brilliance X-ray radiation damage in certain combination techniques.This mini SPPD detector coupled to a beamstop was used as the rear detector in both the conventional sampling scheme and novel high-frequency(HF)sampling scheme to collect the transmission XAFS spectra.Traditional ion chambers were also used to collect the transmission XAFS spectra,which were used as the reference.These XAFS spectra were quantitatively analyzed and compared;the results demonstrated that the XAFS spectra collected by this SPPD in both the conventional sampling scheme and HF sampling scheme are feasible.This study provides a new detector-selection scheme for the acquisition of the quick-scanning XAFS(QXAFS)and HF sampling XAFS spectra.The SPPD detector presented in this study can partially meet the requirements of detector miniaturization.

The Effects by γ Ray Irradiation on Silicon Photodiodes

The relationships between irradiation doses of γ ray and the main photoelectric characteristics of PIN photodiode or conventional photodiode with different structure were studied. The experimental results show that after the photodiodes being irradiated,the photocurrent decreases,especially for short wavelength of light. The dark current of the photodiodes with smaller active area decreases while increases for that with larger active area,and the response time shortens. The plane scanning experiment of laser beam indicates that the homogeneity of the device's surface is not influenced by the irradiation. The results prove that PIN photodiode shows relatively good radioresistance.

硅PIN光电探测器阵列的串扰分析

在利用高密度线性阵列探测器成像时,探测阵列单元间的串扰将直接影响器件的成像质量。文章对厚度为100μm的背照式PIN光电探测器线性阵列的电串扰特性进行了分析,通过Silvaco TCAD器件仿真软件对阵列的暗电流和光电流进行了仿真,分析了像元间的电串扰特性,同时对比分析了保护环结构对器件的暗电流和电串扰特性的影响。仿真结果表明,保护环结构器件的暗电流和电串扰性能均优于无保护环的结构,在有保护环时PIN器件的串扰是无保护环结构的1/5。

中子辐照诱导Si PIN光电二极管暗电流增大的数值模拟

分析了中子辐照诱导Si PIN光电二极管暗电流增大现象的机理,建立了Si PIN光电二极管的器件物理模型和中子辐照效应模型。运用MEDICI软件进行数值模拟计算,得出了1MeV中子在辐照注量为1010～1014cm-2时,Si PIN光电二极管暗电流变化的初步规律。数值模拟结果与相关文献给出的实验结果吻合较好。

紫外和蓝光区域硅PIN光电二极管

描述了采用离子注入、低温慢降温热处理和背面磷吸杂等方法在高阻 (111) N型硅片上研制高性能 PIN光电二极管的工艺技术 ,测量并分析了光电二极管的 I- V、C- V和光灵敏度等性能 .有源区面积为 16 mm× 17mm的二极管样品在全耗尽偏置电压下 (Vd=70 V) ,环境温度为 2 5℃时的暗电流和端电容典型值分别达到≤ 5 n A和≤ 12 0 p F.探测器在波长区域 (380～ 5 0 0 nm )的光谱响应典型值 :4 0 0 nm为 0 .2 6 A/ W,5 0 0 nm为 0 .33A / W.量子效率在 4 0 0～90 0 nm光谱范围内达到 70 %～ 80 % .对于紫外光至蓝光区域 。

PIN硅光电二极管用于γ射线探测的试验研究

在X、γ射线的剂量或剂量率测量场合,常用到PIN硅光电二极管。比起传统的电离室等,它有体积小、灵敏度高、成本低、不需要高压等优点;与计数管、闪烁探测器相比,其电流输出的特性可以避免脉冲场下的死时间问题。但大剂量照射造成的辐射损伤是影响其性能的最大因素。以XRB100s-CB380为例,通过试验研究了PIN硅光电二极管的特性,包括灵敏度、偏压影响、温度补偿、辐射损伤及退火等,并简单介绍了实际应用中对输出电流信号的处理方法。

硅PIN光电二极管γ电离脉冲辐射的数值模拟

分析了γ电离脉冲辐射诱发硅PIN光电二极管产生光电流的机理。建立了硅PIN光电二极管的器件物理模型以及γ电离脉冲辐射效应模型;运用MEDICI软件,进行了辐射效应数值模拟计算。得出了γ电离脉冲辐射剂量率在100～109Gy(Si)/s范围内,诱发硅PIN光电二极管光电流变化的初步规律。对比了辐射效应数值模拟结果与国外相关文献给出的辐照实验结果。

