单光子探测器APD无源抑制特性研究

为了选择高性能单光子探测器件，采用无源抑制方法对工作在盖革模式下的雪崩光电二极管（APD: avalanche photodiode）特性进行了测量。利用APD两端的电压在雪崩后趋于稳定的特性，获得了一种确定暗击穿电压的方法。特性测量实验结果表明：降低温度能加宽APD的最佳工作区域范围，并提高最佳增益值，从而使APD具有更高的灵敏度。通过对EG&;G系列APD和外延APD暗电流和信噪比特性进行比较，发现外延 APD具有良好的噪声性能和信噪比性能，适用于单光子探测。     

单光子探测器雪崩光电二极管的低温控制系统及其温度特性

根据单光子探测系统的要求及其特点,采用半导体制冷技术,研制出了用于单光子探测的雪崩光电二极管(APD)的水循环散热制冷腔。通过配备测量精度为0.1℃的温控仪,降低了APD的工作环境温度。通过实验探讨了APD的温度特性,得到了APD的雪崩电压、暗电流、光电流、等效噪声功率与温度的关系。结果表明:降低APD的工作温度有利于减小APD的等效噪声功率,APD存在最佳工作温度。     

APD探测器模块性能及噪声检测

为了实现可见光通信系统的探测器模块微小型化,设计并制作了一款50 cm3的温控APD探测器模块,并对模块的稳定性、温控效果和噪声特性进行了检测。结果表明,APD探测器模块的光电流测量平均相对偏差为0.795%;APD探测器的雪崩增益和响应度随着温度的降低而提高;APD探测器电阻的变化影响负载电阻分压,使得过剩噪声因子的测量值远大于真实值,且会随着入射光功率的增大而增大。可以得出结论:提高反向偏置电压与降低温控温度相配合,更有利于弱光信号检测;检测电路中的负载电阻影响APD探测器噪声特性。     

倍增层厚度对In0.53Ga0.47As/InP雪崩二极管器件特性的影响

利用Zn扩散方法制备了倍增层厚度为1.5,1.0,0.8μm的In_0.53Ga_0.47As/InP雪崩光电二极管(APDs),研究了该器件特性。随着倍增层厚度的增加,器件的贯穿电压和击穿电压均呈现增大趋势。基于Silvaco模拟计算了APD器件的倍增层厚度对电场强度、电流特性、击穿电压与贯穿电压的影响规律,结果表明,随着倍增层厚度的增加,倍增层内电场强度减小,贯穿电压和击穿电压同时增大,与实验结果吻合。进一步研究发现,当倍增层的厚度小于0.8μm时,击穿电压随着倍增层厚度的增加会先减小后增大,贯穿电压则会单调增大。     

基于APD线列的单光子探测计数研究

单光子探测系统可以对单个光子进行探测;探测系统含有探测部分、淬灭电路部分和计数部分;探测部分主要由工作在盖革模式下的雪崩光电二极管组成;在盖革模式下的雪崩光电二极管发生雪崩后不能自然停止,淬灭部分主要为了主动抑制雪崩电流,快速降低雪崩电压,以达到提高探测效率,降低错误计数的目的;APD线列产生多个光子脉冲信号,计数部分的主要功能是对多路光子脉冲信号进行计数、显示并且可以控制每路APD的比较电压,保证每路APD淬灭电路的正常工作。     

在高于253 K温度下的1550 nm波长单光子探测实验

介绍了在高于253 K的温度下,实现红外单光子探测的实验.选用拉通电压较高的雪崩光电二极管（APD）,设计制作了非线性限流技术保护高温工作的APD,利用半导体热电制冷器,在256.8K的温度下,实现了1550 nm波段的单光子探测实验.单光子探测的暗记数率为3.13×10－5 ns,在220 kHz/s的单光子脉冲速率下,探测效率为2.08%.     

高探测效率CMOS单光子雪崩二极管器件

基于标准0.35μm CMOS工艺设计了一种单光子雪崩二极管器件.采用p+n阱型二极管结构,同时引进保护环与深n阱结构以提高单光子雪崩二极管性能;研究了扩散n阱保护环宽度对雪崩击穿特性的影响;对器件的电场分布、击穿特性、光子探测效率、频率响应等特性进行了分析.仿真结果表明:所设计的单光子雪崩二极管器件结构直径为10μm,扩散n阱保护环宽度为1μm时,雪崩击穿电压为13.2 V,3 dB带宽可达1.6 GHz;过偏压为1 V、2 V时最大探测效率分别高达52%和55%;在波长500~800 nm之间器件响应度较好,波长为680 nm时单位响应度峰值高达0.45 A/W.     

硅雪崩二极管光子辐射特性的实验研究

利用计数统计测量的方法，对工作在击穿状态下的硅雪崩光电二极管(APD)光子辐射的暂态特性以及计数统计特性进行了实验研究.将APD辐射光子的计数统计曲线与相应Poisson、热光场进行比较，发现其在采样时间为10 ms的情况下计数统计服从Super-Poisson分布.另外实验给出了APD光子辐射的光谱特性.     

