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。     

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。     

雪崩光电二极管的雪崩发光串扰研究

在使用时间关联单光子计数的量子保密通信、量子密码术等量子光学领域中,雪崩光电二极管(APD)拥有广泛的应用。然而在其工作过程中,吸收层接收到光子形成载流子,载流子个数在倍增层进行指数型增益,每个载流子通过P-N结结点均有一定概率发出光子,发出的光子在一定条件下会串扰进入另一个雪崩二极管。在盖革模式下进行单光子探测时,这种串扰光子会严重影响时间关联单光子计数的实验结果。研究了APD雪崩原理,实验中做出了串扰峰对比度比较高的现象,分析了影响串扰峰间距和形状的因素,提出通过光隔离规避串扰现象,并通过实验验证了这种避免串扰方法的可行性。     

基于雪崩光电二极管的弱光探测技术研究

通过采用无源抑制方法对雪崩光电二极管的弱光探测技术进行了研究,分析了工作在盖革模式下的InGaAs APD的特性。利用APD两端的偏置电压VB在其雪崩后趋于稳定的特性,确定了其雪崩暗击穿电压,并且在水冷温控系统中,测得了APD雪崩暗击穿电压与温度的关系。结果表明,APD的雪崩暗击穿电压随着温度的上升而增大,光子群(弱光)到达时,APD探测到的在某一幅值处的脉冲数明显增加,其脉冲幅度也将增大。     

红外InGaAs/InP单光子探测器的温度特性研究

分析了SAGM-APD单光子探测器暗电流产生的机理;得出工作温度和偏置电压是影响SAGM InGaAs/InP单光子探测器探测性能的重要因素.通过实验,分析了三种APD在不同温度下暗电流、光电流与偏置电压的关系曲线,得出一些结论.     

一种基于雪崩二极管电容特性提取通讯波段单光子信号的方法

InGaAs/InP雪崩二极管(APD)可用于探测光通讯波段的单光子.APD工作于门模盖革模式时,单个光子引起的雪崩电流信号通常淹没在电容瞬时充放电脉冲中,光电流信号提取困难.本文通过调整实验参数和APD的寄生电容,使雪崩信号与放电脉冲在时域上有效叠加,并由高速比较器将光电流信号直接甄别出来.本文设计的基于InGaAs/InP APD的单光子探测系统,运行稳定,方法简单可靠,说明这种利用APD的电容特性提取单光子信号是一种有效的方法.     

基于1.5GHz多次谐波超短脉冲门控InGaAs/InP雪崩光电二极管的近红外单光子探测技术研究

提出了一种高速门控盖格模式的铟镓砷/铟磷雪崩光电二极管(InGaAs/InP APD)单光子探测技术。将1.5GHz多次谐波超短脉冲加载到InGaAs/InP APD上,盖革模式下的光生雪崩信号埋藏在短脉冲充放电形成的噪声中,采用700MHz低通滤波器实现了50.6dB的噪声抑制比,有效地提取出了雪崩信号。通过半导体制冷,使InGaAs/InP APD工作在-30℃,1.5GHz短脉冲驱动下的InGaAs/InP APD在1550nm的探测效率为35%,暗计数率为每门6.4×10-5,超过了单纯使用1.5GHz正弦门的探测性能,而且在15%的探测效率下,2.7ns后发生后脉冲的概率仅为每门6.0×10-5。     

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。     

基于双模式探测器的大动态范围激光测距EI北大核心CSCD

开发了一种基于双模式探测的大动态范围激光测距方法.使用基于硅雪崩光电二极管（APD）的单个探测器在线性模式与盖革模式之间切换,实现了平均光子数为1~105的大动态强度范围光信号探测.在此基础上,进行了30m的室内线性探测模式测距和500m的室外盖革探测模式测距实验,利用时间相关单光子计数设备记录的信号详细分析了两种模式测距的时间特性,证明了这种方法可以根据探测距离和背景环境进行探测模式切换,从而实现大动态范围激光测距.并且进一步分析了APD偏置电压的调节对测距系统测量精度以及探测背景噪声的影响.     

基于双模式探测器的大动态范围激光测距

开发了一种基于双模式探测的大动态范围激光测距方法.使用基于硅雪崩光电二极管(APD)的单个探测器在线性模式与盖革模式之间切换,实现了平均光子数为1~105的大动态强度范围光信号探测.在此基础上,进行了30m的室内线性探测模式测距和500m的室外盖革探测模式测距实验,利用时间相关单光子计数设备记录的信号详细分析了两种模式测距的时间特性,证明了这种方法可以根据探测距离和背景环境进行探测模式切换,从而实现大动态范围激光测距.并且进一步分析了APD偏置电压的调节对测距系统测量精度以及探测背景噪声的影响.     

Estimation of the parameters of charge carriers in polymers in the vicinity of the threshold of thermally stimulated switching

The temperature dependences of the parameters of charge carriers in thin films of an electroactive poly(diphenylenephthalide) polymer are investigated in the range preceding the thermally stimulated electronic switching (110–400 K). The thermally stimulated current spectra and current-voltage characteristics are measured in the same temperature range. The parameters of charge carriers are estimated in the framework of the model of injection currents limited by the space charge. It is revealed that the charge carrier mobility decreases with an increase in the temperature in the range from 110 to 400 K. A correlation between the temperature behavior of the current-voltage characteristics and the thermally stimulated current spectra is established. The possible contribution of the Pool-Frenkel effect is considered, and the inference is made that the electric field plays an important role in the thermally stimulated electronic switching.     

