Volume 52 Issue 3
Mar.  2023
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Guo Huijun, Chen Lu, Yang Liao, Shen Chuan, Xie Hao, Lin Chun, Ding Ruijun, He Li. Linear-mode HgCdTe avalanche photodiode detectors for photon-counting applications (invited)[J]. Infrared and Laser Engineering, 2023, 52(3): 20230036. doi: 10.3788/IRLA20230036
Citation: Guo Huijun, Chen Lu, Yang Liao, Shen Chuan, Xie Hao, Lin Chun, Ding Ruijun, He Li. Linear-mode HgCdTe avalanche photodiode detectors for photon-counting applications (invited)[J]. Infrared and Laser Engineering, 2023, 52(3): 20230036. doi: 10.3788/IRLA20230036

Linear-mode HgCdTe avalanche photodiode detectors for photon-counting applications (invited)

doi: 10.3788/IRLA20230036
Funds:  National Natural Science Foundation of China (62104240, 62204248)
  • Received Date: 2023-01-29
  • Rev Recd Date: 2023-02-23
  • Available Online: 2023-03-20
  • Publish Date: 2023-03-25
  •   Significance   Single-photon counting has great application prospects in weak signal detection and time ranging. Since the first photon counting system in the visible spectrum was developed in the 1970s, in order to fully amplify the photon signal and reduce the readout noise of electronic equipments, many groups in the research field are constantly developing and improving the photon counting techniques. Electron multiplying charge coupled devices (EMCCDs) can replace the traditional visible light photon counting system and have higher quantum efficiency. While due to large avalanche noise, accurate acquisition of incident photon number under multiplication is difficult. The excess noise factor of mercury cadmium telluride avalanche photodiode (HgCdTe APD) is close to 1, there is almost no excess noise. Compared with the Geiger mode avalanche photodiodes, the linear mode HgCdTe APD has no dead time and after pulse, does not need to quench the circuit, has ultra-high dynamic range and adjustable spectrum with wide response range. Its detection efficiency and false count rate can be independently optimized. It opens up a new infrared photon band counting imaging application. It is of great value in astronomical exploration, laser radar, free space communication and other applications.   Progress   Raytheon and DRS Technologies in the United States, CEA/LETI Laboratory and Lynred in France, and Leonardo in the United Kingdom have successively realized single photon counting of linear HgCdTe APD detectors. This paper summarizes the technical routes and research status of linear mode photon counting HgCdTe APD detectors in Europe and America. The performance of HgCdTe APDs, photon counting ability and the advantages and disadvantages of detector preparation with three structures, namely, separation of absorption and amplification (SAM), planar PIN type and high density vertically integrated photodiode (HDVIP), are analyzed. Raytheon Company has prepared SAM short-wave HgCdTe APD detectors with hole multiplication mechanism by molecular beam epitaxy (MBE), with gain of 350, photon detection efficiency of more than 95% and operating temperature of more than 180 K. DRS Technologies has prepared an electron-multiplication HDVIP medium wave HgCdTe APD detector using liquid phase epitaxy (LPE) material. The detector can respond in the visible to mid-infrared band from 0.4 μm to 4.3 μm, with the highest gain up to 6100 and the photon detection efficiency greater than 70%. It can realize free space communication of 110 Mbps data transfer. CEA/LETI Laboratory and Lynred Company have prepared PIN-type short-wave and medium-wave HgCdTe APD detectors with electron multiplication mechanism by molecular beam epitaxy or liquid phase epitaxy. The gain of short-wave detector is up to 2 000, the maximum gain of medium-wave is up to 13000, the internal photon detection efficiency is up to 90%, the free space communication of 80 Mbps data transfer is realized, and bandwidth up to 10 GHz is achieved at 300 K and gain of 1. British Leonardo Company has prepared SAM type HgCdTe APD detector with electron multiplication mechanism by metal organic vapor deposition (MOVPE). The detectors were named Selex Avalanche Photodiode HgCdTe Infrared Array (SAPHIRA), the device gain can reach 66@14.5 V, single photon detection efficiency is more than 90%. A 24 μm pitch 320×256 array SAPHIRA detectors were supplied to First Light Imaging Company in France to develop a C-RED ONE camera. The C-RED ONE camera was successfully applied to the Michigan Infrared Combiner (MIRC) for astronomical exploration in the United States, which reduced the system noise of MIRC by 10 to 30 times and greatly improved the signal-to-noise ratio of fringe detection. The research on HgCdTe APD detectors started relatively late in China. The main research institutions include Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Kunming Institute of Physics and North China Research Institute of Electro-Optics. Limited by chip preparation technology and circuit technology of HgCdTe APDs, the ability of photon counting has not been realized at present, but some progress has been made in the development of focal plane at home. The single element, 128×128 array and 320×256 array medium wave HgCdTe APD detectors with PIN structure are developed by Shanghai Institute of Technical Physics, Chinsese Academy of Sciences. The gain of the detectors can reach more than 1000, the gain normalized dark current density is less than 1×10−7 A/cm2 within the gain of 100, and the excess noise factor is less than 1.5 within the gain of 400. At the gain of 133, the noise equivalent photon number is 12, and the short integration time fast imaging is demonstrated. Bandwidth of single element detector is up to 300-600 MHz. The single element and 256×256 array medium wave HgCdTe APD device with PIN structure are developed in Kunming Institute of Physics. The gain of the single element detector can reach more than 1 000. When the bias voltage is less than 8.5 V, the average gain normalized dark current of focal plane is 9.0×10−14-1.6×10−13 A, and the excess noise factor F is between 1.0 and 1.5.  Conclusions and Prospects   In China, HgCdTe APD devices with planar PIN structure are mainly developed, and the technical path is basically the same as that of France. Therefore, our country can learn from the successful experience of CEA/LETI Laboratory and the business model of Lynred Company, and continue to promote research on HgCdTe APD detectors in order to reach the international advanced level as soon as possible, and realize single-photon detection and photon counting application.
  • [1] 龚思夏. 基于APD的光子计数成像系统研究与设计 [D]. 南京: 南京理工大学, 2010.
    [2] Denvir D J, Conroy E. Electron multiplying CCD technology: The new ICCD [C]//Proceedings of SPIE, 2002, 4796: 164-174.
