Short-wavelength infrared array avalanche photodetectors on the basis of InGaAs heteroepitaxial structures

SWIR ADP 320 × 256 FPAs based on p–i–n photodiodes in InGaAs heterostructures have been developed and investigated. The typical InGaAs/InP PIN heterostructures are formed by Metal Organic Vapor Phase Epitaxy (MOVPE) on n⁺ type InP substrates. The InGaAs/InP PIN photodiodes performance have been estimated by measuring current-voltage characteristics. APD arrays are designed using a mesa-passivated avalanche photodiode device array of p–i–n junctions in heterostructure with common absorption and multiplication regions. The optimal operating point for managing avalanche application depended on various factors has been started at 15 V bias and the multiplication coefficient was of 2–4.     

Performance dependence of InGaAs MSM photodetectors on barrier-enhancement layer structures

The advantage of the graded superlattice layer over the abrupt junction is demonstrated for the continuous wave (CW) and pulse responses of InGaAs metal-semiconductor-metal photodetectors (MSM PDs). The measured pulsewidth of 44 ps for the 0.75 mu m MSM PD with the graded superlattice layer when corrected for the measurement system bandwidth implies an impulse response of 22 ps.<>     

High-speed InGaAs on Si metal-semiconductor-metal photodetectors

High-speed long-wavelength metal-semiconductor-metal (MSM) photodetectors were fabricated on the Fe-doped InP/GaAs material system on Si. The detector layers were grown by MOCVD on exactly oriented Si(001) patterned with submicrometre pitch V-grooves. The devices show a fast impulse response (44 ps FWHM, 83 ps fall time) and a large bandwidth of 3.4 GHz for illumination with 1.31 μm light pulses at 5 V bias     

Integrated dielectric wavelength filters on InGaAs PIN photodetectors

There is an increasing desire to employ wavelength division multiplexing (WDM) techniques in optical communication systems to increase the useable capacity of optical fibre links. WDM transmitters usually consist of several narrow linewidth lasers, with their operating wavelengths suitably spaced. WDM demultiplexers or receivers employ either discrete gratings or discrete transmission filters to separate the various wavelengths. The disadvantage of such demultiplexers is that precise mechanical alignment of the many components is required. Together with the high cost of components such as gratings this makes such demultiplexers unsuitable for mass production. The authors describe a method of producing a dielectric wavelength filter integrated onto an InGaAs PIN photodiode for use in WDM systems and give results for the transmission characteristics of the filters and quantum efficiency of the whole structure.<>     

Ultrafast long-wavelength photodetectors fabricated onlow-temperature InGaAs on GaAs

The authors report the first successful demonstration of a metal-semiconductor-metal photodetector (MSMPD) fabricated on low-temperature InGaAs grown on GaAs by molecular beam epitaxy (MBE) for long-wavelength fiber optic applications. Interdigitated MSMPDs with finger widths and spacings of 0.2, 0.5, 1.0, and 2.0 μm were tested using a femtosecond pulsed laser and high-speed electrooptic sampling. A FWHM pulsed response of 2 and 1.3 ps was measured for low-temperature In _0.25Ga_0.75As and In_0.35Ga_0.65As, respectively. The latter is the fastest response reported to data for a photodetector capable of detection to wavelengths as long as 1.3 μm     

基于深度测量的三维成像技术

由于三维（3D）成像技术有着广泛的应用,尤其是在信息和生命科学领域的应用,因此越来越受到人们的关注。这些技术大致可分为两类:基于光线的三维成像技术和基于波前的三维成像技术。传统成像技术存在系统装置复杂和成像质量不尽人意等问题,极大限制了其在相关领域的应用,因此基于深度测量的三维成像技术越来越受到重视。文中概述了基于深度测量的三维成像技术,分别详细描述了基于深度测量三维成像的光线场和光波场的相关技术,给出了光线场和光波场成像技术之间的联系,基于这些描述和分析,给出了基于深度测量三维成像研究领域的研究方向。     

Metal-semiconductor-metal demultiplexing waveguide photodetectors in InGaAs/GaAs quantum well structures by selective bandgap tuning

A two-wavelength demultiplexing metal-semiconductor-metal (MSM) waveguide photodetector has been fabricated using impurity-free vacancy diffusion and partial intermixing of an InGaAs/GaAs strained layer quantum well structure. The importance of growth and process parameters, such as aluminium composition in the cladding layer and the oxygen plasma treatment of the sample during processing, on the related device performance is discussed. This photodetector is a potential candidate for monolithic integration with other optoelectronic devices.<>     

基于数字视频的微细作业系统立体成像方案

分析了现有模拟分时立体成像系统的原理和存在闪烁问题的原因,由于两路CCD信号分时显示使帧频下降,图像存在一定的闪烁感,提出了一种改进的立体成像方案,该方案基于数字视频处理,采用高速的视频解码芯片和DSP芯片,提高了图像显示帧频达到无闪烁立体成像的目的,而且利用插场算法提高了图像的清晰度,有利于对进一步实现视觉跟踪控制或利用视觉信息进行自动控制。     

Investigation of planar photodiodes of a focal plane array based on a heteroepitaxial InGaAs/InP structure

The results of investigation of planar photodiodes (PDs) in a focal plane array (FPA) based on a heteroepitaxial InGaAs/InP structure are reported. The FPA has a size of 320 × 256 elements with a pitch of 30 μm, which are hybridized with various ROIC readout circuits. It is demonstrated that the PD reverse bias should be no lower than 2 V in order to suppress the FPA intercoupling at the room temperature. It is found that the dark current may be reduced considerably by cooling the FPA to–20°С with a two-stage thermoelectric cooler. The best average room-temperature dark current over the FPA planar photodiodes is 0.22 pA at an optimum PD bias of–2.4 V.     

