航天碲镉汞红外探测器工艺及暗电流研究

发布时间：2018-01-20 23:50

本文关键词： 碲镉汞光伏器件暗电流亚表面损伤 γ辐照效应浸没透镜　出处：《中国科学院研究生院(上海技术物理研究所)》2016年博士论文　论文类型：学位论文

【摘要】：本论文密切联系目前的航天应用需求,针对航天应用中的重要化合物半导体光电器件—碲镉汞光伏器件的制备工艺和暗电流特性展开了相关的研究。碲镉汞光伏器件的暗电流特性是影响器件性能的关键因素。论文中在对碲镉汞光伏器件暗电流的物理机制进行分析的基础上,就制备扩散电流限制的器件为目标,讨论了器件优化设计中的表面复合速率的影响和p型碲镉汞材料掺杂浓度的选择。针对大面积光伏器件中耗尽区太大导致的暗电流过大现象,讨论了子像元结构的应用可行性,通过短波和长波两个波段子像元结构大面积光伏器件的制备,发现若器件工作于体电流限制下,子像元结构在降低器件暗电流方面表现出明显的优势,并提出了漏电体积这一参量来对不同子像元结构的暗电流抑制效果进行对比评价。当器件工作于表面漏电流限制的范围时,由子像元结构引入的过多边界而导致的表面漏电会成为影响器件暗电流的决定性因素,此时子像元结构器件的暗电流反而会更大。分析了短波光伏器件制备中电极工艺的金属-碲镉汞接触特性。发现同样的接触金属结构在不同的温度下会表现出不同的接触特性,并利用激光束诱导电流(LBIC)方法扫描了不同温度下器件电极区的变化;通过理论分析认为高温下p型碲镉汞形成欧姆接触是由热发射电流和耗尽区复合电流共同作用的结果,而n型碲镉汞则主要是场发射所致;给出了碲镉汞光伏器件制备中电极工艺的改进方向,即对于n型电极,可以通过增加n型损伤而形成欧姆特性接触,对于p型电极一方面可以通过增加一个高浓度p型掺杂区来实现,另一方面也可以通过增加金属-碲镉汞Schottky结耗尽区中的复合漏电流来实现。分析了长波碲镉汞光伏器件测试工艺中背景辐射的影响。由于器件工作波段接近背景辐射的峰值,背景辐射在器件中会产生大量的光生载流子而影响器件的性能,提出了光生载流子的等效热激发模型(低反向偏压下),并结合光电流碰撞电离倍增模型(高反向偏压下),对于反向偏压下通过pn结的电流进行了有效的解释和拟合。背景辐射的直接影响是导致器件响应信号下降和噪声增加,对器件进行背景屏蔽后光电性能会明显改善。用椭圆偏振光谱方法研究了体晶材料碲镉汞光伏器件制备中抛光工艺所形成的亚表面损伤层,通过有效介质模型(EMA)拟合发现化学机械抛光会在碲镉汞表面形成15微米左右的亚表面损伤层,而溴抛光工艺所形成的亚表面损伤层只有几微米。通过MIS器件的制备研究了不同的抛光工艺对器件表面/界面特性的影响,发现化学机械抛光得到的MIS器件的钝化层固定正电荷密度为1.2×1012cm-2,而溴抛光工艺器件的钝化层固定正电荷密度只有2.4×1011cm-2。通过正向和反向电压扫描电容测试,得到对于化学机械抛光工艺制备的器件,其慢界面态密度为3.76×1010cm-2eV-1,而溴抛光样品为1.65×1010cm-2 eV-1。通过变结面积阵列器件的制备研究了不同的抛光工艺对器件暗电流特性的影响,发现对于化学机械抛光工艺制备的器件,暗电流以表面漏电为主,溴抛光工艺器件则主要由体效应决定;同样面积的器件,溴抛光工艺制备的器件具有更低的暗电流,噪声谱测试表明其噪声更小。采用反应耦合等离子体(ICP)工艺研究了氢钝化降低碲镉汞光伏器件暗电流的物理机制。发现氢钝化后碲镉汞光伏器件n区的电子浓度降低,p区的空穴浓度增加。通过将氢原子钝化区域扩展到离子注入区之外,发现对离子注入区之外的区域进行氢钝化也会明显降低器件的暗电流。暗电流拟合分析表明氢原子钝化使得器件耗尽区中载流子产生-复合寿命增加从而导致暗电流变小。通过对中波碲镉汞光伏器件进行实时γ辐照,研究了其动态γ辐照效应,发现器件表现出两种典型的辐照效应:电离效应和位移效应。电离效应反映在辐照过程中产生了类似光电流的零偏电流,位移效应则通过辐照过程中器件串联电阻的增加来体现出来,并利用少子引入和多子去除两辐照损伤能级模型进行了定性解释。同时发现氢钝化工艺对于器件的电离效应没有明显的改善作用,但却有助于改善器件的辐照位移效应。研制了可以在室温及近室温条件下工作的具有集成浸没透镜结构的碲镉汞中波红外单元光伏器件。直径为1.5mm高度为0.97mm的超半球结构浸没透镜是通过在碲锌镉衬底上采用单点金刚石切削工艺加工得到,带有集成浸没透镜的器件其黑体探测率增加了4倍左右;对于pn结电学面积为180μm×180μm的器件,LBIC扫描表明其光学响应区域接近1300μm×1300μm。
[Abstract]:This paper closely links the current aerospace applications, the preparation process of space in the application of important compound semiconductor optoelectronic devices - HgCdTe photovoltaic devices and dark current characteristics research is launched. The dark current characteristics of HgCdTe photovoltaic devices are the key factors affecting the performance of the device. This paper analyzed the physical mechanism of HgCdTe the dark current of photovoltaic device, device for preparing diffusion current limit as the goal, discusses the selection of doping concentration effect of surface recombination rate in the design and P type HgCdTe devices for optimization. Too large to large area photovoltaic devices in the depletion region of dark current phenomenon, discussed the feasibility of the application of sub pixel the structure of the short wave and long wave band two sub pixel structure for large area photovoltaic device fabrication, if the device works in current limit, like The dual structure in the reduced dark current shows its advantages, and puts forward the leakage volume parameter to evaluate the different sub pixel structure on the dark current suppression effect. When the device works in the range of surface leakage current restrictions, leading to excessive surface leakage and introduced by the boundary pixel structure will become the decisive factors influencing the dark current, the dark current sub-pixel structure devices would be more big. Analysis of the electrode preparation technology for metal - HF photovoltaic device of HgCdTe contact characteristics. It is found that the contact metal structure will show the same contact characteristics at different temperatures, and using laser beam induced current (LBIC) method scanning devices change electrode area at different temperature; through theoretical analysis that the P type high temperature HgCdTe ohmic contact is formed by thermal emission current and the depletion region complex Current common result, while the N type is mainly caused by field emission of HgCdTe; gives the improvement direction of electrode HgCdTe photodiodes in the preparation process, the N type electrode, can form ohmic contact characteristic of the increase of N type P type electrode for damage, one hand can be achieved by adding a high the concentration of P type doping area, on the other hand can also be achieved by increasing the metal HgCdTe Schottky junction