用于超导纳米线单光子探测器的低温集成电路研究

发布时间：2018-03-26 13:11

本文选题：低温电路　切入点：射频放大器　出处：《南京大学》2017年博士论文

【摘要】：超导纳米线单光子探测器(SNSPD)发展至今已具备很多性能上的优势,但是它通常工作在很强的非线性模式下,即使有多个光子同时被吸收,也只有一个脉冲信号产生,然而在光谱分析、通信、生物成像、宇宙观测和量子信息处理等诸多应用场合中,不仅需要对入射的光子作出响应,还需要对入射的光子数,甚至光子入射的时间和空间位置进行分辨。因此,发展SNSPD阵列,实现光子数分辨、时间分辨和空间分辨是SNSPD发展的一大趋势。目前,采用集成复用方式,研究者们已经可以通过16根同轴线在室温下读出8×8阵列的信号,实现对入射光子位置的分辨。此外,利用SFQ这种超导电路在低温下对8×8阵列进行读出的研究工作也在进行当中。受同轴线数量和热负载的限制,集成复用的读出方式最终依然会限制阵列的规模,而SFQ的设计和制作过程较为复杂,工作时还需增加额外的磁屏蔽,使用时较为不便。串联结构的SNSPD阵列采用传统方式即可读出,通过选用特定大小的并联电阻也可以实现空间分辨,从这方面看比多像元阵列更具优势。但当串联的像元数目较多时,则需要一种能够工作在低温环境下且具有高输入阻抗的特殊射频放大器以便能对不同入射光子数下的脉冲幅度进行清晰地分辨。本论文针对串联结构SNSPD阵列的这一需求,采用Tower Jazz的0.18μm SiGe BiCMOS工艺,研制了具有高输入阻抗的低温射频集成放大电路,主要工作围绕两点展开,首先是如何保证基于SiGe HBT的放大电路在液氦温区能够正常工作,其次是如何利用射频波段的50 Ω测量系统表征高输入阻抗电路,正确提取出相应参数。研究成果分述如下:第一,搭建实验平台,在300 K至4.2 K的温度范围内研究分析了电阻、电容和电感等基本电路元件的温度特性。并在不同的温度下,研究分析了 Tower Jazz工艺中的SiGe HBT以及两种商用SiGe HBT的输入输出特性,总结了 SiGe HBT的直流特性随温度降低的一般规律,分析了低温下差异可能出现的原因。此外,测量了基于SiGe HBT的比例电流源的温度特性。这些工作为低温集成射频放大电路的设计和优化提供了重要的技术保证。第二,通过改变供电方式,使初始研制的50Ω输入阻抗电路在4.2 K获得了10 dB增益和2 MHz～1 GHz带宽,并成功读出SNSPD的脉冲信号,验证了 SiGe工艺在液氦温区工作的可行性。在此基础上,参与设计了具有高输入阻抗的单端、差分两种结构的射频集成放大电路,采用直流工作点可调的方式,克服了缺乏低温工艺模型库这一设计过程中的难题,从工程的角度保证了 SiGe HBT在4.2 K下可以偏置于合适的直流工作点,使得电路能够正常工作。第三,使用网络分析仪研究了高输入阻抗射频放大电路特征参数的提取,从电压的角度分析了在阻抗不匹配情况下的信号分配比例,证实了由50 射频测量系统得到的高阻放大器增益会比实际值高6 dB。此外,通过对比不同校准位置下的测量结果,明确了系统中连接低温和室温环境的较长同轴线对于阻抗和增益测量的影响。这些工作既为高输入阻抗射频电路的低温表征提供了技术方法,又有助于低温电路与SNSPD的正确互连。第四,利用高阻抗射频电路的测试方法,使用网络分析仪成功表征了具有高输入阻抗的单端、差分两种结构射频集成放大电路的性能。在常温下,二者的测量结果与仿真值吻合良好。在4.2K下,单端结构的增益为20 dB,带宽为3.8 MHz～1 GHz,输入阻抗最大可达6.7Ω,功耗仅为0.6 mW,双端结构的增益可达26 dB,带宽为100 kHz～1 GHz,输入阻抗最大可达10kΩ,功耗约为0.9 mW。第五,搭建并逐步优化了低温读出电路与SNSPD的互连测试系统,并成功将各种结构的低温电路与SNSPD互连,读出了相应的脉冲信号。该互连测试系统不仅可以对低温电路的增益进行监测,确保电路处于正常工作状态,同时具备传统读出方式中可以对器件的Ⅰ-Ⅴ曲线进行扫描的优点,便于确定SNSPD偏置电流的大小以及评估低温电路对于器件超流压缩的影响,为低温电路与SNSPD的互连测试奠定了良好的基础。
[Abstract]:Superconducting nanowire single photon detector (SNSPD) has developed have many advantages, but it usually works in the nonlinear model is very strong, even if there are multiple photon absorption at the same time, there is only one pulse signal is generated in the spectral analysis, communication, biological imaging, space observation and quantum information processing in many applications, not only need to respond to the incident photon, photon number also need to incident, even photon incident time and space position resolution. Therefore, the development of the SNSPD array, realize photon number resolution, time resolution and spatial resolution is a major trend in the development of SNSPD. At present, the integration of reuse the way, the researchers can through 16 coaxial read 8 * 8 array signal at room temperature, the resolution of the incident photon position. In addition, at a low temperature of 8 * 8 array of the use of SFQ superconducting circuit Column readout research work is also underway. By limiting the number of coaxial and thermal load, readout integrated multiplexing eventually will still limit the array size, and design and manufacture process of SFQ is more complex, the work needed to increase the use of additional magnetic shielding, is inconvenient. The series SNSPD array structure the traditional way to read through the selection of specific size of the shunt resistance can also achieve spatial resolution, has more advantage than the multi pixel array from this aspect. But when the number of pixels in series is large, you need a special RF amplifier with high input impedance and working in low temperature environment so as to pulse amplitude under the different incident photon number resolution. This thesis focuses on the demand structure of SNSPD series array, using 0.18 m SiGe BiCMOS Tower Jazz technology, developed with high Low temperature RF integrated amplifier input impedance, mainly focused on two aspects, the first is how to ensure the SiGe amplifier circuit based on HBT can work normally in liquid helium temperature