InGaAs单光子雪崩焦平面研究进展（特邀）

雪崩光电二极管（APD）是一种高灵敏度光电器件。按照工作电压的不同可分为线性APD和盖革APD。其中,盖革APD的工作电压高于击穿电压,利用半导体材料内部载流子的高雪崩增益可实现单光子级信号探测,也被称为单光子雪崩光电二极管（SPAD）。InGaAs材料SPAD在0.9~1.7 μm光谱范围内有高量子效率,是1.06、1.55 μm主动激光探测的理想探测器。通过将高效率InGaAs SPAD阵列芯片与CMOS计时/计数读出电路芯片集成封装,制备的雪崩焦平面探测器可对光子信号进行时间量化,在三维激光雷达、远距离激光通信、稀疏光子探测等领域有广泛应用。介绍了InGaAs单光子雪崩焦平面的器件结构及基本原理,在此基础上回顾了国内外雪崩焦平面技术的研究进展,并对未来发展方向进行了展望。     

基于APD阵列的单光子计数成像研究

简要介绍了雪崩光电二极管(APD)阵列光子计数成像原理,建立了基于泊松点过程的APD阵列的单光子响应模型.将由光子数、像素点相关组成的目标图形作为激励源加入到APD阵列的单光子响应模型中去,采用蒙特卡洛仿真方法得到多次门控信号下的目标图像.仿真结果与相同照度下的微光图像的比较证明,采用APD阵列进行光子计数被动成像具有灵敏度高、响应速度快的特点,可以广泛地应用到多个科研领域.但是由于器件恢复时间的限制,该项技术目前还只能应用于主动成像和极微弱光照度条件下的被动成像.     

基于MAX5026的单光子探测器直流偏压源设计

讨论了单光子探测器核心器件雪崩光电二极管(Avalanche Photodiodes,APD)的特殊工作原理,并在此基础上介绍了使用PWM升压变换器MAX5026设计出的一种APD直流偏压源方法。阐述了电路的主要设计要点,对电路性能进行了分析说明。实验结果表明:这种小功率直流偏压源电路工作性能良好,具有高稳定性和低纹波输出,能满足单光子探测时APD雪崩击穿对电源电压的要求,是一种理想APD直流偏压源。     

平面型APD抑制边缘击穿的方法研究

雪崩光电二极管(APD)作为一种具有内部增益的光电探测器,被广泛地应用于光纤通信领域,其中平面型APD具有暗电流低、可靠性高等优点而被大量研究。但是平面型APD边缘处由于高电场易被提前击穿,影响器件性能。文章对抑制平面型APD边缘击穿的不同方法进行了综述,指出它们的结构差别,并重点介绍保护环法的原理及保护环各个参数的优化。     

155μm InGaAs APD单光子探测中的小脉冲现象

对InGaAs/InP雪崩光电二极管(APD)在探测单光子过程中出现的小脉冲现象进行了研究,分析了小脉冲的产生原因,并讨论了其对光子计数及时间精度的影响。同时在准单光子条件下进行了试验,并在此基础上提出了改进方案。APD最大输出脉冲峰值约200mV,最大脉宽为30～40ns时,鉴幅电平取其峰值的1/e,同步符合门宽取最大脉宽的2/e,将获得较好的结果。     

雪崩光电二极管特性与测量

本文首先介绍了雪崩光电二极管的应用特性及工作原理,随后在不同通信速率及不同偏压条件下对APD的灵敏度进行了即时测量,对光通信领域的接收性能提升提供了较好的理论指导及技术支持。     

APD阵列探测器在自由空间光通信上的应用研究

自由空间光通信(free space optical communication,FSO)技术是通信前沿技术之一,雪崩光电二极管(avalanche photodiode,APD)阵列探测器以其高灵敏度、高带宽、低噪声的优势应用于FSO系统,成为国内外研究热点。本文分析了FSO对APD阵列探测器的性能需求,回顾了国内外近年来用于无线光通信的APD阵列的研究现状,其中重点介绍了美国林肯实验室以及海军实验室的研究成果,最后对APD阵列探测器在FSO应用的发展方向进行了预测与总结。     