composite leakage current in the depletion region. Analysis of the impact of the background of long wave radiation in the photovoltaic device testing technology. As the peak device close to the band of background radiation, background radiation in the device will produce carrier and impact device the performance of a large number of light excitation model equivalent heat photocarrier proposed (low reverse bias), and combined with the photocurrent multiplication model of impact ionization (high reverse bias), the anti To the bias current through the PN junction were explained and fitting effectively. The influence of background radiation is directly lead to the increase of device response signal and noise decreased, the background of the shield on the device after the photoelectric performance will be significantly improved. The sub surface crystalline material tellurium cadmium mercury photovoltaic device in the preparation of polishing process formed by the damage layer study on the spectroscopic ellipsometry method, through effective medium model fitting (EMA) found that chemical mechanical polishing will be formed around 15 micron sub surface damage layer in HgCdTe surface, while bromine polishing process formed by the sub surface damage layer of only a few microns. Through the MIS fabrication of different polishing effect on device surface / interface, MIS device for chemical mechanical polishing of the passivation layer fixed positive charge density is 1.2 * 1012cm-2, and the bromine polishing process device passivation layer fixed positive charge density Only 2.4 * 1011cm-2. by forward and reverse voltage test device for scanning capacitance, process for chemical mechanical polishing preparation, the slow interface states density is 3.76 * 1010cm-2eV-1, and bromine polished samples of 1.65 * 1010cm-2 eV-1. through the junction area array preparation effects of different polishing processes on the dark current characteristics of the device the discovery process of chemical mechanical polishing device for preparation of the dark current to the surface leakage, bromine polishing device is mainly determined by body effect; the same area of the device, the device fabricated with bromine polishing dark current has lower noise spectrum, less noise. The test results show that the reaction coupled plasma (ICP the process of hydrogen passivation) to reduce the physical mechanism of HgCdTe photovoltaic dark current. To reduce the electron concentration of HgCdTe photovoltaic devices n region found that hydrogen passivation, hole concentration of P area increased And through the hydrogen passivation region is extended to the ion implantation area, found the area outside of the ion implanted region of hydrogen passivation will significantly reduce the dark current. The dark current regression analysis show that hydrogen passivation makes depletion region carrier generation recombination lifetime increase resulting in dark current through the smaller. Real time gamma irradiation on MW HgCdTe photovoltaic devices, studies the dynamic effects of gamma irradiation, found that the device exhibits two typical irradiation effects: ionization and displacement. The ionization effect produces zero bias current reflect similar photocurrent during irradiation, displacement effect by increasing the irradiation process in series resistance of the device to reflected, and less use of sub introduction and removal of two multi level model of radiation damage are explained qualitatively. At the same time that the hydrogen passivation process for ionization device no There is obvious improvement, but helps to improve the displacement effect of irradiation device is developed. The infrared HgCdTe photovoltaic device unit can be integrated immersion lens structure has work at room temperature and near room temperature. The diameter is 1.5mm the height of the structure of the 0.97mm super hemisphere immersion lens is obtained by using single point diamond turning in the process of CdZnTe substrate, device with integrated immersion lens of the blackbody detection rate increased by 4 times; the PN junction area of 180 mu m electrical device * 180 m, LBIC scan showed that the optical response region close to 1300 m * 1300 m.

【学位授予单位】：中国科学院研究生院(上海技术物理研究所)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN215

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