半导体物理效应及其应用讲座第四讲光吸收跃迁效应与半导体红外探测器的应用发展

光吸收跃迁效应是半导体光电探测器的基本物理过程.文章主要介绍光吸收跃迁效应在窄禁带半导体红外探测器应用方面的研究进展.讨论窄禁带半导体带间光吸收跃迁的理论和实验.文章还介绍了本征光吸收系数的表达式及其在材料表征和确定器件截止波长方面的应用,以及它在解释近年来发现的HgCdTe光电二极管电致负荧光现象方面的应用.     

我国第一支量子阱红外探测器

量子阱红外探测器是一种新型红外探测器.它是利用新型半导体超晶格量子阱材料的子能带光跃迁的红外吸收特性制成的.它具有响应快、灵敏度高、可变波长、可变带宽等特点,并有实现大面积集成和制作大面积二维象素列阵的实际可能性,将成为新一代红外探测器件,在未来五到十年内可能引起红外物理、红外光电子学及其应用领域的变革.两年前,美国贝尔实验室已研制出可与历史悠久的HgCdTe红外探测器性能相比较的GaAs/AlGaAs量子阱探测器. 中国科学院物理研究所从1989年开始,就在器件材料生长、器件物理、器件工艺及器件的性能测试等方面,着手进行…     

红外探测器的新型材料——HgCdTe晶体的生长和应用

H—VI族化合物HgTe与CdTe能无限无溶,形成赝二元系合金Hgl-xCdxTe(以后简称HgCdTe)晶体材料.组分x可以从零到1.材料的物理性质随组分x的变化可连续地从半金属改变到半导体.利用HgCdTe材料制作的红外探测器,有很宽的波长覆盖,它的特点是:介电常数小、光吸收系数大、电子-空穴迁移率比高等.这种晶体是目前最有发展前途的一种红外探测器材料[1]. 一、HgCdTe晶体研究的崛起 五十年代后期以来,随着对环境温度探测的需要,人们希望能得到一种红外材料,它既能响应 8—14μm的红外波段,又能在77K以上温区工作.这就要求这种材料能具有类似InS…     

大口径红外辐射计的光谱定标

介绍了大口径红外辐射计的光谱定标方法。研制了大口径红外辐射计。该辐射计主要由前置光学系统, 红外探测器(热释电探测器和碲镉汞探测器2～14 μm), 机械斩波器,锁相放大器,信号采集器等组成。首先对大口径红外辐射计的光谱定标方法进行了分析,然后建立红外辐射计光谱定标的测量装置,并分别测试腔体热释电探测器和HgCdTe探测器的响应非线性,最后用腔体热释电探测器在该测量装置上对HgCdTe探测器进行红外光谱响应度校准实验。通过两种相对光谱响应度测量方法的对比,给出多次测量结果的平均值及两种方法的对比分析。分析结果表明,测量系统的不确定度优于3.4%。     

X,γ射线谱仪用的半导体探测器

半导体探测器是六十年代发展起来的一种新型探测器.随着硅、锗单晶性能的提高,硅(锂)[Si(Li )]、锗(锂)[Ge(Li)]及高纯锗[HPGe]探测器的制备工艺日趋完善.与此同时,随着电于学线路的改进,Si(Li),Ge(Li),HPGe探测器及低噪声电子学线路和低温装置所组成的X,γ射线谱仪性能得到迅速提高。逐渐发展成高热率、高能量分辨率的X,γ谱仪,这就使应用γ射线核能谱学增添了新的实验数据,同时使微量及痕量元素分析技术达到了新的水平. 半导体探测器一般又称固体探测器[1],它实质上是由一块半导体材料所组成的电离室.对核谱仪用的探测器的基本要求…     

室温中红外HgCdTe光导探测器响应率的温度特性

为了评定基于室温中红外HgCdTe光导探测器的氟化氘激光阵列靶斑仪系统的测量不确定度,需要对HgCdTe光导探测器响应率的温度特性进行定量分析.理论分析了室温中波红外HgCdTe光导探测器响应率与温度和波长的关系,得出了在一定范围内探测器响应率可以近似表示为温度和波长变量分离函数形式的假设.采用波长为3.8μm和1.31 μm激光光源,分别测量了在-40℃～+30℃温度范围内室温中波红外HgCdTe探测器响应率变温特性,实验结果验证了在测量不确定度范围内假设的正确性.基于此结论,提出了一种高效标定HgCdTe光导探测器在氟化氘激光波长处响应率温度特性的实用方法.     

