基于非平衡模式的碲镉汞高工作温度探测器

本文回顾了当前国内外高工作温度碲镉汞红外探测器的技术路线和相应的器件性能,在碲镉汞器件暗电流的温度特性分析的基础上,讨论了基于非平衡工作模式的碲镉汞探测器的基本原理、器件结构设计和暗电流机制,探讨了吸收层全耗尽碲镉汞器件性能与器件结构参数、材料晶体质量的关系,明确了其技术要点和难点,展望了碲镉汞高工作温度器件技术的发展趋势。     

基于nBn势垒阻挡结构的碲镉汞高温器

本文简要介绍了nBn势垒阻挡结构器件的提出、发展过程.讨论了nBn型器件的工作机理及其对暗电流的抑制机理.对比了普通碲镉汞nBn结构器件与经过优化具备俄歇抑制特点的NBvN结构器件的性能.总结了碲镉汞nBn型器件势垒层设计要素及器件价带带阶消除的方法.     

高工作温度碲镉汞红外探测器杜瓦结构研究

随着第三代红外探测器技术的快速发展,高工作温度红外探测器成为重要的发展方向。本文报道了在高工作温度碲镉汞红外探测器杜瓦结构小型化、低功耗、高可靠性方面的研究进展。通过杜瓦结构的优化设计,搭配旋转整体式低温制冷机K562Sshort,制备出组件体积为80mm×61mm×39mm,重量为212 g,启动时间为25min,工作温度达到150K的高工作温度中波碲镉汞红外探测器,并初步完成了组件可靠性试验验证,为高工作温度碲镉汞红外探测器的工程化应用奠定了一定的基础,对高工作温度碲镉汞红外探测器的小型化、低功耗、高可靠性研究具有一定的指导意义。     

高工作温度碲镉汞p-on-n中波1024×768焦平面探测器

提高红外探测器的工作温度对于减小红外系统的尺寸、重量和功耗至关重要,进而实现结构紧凑和成本低廉的红外系统。昆明物理研究所多年来对掺铟和砷离子注入技术的HgCdTe p-on-n技术进行了优化,实现了性能优异的中波红外探测器的研制。本文报道了高工作温度中波1024×768@10 μm红外焦平面阵列探测器的最新结果,并介绍了在150 K工作温度下的器件性能。结果标明,器件在150 K下截止波长为4.97 μm,并测得了不同工作温度下的NETD、暗电流和有效像元率。此外,还展示了在150 K的工作温度下焦平面器件的红外图像,并呈现了99.4%的有效像元率。     

12.5 μm碲镉汞探测器工作温度对输出电平的影响

12.5 μm碲镉汞探测器的输出电平对工作温度非常敏感,因此需要对其温度敏感度进行研究。试验中,通过调节探测器的工作温度来采集其输出电平,并对数据进行分析。结果表明,工作波长和暗电流随温度变化是导致输出电平变化的主要因素;12.5 μm碲镉汞探测器的最佳工作温度在60 K附近。该方法操作简单,无需使用复杂的操作设备。大部分红外实验室均可满足此试验要求。     

高工作温度p-on-n中波碲镉汞红外焦平面器件研究

As注入掺杂的p-on-n结构碲镉汞红外探测器件具有少子寿命长、暗电流低、R₀A值高等优点,是高温器件研究的重要技术路线之一。针对阵列规模640×512、像元中心距15 μm 的As掺杂工艺制备的p-on-n中波碲镉汞焦平面器件,测试了不同工作温度下的性能和暗电流。研究结果表明,在80 K工作温度下,器件响应表现出高响应均匀性,有效像元率达99.98%;随着工作温度升高,器件盲元增多,当工作温度为150 K和180 K时,有效像元率降低至99.92%和99.32%。由于对器件扩散电流更好的抑制,器件在160~200 K温度范围内的暗电流低于Rule-07。并且当工作温度在150~180 K时（300 K的背景下）,器件具有较好的信噪比,极大程度地体现了高温工作的可行性。     

论高工作温度碲镉汞红外探测器（下）

与用其他材料制备的红外光子探测器相比,碲镉汞红外探测器具有带隙灵活可调、量子效率较高以及R_oA接近理论值等优点。碲镉汞探测器的主要缺点是需要低温制冷,以抑制引起噪声的热生自由载流子。期望碲镉汞探测器在具有高工作温度(High Opeating Temperature,HOT)的同时而又无需牺牲性能。HOT碲镉汞探测器的设计目标主要是抑制俄歇过程,从而降低探测器噪声和低温制冷需求。从相关基本概念出发,讨论了对HOT碲镉汞物理机制的理解以及近年来HOT碲镉汞技术的发展状况。     

