ZAP! Introducing the Zero-bias Avalanche Photodiode

A novel heterostructure p-n junction diode is described which provides a photocurrent gain of 2 under zero external bias conditions. The necessary energy required to produce the additional electron-hole pair would be supplied by the internal electric field associated with the heterojunction energy gap difference. The ZAP diode structure has energy conversion applications as a photovoltaic detector whose efficiency may be enhanced by as much as 25% over that obtainable using homojunction solar cells. The device has, however, yet to be built.     

硅基雪崩光电二极管技术及应用

硅基雪崩光电二极管是一种可用于对微弱光甚至单光子进行探测的光电器件,被广泛应用于激光测距、激光成像、量子通信和生物医疗等领域.从工作原理、常见结构和分类3个方面对硅基雪崩光电二极管的技术进行分析,并对其性能发展趋势进行阐述,最后介绍了硅基雪崩光电二极管的应用.     

中红外波段雪崩光子探测器研究进展

近年来,中红外雪崩光电二极管(APD)阵列,以其高增益、高灵敏度和高速探测的优点,成为光纤通信、三维激光雷达成像、天文物理以及大气观测等应用的重要器件.本文具体介绍了中红外雪崩光电探测器的结构和探测原理,对其结构参数相关的性能以及优缺点进行了详细介绍,并展望其发展前景,同时介绍了一些中波红外雪崩光子探测器研究和应用进展.     

Low Dark Count Rate and High Single-Photon Detection Efficiency Avalanche Photodiode in Geiger-Mode Operation

An In_0.53Ga_0.47As-InP avalanche photodiode with very low dark current (0.15 pA at 95% breakdown voltage, 200 K) has been characterized in gated mode for single-photon detection. The temperature dependence of dark current and dark count yields activation energy of ~0.4 eV from 240 K to 297 K. High single-photon detection efficiency (SPDE) at telecom wavelengths with very low dark count rate (DCR) (e.g., DCR =12 kHz at SPDE =45% at 1.31 mum and 200 K) was achieved     

A Theoretical Model for the HgCdTe Electron Avalanche Photodiode

A ballistic model is presented for electron avalanche multiplication in the conduction band of HgCdTe, based upon the concept of an optical phonon limited mean free path for the electron, λ _e. The model predicts avalanche gain as a function of applied bias voltage V, and a threshold voltage for impact ionization V _th. Impact ionization probabilities are calculated analytically using a simplified band structure model for HgCdTe and used to estimate values for the threshold energy for impact ionization. A simple ballistic model is developed to correlate the relationship between electron energy and applied bias voltage, based upon the relevant electron scattering mechanisms in HgCdTe. A comparison with published gain–voltage data suggests that the process is limited by optical phonon scattering, and the relationship between electron energy and applied bias voltage, for a uniform electric field F = V/W, across a diode depletion width W, is given by E = α(E)V, where α(E) = [λ _e(E)/W]. For high electron energies λ _e(E) is independent of E and α(E) depends only on the dielectric parameters of the material. Using this simple model it is easy to predict electron avalanche gain versus voltage for any parametric combination of diode geometry, bandgap, and operating temperature.     

日盲单光子紫外探测器的发展

对于诸如高超音速飞行器的早期探测和预警、以及在日盲紫外波段的应用等非常微弱信号的探测来说,可以光子计数的单光子探测器特别令人感兴趣.雪崩光电二极管( APD)具有高速度、高灵敏度和光学增益大等优点.AlGaN合金易于通过改变摩尔组分来选择截止波长.对于在日盲波段实现单光子灵敏度而言,AlGaN APD是最有希望的半导体器件技术.通过对近年来的国内外相关文献资料的归纳分析,介绍了日盲AlGaN探测器的概念,比较了高超音速飞行器的红外与日盲紫外辐射特征,介绍了基于盖革模式与线性模式APD的日盲紫外单光子探测器的发展动态.     

雪崩光电二极管芯片自动测试系统

利用Keithley 2400源表、AV6381可编程光衰减器、AV 38124 1 550 nm单模半导体激光器和TZ-608B型光电屏蔽探针台搭建雪崩光电二极管芯片自动测试系统.在Labview环境下开发了自动测试软件,通过软件控制测量仪表,实现了雪崩光电二极管芯片的击穿电压、暗电流、穿通电压及10倍增益工作点电压的自动测试及合格判定.探针台可以根据测量系统反馈的判定结果对不合格芯片进行NG标记,方便划片后对不合格芯片进行筛选和剔除.建立的自动测试系统准确性高,测试速度快,软件操作方便,显示结果直观.同时可以实现测试参数的自动存储,方便进行统计过程控制(SPC)分析.     

