High-Performance LWIR MBE-Grown HgCdTe/Si Focal Plane Arrays

We have been actively pursuing the development of long-wavelength infrared (LWIR) HgCdTe grown by molecular beam epitaxy (MBE) on large-area silicon substrates. The current effort is focused on extending HgCdTe/Si technology to longer wavelengths and lower temperatures. The use of Si versus bulk CdZnTe substrates is being pursued due to the inherent advantages of Si, which include available wafer sizes (as large as 300 mm), lower cost (both for the substrates and number of die per wafer), compatibility with semiconductor processing equipment, and the match of the coefficient of thermal expansion with silicon read-out integrated circuit (ROIC). Raytheon has already demonstrated low-defect, high-quality MBE-grown HgCdTe/Si as large as 150 mm in diameter. The focal plane arrays (FPAs) presented in this paper were grown on 100 mm diameter (211)Si substrates in a Riber Epineat system. The basic device structure is an MBE-grown p-on-n heterojunction device. Growth begins with a CdTe/ZnTe buffer layer followed by the HgCdTe active device layers; the entire growth process is performed in␣situ to maintain clean interfaces between the various layers. In this experiment the cutoff wavelengths were varied from 10.0 μm to 10.7 μm at 78 K. Detectors with >50% quantum efficiency and R ₀ A ∼1000 Ohms cm² were obtained, with 256 × 256, 30 μm focal plane arrays from these detectors demonstrating response operabilities >99%. Work supported by the Missile Defense Agency (MDA) through CACI Technologies, Inc. subcontract no. 601-05-0088, NVESD technical task order no. TTO-01, prime contract no. DAAB07-03-D-C214, (delivery order no. 0016)     

红外焦平面探测器的暗电流测试分析及性能研究

针对碲镉汞红外焦平面探测器,研究了两种暗电流测试方法。降低暗电流直接关系到探测器的信噪比。对所研制的碲镉汞光伏探测器在工作条件下的暗电流大小进行了测试分析。通过对比多组测试结果发现,工作温度及工艺对暗电流具有不同程度的影响。该研究为以后改进工艺和提高探测器性能及筛选效率提供了理论依据。     

应用于红外成像导引头的非制冷焦平面探测器

随着非制冷探测器技术的迅猛发展,中大规模、高灵敏度的非制冷焦平面器件实现工程化应用.使用非制冷焦平面器件的红外成像导引头具有效费比高、结构紧凑、易维护等优点,已成为红外成像导引头的重要成员之一.介绍了国内外几款采用非制冷红外成像导引头的反坦克导弹、精确攻击导弹、精确炸弹、反舰导弹,以及所使用的非制冷焦平面器件的性能参数,总结了用于红外成像制导系统的非制冷焦平面器件的特点及发展趋势.     

Progress of MCT Detector Technology at AIM Towards Smaller Pitch and Lower Dark Current

We present our latest results on cooled p-on-n planar mercury cadmium telluride (MCT) photodiode technology. Along with a reduction in dark current for raising the operating temperature (T _op), AIM INFRAROT-MODULE GmbH (AIM) has devoted its development efforts to shrinking the pixel size. Both are essential requirements to meet the market demands for reduced size, weight and power and high-operating temperature applications. Detectors based on the p-on-n technology developed at AIM now span the spectrum from the mid-wavelength infrared (MWIR) to the very long wavelength infrared (VLWIR) with cut-off wavelengths from 5 μm to about 13.5 μm at 80 K. The development of the p-on-n technology for VLWIR as well as for MWIR is mainly implemented in a planar photodetector design with a 20-μm pixel pitch. For the VLWIR, dark currents significantly reduced as compared to ‘Tennant’s Rule 07’ are demonstrated for operating temperatures between 30 K and 100 K. This allows for the same dark current performance at a 20 K higher operating temperature than with previous AIM technology. For MWIR detectors with a 20-μm pitch, noise equivalent temperature differences of less than 30 mK are obtained up to 170 K. This technology has been transferred to our small pixel pitch high resolution (XGA) MWIR detector with 1024 × 768 pixels at a 10-μm pitch. Excellent performance at an operating temperature of 160 K is demonstrated.     