红外光电探测技术研究现状及展望(特邀)

红外探测技术在激光测距、成像、遥感、夜视等领域有重要应用,降低红外光电探测器的尺寸、重量、功耗和成本,以及提高探测器的性能是目前的研究重点。本文综述了红外探测器技术的发展历程、工作原理及研究现状并对其未来发展方向进行了展望。内容主要涵盖基于碲镉汞、Ⅱ类超晶格、量子阱、量子点、硅基锗锡等材料的光子型红外光电探测器及其阵列。红外系统成本降低最终取决于在常温条件下耗尽电流限探测器阵列像素密度是否与系统光学元件的背景极限和衍射极限性能匹配,选择HgCdTe、Ⅱ类超晶格和胶体量子点等材料可提高光子探测器室温性能。各种红外探测器在性能方面各具特色,在实际应用中互为补充。     

HgCdTe256×256用制冷杜瓦集成组件的研制

介绍一种红外焦平面器件用制冷杜瓦组件,该组件用于封装256×256HgCdTe红外焦平面芯片,由直线马达驱动型斯特林制冷机冷却,制冷机与杜瓦的耦合采用IDCA方式;制冷机、杜瓦进行一体化优化设计,使得整个红外探测器组件能耗、重量大大降低,实现了红外探测器组件的小型化.     

准分子激光辐照HgCdTe半导体材料的损伤机理研究

利用光学显微镜和扫描电子显微镜对248 nm准分子脉冲强激光辐照的HgCdTe晶片表面进行了观察,观察到一些与红外波段内激光辐照HgCdTe晶片时大不相同的实验现象.研究表明,红外波段内1 064nm激光辐照HgCdTe半导体材料的损伤机制主要为光热作用,而紫外波段248 nm准分子激光对HgCdTe材料的损伤机制既包含光化学作用也包含光热作用.分析了准分子激光对晶体的机械破坏现象,同时对HgCdTe材料在激光辐照区的条纹产生机理进行了探讨,发现激光驱动声波理论模型比光学模型和热导波模型能更好地解释HgCdTe晶体表面的条纹现象.     

金属框结构对碲镉汞红外焦平面调制传递函数的影响

调制传递函数(MTF)值是表征碲镉汞(HgCdTe)红外探测器成像性能的重要参数。串音是减小探测器MTF值的主要因素之一。合理的器件结构设计可有效地抑制串音,从而提高器件MTF值。介绍了一种含金属框结构的HgCdTe红外焦平面探测器,该器件可有效吸收横向扩散光生载流子并减小器件的串音干扰。对含金属框结构的器件和无金属框结构的器件进行MTF测试及对比分析。测试结果表明,与无金属框结构的器件相比,含金属框结构的器件的MTF值得到显著提高。     

Electrical characteristic signatures for non-uniformity analysis in HgCdTe photodiode arrays

In this paper we present a method of analyzing the performance non-uniformity of HgCdTe photodiode arrays for infrared imaging applications. For quantifying the characteristic behavior of various photodiodes, we have parametrized the dynamic resistance verses voltage signatures in such a way that the obtained signature parameters have some relevance with different physical parameters. We also estimated the sensitivity of the proposed signatures on physical parameters using statistical technique. These characteristics signatures may be used to quantify the non-uniformity of the HgCdTe photodiodes in IR imaging arrays and its analysis. The method presented here is based on theoretical calculation of MWIR HgCdTe photodiodes. However, the method is generic and may be implemented on any other type of diode arrays for theoretical or experimental analysis of their non-uniformity.     