GHz重复频率可调InGaAs/InP单光子探测器

InGaAs/InP雪崩光电二极管（avalanche photodiode APD）可实现近红外波段的单光子检测,具有集成度高功耗低等优势,被广泛应用于量子信息科学、激光测绘、深空通信等领域。通常,为了减小误计数,InGaAs/InP APD工作在门控盖革模式,其门控信号的重复频率直接决定了探测器的工作速率。基于此,采用低通滤波方案,结合集成了GHz正弦门控信号产生、雪崩信号采集、温度控制、偏置电压调节等功能的处理电路,搭建了GHz重复频率可调的高性能InGaAs/InP单光子探测器。GHz门控信号重复频率升高到2 GHz,其相位噪声仍优于-70 dBc/Hz@10 kHz,且尖峰噪声被抑制到热噪声水平,当探测效率为10%时,暗计数仅为2.4×10^-6/门。此外,还验证了该方案下探测器的长时间稳定性,测试了工作速率、偏置电压等对APD关键性能参数的影响,为GHz InGaAs/InP APD的进一步集成及推广奠定基础。     

用于单光子探测的APD的低温特性

采用半导体致冷技术,对雪崩光电二极管(APD)快速降温,最低温度可达到-35℃,并对其低温特性进行了测试.结果表明:APD在低温下工作其雪崩电压下降,暗电流噪声降低,解决了量子密码通信中的红外单光子探测的一个关键技术点.     

平面型InGaAs/InP APD边缘提前击穿行为的抑制

平面型雪崩光电二极管(APD)在结弯曲处具有高的电场,导致在结边缘的提前击穿.运用FEMLAB软件对不同工艺流程制备的三种不同结构平面型InP/InGaAs APD的电场分布进行了二维有限元模拟,在表面电荷密度为5×1011cm-2时分析了吸收层厚度、保护环掺杂浓度、保护环和中央结纵向及横向间距等因素对边缘提前击穿特性的抑制程度.比较了这三种结构的InP/InGaAs APD在边缘提前击穿的抑制特性的优劣.通过理论研究对平面InP/InGaAs APD进行了优化.     

碲镉汞光子计数型线性雪崩探测器(特邀)

单光子计数技术在弱信号探测和时间测距中具有重大的应用前景。自从20世纪70年代可见光的光子计数系统研发以来,国际上该领域内的研发小组在不断地发展完善光子计数技术,充分放大光子信号,以降低电子设备的读出噪声。电子倍增电荷耦合器件(Electron Multiplying Charge Coupled Devices, EMCCDs)具有更高的量子效率,可替代传统的可见光光子计数系统,但较大的雪崩噪声阻碍了倍增下入射光子数的准确获取。碲镉汞线性雪崩器件(HgCdTe APD)的过剩噪声因子接近1,几乎无过剩噪声;相对于盖革模式的雪崩器件,没有死时间和后脉冲,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,在天文探测、激光雷达、自由空间通信等应用中具有重要价值。美国雷神(Raytheon)公司和DRS技术公司、法国CEA/LETI实验室和Lynred公司、英国Leonardo公司先后实现了碲镉汞线性雪崩探测器的单光子计数。文中总结了欧美国家在碲镉汞光子计数型线性雪崩探测器研究方面的技术路线和研究现状,分析了吸收倍增...     