    [3] Stewart A G, Greene-O′Sullivan E, Herbert D J, et al. Study of the properties of new SPM detectors [C]//Proceedings of SPIE, 2006, 6119: 61190A.
    [4] John Degnan, David Wells, Roman Machan, et al. Second generation airborne 3D imaging lidars based on photon counting [C]//Proceedings of SPIE, 2007, 6771: 67710N.
    [5] Ge Peng, Guo Jingjing, Chen Cong, et al. Photon-counting 3D imaging based on Geiger-mode APD array [J]. Infrared and Laser Engineering, 2022, 49(3): 0305007. (in Chinese) doi:  10.3788/IRLA202049.0305007
    [6] Shi Zhu, Dai Qian, Song Haizhi, et al. Low dark count rate InGaAsP/InP SPAD [J]. Infrared and Laser Engineering, 2017, 46(12): 1220001. (in Chinese) doi:  10.3788/IRLA201746.1220001
    [7] Beck J D, Scritchfield R, Mitra P, et al. Linear mode photon counting with the noiseless gain HgCdTe e-APD [C]//Proceedings of the SPIE, 2011, 8033: 80330N.
    [8] Leveque G. Ionization energies in HgxCd1-xTe avalanche photodiodes [J]. Semiconductor Science and Technology, 1993, 8: 1317-1323. doi:  10.1088/0268-1242/8/7/021
    [9] Derelle S, Bernhardt S, Haidar R, et al. Experimental performances and Monte Carlo modelling of LWIR HgCdTe avalanche photodiodes [J]. Journal of Electronic Materials, 2009, 38(8): 1628-1636. doi:  10.1117/12.821185
    [10] Rothman J, de Borniol E, Gravrand O, et al. HgCdTe APD-focal plane array development at DEFIR [C]//Proceedings of SPIE, 2010, 7834: 78340O.
    [11] Jack M, Wehner J , Edwards J, et al. HgCdTe APD-based Linear-Mode photon counting components and LADAR receivers [C]//Proceedings of SPIE, 2011, 8033: 80330M.
    [12] 陈博. 基于APD的光子计数成像系统的开发与实验研究 [D]. 南京: 南京理工大学, 2012.
    [13] Asbrocka J, Baileya S, Baleya D, et al. Ultra-High sensitivity APD based 3 D LADAR sensors: linear mode photon counting LADAR camera for the ultra-sensitive detector program [C]//Proceedings of the SPIE, 2008, 6940: 69402O.
    [14] De Lyon T J, Baumgratz B, Chapman G, et al. MBE growth of HgCdTe avalanche photodiode structures for low-noise 1.55 μm photodetection [J]. Journal of Crystal Growth, 1999, 201-202: 980-984. doi:  https://doi.org/10.1016/S0022-0248(98)01506-1
    [15] Bryan M L, Chapman G, Hall D N B, et al. Investigation of linear-mode, photon-counting HgCdTe APDs for astronomical observations [C]//Proceedings of SPIE, 2012, 8453: 84532F.
    [16] Michael Jack, George Chapman, John Edwards, et al. Advances in LADAR components and subsystems at Raytheon [C]//Proceedings of SPIE, 2012, 8353: 83532F.
    [17] Beck J, Wan C, Kinch M, et al. The HgCdTe electron avalanche photodiode [J]. Journal of Electronic Materials, 2006, 35(6): 1166-1173. doi:  10.1007/s11664-006-0237-3
    [18] Singh A, Srivastav V, Pal R. HgCdTe avalanche photodiodes: A review [J]. Optics & Laser Technology, 2011, 43(7): 1358-1370. doi:  10.1016/j.optlastec.2011.03.009
    [19] William Sullivan III, Jeffrey Beck, Richard Scritchfield, et al. Linear-Mode HgCdTe avalanche photodiodes for photon-counting applications [J]. Journal of Electronic Materials, 2015, 44(9): 3092-3101. doi:  10.1007/s11664-015-3824-3
    [20] Sun Xiaoli, Abshirea James, Krainaka Michael, et al. Single photon HgCdTe avalanche photodiode and integrated detector cooler assemblies for space lidar applications [C]//Proceedings of SPIE, 2018, 10659: 106590C.
    [21] Duke A P, Beck J D, Sullivan III W, et al. Recent advancements in HgCdTe APDs for space applications [J]. Journal of Electronic Materials, 2022, 51: 6803-6814. doi:  10.1007/s11664-022-09873-4
    [22] Krainak M A, Yanga G, Sun X, et al. Novel photon-counting detectors for free-space communication [C]//Proceedings of SPIE, 2016, 9739: 97390T.
    [23] Gautier Vojetta, Fabrice Guellec, Lydie Mathieu, et al. Linear photon-counting with HgCdTe APDs [C]//Proceedings of SPIE, 2012, 8375: 83750Y.
    [24] Johan Rothmana, Eric de Borniol, Sylvette Bisotto, et al. HgCdTe APD-focal plane array development at DEFIR for low flux and photon-counting applications [C]//Quantum of Quasars Workshop, December 2-4, 2009, Grenoble, France, 2009: 1-14.
    [25] Rothman J, Lasfargues G, Abergel J. HgCdTe APDs for free space optical communications [C]//Proceedings of SPIE, 2015, 9647: 96470N.
    [26] Johan Rothman, Pierre Bleuet, Luc Andre, et al. HgCdTe APDs for free space optical communications [C]//Proceedings of SPIE, 2018, 10524: 1052411.
    [27] Rothman J, De Borniol E, Pes S, et al. HgCdTe APDs detector developments for high speed, low photon number and large dynamic range photo-detection [C]//Proceedings of SPIE, 2021, 11852: 118520F.
    [28] Pes S, Rothman J, Bleuet P, et al. Reaching GHz single photon detection rates with HgCdTe avalanche photodiodes detectors [C]//Proceedings of SPIE, 2021, 11852: 118525S.
    [29] Dani Atkinson, Donald Hall, Sean Goebel, et al. Observatory deployment and characterization of SAPHIRA HgCdTe APD arrays[C]//Proceedings of SPIE, 2018, 10709: 107091H.
    [30] Johan Rothman. Physics and limitations of HgCdTe APDs: A Review [J]. Journal of Electronic Materials, 2018, 47(10): 5657-5665. doi:  10.1007/s11664-018-6475-3
    [31] Dani Atkinson, Donald Hall, Shane Jacobson, et al. Photon-counting properties of SAPHIRA APD arrays [J]. The Astronomical Journal, 2018, 155: 220. doi:  10.3847/1538-3881/aabdeb
    [32] Timothée Greffe, Philippe Feautrier, Jean-Luc Gach, et al. C-RED One: The infrared camera using the Saphira e-APD detector [C]//Proceedings of SPIE, 2016, 9907: 99072E.
    [33] Anugu N, Le Bouquinb J-B, Monnier J D, et al. MIRC-X/CHARA: sensitivity improvements with an ultra-low noise SAPHIRA detector [C]//Proceedings of SPIE, 2018, 10701: 1070124.
    [34] Guo Huijun, Cheng Yushun, Chen Lu, et al. The performance of Mid-Wave Infrared HgCdTe e-Avalanche photodiodes at SITP [C]//Proceedings of SPIE, 2019, 11170: 111702M.
    [35] Guo Huijun, Chen Lu, Yang Liao, et al. The latest developments of HgCdTe e-APDs at SITP [C]//Proceedings of the SPIE, 2020, 11717: 1171736.
    [36] Guo Huijun, Yang Liao, Shen Chuan, et al. Developments and characterization of HgCdTe e-APDs at SITP [C]//Proceedings of SPIE, 2023, 12505: 125050C.
    [37] Li Xiongjun, Han Fuzhong, Li Lihua, et al. Gain characteristics of MW HgCdTe avalanche photodiodes [J]. Journal of Infrared and Millimeter Waves, 2019, 38(2): 175-181. (in Chinese) doi:  10.11972/j.issn.1001-9014.2019.02.009
    [38] Li Xiongjun, Zhang Yingxu, Chen Xiao, et al. Study on HgCdTe APD focal plane technology [J]. Journal of Infrared and Millimeter Waves, 2022, 41(6): 965-971. (in Chinese) doi:  10.11972/j.issn.1001-9014.2022.06.004
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Linear-mode HgCdTe avalanche photodiode detectors for photon-counting applications (invited)