Assessment of HgCdTe photodiodes and quantum well infrared photoconductors for long wavelength focal plane arrays

Recent trends in infrared detectors are towards large, electronically addressed two-dimensional arrays. In the long wavelength infrared (LWIR) spectral range HgCdTe focal plane arrays (FPAs) occupy a dominant position. However, the slow progress in the development of large LWIR photovoltaic HgCdTe infrared imaging arrays and the rapid achievements of novel semiconductor heterostructure systems have made it necessary to foresee the future development of different material technologies in fabrication large FPAs. Among the competing technologies in LWIR are the quantum well infrared photoconductors (QWIPs) based on lattice matched GaAs/AlGaAs and strained layer InGaAs/AlGaAs material systems. This paper compares the technical merits of two IR detector arrays technologies; photovoltaic HgCdTe and QWIPs. It is clearly shown that LWIR QWIP cannot compete with HgCdTe photodiode as the single device especially at higher temperature operation (>70 K) due to fundamental limitations associated with intersubband transitions. However, the advantage of HgCdTe is less distinct in temperature range below 50 K due to problems involved in HgCdTe material (p-type doping, Shockley–Read recombination, trap-assisted tunnelling, surface and interface instabilities). Even though the QWIP is a photoconductor, several of its properties such as high impedance, fast response time, long integration time, and low power consumption, well satisfy the requirements of fabrication of large FPAs. Due to the high material quality at low temperature, QWIP has potential advantages over HgCdTe for very LWIR (VLWIR) FPA applications in terms of the array size, uniformity, yield and cost of the systems.     

STUDY OF MOLECULAR BEAM EPITAXIAL GROWTH AND OPTICAL CHARACTERISTICS OF HgCdTe

HgCdTe epilayers were grown by molecular beam epitaxy on GaAs(211)B substrates. Process of the HgCdTe epitaxial growth can be monitored by reflection high-energy electron diffraction. Results of the infrared transmission spectrum, Raman scattering spectrum and infrared photoluminescence spectrum in magnetic field have been studied.     

Competitive technologies of third generation infrared photon detectors

Hitherto, two families of multielement infrared (IR) detectors are used for principal military and civilian infrared applications; one is used for scanning systems (first generation) and the other is used for staring systems (second generation). Third generation systems are being developed nowadays. In the common understanding, third generation IR systems provide enhanced capabilities like larger number of pixels, higher frame rates, better thermal resolution as well as multicolour functionality and other on-chip functions. In the paper, issues associated with the development and exploitation of materials used in fabrication of third generation infrared photon detectors are discussed. In this class of detectors two main competitors, HgCdTe photodiodes and quantum well IR photoconductors (QWIPs) are considered. The performance figures of merit of state-of-the-art HgCdTe and QWIP focal plane arrays (FPAs) are similar because the main limitations come from the readout circuits. However, the metallurgical issues of the epitaxial layers such as uniformity and number of defected elements are the serious problems in the case of long wavelength infrared (LWIR) and very LWIR (VLWIR) HgCdTe FPAs. It is predicted that superlattice based InAs/GaInSb system grown on GaSb substrate seems to be an attractive to HgCdTe with good spatial uniformity and an ability to span cutoff wavelength from 3 to 25 μm.     

HgCdTe technology in France

SOFRADIR is one of the leading companies worldwide for the production of second generation InfraRed (IR) detectors. This success is due to the top level quality of the unique and production oriented French HgCdTe technology for manufacturing IR focal plane arrays based on an HgCdTe array and a CMOS readout and multiplexed silicon array. This technology and main products are presented in this paper. Finally, in order to prepare for future military and industrial needs, SOFRADIR has been working in close relationship with CEA-LETI/LIR on third generation developments based on HgCdTe material using Molecular Beam Epitaxy (MBE) growth. To cite this article: P. Tribolet, C. R. Physique 4 (2003).     

Principal component analysis of non-uniformity in electrical characteristics of HgCdTe photodiode arrays

We present a method of analyzing the non-uniformity in electrical characteristics of HgCdTe photodiode arrays for infrared imaging applications. We have selected dynamic resistance–voltage (R–V) characteristics for analyzing electrical behavior of HgCdTe photodiodes because the dynamic resistance at a given operating voltage directly governs the imager performance and being derivative of current–voltage (I–V) characteristics, it has little impact of the constant shifts due to stray illumination during dark measurements, relaxing the stringent requirement of perfect dark conditions to some extent for performance analysis. We have demonstrated that by using statistical analysis such as correlation of the selected signatures and their principal component analysis, we can identify the root cause of the high non-uniformity among sensor pixels in the array. The method has been implemented using theoretical I–V model of MWIR HgCdTe photodiodes, but it is generic and may be implemented on any other types of diode arrays for theoretical or experimental analysis of their non-uniformity.     