Issues in HgCdTe Research and Expected Progress in Infrared Detector Fabrication

The purpose of this paper is to review the trends in HgCdTe research, illustrating the discussed ideas with the latest results obtained at DEFIR (CEA-LETI and Sofradir joint laboratory). The beginning of this paper is devoted to an extended introduction to today’s issues concerning HgCdTe photodiode performance enhancement. In fact, very high-quality material is mandatory for ultrahigh performance at low temperature as well as for high noise operability at high operating temperature (HOT). Therefore, a strong effort has been carried out during the last few years for lattice-matched CdZnTe substrate and HgCdTe active layer growth improvement, leading to very large substrates and ultraflat liquid-phase epitaxy layers. The same analysis holds for diode process quality and passivation. Therefore, the photodiode process has been completely revisited in order to optimize HOT operability. Also necessary for the next generation of HOT devices, some significant progress has been made in small-pixel-pitch interconnection on silicon read-out circuits. Indeed, the first 10-μm focal-plane arrays (FPAs) have been successfully fabricated this year in the mid-wave infrared (IR) band. The latest avalanche photodiode (APD) realizations are also presented with 15-μm-pitch FPAs for passive imaging and 30-μm-pitch ultrafast arrays running at 1.5 kHz full frame rate. Linear-mode photon counting using APDs is also briefly discussed. Finally, the paper concludes on more complex structures for the third generation of IR detectors, discussing the latest achievements in dual-band FPA fabrication in various spectral bands.     

Physics and Limitations of HgCdTe APDs: A Review

Avalanche photodiodes (APDs) made in HgCdTe have been developed for a large number of applications over the last 15 years. The developments have been motivated by exceptional gain characteristics that enables the detection of a low number of photons with close to negligible loss of information over observation times ranging from sub nanoseconds up to milliseconds. In this communication, we review the present understanding of the physics that governs the gain, noise, and response time characteristics of HgCdTe APDs. Recent data resulting from impulse response measurements are also reported that demonstrate a fast 4 GHz bandwidth response at 80 K and show the capacity to obtain bandwidths in excess of 10 GHz in such detectors.     

HgCdTe多层异质结红外探测材料与器件研究进展

HgCdTe多层异质结技术是未来主流红外探测器发展的重要技术方向,在高工作温度、双/多色和雪崩光电管等高性能红外探测器中扮演着重要的角色。近年来基于多层异质结构的HgCdTe高工作温度红外探测器得到了快速发展,尤其是以势垒阻挡型和非平衡工作P+-π(ν)-N+结构为主的器件受到了广泛的研究。本文系统介绍了势垒阻挡型和非平衡工作P+-π(ν)-N+结构HgCdTe红外探测器的暗电流抑制机理,分析了制约两种器件结构发展的关键问题,并对国内外的研究进展进行了综述。对多层异质结构HgCdTe红外探测器的发展进行了总结与展望。     

Photon counting with silicon avalanche photodiodes

Avalanche photodiodes (APDs) are studied for use as photon-counting detectors. The APD may be biased slightly above (Geiger mode) or slightly below its voltage breakdown point. In the latter case, if the photon absorption rate is low enough, each individual photoelectron current pulse may be resolved with the use of a discriminator. APDs used in this photon-counting mode are shown to give the best performance at low light levels. Experimentally, overall photon detection probabilities of 5.0 and 0.33% were obtained at λ=820 nm and λ=1.064 μm, respectively, with a photon counter dead time as low as 15 ns and a dark current counting rate of 7000/s. The APD photon counter exhibited an exponential photon interarrival time probability density and a near-Poissonian photon-counting probability     