适合空间和地面应用的多色长波红外焦平面列阵技术

使用多个焦平面列阵、滤光片、光束分裂片和致冷电路的传统方法使系统的设计变得复杂化,系统的可靠性也受到影响,同时也为图像在空间和时间上的配准带来了困难。单个多色全分辨率焦平面列阵将大大提高系统在更远距离上的光谱分辨能力。在集成的多色红外焦平面列阵中,单个像元位置敏感两个(或三个)分开的红外波段。在基于空间和地面的各种目标捕获和信号特征识别应用中,集成的多色红外焦平面列阵将成为下一代技术。本文就这种技术的发展和状况进行述评,同时讨论今后的规划以及在发展过程中所遇到的问题。     

Recent Advances in LWIR Type-II InAs/GaSb Superlattice Photodetectors and Focal Plane Arrays at the Center for Quantum Devices

In recent years, Type-II InAs/GaSb superlattice photodetectors have experienced significant improvements in material quality, structural designs, and imaging applications. They now appear to be a possible alternative to the state-of-the-art HgCdTe (MCT) technology in the long (LWIR) and very long wavelength infrared regimes. At the Center for Quantum Devices, we have successfully realized very high quantum efficiency, very high dynamic differential resistance ${hbox{R}}_{0}{hbox{A}}$-product LWIR Type-II InAs/GaSb superlattice photodiodes with efficient surface passivation techniques. The demonstration of high-quality LWIR focal plane arrays that were 100% fabricated in-house reaffirms the pioneer position of this university-based laboratory.      

红外焦平面阵列盲元检测技术研究

盲元的数量及其分布对红外焦平面阵列器件成像质量的影响较大.在给出盲元定义的基础上,对盲元的各种产生机理进行了分析,并给出了具体的盲元检测方法,为盲元补偿技术的研究提供了理论基础.     

Monolithic Integration of Diffractive Microlens Arrays and Infrared Focal Plane Arrays

Monolithic integration method has been demonstrated to increase the fill factor of the infrared focal plane arrays (IRFPA). Which is consists of 256×256 Pt-Si schottky barrier charge coupled devices(CCD) operation in 3-5μm IR region. The relative silicon 256×256 element diffractive microlens arrays have been fabricated on the back side of the substrate of the IRFPA using binary optics technology. The aligning process between IRFPA and microlens arrays on each side of the substrate has been completed by IR mask aligner. The testing results show that the imaging quality is very good and the average optical response of the IR FPA is increased by a factor of 3.0, which is improved by about 25% compared with the hybrid integration method in the previous work.     

基于InPb合金的非制冷焦平面探测器窗口低温焊接工艺研究

研究了采用纯度为99.9%的In70Pb30合金作为焊料片的低温焊接技术,分析了焊接时候的影响因素:焊料片的影响、升温速率、焊接温度、真空度,通过采用甲酸对焊料片预处理去除氧化层,在215℃、5×10-7 torr的真空环境下进行了焊接,焊接后的样品采用X-ray、拉力测试系统、检漏仪测试了样品的孔洞率、焊接强度、漏率,结果表明:焊接后焊接区域合金均匀、无缝隙、孔洞率少、剪切力高、气密性好,能够满足非制冷焦平面的窗口封接的气密性要求.     