region, the second is how to use 50 ohm measurement system characterized with high input impedance circuit of radio frequency band, extract the correct corresponding parameters. The results are as follows: 1. Set up the experimental platform, research and analysis of the resistance in the temperature range from 300 K to 4.2 K, the temperature characteristics of the capacitance and inductance of circuit elements. And at different temperatures on the research and analysis of Tower Jazz technology in SiGe HBT and two kinds of commercial SiGe HBT input and output characteristics, summed up the general rules of DC characteristics SiGe HBT decreases with increasing temperature, analyzed the reason of low temperature differences may occur. In addition, measuring the temperature characteristics of SiGe HBT based on the proportion of the current source. These work for low Wen Jicheng Provide important assurance technology of amplifier circuit design and optimization. Second, by changing the power supply mode, the initial development of 50 ohm input impedance of the circuit was 10 dB gain and 2 MHz ~ 4.2 K in 1 GHz bandwidth, and readout pulse signal SNSPD, verify the feasibility of SiGe technology in liquid helium temperature region. On this basis, in the design of the single ended with a high input impedance, low radio frequency integrated amplifying circuit is divided into two kinds of structure, the DC operating point can be adjusted, to overcome the problem of lacking the design process of low temperature process in the model library, from the perspective of the project to ensure that the SiGe HBT at 4.2 K can offset from the appropriate DC operating point, so that the circuit can work normally. Third, extraction of high input impedance amplifier circuit using the characteristic parameters of the network analyzer, the voltage analysis of the impedance mismatch in the The proportion of signal distribution case, confirmed the high impedance amplifier gain by 50 RF measurement system than the actual value of 6 dB. in addition, by measuring the results of the different calibration position, the system is connected at room temperature and low temperature environment with long axis for impedance and gain measurement. Provide technical method these work not only for low temperature characterization of high input impedance of the RF circuit, the correct connection but also contribute to the low temperature circuit with SNSPD. Fourth, the test method of high impedance of the RF circuit, using a network analyzer to characterize the single ended successfully with high input impedance, the performance of two kinds of structure of RF integrated amplifier at room temperature. Two, measurement results and simulation results agree well. In 4.2K, the single end structure gain of 20 dB bandwidth of 3.8 MHz to 1 GHz, the maximum is 6.7 ohm input impedance, power consumption is only 0.6 mW, double End structure gain up to 26 dB bandwidth of 100 kHz to 1 GHz, the input impedance of up to 10K, power consumption is about 0.9 mW. in fifth, and gradually build optimized interconnect test system with low temperature readout circuit with SNSPD, and the success of the low temperature circuit and SNSPD interconnect structure, read the corresponding pulse signal. The interconnection test system can not only gain of the circuit on the low temperature monitoring, to ensure that the circuit is in the normal working state, at the same time with the traditional way of reading can be advantages of the device I-V curves were scanned, easy to determine the bias current of SNSPD circuit size and evaluation of low temperature influence on super flow compression device, and laid a good foundation for the low temperature interconnect test circuit with SNSPD.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN15;TN40

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