Short-Wave Infrared HgCdTe Avalanche Photodiodes

Short-wave infrared (SWIR) HgCdTe avalanche photodiodes (APDs) have been developed to address low-flux applications at low operating temperature and for laser detection at higher temperatures. Stable multiplication gains in excess of 200 have been observed in homojunction APDs with cutoff wavelengths down to 2.8???m and operating temperatures up to 300?K, associated with low excess noise F?<?1.3 and low 1/f noise. The measured dark current density at 200?K of 6.2???A/cm² is low enough to enable high-sensitivity single-element light detection and ranging (lidar) applications and time-of-flight imaging. Corresponding APD arrays have been hybridized on a readout integrated circuit (ROIC) designed for low-flux low-SNR imaging with low noise and frame rates higher than 1500?frames/s. Preliminary focal-plane array characterization has confirmed the nominal ROIC performance and showed pixel operability above 99.5% (pixels within ±50% of average gain). The bias dependence of the multiplication gain has been characterized as a function of temperature, cadmium composition, and junction geometry. A qualitative change in the bias dependence of the gain compared with mid-wave infrared (MWIR) HgCdTe has motivated the development of a modified local electric field model for the electron impaction ionization coefficient and multiplication gain. This model gives a close fit to the gain curves in both SWIR and MWIR APDs at temperatures between 80?K and 300?K, using two parameters that scale as a function of the energy gap and temperature. This property opens the path to quantitative predictive device simulations and to estimations of the junction geometry of APDs from the bias dependence of the gain.     

Fully Integrated Single Photon Avalanche Diode Detector in Standard CMOS 0.18- $mu$m Technology

Avalanche photodiodes (APDs) operating in Geiger mode can detect weak optical signals at high speed. The implementation of APD systems in a CMOS technology makes it possible to integrate the photodetector and its peripheral circuits on the same chip. In this paper, we have fabricated APDs of different sizes and their driving circuits in a commercial 0.18-mum CMOS technology. The APDs are theoretically analyzed, measured, and the results are interpreted. Excellent breakdown performance is measured for the 10 and 20 m APDs at 10.2 V. The APD system is compared to the previous implementations in standard CMOS. Our APD has a 5.5% peak probability of detection of a photon at an excess bias of 2 V, and a 30 ns dead time, which is better than the previously reported results.     

History-Dependent Impact Ionization Theory Applied to HgCdTe e-APDs

The variation of the gain and the excess noise factor in HgCdTe avalanche photodiodes (APDs) with different junction geometries are compared with published theoretical and numerical work. It is shown that, although some features of the gain curves are reproduced, such as the constant exponential increase in the gain, the theoretical work fails to predict the observed variation of the gain as a function of multiplication layer width. In contrast, a new analytical gain model based on local impact ionization coefficients and a first direct comparison of the prediction of history-dependent impact ionization theory are shown to give a good general fit to the experimental gain data. A generic model of the gain in HgCdTe APDs has been obtained by fitting the analytical local model to gain curves of APDs with various geometries and cut-off wavelengths. The study of different hypotheses on the electric field dependence of the dead-space length and the saturation value of the impact ionization coefficient has shown that a variable dead-space effect has a direct impact on the excess noise of APDs, which is why exact excess noise measurements are necessary to achieve a pertinent estimation of the nonlocal impact ionization function.     

MBE生长的PIN结构碲镉汞红外雪崩光电二极管

对中波红外碲镉汞雪崩光电二极管(APD)特性进行理论计算,获得材料的能量散射因子及电离阈值能级与材料特性的相互关系,从而计算器件的理论雪崩增益与击穿电压.通过对材料特性(组分,外延厚度,掺杂浓度等)的优化,设计并生长了适合制备PIN结构红外雪崩光电二极管的碲镉汞材料,并进行了器件验证.结果显示,在10V反偏电压下,该器件电流增益可达335.     

碲镉汞线性雪崩焦平面器件评价及其应用(特邀)

碲镉汞线性雪崩焦平面探测器具有高增益、高带宽及低过剩噪声等特点,在航空航天、天文观测、军事装备及地质勘探等领域展现了巨大的应用潜力。目前,国内已经开展了碲镉汞线性雪崩焦平面器件的研制工作,但缺乏评价其性能的方法及标准,同时对其的应用仍然处于探索阶段。首先分析了表征线性雪崩焦平面器件性能的关键参数,同时基于碲镉汞线性雪崩焦平面器件的特点,探讨了雪崩焦平面器件在主/被动红外成像、快速红外成像等领域的应用,最后对碲镉汞雪崩焦平面器件的未来发展进行了展望。