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.     

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。     

Zn扩散对InGaAs/InP单光子雪崩光电二极管雪崩击穿概率的影响

对InGaAs/InP单光子雪崩光电二极管进行结构设计与数值仿真,得到相应的电学与光学参数。针对雪崩击穿概率对器件光子探测效率的影响,研究了两次Zn扩散深度差、Zn扩散横向扩散因子、Zn掺杂浓度以及温度参数与器件雪崩击穿概率的关系。研究发现,当深扩散深度为2.3μm固定值时,浅扩散深度存在对应最佳目标值。浅扩散深度越深,相同过偏压条件下倍增区中心雪崩击穿概率越大,电场强度也会随之增加。当两次Zn扩散深度差小于0.6μm时,会发生倍增区外的非理想击穿,导致器件的暗计数增大。Zn扩散横向扩散因子越大,倍增区中心部分雪崩击穿概率越大,而倍增区边缘雪崩击穿概率会越小。在扩散深度不变的情况下,浅扩散Zn掺杂浓度对雪崩击穿概率无明显影响,但深扩散Zn掺杂浓度越高,相同过偏压条件下雪崩击穿概率越小。本文研究可为设计和研制高探测效率、低暗计数InGaAs/InP单光子雪崩光电二极管提供参考。     

同轴电缆反射方案单光子探测器的特性研究

分析了用于消除门控单光子探测器电尖峰噪声的同轴电缆反射方案的特性.重点分析了该方案中,雪崩光电二极管的偏置电压和输出信号的变化特性.根据理论分析的结果,给出了不同的单光子信号与两个门控脉冲的时序关系的确定依据,以及该方案对电尖峰噪声的消除效果,同时给出了探测系统的最小探测周期.并对理论分析的结果进行了实验验证,实验中测得尖峰噪声的抑制比为25.1dB,实验结果与理论分析相符.这些分析结果将有助于红外单光子探测器的设计和性能的优化.     

门控下InGaAs/InP单光子探测器用于符合测量的时域滤波特性研究

基于砷化镓/磷化铟雪崩光电二极管(InGaAs/InP APD)的半导体单光子探测器因工作在通信波段,且具有体积小、成本低、操作方便等优势,在实用化量子通信技术中发挥了重要作用.为尽可能避免暗计数和后脉冲对单光子探测的影响,InGaAs/InP单光子探测器广泛采用门控技术来快速触发和淬灭雪崩效应,有效门宽通常在纳秒量级.本文研究揭示了门控下单光子探测器可测量的最大符合时间宽度受限于门控脉冲的宽度,理论分析与实验结果良好拟合.该研究表明,门控下InGaAs/InP单光子探测器用于双光子符合测量具有显著的时域滤波特性,限制了其在基于双光子时间关联测量的量子信息技术中的应用.     

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。     

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.     

红外波段单光子探测器及其在量子通信领域中的应用

本文简要介绍了红外波段单光子探测器的种类，分析了InGaAs／InP雪崩光电二极管（InGaAs／InPAPD）与超快超导单光子探测器（SSPD）的相关性能，并概述了二者在量子通信中的应用。     

硅雪崩光电二极管单光子探测器

将硅雪崩光电二极管应用于盖革模式下,制作出高量子效率、低噪音、短死时间的单光子探测器.设计并制作了雪崩抑制电路,获得探测器特性参量为无源抑制方式下死时间1μs,有源抑制下60～80ns,输出脉冲宽度15～20ns.并详细检测了探测器直到液氮温度下的特性.观察到一些新现象.     

Strain-Compensated InGaAs/InAlAs Quantum Cascade Detector of 4.5 μm Operating at Room Temperature

We present a strain-compensated InP-based InGaAs/InAlAs photovoltaic quantum cascade detector grown by solid source molecular beam epitaxy. The detector is based on a vertical intersubband transition and electron transfer on a cascade of quantum levels which is designed to provide longitudinal optical phonon extraction stairs. By careful structure design and growth, the whole epilayer has a residual strain toward InP substrate of only -2.8× 10^-4. A clear narrow band detection spectrum centered at 4.5 μm has been observed above room temperature for a device with 200／times 200 ×μm^2 square mesa.     

High-depth-resolution SIMS analysis for InGaAs/InP interfaces

The influence of the primary ion impact conditions and of the surface chemical composition on beam-induced effects is investigated in order to achieve a high-depth-resolution analysis for the InGaAs/InP interfaces. The main result is that the oxygen adsorption with an appropriate pressure on the Cs⁺ bombarded surface can suppress the element-dependence of depth resolution which is an artefact in SIMS analysis.     

Single Photon Detector at Telecom Wavelengths for Quantum Key Distribution

Using InGaAs/InP avalanche photodiodes as sensors and coaxial cables as reflection lines to reject spike signals, we have firstly employed the ＂timing filtering＂ gates to pick out avalanche signals and have realized the single photon detection at 1550nm in the temperature range of thermoelectric cooling. A ratio of the dark count rate to the detection efficiency was obtained to be 9 × 10^-5 at 223K. When the detector is applied to a practical quantum key distribution system, the transmission distance can reach 89.5km and the repetition rate can reach 0.33 MHz.     

InGaAs/InGaAlAs Strain-compensated Multiple-quantum-well Lasers with Improved Temperature Characteristic

It is reported on realization of pulsed operation of InGaAs/InGaAlAs strain-compensated multiple-quantum-well lasers at room temperatures. The working wavelength is 1.56 μm;the threshold current density for the stripe waveguide lasers is less than 1.85 kA/cm2;for the ridge waveguide lasers,the threshold current is 35 mA. The incorporation of compensated strain,which makes the multiple-quantum-well design applicable,leads to an obvious improvement on device temperature characteristic.     

InGaAs/InGaAlAs Strain-compensated Multiple-quantum-well Lasers with Improved Temperature Characteristic

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Dielectrics for passivation of planar InP/InGaAs diodes

We have investigated dielectrics for passivating planar InP or InGaAs photodiodes: thermally evaporated Al₂O₃ and SiO, sputtered Si₃N₄ and SiO₂ and also SiO₂ using chemical vapour deposition. The measured bulk and field-effect properties of all dielectrics excluding sputtered SiO₂ were suitable for this application. In planar InGaAs diodes with Cd diffused or Mg implanted p⁺-region a disordered dielectric/semiconductor surface led to high reverse current densities above 1 mA/cm². In InP diodes with p⁺-diffusion and dielectrics exhibiting positive flatband voltages, e.g. Si₃N₄ and Al₂O₃, reverse current densities of 10 μA/cm² were measured probably caused by a slight inversion of the semiconductor surface. With a SiO or CVD-SiO₂ passivating layer on n-InP lowest leakage current densities (10 nA/cm²) were achieved. Very low dark-current planar photodiodes InP/InGaAsP/InGaAs have been fabricated using SiO passivation (30 nA/cm²).     

Interdiffused InGaAs/InP quantum wells for polarization-independent electroabsorption

The interdiffusion of In0.53Ga0.47As/InP quantum well structures is presented as an approach for achieving polarization-independent electroabsorption. By considering different interdiffusion rates on group III and group V sublattices, the TE and TM absorption coefficient spectra calculated for the interdiffused InGaAs/InP quantum well show that with a suitable interdiffusion process the tensile strain induced in the interdiffused quantum well can provide polarization-independent absorption properties. For the quantum well structure and interdiffusion process considered here polarization-independent electroabsorption can be achieved around 1.3 μm, which is of considerable interest for optical switching and modulating devices. This revised version was published online in November 2006 with corrections to the Cover Date.