非致冷红外焦平面阵列读出电路的噪声抑制

读出电路(ROIC)是非致冷红外焦平面阵列器件(UIRFPA)的关键组成部分之一。RO-IC性能的好坏直接影响到UIRFPA的性能,非致冷红外焦平面阵列读出电路的噪声抑制也是一个研究的热点。文章探讨了非致冷红外焦平面阵列读出电路的噪声及抑制方法。仿真实验结果表明,该方法具有一定的先进性。     

红外焦平面非均匀校正的综合处理算法

时域高通滤波的算法具有简单,易于实现的优点.但其在既有加性噪声,又有乘性噪声时校正效果难以令人满意.神经元网络算法在噪声较强时,校正效果受到了限制.针对既有加性噪声,又有乘性噪声,且加性噪声较强的情况,提出了红外焦平面非均匀校正的综合处理算法.仿真证明,新算法具有较好的校正效果.     

碲镉汞双色红外焦平面读出电路研究进展

介绍了碲镉汞（MCT）双色红外焦平面探测器的研制背景,及美、英、法等西方发达国家的发展现状。从读出电路（ROIC）设计角度出发,重点阐述了上述3个发达国家的碲镉汞双色焦平面器件结构类型和相应读出电路设计特点。最后介绍了国内昆明物理研究所在碲镉汞双色焦平面读出电路研究方面取得的进展。昆明物理研究所研制出两种碲镉汞双色焦平面读出电路,一种是适用于双铟柱半平面器件结构的128×128双色信号同步积分读出电路,另外一种是适用于单铟柱叠层器件结构的640×512双色信号 TDMI（时分多路积分）读出电路。两种读出电路芯片在77 K 条件下正常工作,主要功能及性能指标与国外同类产品相当。     

红外焦平面阵列盲元补偿算法研究

提出了一种补偿盲元的新算法,它首先利用自适应中值滤波检测红外焦平面阵列上可能的盲元点,然后再使用细节保持变分法对所挑出的盲元点进行补偿.这样,由于既保护了边缘又抑制了噪声,因此恢复出的图像质量明显优于传统的平滑滤波方法.仿真结果表明,本算法对噪声水平为25%的图像进行恢复后,其峰值信噪比仍可达到34.918 dB.     

Study of LWIR and VLWIR Focal Plane Array Developments: Comparison Between p-on-n and Different n-on-p Technologies on LPE HgCdTe

The very long infrared wavelength (>14 μm) is a very challenging range for the design of mercury cadmium telluride (HgCdTe) large focal plane arrays (FPAs). The need (mainly expressed by the space industry) for very long wave FPAs appears very difficult to fulfil. High homogeneity, low defect rate, high quantum efficiency, low dark current, and low excess noise are required. Indeed, for such wavelength, the corresponding HgCdTe gap becomes smaller than 100 meV and each step from the metallurgy to the technology becomes critical. This paper aims at presenting a status of long and very long wave FPAs developments at DEFIR (LETI-LIR/Sofradir joint venture). This study will focus on results obtained in our laboratory for three different ion implanted technologies: n-on-p mercury vacancies doped technology, n-on-p extrinsic doped technology, and p-on-n arsenic on indium technology. Special focus is given to 15 μm cutoff n/p FPA fabricated in our laboratory demonstrating high uniformity, diffusion and shot noise limited photodiodes at 50 K.     

FIB-SEM双束系统在红外焦平面探测器研制中的应用

聚焦离子束扫描电子显微镜(Focused Ion Beam Scanning Electron Micro-scope,FIB-SEM)双束系统结合了扫描电子显微镜与聚焦离子束系统的优势.基于该系统的高分辨率、原位加工及观测的特点,研究了它在缺陷与像元解剖分析、透射电镜样品制备以及电路修复等方面的应用.详细介绍了用FI...     