基于光照强度的PIN光电二极管响应时间分析

在PIN光电二极管应用中发现,光照强度对响应速度具有很大影响。论文研究了光强对响应速度的影响,提出了内部PIN结等效电场模型,并搭建了实验电路对PIN光电二极管在不同光照强度下的响应速度进行检测,验证提出的结模型,很好的解释了光电二极管从无光照到有光照这一过程中,光强越强,响应时间越短;而当光电二极管从有光照到无光照这一过程中,光强越强,响应时间越长这一现象。提出的模型和实验验证为光电二极管在响应速度要求较高的系统中的应用提供了理论分析依据,也为进一步提高PIN光电二极管的速度提出了有益的探索。

PIN结构自扫描光电二极管列阵的研究

通过对再充电采样方式的自扫描光电二极管列阵（ＳＳＰＡ）工作原理分析，对列阵中光电二极管工作模式进行较深入的探讨，指出影响其性能的主要因素。提出了用ＰＩＮ结构代替常用的ＰＮ结结构的光电二极管组成ＳＳＰＡ。经过ＰＩＮ结构和ＭＯＳ电路兼容工艺方案的分析及实验，测试结果表明ＰＩＮ结构有利于改进ＳＳＰＡ的性能，是研究高性能ＳＳＰＡ的新结构。

PIN结构自扫描光电二极管列阵

从自扫描光电二极管列阵（ＳＳＰＡ）的工作原理出发，提出采用外延、离子注入、推阱的技术，研究一种新颖的高响应度的ＰＩＮ结构的ＳＳＰＡ器件，详细的分析了工艺设计方案和实验方法，最后提供了样品的测试参数。

PIN光电二极管探测器响应特性测试

介绍了PIN光电二极管探测器的工作原理及基本结构,设计了探测器的测试系统,说明了测试系统中各个组成部分的结构和功能。利用该系统对PIN管光探测器电路的电特性进行了测试,测试结果表明PIN光电二极管探测器的响应特性符合技术要求。

用于电路模拟的PIN雪崩光电二极管模型

针对PIN结构的特殊性，作了适当的合理近似，考虑了p，n区少子扩散，i区载流子漂移，给出一个完整的PIN雪崩光电二极管电路模型。该模型适于在开发OEIC电路模拟软件中采用，亦可加到现有电路模拟软件中。它可用于直流、交流、瞬态分析。该模型完全适用于PIN结构光电二极管。

Measurement of charge transfer potential barrier in pinned photodiode CMOS image sensors

The charge transfer potential barrier （CTPB） formed beneath the transfer gate causes a noticeable image lag issue in pinned photodiode （PPD） CMOS image sensors （CIS）, and is difficult to measure straightforwardly since it is embedded inside the device. From an understanding of the CTPB formation mechanism, we report on an alternative method to feasibly measure the CTPB height by performing a linear extrapolation coupled with a horizontal left-shift on the sensor photoresponse curve under the steady-state illumination. The theoretical study was pertbrmed in detail on the principle of the proposed method. Application of the measurements oil a prototype PPD-CIS chip with an array of 160 ×160 pixels is demonstrated. Such a method intends to shine new light oil the guidance for the lag-free and high-speed sensors optimization based on PPD devices.

基于PIN型硅光电二极管的激光偏振态探头

综合考虑了PIN型硅光电二极管的高灵敏性、高稳定性、高响应速度、小体积及低成本的优点,主要研究了基于PIN型硅光电二极管的光强探测电路在激光偏振态测量系统中的应用。采用Stockes参量测量的LCVR调制法,将光强探测电路和光学检偏系统封装在一起构成激光偏振态测量探头,探头以STM32F103为控制器通过USB协议实现数据在上位机与控制器之间的传输。利用该探头完成808nm激光的偏振态测量,实验结果显示该偏振态测量探头具有较高的测量精度,且该偏振态测量探头具有结构简单、测量精度高、体积小、人机交互便捷、操作简单的特点。

高抑制比背照式Al_xGa_(1-x)N pin日盲紫外探测器研究

利用现有外延材料生长技术和器件工艺技术,生长了背照式AlxGa1-xN pin外延材料,并用生长的材料制作了日盲紫外探测器,测试结果表明器件在0V偏压下抑制比达到了6 400。在此基础上,较详细地分析了偏置电压、p-AlxGa1-xN载流子浓度和Al组分、极化效应对背照式AlxGa1-xN pin日盲紫外探测器抑制比的影响及非日盲光生载流子的限制机制。分析表明,提高p-AlxGa1-xN载流子浓度和GaN/AlxGa1-xN异质结极化强度是现有技术条件下提高器件抑制比的有效途径。

采用Taguchi方法优化一种带外延层的PPD工艺参数

引入Taguchi方法分析并优化一种带外延层的PPD结构(EPPD),并通过SILVACO软件进行验证。实验结果显示该方法通过对EPPD像素结构工艺参数的优化,提升了该结构抑制噪声的能力和光电转换性能。