Recent advances in flexible photodetectors based on 1D nanostructures

Semiconductor nanowires have demonstrated excellent electronic and optoelectronic properties. When integrated into photodetectors, excellent device performance can be easily attained. Apart from the exceptional performance, these nanowires can also enable robust and mechanically flexible photodetectors for various advanced utilizations that the rigid counterparts cannot perform. These unique applications include personal healthcare, next-generation robotics and many others. In this review, we would first discuss the nanowire fabrication techniques as well as the assembly methods of constructing large-scale nanowire arrays. Then, the recent development of flexible photodetectors based on these different nanowire material systems is evaluated in detail. At the same time, we also introduce some recent advancement that allows individual photodetectors to integrate into a more complex system for advanced deployment. Finally, a short conclusion and outlook of challenges faced in the future of the community is presented.     

Investigation of signal-code structures based on 3D error-locating codes

The signal-code structures based on 3D generalized error-locating codes are investigated. Data transmission over a q-ary optical channel with erasure and errors of decoding and a channel using 64-level quadrature amplitude modulation is discussed. The theoretical estimates of the erroneous decoding probability, as well as simulation results, are presented.     

Lattice mismatched InGaAs on silicon photodetectors grown by molecular beam epitaxy

In_0.5Ga_0.5As on silicon photodetectors, including three types of interdigitated-finger devices as well as linear photoconductors, were fabricated and measured. The InGaAs/Si structure was grown by molecular beam epitaxy and utilized a 100 Å GaAs intervening nucleation layer between the silicon substrate and the InGaAs layers, step-graded In_xGa_1?xAs layers, and an in-situ grown 40 Å thick GaAs surface layer, which substantially enhanced the metal-semiconductor barrier height (Φ_b = 0.67 V) for the InGaAs. Schottky diodes fabricated independently of the photodetectors had nearly ideal characteristics with an ideality factor (n) of 1.02 and a reverse breakdown voltage of 40 V. The interdigitated Schottky photodetectors showed dark currents between <3nA and 54 μA at a 3 V bias and initial photoresponse rise times in the range of 600 to 725 ps, comparable to similar InGaAs metal-semiconductor-metal photodetectors grown lattice matched on InP. The photoconductors fabricated in the same material had rise times in the range of 575 to 1300 ps, thus being slightly slower, and had dark currents of 7 to 80 mA. The responsivity of the photoconductors was typically greater than that of the diodes by a factor of five to fifteen. The results show potential for monolithic integration of InGaAs photodetectors on silicon substrates.     

基于盖革APD阵列的光子计数三维成像

基于盖革APD阵列的激光主动探测系统具有较高的灵敏度、空间分辨率和测距精度,在遥感探测、目标识别等领域具有广泛的应用前景。受探测模式、噪声等因素影响,盖革APD阵列需要大量累积光子探测来实现高精度成像。针对该问题,基于目前国内规模最大的InGaAs盖革APD阵列,搭建了1 064 nm激光探测实验装置,对室外600 m外目标进行了成像。通过分析光子计数物理过程,建立了目标反射率与距离的极大似然估计。结合自然图像稀疏的先验知识,采用正则化图像重构方法,改善了累积光子数较少情况下的成像精度。通过对比,验证了正则化图像重构方法能够抑制光子数涨落引起的参数估计偏差,提升了成像质量。     

Hooge parameter of InGaAs bulk material and InGaAs 2DEG quantum well structures based on InP substrates

The 1/f noise of various InGaAs layers lattice matched to InP is investigated systematically at room temperature. To elucidate the origin of the 1/f noise in this type of III–V compound semiconductor, thick n-type doped InGaAs layers, typical InP based InAlAs/InGaAs or InP/InGaAs heterostrucuture field-effect transistor (HFET) structures, respectively, as well as InP based InAlAs/InGaAs quantum well structures with doped InGaAs two-dimensional electron gas (2DEG) channel are analysed. From the experiments it is found that mobility fluctuation is the only origin for the 1/f noise observed both in InGaAs bulk material and in 2DEG heterostructures of high quality. A Hooge parameter attributed to phonon scattering α_Hphon in the bulk material is found to be about 7×10⁻⁶ and agrees with those obtained from HFET structures with the highest mobilities (α_H≈1.5×10⁻⁵). Furthermore, the Hooge parameter of 2DEG structures strongly depends on the channel design and on the doping concentration in the n-type doped 2DEG channels.     