红外焦平面探测器非均匀性的简化数学模型

红外焦平面探测器非均匀性对红外成像系统的性能产生很大的影响,本文主要讨论了 对非均匀性进行校正各种数学模型,详细分析了电噪声的作用,并对各种模型的适用范围进行了讨论。     

红外焦平面阵列响应度非均匀性的校正算法

本文分析了红外焦平面阵列探测器的响应度非均匀性对成像系统灵敏度的影响和单个探测单元的积分时间响应非线性对成像质量的影响。提出了一种基于场景的运动扫描平均值校正与积分时间校正相结合的红外焦平面阵列响应度非均匀性的校正算法。从而使得系统不仅能够得到均匀性良好的响应度,而且还能使响应度不会受到积分时间改变的影响,进一步扩展了红外焦平面探测器的实际应用范围。     

用于红外焦平面阵列非均匀性校正的辐射参考源

概述了4种红外焦平面阵列非均匀性过程中使用到的参考源.成为产品前,通常使用面源黑体作为参考源对红外焦平面阵列进行非均匀性校正;在热成像系统应用中动态非均匀性校正中,普遍使用的辐射挡板由于没有连有控温装置,只能进行一点校正,在场景温度偏离校正温度时,校正效果会受到影响;美国第三代前视红外成像系统中使用连有热电制冷器的热电参考源,利用热电制冷器对发射表面进行控温,可实现两点校正算法;为基于边框的SBNUC校正算法设计的U型边框黑体光阑,对视场中心没有遮挡,利用半导体制冷器对U型边框黑体光阑的进行控温,能根据场景信息自适应地实现的两点校正.     

Comparison of Long-Wave Infrared Quantum-Dots-in-a-Well and Quantum-Well Focal Plane Arrays

This paper reports on a comparison between a commercially available quantum-well infrared focal plane array (FPA) and a custom quantum-dot (QD)-in-a-well (DWELL) infrared FPA in the long-wave infrared (LWIR). The DWELL detectors consist of an active region composed of InAs QDs embedded in $ hbox{In}_{.15}hbox{Ga}_{.85}hbox{As}$ quantum wells. DWELL samples were grown using molecular beam epitaxy and fabricated into 320 $times$ 256 pixels FPA with a flip-chip indium bump technique. Both the DWELL and QmagiQ commercial quantum-well detector were hybridized to an Indigo ISC9705 readout circuit and tested in the same camera system. Calibrated blackbody measurements at a device temperature of 60 K with LWIR optics yield a noise equivalent change in temperature of 17 mK and 91 mK for quantum-well and DWELL FPAs operating at 0.95- and 0.58-V biases, respectively. The comparison of the DWELL and quantum-well FPA when imaging a 35 $^{circ}hbox{C}$ black body showed that the DWELL had a signal-to-noise ratio of 124 while the quantum-well FPA showed 1961. As well, the quantum-well FPA showed a higher collection efficiency of 1.3 compared to the DWELL.      

Two-Dimensional Long-Wavelength and Very Long-Wavelength Focal-Plane Arrays at AIM

In recent years AIM has expanded its portfolio of standard infrared (IR) focal-plane arrays in the 3 μm to 5 μm (mid-wavelength infrared, MWIR) and 8 μm to 10 μm (long-wavelength infrared, LWIR) spectral ranges with two-dimensional IR detectors, sensitive in the 0.9 μm to 2.5 μm (short-wavelength infrared, SWIR) and especially in the 10 μm to 15 μm (very long-wavelength infrared, VLWIR) spectral ranges. This paper reports on the latest technological advancements that will benefit not only prototype applications for which they are demonstrated but a wide range of AIM products. A reduction of the pixel pitch from 24 μm to 15 μm is the result of increasing demands for compact detection modules with reduced weight, size, power consumption, and cost efficiency. Performance characterization for such a reduced-pitch 640 × 512 module in the LWIR (cut-off 10.5 μm at 67 K) yields mean noise equivalent temperature difference of 32.2 mK and defective pixel rate of only 0.5%. Extending the detection wavelength further into the VLWIR is of major interest for space applications such as the Meteosat Third Generation, which poses challenging requirements for sensor material homogeneity and dark-current density. To meet this requirement, an extrinsic doping approach is utilized on a 256 × 256 mercury cadmium telluride (MCT) focal-plane array with ～14 μm cut-off wavelength at 55 K operating temperature, and a dark- current density of about 1 pA/μm² is demonstrated.