doi: 10.3788/IRLA20230036
  • 1. Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
  • 2. School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China
Fund Project:  National Natural Science Foundation of China (62104240, 62204248)

Abstract:   Significance   Single-photon counting has great application prospects in weak signal detection and time ranging. Since the first photon counting system in the visible spectrum was developed in the 1970s, in order to fully amplify the photon signal and reduce the readout noise of electronic equipments, many groups in the research field are constantly developing and improving the photon counting techniques. Electron multiplying charge coupled devices (EMCCDs) can replace the traditional visible light photon counting system and have higher quantum efficiency. While due to large avalanche noise, accurate acquisition of incident photon number under multiplication is difficult. The excess noise factor of mercury cadmium telluride avalanche photodiode (HgCdTe APD) is close to 1, there is almost no excess noise. Compared with the Geiger mode avalanche photodiodes, the linear mode HgCdTe APD has no dead time and after pulse, does not need to quench the circuit, has ultra-high dynamic range and adjustable spectrum with wide response range. Its detection efficiency and false count rate can be independently optimized. It opens up a new infrared photon band counting imaging application. It is of great value in astronomical exploration, laser radar, free space communication and other applications.   Progress   Raytheon and DRS Technologies in the United States, CEA/LETI Laboratory and Lynred in France, and Leonardo in the United Kingdom have successively realized single photon counting of linear HgCdTe APD detectors. This paper summarizes the technical routes and research status of linear mode photon counting HgCdTe APD detectors in Europe and America. The performance of HgCdTe APDs, photon counting ability and the advantages and disadvantages of detector preparation with three structures, namely, separation of absorption and amplification (SAM), planar PIN type and high density vertically integrated photodiode (HDVIP), are analyzed. Raytheon Company has prepared SAM short-wave HgCdTe APD detectors with hole multiplication mechanism by molecular beam epitaxy (MBE), with gain of 350, photon detection efficiency of more than 95% and operating temperature of more than 180 K. DRS Technologies has prepared an electron-multiplication HDVIP medium wave HgCdTe APD detector using liquid phase epitaxy (LPE) material. The detector can respond in the visible to mid-infrared band from 0.4 μm to 4.3 μm, with the highest gain up to 6100 and the photon detection efficiency greater than 70%. It can realize free space communication of 110 Mbps data transfer. CEA/LETI Laboratory and Lynred Company have prepared PIN-type short-wave and medium-wave HgCdTe APD detectors with electron multiplication mechanism by molecular beam epitaxy or liquid phase epitaxy. The gain of short-wave detector is up to 2 000, the maximum gain of medium-wave is up to 13000, the internal photon detection efficiency is up to 90%, the free space communication of 80 Mbps data transfer is realized, and bandwidth up to 10 GHz is achieved at 300 K and gain of 1. British Leonardo Company has prepared SAM type HgCdTe APD detector with electron multiplication mechanism by metal organic vapor deposition (MOVPE). The detectors were named Selex Avalanche Photodiode HgCdTe Infrared Array (SAPHIRA), the device gain can reach 66@14.5 V, single photon detection efficiency is more than 90%. A 24 μm pitch 320×256 array SAPHIRA detectors were supplied to First Light Imaging Company in France to develop a C-RED ONE camera. The C-RED ONE camera was successfully applied to the Michigan Infrared Combiner (MIRC) for astronomical exploration in the United States, which reduced the system noise of MIRC by 10 to 30 times and greatly improved the signal-to-noise ratio of fringe detection. The research on HgCdTe APD detectors started relatively late in China. The main research institutions include Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Kunming Institute of Physics and North China Research Institute of Electro-Optics. Limited by chip preparation technology and circuit technology of HgCdTe APDs, the ability of photon counting has not been realized at present, but some progress has been made in the development of focal plane at home. The single element, 128×128 array and 320×256 array medium wave HgCdTe APD detectors with PIN structure are developed by Shanghai Institute of Technical Physics, Chinsese Academy of Sciences. The gain of the detectors can reach more than 1000, the gain normalized dark current density is less than 1×10−7 A/cm2 within the gain of 100, and the excess noise factor is less than 1.5 within the gain of 400. At the gain of 133, the noise equivalent photon number is 12, and the short integration time fast imaging is demonstrated. Bandwidth of single element detector is up to 300-600 MHz. The single element and 256×256 array medium wave HgCdTe APD device with PIN structure are developed in Kunming Institute of Physics. The gain of the single element detector can reach more than 1 000. When the bias voltage is less than 8.5 V, the average gain normalized dark current of focal plane is 9.0×10−14-1.6×10−13 A, and the excess noise factor F is between 1.0 and 1.5.  Conclusions and Prospects   In China, HgCdTe APD devices with planar PIN structure are mainly developed, and the technical path is basically the same as that of France. Therefore, our country can learn from the successful experience of CEA/LETI Laboratory and the business model of Lynred Company, and continue to promote research on HgCdTe APD detectors in order to reach the international advanced level as soon as possible, and realize single-photon detection and photon counting application.