高工作温度中波红外碲镉汞焦平面研究

该文报道了昆明物理研究所高工作温度中波红外碲镉汞焦平面探测器器件的研究情况。通过优化焦平面器件结构参数,采用As离子注入形成p-on-n平面结器件技术,在液相外延生长的高质量原位In掺杂的碲镉汞薄膜上制备了阵列规格为640×512@15μm的中波红外焦平面探测器。利用变温杜瓦测试了焦平面芯片在不同工作温度下的光谱响应、器件暗电流、噪声等效温差、有效像元率以及盲元分布等,测试结果表明器件具备180K以上工作温度的能力。     

论高工作温度碲镉汞红外探测器（上）

与用其他材料制备的红外光子探测器相比,碲镉汞红外探测器具有带隙灵活可调、量子效率较高以及R_0A接近理论值等优点。碲镉汞探测器的主要缺点是需要低温制冷,以抑制引起噪声的热生自由载流子。期望碲镉汞探测器在具有高工作温度(High Operating Temperature,HOT)的同时而又无需牺牲性能。HOT碲镉汞探测器的设计目标主要是抑制俄歇过程,从而降低探测器噪声和低温制冷需求。从相关基本概念出发,讨论了对HOT碲镉汞物理机制的理解以及近年来HOT碲镉汞技术的发展状况。     

碲镉汞高温红外探测器组件进展

高工作温度红外探测器组件是第三代红外探测器技术的重要发展方向,可用于高工作温度红外探测器的基础材料主要有锑基和碲镉汞两大类。介绍了昆明物理研究所在高工作温度红外焦平面探测器组件方面的最新研究进展,其中基于碲镉汞材料p-on-n技术研制的高工作温度中波640×512探测器组件在150 K温区性能优异,探测器的噪声等效温差(NETD)小于20 mK,配置了高效动磁式线性制冷机的高温探测器组件(IDDCA结构),质量小于270 g,探测器组件光轴方向长度小于70 mm(F4),室温环境下组件稳态功耗小于2.5 Wdc,降温时间小于80 s,声学噪声小于27 dB,探测器光轴方向自身振动力最大约1.1 N。目前正在进行环境适应性和可靠性验证,完成后就可实现商用量产。     

碲镉汞线列红外探测器模块温度循环的可靠性

针对直接倒焊(Ⅰ型)、间接倒焊(Ⅱ型)两种红外探测器模块,两者中的探测器芯片、硅读出电路和引线基板的尺寸完全相同,只在倒焊封装结构上有所差异,用有限元方法分析比较了这两种封装形式的基本模块于液氮温度时的热应力和形变大小情况,分析结果与实验现象符合较好,模块低温形变值的测量验证了有限元分析结果的合理性.     

通过成结模拟器研究n+-n--p碲镉汞高温探测器

第三代红外探测器发展的一个重要方向是高工作温度探测器。对于碲镉汞n-on-p探测器而言,n⁺-n^--p结构以及良好的钝化工艺能够有效的抑制暗电流的产生,从而在高工作温度条件下获得较好的探测器性能。基于自行开发的成结模拟器,对n⁺-n^--p结构地高温器件进行了工艺仿真和器件仿真,获得成结过程的制备参数,并结合抑制表面漏电的组分梯度钝化工艺,将高工作温度下的暗电流抑制至理论极限,研制出可以在更高温度工作下的碲镉汞n-on-p红外焦平面探测器。经测试,中波n-on-p红外焦平面器件在不同工作温度下性能优异,在80 K工作温度下噪声等效温差(NETD)达到了6.1 mK,有效像元率为99.96%;而在150 K工作温度下噪声等效温差(NETD)为11.0 mK,有效像元率为99.50%,达到了同类器件的理论极限。     

高工作温度碲镉汞红外探测器研究进展

高工作温度碲镉汞红外探测器作为最近来发展起来的新型探测器,在保证性能不变的基础上,实现了尺寸小、重量轻、功耗低等功能,成为军事侦察、无人机、无人平台的重要探测器件。本文阐述了高工作温度碲镉汞红外探测器的基本原理,重点介绍了碲镉汞P-on-N红外探测器的器件结构设计,并且对美国Raytheon、法国Sofradir、德国AIM、美国Teledyne、美国DRS等公司的研究进展进行了综述性介绍。     