In0.83Al0.17As倍增层对In0.83Ga0.17As/GaAs雪崩光电探测器的特性影响

倍增层对雪崩光电探测器内部载流子的碰撞电离至关重要,因此,采用三元化合物In_0.83Al_0.17As作为倍增层材料,借助器件仿真工具Silvaco-TCAD,详细探究了In_0.83Ga_0.17As/GaAs雪崩光电探测器的倍增层厚度及掺杂浓度对其内部电场强度、电流特性和电容特性的影响规律。研究表明,随着倍增层厚度的增加,器件的电场强度和电容呈减小趋势。同时,倍增层掺杂浓度的增大会引起电容和倍增层内的电场强度峰值增加。进一步研究发现,随着倍增层厚度的增加,器件的穿通电压线性增大,击穿电压先减小后增大,但倍增层掺杂浓度的增加会引起器件击穿电压的减小。此外,用电场分布和倍增因子的结合解释了器件穿通电压与击穿电压的变化。     

高压IGBT雪崩鲁棒性的研究

随着绝缘栅双极晶体管(insulated gate bipolar transistor, IGBT)电压等级的提升和电流容量的增大,雪崩效应已成为限制器件安全工作区(safe operating area, SOA)的重要因素.雪崩发生后IGBT背面p+n结的空穴注入是其雪崩效应区别于其他器件的主要特征.本文通过理论分析与数值模拟的方法研究了IGBT雪崩击穿特性以及雪崩产生电流丝的性质,揭示了控制雪崩产生电流丝性质的物理机制.结果表明IGBT背面的空穴注入导致其雪崩击穿曲线上产生额外的负微分电阻分支;器件共基极电流增益α_pnp是决定雪崩产生电流丝的关键因素,随着α_pnp的增大,雪崩产生的电流丝强度越强、移动速度越慢,从而导致器件的雪崩鲁棒性越弱.     

通讯波段单光子探测器的研制

将InGaAs/InP雪崩光电二极管应用于盖革模式下,采用门脉冲模式淬灭雪崩,并使用魔T混合网络抑制尖峰噪声,实现了通信波段1550 nm的单光子探测.在APD工作温度为223 K时,测得暗计数率与探测效率的比值为0.035.     

Monte Carlo simulation of electron avalanches and avalanche size distributions in methane

The simulation of electron avalanches and avalanche size distributions in methane is presented in this paper. A model for electron transport under the influence of a constant electric field based on the Monte Carlo method is described in detail. The model is verified and then used to simulate the avalanche development, to calculate the number of electrons in the avalanche (avalanche size), and to determine the avalanche size distribution. The simulated avalanche size distributions in methane are compared with the experimental results, and a good agreement is observed. The influence of inter‐electrode distance, pressure, and reduced electric field on the shape of the avalanche size distribution is discussed. The assumption from the literature that for a constant reduced electric field the shape of the reduced avalanche size distribution is independent of the mean size of the avalanche is confirmed for a wide range of experimental conditions. The simulations have shown that avalanche size distributions depend only on the reduced electric field, confirming the similarity principle.     

减小雪崩光电二极管温度影响的研究

本文就如何减小温度对雪崩光电二级管响应度的影响进行了研究。文中从理论上分析了温度以及偏置电压对雪崩光电二极管响应度的影响，并在此基础上提出了两种减小温度影响的可行方法：恒温恒压法和偏置电压温度补偿法，并进行了实验验证     

Self-organized Criticality in an Integrate-and-Fire Neuron Model Based on Modified Aging Networks

Based on an integrate-and-fire mechanism, we investigate self-organized criticality of a simple neuron model on a modified BA scale-free network with aging nodes. In our model, we find that the distribution of avalanche size follows power-law behavior. The critical exponent τ depends on the aging exponent α. The structures of the network with aging of nodes change with an increase of α. The different topological structures lead to different behaviors in models of integrate-and-fire neurons.     

四能级稳态雪崩上转换过程的计算分析

通过建立四能级雪崩上转换的速率方程,对稳态雪崩过程进行了详细的讨论和分析,阐明了雪崩上转换是个有阈值过程,并给出了各个能级布居随交叉弛豫P和跃迁速率Qi的变化。     

Different Avalanche Behaviors in Different Specific Areas of a System Based on Neural Networks

Based on the standard self-organizing map (SOM) neural network model and an integrate-and-fire mecha-nism, we introduce a kind of coupled map lattice system to investigate scale-invariance behavior in the activity of modelneural populations. We find power-law distribution behavior of avalanche size in our model. But more importantly, wefind there are different avalanche distribution behaviors in different specific areas of our system, which are formed by thetopological learning process of the SOM net.     

MgZnO avalanche photodetectors realized in Schottky structures

MgZnO‐based ultraviolet avalanche photodetectors (APDs) have been fabricated from Au/MgO/Mg_0.44Zn_0.56O/MgO/Au Schottky structures. The carrier avalanche multiplication is realized via an impact ionization process occurring in the MgO layer under relatively large electric field. The APDs exhibit an avalanche gain of 587 at 31 V bias, and the response speed of the APDs is in the order of microseconds.

     

Self-Organized Criticality in a Simple Neuron Model Based on Scale-Free Networks

A simple model for a set of interacting idealized neurons in scale-free networks is introduced. The basic elements of the model are endowed with the main features of a neuron function. We find that our model displays powerlaw behavior of avalanche sizes and generates long-range temporal correlation. More importantly, we find different dynamical behavior for nodes with different connectivity in the scale-free networks.     

Self-organized Criticality in Hierarchical Brain Network

It is shown that the cortical brain network of the macaque displays a hierarchically clustered organization and the neuron network shows small-world properties. Now the two factors will be considered in our model and the dynamical behavior of the model will be studied. We study the characters of the model and find that the distribution of avalanche size of the model follows power-law behavior.     

Effects of Interactive Function Forms in a Self-Organized Critical Model Based on Neural Networks

Based on the standard self-organizing map neural network model and an integrate-and-fire mechanism, we introduce a kind of coupled map lattice system to investigate scale-invariance behavior in the activity of model neural populations. We let the parameter β, which together with α represents the interactive strength between neurons, have different function forms, and we find the function forms and their parameters are very important to our model‘s avalanche dynamical behaviors, especially to the emergence of different avalanche behaviors in different areas of our system.