    • 光子计数技术能将光子信号充分放大以克服电子器件的读出噪声,利用弱光照射下探测器输出电信号自然离散的特点,记录一定时间内探测器输出的光子数,根据光子计数值推算出被测目标的信息。为了实现极微弱的光探测,各国先后研究了多种不同种类的具有光子探测能力的仪器。早期的光子计数成像系统(Intensified Photon Counting Systems, IPCS)于20世纪70年代由英国率先研制,是将四级级联磁聚焦像增强器通过光导摄像管电视摄像机与光学系统耦合而成。随后在80年代英国采用微通道板(Micro-Channel Plate, MCP)像增强器作为核心探测器构建出新型光子计数成像系统(MCP Intensified CCD, MIC)。同一时期,日本滨松公司以三级微通道板像增强器作为光子计数成像头,成功研制出与四象限光子位敏传感器组合而成的光子计数图像采集系统(Photon-Counting Image Acquisition System, PIAS)。80年代后期,美国开发了一种基于新型多阳极微通道板阵列(Multi-Anode Microchannel Array, MAMA)的光子计数成像系统,该系统尺寸小、功耗低、可靠性高,非常适用于空间技术研究,但量子效率低、光谱适应范围较窄,主要工作在紫外和可见光波段,对红外光谱响应较低[1]。在总结了早期微弱光环境下单光子成像技术的优缺点基础上,2001年,由Andor Technology Ltd公司首先将片上增益的电子倍增电荷耦合器件(Electron Multiplying Charge Coupled Devices,EMCCD)用于i-Xon系列高端超高灵敏度相机上[2]。虽然EMCCD具有体积小、量子效率高、增益可达1000倍以上等优势,但EMCCD在对信号增强的同时也放大了暗电流噪声,其暗电流噪声水平对探测灵敏度及信噪比的影响较大。固态雪崩光电二极管(Avalanche Photodiode,APD)是利用内光电效应探测光信号的器件。与真空器件相比,固态器件在响应速度、暗计数、功耗、体积和对磁场敏感性等方面具有明显的优势,国外先后开展了基于固态APD光子计数成像技术的研究[3-4]

      APD器件有盖革模式(Geiger Mode,GM)和线性模式(Linear Mode, LM)两种工作模式,目前APD光子计数成像技术主要采用盖革模式APD器件[5-6]。盖革模式APD器件具备单光子级别的高灵敏度、达数十纳秒的高速响应速度,可获得高时间精度。但盖革模式APD存在探测器死时间、探测效率低、光串音大、空间分辨率不高等问题,很难优化折中高探测率和低虚警率的矛盾。而基于近无噪声高增益HgCdTe APD器件的光子计数器工作于线性模式,没有死时间和光串音限制,没有与盖革模式相关的后脉冲,不需要淬灭电路,具有超高动态范围,光谱响应范围宽且可调,探测效率和误计数率可独立优化,开辟了红外波段光子计数成像的新应用领域,是光子计数器件的重要发展方向,在天文观测、自由空间通信、主被动成像、条纹跟踪等方面有广阔的应用前景[7]

    • 基于HgCdTe材料的APD器件可覆盖波长范围广,电子和空穴的离化系数差异大(见图1(a)),在截止波长1.3~11 µm内表现了单载流子倍增机制[8-9],近乎无过剩噪声(相比于Si APD器件的过剩噪声因子FSi~2-3,III-V族器件FIII-V~4-5(见图1(b)),使得器件信噪比随增益增加几乎不发生衰退[10-11],是比较理想的雪崩红外探测器。

      Figure 1.  (a) Relationship between impact ionization coefficient ratio and Cd component x of HgCdTe materials; (b) Comparison of excess noise factor F for various APD materials

      表1比较了盖革模式(GM)和线性模式(LM)的光子计数技术。两者都能探测单光子事件,但是线性模式可以确定每个脉冲返回的光子数量,动态范围可以是几百到上千。另一个关键的区别是,盖革雪崩器件能产生几十万上百万的倍增载流子实现高的增益,而线性雪崩器件只需要100~200的增益。盖革雪崩击穿一旦触发,除非淬灭,否则雪崩将一直持续。淬灭雪崩的时间为死时间,在死时间内,盖革雪崩器件不能探测信号光子。盖革雪崩器件的另一个问题是光学串扰。线性雪崩器件没有持续的雪崩发生,雪崩的自然猝灭时间不到1 ns,因此,没有后脉冲或辐射复合引起的光学串扰,可以实现脉冲间隔1 ns的时间分辨率。通过定量测试信号强度,可以实现:(1)区分表面暗电流和雪崩暗电流;(2)区分伽玛或质子辐射和信号引起的事件;(3)区分暗计数和少量光子返回的信号。对于线性雪崩器件,光子探测效率(PDE)可以接近大于90%的光学量子效率。而盖革雪崩器件光子探测效率通常为30%~50%。为了弥补死时间问题,盖革雪崩器件通常使用多次激光拍摄(通常为100次或更多)来获取信号的场景信息,以提供强度以及两个物体之间的距离信息。然而,使用没有死时间的线性雪崩器件,可以优化利用激光能量,并10倍以上减少获取图像信息所需的时间[4]