Performance and Modeling of the MWIR HgCdTe Electron Avalanche Photodiode

The operation of the mid-wave infrared (MWIR) HgCdTe cylindrical electron injection avalanche photodiode (e-APD) is described. The measured gain and excess noise factor are related to the collection region fill factor. A two-dimensional diffusion model calculates the time-dependent response and steady-state pixel point spread function for cylindrical diodes, and predicts bandwidths near 1 GHz for small geometries. A 2 μm diameter spot scan system was developed for point spread function and crosstalk measurements at 80 K. An electron diffusion length of 13.4 μm was extracted from spot scan data. Bandwidth data are shown that indicate bandwidths in excess of 300 MHz for small unit cells geometries. Dark current data, at high gain levels, indicate an effective gain normalized dark density count as low as 1000 counts/μs/cm² at an APD gain of 444. A junction doping profile was determined from capacitance–voltage data. Spectral response data shows a gain-independent characteristic.     

InGaAs/InAlAs雪崩光电二极管仿真设计

设计了一种InGaAs/InALAs雪崩光电二极管(APD),并利用MEDICI软件进行了模拟仿真.器件采用背入射探测方式.雪崩增益区采用埋层设汁,省略了保护环等结构;并使用双层掺杂,有效降低了增益区电场的梯度变化.由于结构简单,因此仪需要利用分子束外延(MBE)生长精确控制每层结构即可.由于InAlAs材料的空穴与电子的离化率有较大的筹异,因此器件具有较低的噪声因子.     

盖革模式雪崩光电二极管的主动淬灭电路研究

紫外光通信作为新型通信方式,在短距离通信领域具有潜在的应用前景.紫外光通信的探测电路可分为线性模式和盖革模式,盖革模式探测电路在系统带宽和探测灵敏度等方面具有显著优点.本文研究了基于盖革模式雪崩光电二极管(Avalanche Photodiode,APD)的单光子探测电路,实现对微弱紫外光信号的探测.采用主动淬灭快恢复电路,通过淬灭信号和恢复信号控制APD阳极电位,从而减小死时间,提高系统的计数上限.实验发现,对于主动淬灭电路而言,当死时间过小时,淬灭时间和恢复时间除了受到淬灭信号和恢复信号控制外,还会受到电路中电容充放电时间的影响.本文从理论和实验两方面研究了电路中电容和电阻对死时间的影响,为进一步缩短死时间提供了理论指导.     

一种雪崩光电二极管自耦型偏压电源升压电路

设计采用自耦变换方法设计了一种适用于低电压的小型低功耗偏压电路,实现了5 V至100~600 V的变换,降低了对升压器件的耐压要求,简化了电路结构,也减小了探测电路体积和功耗,使得相关探测一类的应用得以小型化。     

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。     

Equivalent Circuit Modeling of Separate Absorption Grading Charge Multiplication Avalanche Photodiode

In this paper, a novel equivalent circuit model for the frequency performance of separate absorption grading charge multiplication (SAGCM) avalanche photodiode (APD) is developed. This model includes effects of carrier transit time, avalanche buildup time, and parasitic RC elements. Based on the equivalent circuit model, frequency and bandwidth characteristics of SAGCM APD can be simulated in advance to device fabrication, and the simulation results are in good agreement with experimental data. Conventional pin photodiodes can also be simulated as a special case when M=1. In addition, the frequency response of SAGCM APDs and pin photodiodes with different illumination directions are investigated.     

Evaluation of a Junction Termination Extension Avalanche Photodiode for X-Ray Detection

An avalanche photodiode (APD) with a ring structure around the active area was built. The junction termination extension (JTE) APD has three diffused rings around the main junction to reduce the electric field at the surface. This design has the advantage that it does not need a sharp bevel edge or grooves to avoid early breakdown at the surface. The JTE rings can be obtained by a well-controlled ion-implantation through a single mask. The process uses standard planar technology for silicon devices. Several APDs with 2-mm diameter active area have been built by implantation of boron with a dose of 2, 3, 4, and 5 x 10¹² cm^-2, followed by deep diffusion to 14 mum. The dark current is strongly dependent on the implantation charge, decreasing with decreasing charge. For the APDs with an implanted dose of 5 x 10¹² cm^-2, a gain of 8 is obtained at 1120 V, indicating that the devices have premature breakdown. The energy resolution from a 109Cd X-ray source (22.16 keV) was measured to be 4.7-keV full-width at half-maximum, which corresponds to 560 rms electrons noise. We have also performed simulations of the gain and breakdown voltage that correlate well with the results up to a gain of 5.     