Progress in MOVPE of HgCdTe for advanced infrared detectors

This paper reviews the significant progress made over the past five years in the development of metalorganic vapor phase epitaxy (MOVPE) for the in situ growth of HgCdTe p-n junction devices for infrared detector arrays. The two basic approaches for MOVPE growth of HgCdTe, the interdiffused multilayer process (IMP), and direct alloy growth (DAG) are compared. The paper then focuses on the progress achieved with the IMP approach on lattice-matched CdZnTe substrates. The benefits of the precursors ethyl iodide (EI) and tris-dimethylaminoarsenic (DMAAs) for controlled iodine donor doping and arsenic acceptor doping at dopant concentrations relevant for HgCdTe junction devices are summarized along with the electrical and lifetime properties of n-type and p-type HgCdTe films grown with these precursors. The relative merits of the two CdZnTe substrate orientations we have used, the (211)B and the (100) with 4°–8° misorientation are compared, and the reasons why the (211)B is preferred are discussed. The growth and repeatability results, based on secondary ion mass spectrometry analysis, are reported for a series of double-heterojunction p-n-N-P dual-band HgCdTe films for simultaneous detection in the 3–5 μm and 8–10 μm wavelength bands. Finally, the device characteristics of MOVPE-IMP in situ grown p-on-n heterojunction detectors operating in the 8–12 μm band are reviewed and compared with state-of-the-art liquid phase epitaxial grown devices.     

HgCdTe/Si materials for long wavelength infrared detectors

The heteroepitaxial growth of HgCdTe on large-area Si substrates is an enabling technology leading to the production of low-cost, large-format infrared focal plane arrays (FPAs). This approach will allow HgCdTe FPA technology to be scaled beyond the limitations of bulk CdZnTe substrates. We have already achieved excellent mid-wavelength infrared (MWIR) and short wavelength infrared (SWIR) detector and FPA results using HgCdTe grown on 4-in. Si substrates using molecular beam epitaxy (MBE), and this work was focused on extending these results into the long wavelength infrared (LWIR) spectral regime. A series of nine p-on-n LWIR HgCdTe double-layer heterojunction (DLHJ) detector structures were grown on 4-in. Si substrates. The HgCdTe composition uniformity was very good over the entire 4-in. wafer with a typical maximum nonuniformity of 2.2% at the very edge of the wafer; run-to-run composition reproducibility, realized with real-time feedback control using spectroscopic ellipsometry, was also very good. Both secondary ion mass spectrometry (SIMS) and Hall-effect measurements showed well-behaved doping and majority carrier properties, respectively. Preliminary detector results were promising for this initial work and good broad-band spectral response was demonstrated; 61% quantum efficiency was measured, which is very good compared to a maximum allowed value of 70% for a non-antireflection-coated Si surface. The R₀A products for HgCdTe/Si detectors in the 9.6-μm and 12-μm cutoff range were at least one order of magnitude below typical results for detectors fabricated on bulk CdZnTe substrates. This lower performance was attributed to an elevated dislocation density, which is in the mid-10⁶ cm⁻² range. The dislocation density in HgCdTe/Si needs to be reduced to <10⁶ cm⁻² to make high-performance LWIR detectors, and multiple approaches are being tried across the infrared community to achieve this result because the technological payoff is significant.     

Numerical analysis of HgCdTe simultaneous two-color photovoltaic infrared detectors

In this paper, we present a physics-based full three-dimensional (3-D) numerical simulation of simultaneous two-color medium-wave infrared long-wave infrared (MWIR-LWIR) and LWIR-very-long-wave infrared (VLWIR) detectors. The present approach avoids geometrical simplifications typical of one- or two-dimensional models that can introduce errors which are difficult to quantify. We include all the relevant material physics and the drift-diffusion equations are solved on a 3-D finite element grid. We simulate device structures that have been fabricated and characterized for operation in the MWIR-LWIR spectral regions and compare the numerical results with the measured values. Furthermore, we apply the same model to predict the performance of similar detector structures intended for operation in the LWIR-VLWIR spectral regions.     