      ParametersLinear modeGeiger mode
      Able to sense single photon eventYesYes
      Single event dynamic range>1000∶11 photon same as 2 or 1000
      APD gain>60105-106
      ROIC front endHigh gain, low noiseLow gain, high noise
      Repetitive pulse resolution1-2 ns100-1000 ns(1)
      Optical crosstalkMinimalSignificant radiative recombination of a large number of carriers
      Range resolution (pulse-to-pulse)~20 cm1500-15000 cm(2)
      Discriminate gained signal from ungained surface dark currentYes, by thresholdingYes, by thresholding
      Discriminate gained signal from gained radiation (γ, p)Yes, by amplitudeNo, Can’t discriminate with single pulses(3)
      Discriminate gained “few” photon signal from gained bulk IdarkYes, by amplitudeNo, can’t discriminate with single pulses returns(3)
      Photon detection efficiencyOptical QE>90%Geiger efficiency ~30%– 50%
      备注:(1) 由于后脉冲的捕获和再发射大量载流子导致的死时间限制了脉冲间隔分辨率。
         (2) 多脉冲盖革统计能达到10 cm的距离分辨率。
         (3) 通过多次事件符合过滤可以区分倍增的光子信号和倍增的体暗电流。

      Table 1.  Comparison of linear and Geiger mode technology

    • 光电探测器接收单个光子后会激发出光电子脉冲,光子计数技术即是通过分辨这些光子激发脉冲,把光信号从热噪声中以数字化方式提取出来的一种新技术。由于微光信号在时间域上表现的较为分散,因此探测器输出的电信号也是自然而离散的。根据微弱光的这一特点,通常采用脉冲放大,脉冲甄别以及数字计数技术来对极弱光进行探测。现代光子计数技术具有信噪比高、区分度高、测量精度高、抗漂移性好、时间稳定性好等诸多优点,并且可以将数据以数字信号的形式输出给计算机进行后续的分析处理,这是其他探测方法所不能比拟的。目前,光子计数系统在工业测量领域以及微光探测领域有了广泛的应用,例如非线性光学、分子生物学、超高分辨率光谱学、天文测光、大气测污等,都与微弱光号的采集检测有关。图2为光子计数系统的结构图,可以看出系统主要由光电探测器、前置放大器、脉冲幅度甄别器和计数器这四个部分组成。

      Figure 2.  Diagram layout of photon counting system

      对于成像来说,一幅图像实际上是一种二维空间的光强或光场的分布,光经过不同物体、不同表面反射后产生的非均匀光信号在探测器的不同像元进行能量积分,产生的光电流经过倍增、处理后得到不同灰度等级像素单元组成的图像。这幅图像可以被视为一个二维函数F(x,y),xy为空间坐标,(x,y)对应图像中任意一个像素,F(x,y)则为该像素处图像的亮度或灰度。

      若采用单个光电探测器进行扫描探测,从理论上来讲对二维图像进行采样时只要满足奈奎斯特抽样定理,便可以恢复出图像。因此,可以预先设计好待测目标的采样范围和采样间隔,利用光电探测器获取每一个采样点处的光子计数值便能对应到该点的亮度信息,通过数据反演即可恢复出被测目标的图像。

    • 国际上对 HgCdTe APD的研究开始于20世纪70年代末,主要集中在美、英、法、德等国,已经形成了各自的特点和研究成果,并实现了一定的产品化。主要有美国的雷神公司(Raytheon)和DRS技术公司 、法国 的CEA/LETI实验室和Lynred公司(前身为Sofradir公司)、英国的Leonardo公司(前身为Selex公司)、德国 AIM公司等致力于线性模式 HgCdTe APD焦平面的研发。其中, 美国雷神公司和DRS公司、法国CEA/LETI实验室和Lynred公司和英国的Leonardo公司先后开展了HgCdTe APD器件的光子计数探测应用研究。

    • 雷神公司在碲锌镉(CdZnTe)衬底上采用分子束外延(Molecular-Beam Epitaxy,MBE)技术生长多层异质结的HgCdTe APD结构,即吸收区和倍增区分离(Separate Absorption and Multiplication,SAM)的结构[13],如图3(a)所示。该结构一般为台面结构,它的吸收区用于吸收光子而产生光生载流子,光生载流子在电场作用下进入倍增区发生碰撞电离,吸收层为N型层,倍增层Cd组分为0.73,是利用空穴电离谐振引发雪崩增益的短波器件[14],如图3(b)所示。SAM结构的优点在于可设计各层材料的组分、厚度、浓度等参数以获得高增益、高量子效率和低过剩噪声;缺点是多层结构的设计和材料生长是一项工作量极大的任务,工艺复杂性高。

      Figure 3.  (a) Diagram of HgCdTe SAM-APD structure; (b) Epitaxial structure of HgCdTe SAM-APD grown by molecular-beam epitaxy

    • 为解决远距离(百万米距离)探测和卫星跟踪的信号脉冲衰减严重的问题,雷神公司2007年开发了具有单光子探测能力的4×4阵列规模的HgCdTe APD器件(见图4),读出电路带宽达1~3 GHz,在增益50~200时输出信号,实现了近无噪声的单光子探测[15]。如图5所示,在每脉冲的平均照明强度为1个光子时,器件能探测分辨出0、1和2个光子(见图5(a)),分辨单光子的两个脉冲间隔时间小于6 ns (见图5(b))。2010年,通过进一步优化电路,限制热载流子发出的辉光,实现了信噪比大于10,探测率大于95%,虚警率小于1%,性能指标见表2[16],并将开发256×256阵列规模的HgCdTe APD光子计数器件。