MOS Integrated circuits fabricated on multilayer heteroepitaxial silicon-insulator structures for applications to 3-D integrated circuits

Multiple layers of single-crystal silicon and boron phosphide have been grown on silicon and silicon-on-sapphire substrates. Up to four layers have been grown on silicon and two layers on silicon-on-sapphire. The quality of the silicon layers was confirmed by fabricating PMOS integrated circuits on the top silicon layer in all of these structures. The integrated circuits contained individual transistors, p-n diodes, inverters, flip-flops, and ring oscillators. All circuits successfully operated on all of the layers tested. The transistor mobilities tended to drop as more layers were added to the structure. The delay time of the ring oscillators rose as the number of layers increased reflecting the drop in transistor mobilities. By fabricating circuits on the various layers, the quality of the individual layers has been shown to be sufficiently high to consider this material combination as a possible candidate for 3-D integrated circuits. The boron phosphide was used not only as an insulator but also for the fabrication of vertical resistors and p-n junctions.     

基于GRT-CLEAN的高速旋转目标快速三维成像方法

针对传统高速旋转目标三维成像算法存在成像效果差、计算复杂度大、鲁棒性差的缺点,本文提出一种加速的GRT-CLEAN高速自旋目标三维成像方法。采用广义Radan变换(GRT)与CLEAN技术相结合的方法进行目标三维特征提取,实现高分辨精确目标成像;采用"先粗网格,后精确网格"的策略,分两步对散射点目标进行估计,降低计算复杂度,计算复杂度从Ο(N×P×Q×T)降为Ο(10~(-4)×N×P×Q×T),大幅提高成像速度。仿真实验与数值分析验证了本文所提方法的有效性。实验结果表明,本文所提成像在低信噪比和目标存在遮挡的情况下,依然能对目标进行有效成像;与传统的GRT-CLEAN成像方法相比,本文所提成像方法大幅降低计算复杂度。     

基于压缩感知的非视域物体激光三维成像系统

以提升非视域物体激光三维成像的图像质量为目的,设计基于压缩感知的非视域物体激光三维成像系统.系统整体结构主要包括激光发射模块、探测器模块、AD转换器、数据采集卡以及计算机等.激光发射模块中激光发射器发射激光脉冲,该脉冲通过准直透镜的整形处理后能够抑制光束扩散的影响.激光反射透射至非视域目标物体上形成光束散射;探测器模块...     

基于InGaAs探测器的制冷试验分析

为解决红外图像高质量要求与紧张的卫星有效载荷资源间矛盾,针对Xenics公司的InGaAs短波红外探测器XLIN-1.7-2048开展电制冷试验以确定其工作模式。对比暗背景与不同光辐照情况下,探测器开启半导体热电制冷与不制冷时的像元均值、噪声与灵敏度,综合考虑系统要求、功耗、辐冷板面积、重量及可靠性等因素,最终确定常温工作状态下的工作模式。     

Smooth, 3D Ge transistor channels by heteroepitaxial growth

Crystalline germanium (Ge) is a prime candidate as a material for high-performance transistors due to its higher electron and hole mobility with respect to those of silicon. In this study, we present a novel method of fabricating epitaxial Ge structures of high crystalline and morphological quality directly onto Si substrates, in which 3D Ge structures are grown by selective epitaxy then annealed in a hydrogen ambient at 850 °C. Under such annealing, the surface of the Ge structures deform by surface diffusion to form smooth, rounded shapes for which the surface energy is at a local minima. The apparent smoothness of the surface, along with the decreased defect density expected to exist in these heteroepitaxial Ge structures, suggest they are adequate for use as transistor channels.     

Optical properties of Zn-diffused InP layers for the planar-type InGaAs/InP photodetectors

Zn diffusion into InP was carried out ex-situ using a new Zn diffusion technique with zinc phosphorus particles placed around InP materials as zinc source in a semi-closed chamber formed by a modified diffusion furnace.The optical characteristics of the Zn-diffused InP layer for the planar-type InGaAs/InP PIN photodetectors grown by molecular beam epitaxy (MBE) has been investigated by photoluminescence (PL) measurements.The temperature-dependent PL spectrum of Zn-diffused InP samples at different diffusion temperatures showed that band-to-acceptor transition dominates the PL emission,which indicates that Zn was commendably diffused into InP layer as the acceptor.High quality Zn-diffused InP layer with typically smooth surface was obtained at 580 ℃ for 10 min.Furthermore,more interstitial Zn atoms were activated to act as acceptors after a rapid annealing process.Based on the above Zn-diffusion technique,a 50μm planar-type InGaAs/InP PIN photodector device was fabricated and exhibited a low dark current of 7.73 pA under a reverse bias potential of-5 V and a high breakdown voltage of larger than 41 V (I ＜ 10 μA).In addition,a high responsivity of 0.81 A/W at 1.31 μm and 0.97 A/W at 1.55 μm was obtained in the developed PIN photodetector.