高工作温度锑化物红外探测器研究进展

随着材料制备和器件工艺技术的进步,制冷型红外探测器向着体积小、重量轻、低功耗、高性能和低成本的目标迈进。锑化物材料因其自身特殊的能带结构以及优异的光学性能,在低暗电流和高工作温度应用方面有巨大的发展潜力,可满足多种应用场景的需求。因此,开展高工作温度锑化物红外探测器的研究,具有非常重要的意义。本文综述了高工作温度锑化物红外探测器的发展状况,并对未来的发展趋势进行了展望。     

Study of the pixel-pitch reduction for HgCdTe infrared dual-band detectors

The third generation of HgCdTe infrared-detector focal-plane arrays (FPAs) should be able to detect simultaneously in two spectral bands. The feasibility of this type of dual-band detectors has already been shown in our laboratory with a pixel size of 50 μm in the 3–5-μm wavelength range. To improve the detector resolution, it is necessary to decrease the pixel pitch. Dry etching is a key process technology to fulfill this goal because of the high aspect-ratio structures needed (typically 10–15-μm deep and 2–5-μm wide trenches). In this paper, we present results of a parametric study on HgCdTe dry etching, as well as results obtained on detector arrays made with the dry-etching technique. The etching study has been done in a microwave plasma reactor with the aim of controlling the surface roughness, the etch rate, and the slope of the trench side. We show how these parameters are influenced by the reactive gas-mixture composition (based on CH₄, H₂, and Ar) and the substrate self-bias. We show how polymer film deposition can prevent etching from occurring but can improve anisotropy. We show some examples of results obtained when manufacturing the trenches that separate the pixels, keeping a high fill factor, and anisotropic etching. We also show results of the material surface characterizations done with scanning electron microscopy (SEM) and Hall effect measurements. These studies allow us to evaluate and compare the damages done to the HgCdTe surface with different etching conditions. Our best process allows us to make a light electrical damage, confined to less than a micron deep in the material. Using the dry-etching process, we have developed detector arrays fabricated with a pixel pitch as low as 30 μm. We finally present the results of the first electrical characterizations made on these arrays, showing promising results for the development of high-resolution dual-band detectors.     

HgCdTe/CdTe/Si infrared photodetectors grown by MBE for near-room temperature operation

Conventional HgCdTe infrared detectors need significant cooling in order to reduce noise and leakage currents resulting from thermal generation and recombination processes. Although the need for cooling has long been thought to be fundamental and inevitable, it has been recently suggested that Auger recombination and generation rates can be reduced by using the phenomena of exclusion and extraction to produce nonequilibrium carrier distributions. The devices with Auger suppressed operation requires precise control over the composition, and donor and acceptor doping. The successful development of the molecular beam epitaxy (MBE) growth technique for multi-layer HgCdTe makes it possible to grow these device structures. Theoretical calculations suggest that the p n+ layer sequence is preferable for near-room temperature operation due to longer minority carrier lifetime in lightly doped p-HgCdTe absorber layers. However, because the low doping required for absorption and nonequilibrium operation is easier to achieve in n-type materials, and because Shockley-Read centers should be minimized in order to obtain the benefits of Auger suppression, we have focused on p⁺ n structures. Planar photodiodes were formed on CdTe/Si (211) composite substrates by As implantation followed by a three step annealing sequence. Three inch diameter Si substrates were employed since they are of high quality, low cost, and available in large areas. Due to this development, large area focal plane arrays (FPAs) operated at room temperature are possible in the near future. The structures were characterized by FTIR, x-ray diffraction, temperature dependent Hall measurements, minority carrier lifetimes by photoconductive decay, and in-situ ellipsometry. To study the relative influence of bulk and surface effects, devices with active areas from 1.6 10⁻⁵ cm² to 10⁻³ cm² were fabricated. The smaller area devices show better performance in terms of reverse bias characteristics indicating that the bulk quality could be further improved. At 80 K, the zero bias leakage current for a 40 m 40 m diode with 3.2 m cutoff wavelength is 1 pA, the R₀A product is 1.1 10⁴-cm² and the breakdown voltage is in excess of 500 mV. The device shows a responsivity of 1.3 10⁷ V/W and a 80 K detectivity of 1.9 10¹¹ cm-Hz^1/2/W. At 200 K, the zero bias leakage current is 5 nA and the R₀A product 2.03-cm², while the breakdown voltage decreases to 40 mV.