      Figure 4.  HgCdTe APD 4×4 photon counting sensor chip assembly

      Figure 5.  (a) Multiple acquisitions showing detection of 0, 1 and 2 photons with average illumination of one photon; (b) Single photon acquisition with double pulses closely spaced time (<6 ns) without afterpulsing observed

      ParametersResults
      Response waveband1.55 μm
      Operating voltages<20 V
      Operating temperature80-180 K or greater
      Maximum gain200-350
      Dark count rate (DCR) (counts/s) at M>100<104 (80-160 K)
      , <105 (180 K)
      Surface dark current<10−13 A
      Max reset time10 ms
      Operability>90%
      Probability of detection>95%
      False alarm rate<1%

      Table 2.  Performance of HgCdTe APD 4×4 photon counting sensor chip assembly

    • DRS技术公司基于早期的N/P环孔器件结构开发出了高密度垂直集成器件(high density vertically integrated photodiode, HDVIP)结构,成功研制出高性能的HgCdTe e-APD器件,其结构示意图如图6所示[17]。这种结构的器件大多采用IB族掺杂的P型材料[18],通过刻蚀工艺形成通孔用于芯片和读出电路间的连接,刻蚀或注入形成的Hg填隙向内部扩散过程中,P型掺杂由于knock-out效应会一起迁移,有助于低掺杂的N-区的形成。因此,HDVIP的单元结构是横向的N+-N--P结,与平面PIN型APD有很大的相似之处。这种结构的优点在于:(1)器件上下表面都进行了CdTe钝化,并进行了互扩散退火工艺,有效降低1/f噪声;(2)器件的电流信号通过刻蚀后的N区和Si读出电路的电极直接相连,不需要通过In柱进行互联,因此器件的热循环稳定性得到很大提高,并且与像元尺寸及面阵大小无关;(3)其结构的取向使得PN结界面与外延材料中的穿越位错接近平行,有效降低了从PN结中穿越的位错密度,这有助于器件漏电流的减小;(4) HDVIP为正入射器件,有利于探测率D*、量子效率和调制传递函数MTF的提高;(5)外延材料的衬底全部去除后,衬底与读出电路间的热失配问题可以得到解决。但制备技术比较复杂,难度高,尤其是需要完整去除碲锌镉衬底,同时不对碲镉汞薄膜造成损伤,因此限制了该技术方案的应用。

      Figure 6.  Cross section and top view of HDVIP HgCdTe APD structure

    • 2011年,DRS首次报道了2010年研制的2×8阵列规模的中波HgCdTe APD光子计数器件(见图7[7],器件光谱响应范围从可见光到中波红外,为0.4~4.3 μm,是响应光谱最宽的光子计数器件,过剩噪声接近于1,在增益500~1000之间可以稳定探测光子;13 V偏压下,增益为500,暗电流约1 pA,暗计数率低于20 kHz;光子脉冲信噪比为13.7,实现了单光子探测;光背景限制的光子探测假事件率(False Event Rate, FER)为1 MHz时,光子探测效率为50%,分辨单光子的两个脉冲间隔时间小于10 ns。此处的假事件率是指与目标信号无关的任何光子探测,是在没有任何有意的光子通量入射到探测器时测量的值,杜瓦光泄露、热背景、暗电流和读出电路的辉光都会影响假事件率的值。相对于短波HgCdTe APD器件,中波HgCdTe APD有几个重要的优点:(1)增益大于1000时,产生复合和扩散暗电流可以忽略不计;(2)实现所需雪崩增益的APD偏置电压要低得多,简化了读出电路的设计,大大提高了APD的可靠性;(3)能够在更宽的光谱范围内检测光子,具有高且几乎均匀的量子效率。

      Figure 7.  2×8 linear middle wave HgCdTe APD photon counting focal plane array

      为了进一步提升光子探测效率和降低光子探测假事件率,DRS于2013年改善了设计和工艺条件,获得了性能更好的两款器件A8237-8-2和A8237-14-1[19],器件性能对比见表3。相对于2010年的器件,光子探测效率提升至60%以上,增益可达到1 900,假事件率降至150 kHz。并于2018年研发了应用于空间雷达的单光子计数HgCdTe APD组件,在0.9~4.3 μm间光子探测效率大于60%,暗计数率低于250 kHz[20]。2022年,通过进一步优化电路,降低了电路辉光诱导的暗计数,假事件率降至35 kHz,并研制了4×4、2×30、7×8阵列规模的光子计数器件,4×4阵列器件的平均增益可达6100[21]

      ParametersArray in 2010Two arrays in 2013
      A8327-8-2A8327-14-1
      P-type dopingVHgCu+VHgVHg
      Cd composition0.330.330.33
      Gain470@
      13 V
      1910@12.9 V1100@12.9 V
      Maximum Photon Detection Efficiency(PDE)50%@14 V72%@12.9 V66%@12.9 V
      FER@PDE=50%>1 MHz151 kHz158 kHz
      Mean single photon SNR13.721.912.3
      Excess noise factor, F1.3-1.41.251.20
      Measured RMS jitter632 ps2370 ps1570 ps
      Minimum time between events8 nsNo measured9 ns

      Table 3.  Comparison of performance of 2×8 linear HgCdTe APDs photon counting arrays in 2010 and 2013

      采用2013年研发的2×8阵列规模的光子计数器件,DRS于2016报道了HgCdTe APD器件在自由空间通信上的应用性能,器件搭载CubeSat卫星进行了通信验证,在1550 nm激光波段可实现50 Mbps的数据传输,通过高通滤光片和多像素阵列组合,在8×10−8的误码率下可实现110 Mbps的数据传输[22]