Long wavelength photodetectors

The role of long wavelength systems (1.0μm<λ< 10.0μm) in fiber optics communications is evaluated. For high-bit rate optical telecommunications at 1.3 μm or 1.5 μm, GaInAs p-i-n detectors have emerged as the preferred choice because of their low noise, excellent sensitivity, and high temperature stability. Ge and HgCdTe photodiodes offer nearly equivalent performance and a somewhat more advanced production technology. Beyond 2 μm, HgCdTe would seem to be the clear choice for photodetector applications. Avalanche photodiodes in long wavelength optical fiber links may find uses in situations involving high bit rate transmission using low cost components. Although avalanche gain will always improve the system sensitivity, the LED/APD combination is only half as sensitive as a laser/p-i-n system, as well as being bandwidth limited. Nontelecommunications applications involving data base and fiber guidance systems are discussed, and a prospective look is taken at the uses, such as power transmission, of ultra low-loss fibers in the 2 to 10 μm region of the optical spectrum.     

Heterostructure infrared photovoltaic detectors

HgCdTe remains the most important material for infrared (IR) photodetectors despite numerous attempts to replace it with alternative materials such as closely related mercury alloys (HgZnTe, HgMnTe), Schottky barriers on silicon, SiGe heterojunctions, GaAs/AlGaAs multiple quantum wells, InAs/GaInSb strained layer superlattices, high temperature superconductors and especially two types of thermal detectors: pyroelectric detectors and silicon bolometers. It is interesting, however, that none of these competitors can compete in terms of fundamental properties. In addition, HgCdTe exhibits nearly constant lattice parameter which is of extreme importance for new devices based on complex heterostructures. The development of sophisticated controllable vapour phase epitaxial growth methods, such as MBE and MOCVD, has allowed fabrication of almost ideally designed heterojunction photodiodes. In this paper, examples of novel devices based on heterostructures operating in the long wavelength, middle wavelength and short wavelength spectral ranges are presented. Recently, more interest has been focused on p–n junction heterostructures. As infrared technology continues to advance, there is a growing demand for multispectral detectors for advanced IR systems with better target discrimination and identification. HgCdTe heterojunction detectors offer wavelength flexibility from medium wavelength to very long wavelength and multicolour capability in these regions. Recent progress in two-colour HgCdTe detectors is also reviewed.     

Study on Surface Oxidative Characterization of LPE HgCdTe Epilayer by X-Ray Photoelectron Spectroscopy

This report presents a surface pre-treatment method of LPE HgCdTe epilayer to reduce and remove the oxides and contaminants. The surface oxidative characterization of LPE HgCdTe epilayer has been studied by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). HgCdTe surface exposed by various processing steps has been measured and analyzed, the results show the native oxide film can be removed by the solution of lactic acid in ethylene glycol after etching by bromine in absolute ethyl alcohol. It indicates that the mainly optical and electrical parameters of LPE HgCdTe epilayer have not been changed. It is evident that the pre-treatment before HgCdTe surface passivation affects the passivant/HgCdTe interface properties.     

Molecular beam epitaxy growth of HgCdTe for high performance infrared photon detectors

Significant progresses have been made in the molecular beam epitaxy (MBE) growth of HgCdTe for high performance infrared photon detectors with the aid of in situ and ex situ characterization techniques. Superlattice interfacial layers compensate in part for the influence of non-ideal CdZnTe substrates and hence improved the material quality as well as yield. They result in photoconductive carrier recombination lifetimes approaching theoretical limits set by the intrinsic radiative and Auger recombination mechanisms for 8–14 μm long-wavelength infrared HgCdTe. Very high composition and thickness uniformities have also been achieved. However, the Urbach tail energy, which is associated with structural disorder, was found to be non-uniform for both large wafer (up to 20 × 20 mm²) and very small area (down to 200 × 200 μm²). After several years of improvements in MBE HgCdTe growth techniques, substrates once again have become a bottleneck to further improvements.