Temperature dependence of dark current-voltage characteristics of <Emphasis Type="Italic">n</Emphasis>InSb-<Emphasis Type="Italic">n</Emphasis>PbTe-<Emphasis Type="Italic">n</Emphasis>CdTe isotype structure

The temperature dependence of dark current-voltage characteristics of an nInSb-nPbTe-nCdTe structure is investigated. It is shown that in the temperature range from 115 K to 125 K an energy barrier exists for charge carriers through the InSb layer, which is strictly connected with different temperature dependences of electron concentrations in nInSb and nPbTe.     

Characteristics of p-ZnO/n-GaN heterojunction photodetector

Thin film heterojuction of the type p-ZnO/n-GaN was prepared by spray pyrolysis and electron beam evaporation technique, respectively. Hall measurements demonstrate the firm p-type conductivity of the p-doped ZnO film. The structural and electrical properties of the p-ZnO/n-GaN heterojunction are investigated by X-ray diffraction (XRD) and current-voltage (I-V) measurements. The XRD shows that the p-ZnO/n-GaN heterojunction is highly crystalline in nature with preferred orientation along the [0001] direction. The current-voltage curve of the heterojunction demonstrates obvious rectifying diode behavior in the dark and under illumination conditions. The ideality factor of the detector was determined in case of forward bias at low voltages and it was found to be 13.35. The turn-on voltage appears at about 1V under forward-biased voltage, and the reverse breakdown voltage is about 4V. It was found that the current of the illumination increases with the increase of bias voltages.     

Conductivity and current-voltage characteristics of PZT thin-film heterostructures

The conductivity of thin-film Pt/PZT/Pt structures has been studied using the method of current-voltage characteristics. The asymmetry of current-voltage characteristics has been revealed, which indicates that the potential barriers at the interfaces between the studied structures are different, and this asymmetry changes depending on the conditions of synthesis. It has been found that the current-voltage curve on semilogarithmic scales has several linear regions, which gives evidence that several mechanisms determine the conductivity of this structure. Two main conductivity mechanisms have been determined: ohmic mechanism and Frenkel-Poole emission. The conductivity of these structures increases with an increase in temperature, but the shape of the current-voltage characteristics remains unchanged.     

Current-voltage characteristics simulation and analysis of 4H-SiC metal-semiconductor-metal ultraviolet photodetectors

The current-voltage (I-V) characteristics of 4H-SiC metal-semiconductor-metal (MSM) ultraviolet pho-todetector with different finger widths and spacings, different carrier concentrations and thicknesses of n-type epitaxial layer are simulated. The simulation results indicate that the dark current and the pho-tocurrent both increase when the finger width increases. But the effect of finger width on the dark current is more significant. On the other hand, the effect of finger spacing on the photocurrent is more significant. When the finger spacing increases, the photocurrent decreases and the dark current is almost changeless. In addition, it is found that the smaller the carrier concentration of n-type epitaxial layer is, the smaller the dark current and the larger the photocurrent wiU be. It is also found that I-V characteristics of MSM detector also depend on the epitaxial layer thickness. The dark current of detector is smaller and the photocurrent is larger when the epitaxial layer thickness is about 3 μm.     

磁场对聚合物光电池中电流的影响

制备了结构为 ITO/PEDOT:PSS/P3HT:PCBM/Ca/Al的聚合物光电池器件,并在不同偏压下,分别测量了器件的光电流和暗电流随外加磁场的变化. 发现随外加磁场增加,光电流增强,暗电流减弱. 从聚合物光电池中光电流和暗电流的产生机制出发,对该现象进行了解释,认为外加磁场可以有效改变单重态极化子对和三重态极化子对之间的相对比例,进而使自由载流子浓度增加. 光生自由载流子浓度增加是光生电流增强的原因,而自由载流子与三重态激子的相互作用导致了暗电流减弱. 开路电压附近,光电流随磁场增加而增强可以近似 关键词： 聚合物光电池 磁场效应 光生电流 极化子对     

MSM结构Mg0.2Zn0.8O可见盲光电探测器

采用射频磁控溅射,通过传统的紫外曝光和湿法腐蚀的方法,制备了不同电极间距的金属-半导体-金属(MSM)结构Mg0.2Zn0.8O可见盲光电探测器.研究了器件的暗电流和响应度随电极间距的变化关系,当施加的电压没有达到贯穿电压的时候,暗电流和响应度均随着电极间距的增加而减小,并对其具体的机制进行了研究.     

Anomalies in the electrophysical, thermal, and elastic properties of layered ferroelectric semiconductor TlGaSe2: Instability in the electronic subsystem

The temperature dependences of the permittivity, dark current, and current-voltage characteristics of the layered ferroelectric semiconductor TlGaSe₂ were measured over the range 77–300 K. The ε(T) curve measured perpendicular to the layers at low frequencies is discovered for the first time to exhibit an anomalous dip with clearly defined boundaries at ～150 and ～200 K. Electrical instability in the form of low-frequency oscillations of current in current-voltage characteristics of a sample in the same temperature range are also observed experimentally for the first time. It is shown that this instability occurs only if an electric field is applied to a sample using potential-controlling contactless electrodes in the form of thin mica spacer layers. The nature of the instability and its influence on various physical properties of the layered TlGaSe₂ crystal are discussed.     

红外InGaAs/InP单光子探测器暗计数的研究

在开发探测器灵敏度极限实现单光子探测时,暗计数是影响探测效率的主要原因.本文分析了在红外波段采用InGaAs/InP雪崩光电二极管工作于雪崩击穿电压之上(盖革模式),进行单光子探测时暗计数的三个主要来源,指出隧穿效应对暗计数的贡献是很小的,并且针对热噪声和后脉冲分析了减小暗计数的有效方法.