硅基雪崩光电探测器倍增层掺杂的研究

硅基雪崩光电探测器的器件性能与倍增层的掺杂浓度有着密切联系。研究了硅基雪崩光电探测器倍增层的掺杂浓度对雪崩击穿电压和光谱响应度等特性的影响。在硼的注入剂量由5.0×1012 cm-2减小为2.5×1012cm-2时,倍增层内电场强度逐渐降低,吸收区电场强度迅速增大,器件的雪崩击穿电压由16.3V迅速上升到203V,而光谱响应在95%的击穿电压下,峰值响应波长由480nm红移至800nm,对应的响应度由11.2A/W剧增到372.3A/W。综合考虑光谱响应和雪崩击穿电压的影响,在硼注入剂量为3.5×1012 cm-2时,可获得击穿电压为43.5V和响应度为342.5A/W的器件模型,对实际器件的制备具有一定参考价值。     

Analytical Description of Avalanche Photodiode Characteristics. An Overview: Part II

Journal of Communications Technology and Electronics - This paper deals with the second part of the overview on analytical calculations of the characteristics of avalanche photodiodes (APDs) based...     

基于硅雪崩光电二极管的紫外盖革模式电路的研制

本文旨在研制盖革模式电路并在两种紫外光照射下测试电路性能,为紫外通信提供数据参考.研制了适用于硅雪崩光电二极管(APD)的主动、被动两种盖革模式电路,设计并实现了输出可调至300.0 V的高稳定直流高压偏置电源,实测纹波电压小于20.4mV,纹波系数小于6.8×10-5.分别在可见盲和日盲两种紫外光照下,测试了被动盖革模式APD的死时间、暗计数和光子计数,给出了被动盖革模式工作的较佳高压偏置范围;紫外光照下,被动盖革模式APD的电路输出脉冲的死时间为1.0μs.基于被动盖革模式电路测试的参数,研制了主动盖革模式电路,实验结果表明:主动盖革模式电路输出脉冲的死时间为102.0 ns,光子计数的上限由被动盖革模式的1.0 MHz提高到主动盖革模式的9.8 MHz.因此主动盖革模式电路在数据传输时有更高的传输带宽,预计可满足一些图像传输或者视频通信的基本要求.     

Effects of Ionization Velocity and Dead Space on Avalanche Photodiode Bit Error Rate

A model is presented for the bit error rate (BER) contributed by the receiver in an optical telecommunications system that includes the effects of ionizing carrier velocity and dead space in the avalanche photodiode (APD) and of additive circuit noise. The probability distribution functions of bit charge used to calculate BER are not, as is commonly assumed, Gaussian, confirming the need to directly compute the receiver statistics. Integrating the current over the central section of the bit period can minimize intersymbol interference. The assumption that carriers travel to ionization with infinite velocity underestimates BER in InP APDs with short avalanche region widths, and overestimates BER when . Models assuming constant carrier velocity or allowing for velocity enhancement predict distinctly different BER over a wide range of avalanche width and multiplication because of the manner in which the current evolves during the bit period.     

级联倍增InAlAs/InAlGaAs雪崩光电二极管暗电流成分分析

实验制备了级联倍增InAlAs/InAlGaAs雪崩光电二极管,对二极管暗电流随台面直径和温度的变化进行了研究分析。结合暗电流函数模型,利用Matlab软件对暗电流的各成分进行了数值计算,并仿真研究了芯片结构的缺陷浓度Nt和表面复合速率S对暗电流的影响。结果表明,二极管暗电流主要来自于体暗电流,而非表面漏电流。在工作点偏压90V处,受缺陷影响的缺陷辅助隧穿电流Itat在暗电流中占据了主导,并推算出了芯片结构的缺陷浓度Nt约为1019 m-3、吸收区中的缺陷浓度NInGaAs约为7×1015 m-3。由于芯片结构的缺陷主要来源于InAlAs/InAlGaAs倍增区和InGaAs吸收区,而吸收区缺陷占比很少,因此认为缺陷主要来自于异质结InAlAs/InAlGaAs倍增区。     

InGaAs/InP盖革模式雪崩光电二极管阵列性能一致性研究

InGaAs/InP盖革模式雪崩光电二极管(APD)阵列的性能与阵列片内均匀性密切相关.阵列面元的主要结构参数有倍增区厚度、电荷层厚度和掺杂浓度、吸收区的厚度以及器件工作的过偏压.它们的不一致性不仅会造成器件本身性能的差异,还为后续的读出电路带来了巨大的挑战.通过研究APD结构参数变化对其击穿电压(Vbreak)、暗计数率(DCR)和单光子探测效率(PDE)的影响,将APD阵列面元间击穿电压波动控制在±1V以内,使暗计数率和光探测效率的波动小于10％,从而得到不同温度下各个结构参数的最大允许波动值,确定了每个温度下制约器件性能的主要因素,为大规模、高性能盖革模式雪崩光电二极管阵列的材料生长和工艺制备提供了理论依据.