    • 法国CEA/LETI实验室和Lynred公司(前身为Sofradir公司)采用平面PIN型结构制备HgCdTe e-APD器件,结构示意图如图8所示[23]。这种结构是在普通PN结器件中间加入一个本征层I,人为地增大空间电荷区的宽度,用于载流子的雪崩倍增。不过,由于本征型和浅掺的P-型的HgCdTe很难获得,实际中一般用浅掺的N-型代替。这种结构的优点在于工艺简单成熟、步骤简单、成品率高和N+-N--P结可控性好。其缺点也是所有平面N-on-P器件存在的问题,其产生复合电流和漏电流的水平都会比P-on-N器件大;另外器件的占空比无法继续提升,当焦平面器件往更小像元、更高密度的方向发展时,由于非平衡载流子的横向扩展或者表面漏电的原因会使得平面结器件的电学串音随之增加。

      Figure 8.  Schematic diagram of planar PIN HgCdTe APD structure

    • CEA/LETI实验室和Sofradir公司于2010年报道了应用于低光通量和光子计数的HgCdTe APD器件[24],Cd组分为0.3~0.41,器件增益如图9所示,短波和中波器件典型性能见表4,最大增益带宽积达2.1 THz,脉冲响应时间几乎不随增益变化。图10展示了探测到1个光子和2个光子时的概率分布以及倍增层中均匀分布的暗电流。从图可知,探测到1个光子事件和探测到2个光子事件的概率分布被很好的分离开了。因而,HgCdTe e-APD探测器可以分辨出1个光子或者2个光子探测事件,可实现比例光子计数。受残余热光子限制,中波器件的暗计数率(DCR)约为1 MHz;受隧穿暗电流噪声限制,短波器件高增益下的DCR为100 kHz;器件的内光子探测效率(PDE)可达90%[23]

      Figure 9.  HgCdTe e-APD gain curves measured at T=80 K for λc=2.9 μm to 5.3 μm

      ParametersSWIRMWIR
      Quantum efficiency (QE)60%-80%
      Max gain2 00013000
      Bias at M=10012-14 V7-10 V
      F1.1-1.4
      QE to F ratios40%-70%
      Typical response time0.5-20 ns
      Maximum gain-bandwidth product2.1 THz

      Table 4.  Typical performance of SWIR and MWIR Hg-CdTe APDs at T= 80 K

      Figure 10.  Probability distributions for detecting 1 and 2 photons events and uniformly distributed dark current generation in the multi-plication layer

      2015年,法国CEA/LETI公司报道了80~200 μm的大面积单元器件,器件带宽在20~100 MHz之间,噪声等效功率NEP为20~70 fW/$\sqrt {{\rm{Hz}}} $,成功进行了月球激光通信演示,在环月球运行的LADEE太空船和位于特内里费(Teneriffe)的ESAs光学地面站之间可以实现80 Mbps的数据传输[25]。通过结构优化,设计了吸收区组分梯度(见图11),在增益100时,芯片带宽达到80 K下4 GHz和273 K下3 GHz [26]。于2021年实现300 K下增益为1时带宽达10 GHz、更大增益时带宽达3 GHz,并应用于大动态范围空间激光雷达,其指标要求见表5[27],实现了GHz单光子探测速率[28]

      Figure 11.  Illustration of a fast response HgCdTe APD architecture with separate absorption and multiplicaiton layer, the corresponding band gap variation

      ParametersObjetive
      Response waveband0.3-3 μm
      F1.2
      Quantum efficiency (QE)90%
      Temporal resolution5 ns-10 μs
      Photon noise limited dynamic range60 dB
      Detector noise<1 photon
      Minimum detected photon noise limited signal<1 photon

      Table 5.  HgCdTe APD performance index for space lidar application

    • 英国Leonardo公司开发了金属有机气相外延(Metal Organic Vapor Phase Epitaxy, MOVPE)生长Hg-CdTe薄膜技术,采用低成本化的GaAs衬底,制备了中心距为24 μm的异质结HgCdTe APD 320×256阵列器件,命名为Selex Avalanche Photodiode HgCdTe In-frared Array(SAPHIRA),器件结构图和能带结构图如图12所示。器件结构包含吸收区、倍增区和两者之间的缓冲层。吸收区的截止波长为2.5 μm,倍增区的截止波长为3.5 μm,倍增区采用窄带隙可有效提高增益,吸收区和倍增区之间的缓冲层为HgTe和CdTe,用以减少陷阱辅助隧穿电流(TAT)和陷阱相关的热电流,以及减缓GaAs衬底引起的晶格失配。采用MOVPE外延异质结HgCdTe APD器件的优点在于能大尺寸批量生产,成本低;缺点在于位错密度难以降低,制备的APD器件受吸收层中陷阱载流子限制,响应时间较慢,带宽限制在kHz范围[29-30]

      Figure 12.  (a) Structure schematic and (b) band structure of MOVPE heterostructure HgCdTe APD array

    • Leonardo公司2018年报道了SAPHIRA器件的光子计数性能[31],器件能够探测到单个光子,但吸收了两个或多个光子,在一次读取中是不能分辨的;器件的单光子探测率大于90%,时间分辨率为125 μs,暗电流为21 e·s−1·pixel−1,对应暗计数率为21 Hz/pixel。器件具备近红外光子计数能力,并应用于天文探测,探测器性能将进一步优化。

      法国First Light Imaging公司2016年基于SA-PHIRA 320×256 HgCdTe APD短波器件,研发出了C-RED ONE相机(见图13[32],在3500帧频下,读出噪声小于一个电子,过剩噪声因子小于1.25,有效像元率达99.3%,可应用于自适应光学、空间碎片跟踪和条纹跟踪等天文应用,并成功应用于美国天文探测的密歇根红外组合器(Michigan Infrared Combiner, MIRC)(见图14),将MIRC的系统噪声降低了10~30倍,大大提高了条纹探测的信噪比[33],C-RED ONE相机性能见表6。这也极大促进了HgCdTe APD器件产品化和商业化进程。

      Figure 13.  C-RED ONE camera

      Figure 14.  Installation of C-RED ONE at MIRC optics

      ParametersResults
      Maximum frame frequency3500 fps
      Mean dark + readout noise at 3500 fps and
      Gain~30
      < 1 e
      Quantization16 bit
      Operating temperature80 K
      Peak quantum efficiency from 0.8 μm to 2.5 μm> 70%
      Operability99.30%
      Image full well capacity at gain 1, 3500 fps50000 e
      F< 1.25

      Table 6.  C- RED ONE camera performances

    • 国内对HgCdTe APD器件的研究开始于2010年左右,研究机构主要有中国科学院上海技术物理研究所(Shanghai Institute of Technical Physics, Chinese Academy of Sciences, SITP)、昆明物理研究所(Kun-ming Institute of Physics, KIP)和华北光电技术研究所,主要集中在平面PIN结的中波HgCdTe APD器件的研究,近五六年在HgCdTe APD器件的研制上取得了一定进展,但未形成光子计数应用的能力。

      中国科学院上海技术物理研究所采用液相外延(Liquid Phase Epitaxy, LPE)生长的中波碲镉汞材料,制备了平面PIN结构单元器件和中心距为50 μm的128×128阵列中波HgCdTe APD焦平面器件,单元器件增益可达1000以上[34],焦平面器件性能如图15(a)~(c)所示[35-36],在反偏−10 V下器件增益达到728,反偏−8 V以下增益归一化暗电流密度GNDCD<1×10−7 A/cm2,过剩噪声因子F<1.5@增益M<400,噪声等效光子数NEPh约为12@增益M=133,与DRS的GNDCD~1×10−7 A/cm2水平下的NEPh相当。设计了带宽结构的单元器件,通过减薄P区厚度,实现了器件带宽从30~60 MHz提升至300~600 MHz[36],如图15(d)所示。此外,还制备了中心距30 μm的320×256阵列的中波HgCdTe APD焦平面器件,对焦平面器件进行了成像演示,表明HgCdTe APD器件适合应用短积分快速成像[36]

      Figure 15.  Performances of MWIR HgCdTe APD at 80 K. (a) Photocurrent, dark current and gain; (b) Variation of excess noise factor F with gain M; (c) Noise equivalent photon (NEPh) compared with DRS HgCdTe APD detectors; (d) Bandwidth

      昆明物理研究所采用LPE生长的中波碲镉汞材料,通过B离子注入N-on-P平面结技术制备了单元器件和规模为256×256、像元中心距为30 μm的碲镉汞APD焦平面探测器芯片。单元器件的增益可达1000以上[37]。焦平面芯片在−8.5 V反偏下平均增益达到166.8,增益非均匀性为3.33%;在0~−8.5 V反向偏置下,APD器件增益归一化暗电流为9.0×10−14~1.6×10−13 A,过噪因子F介于1.0~1.5之间。对碲镉汞APD焦平面进行了成像演示,并获得了较好的成像效果,如图16所示[38]

      Figure 16.  Imaging demonstration of a HgCdTe APD focal plane under different gains with Tint=20 μs. (a) M=1; (b) M=19

      表7对比了不同研究机构的光子计数HgCdTe APD器件的性能。相比于国际先进水平,国内碲镉汞雪崩器件的暗电流要高出一两个量级,其中一个原因是抑制器件表面漏电的表面钝化工艺需要进一步完善。国内碲镉汞雪崩器件集成时间计数信号的高速读出电路尚处于研制当中,未见主被动双模成像报道。总体上,国内雪崩器件的制备技术及其读出电路技术落后国际先进水平10来年。

      ParametersRaytheonDRSCEA/TETILeonardoSITPKIP
      Able to sense single photon eventYesYesYesYesNoNo
      APD structureSAMHDVIPPINSAMPINPIN
      Epitaxial techniqueMBELPEMBE/LPEMOVPELPELPE
      Cut-off wavelength @77 K1.55 μm at absorption region, 1.27 μm at gain region4.3 μm2.5-5.3 μm2.5 μm at absorption region, 3.5 μm at gain region4.7-5.2 μm4.6 μm
      Multiplication mechanismHole multiplicationElectron multiplicationElectron multiplicationElectron multiplicationElectron multiplicationElectron multiplication
      Maximum gain35061002 000 for SW
      13000 for MW
      66@14.5 V>1000>1000
      FF~11.21.1-1.4< 1.25<1.5@M<400<1.5@<8.5 V
      Bandwidth (BW)1-3 GHz of ROIC BWNo givenMax BW 10 GHz@M=1 300 KNo given, low BW300-600 MHzNo reported
      Dark count rate (DCR)<10 kHz(80-160 K);
      <100 kHz (180 K)
      <20 kHz100 kHz for SW
      1 MHz for MW
      21 Hz/pixelCalculated by dark current: 100 kHz-3 GHzCalculated by dark current: 560 kHz-170 MHz
      Photon detection efficiency (PDE)>95%72%~90%>90%No reportedNo reported
      Minimum time between events<6 ns8 ns5 ns-10 μs125 μsNo reportedNo reported

      Table 7.  Performances of HgCdTe APD for photon-counting application from different research institutes

    • 碲镉汞雪崩探测器几乎无过剩噪声,随着增益增加,信噪比不发生衰减,没有盖革雪崩器件相关的死时间和后脉冲限制,非常适合应用于光子计数,是未来光子计数器件的重要发展方向。文中介绍了线性模式相对于盖革模式光子计数的优势,总结了美国雷神和DRS公司、法国CEA/LETI实验室和Lynred公司、以及英国Leonardo公司的HgCdTe APD器件在光子计数应用方面的技术路径和发展现状。各公司根据自身技术水平选择了不同的技术路线,并且根据结构需要选择不同的制备技术生长碲镉汞材料,成功制备了高性能线性雪崩器件并实现了单光子探测,将应用于天文探测、空间雷达、自由空间通信、条纹跟踪等方面。

      国内碲镉汞雪崩探测器研究起步比较晚,虽然在HgCdTe APD单元器件和焦平面研制上取得了一定的进展,但与国际先进水平仍存在一定差距,在光子计数应用方面未见到有关的进展情况。目前国内主要是研制平面PIN结构的HgCdTe APD器件,技术路径与法国CEA/LETI实验室相近。因而,我国可借鉴CEA/LETI实验室成功经验和Lynred公司的运营模式,持续推进HgCdTe APD器件的研究,以早日达到国际先进水平,实现单光子探测和光子计数应用。

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