Silicon readout ICs for third-generation 2D IR focal-plane arrays operating over the wavelength range 8–12 μm

A new design is described of silicon readout IC for 2D long-wavelength hybrid IR focal-plane arrays. Its essential feature is that the input array is made up of 2 × 2 subarrays of cells. This provides an almost tenfold increase in charge-handling capacity, a major parameter of the readout ICs considered. The design also includes an adaptive digital preprocessing unit in on-chip form.     

Extended-wavelength 640 × 1 linear InGaAs detector arrays using N-on-P configuration for back illumination

在N-on-P型In0.78Al0.22As/In0.78Ga0.22As外延材料上,采用感应耦合等离子体(ICP)刻蚀技术制备了背照射640×1线列InGaAs探测器芯片,研究了探测器光电性能.结果表明,室温下单元器件响应截止波长和峰值波长分别为2.36 μm和1.92 μm,平均优值因子(R0A)为16.0Ω·cm2,峰值量子效率达到了37.5％;在1 ms积分时间下焦平面探测器平均峰值探测率达到了2.01×1011 cmHz1/2/W,响应非均匀性为8.77％,盲元率约为0.6％.     

Gated IR Imaging with 128 × 128 HgCdTe Electron Avalanche Photodiode FPA

The next generation of infrared (IR) sensor systems will include active imaging capabilities. One example of such a system is a gated active/passive system. The gated active/passive system promises target detection and identification at longer ranges compared to conventional passive-only imaging systems. A detector that is capable of both active and passive modes of operation opens up the possibility of a self-aligned system that uses a single focal plane. The mid-wave infrared (MWIR) HgCdTe electron injection avalanche photodiode (e-APD) provides state-of-the-art 3 μm to 5 μm performance for the passive mode and high, low-noise, gain in the active mode, and high quantum efficiency at 1.5 μm. Gains of greater than 1000 have been measured in MWIR e-APDs with a gain-independent excess noise factor of 1.3. This paper reports the application of the mid-wave HgCdTe e-APD for near-IR gated-active/passive imaging. Specifically a 128 × 128 focal-plane array (FPA) composed of 40-μm-pitch MWIR cutoff APD detectors and custom readout integrated circuit was designed, fabricated, and tested. Median gains as high as 946 at 11 V bias with noise equivalent photon inputs as low as 0.4 photon were measured at 80 K and 1 μs gate times. This subphoton sensitivity is consistent with the high gains, low excess noise factor, and low effective gain normalized dark-current densities, near or below 1 nA/cm², that were achieved in these FPAs. A gated imaging demonstration system was designed and built using commercially available parts. High resolution and precision gating was demonstrated in this system by imagery taken at ranges out to 9 km.     

Implementation of the time delay and integration mode in a scanning 576 × 6 focal-plane array of the long-wave infrared range

The results of the development of a focal-plane array (FPA) of the 576 × 6 format with the time delay and integration (TDI) mode are presented. The comparative analysis of different variants of implementation of the TDI mode in ROIC is conducted. The expedience of the upgrade of existing scanning photodetectors of the 288 × 4 format on the basis of the developed 576 × 6 FPA is justified. The result of this upgrade will be simplification of the optical–mechanical scanning unit and improvement of the quality of thermal image.     

HgCdTe红外焦平面用1×288 CCD读出电路

设计和研制了一种采用多晶硅交叠栅结构的1×288红外信号处理器读出电路.制作中采用了多重吸杂技术和大剂量离子注入技术,提高了电路的信号处理能力,降低了信号噪声.该电路具有分割、抗晕、背景撇出功能.其功耗小于等于50 mW,动态范围大于等于60 dB,转移效率大于等于99.99%.详细介绍了这种1×288红外读出电路的理论设计和研制方法,给出了工艺流程及器件的测试方法.     

768×576的红外扫描成像电路设计

文中设计了768×576的红外扫描成像电路,其探测器焦平面阵列为576×6元。成像电路为红外扫描焦平面阵列提供直流偏置电压、积分信号和时钟信号,对探测器的输出进行8路数据采集与排序,然后将排序结果输出给上位机。其主要功能由FPGA和DSP完成,达到了系统结构简化及性能优化的目的。结果表明,该系统工作正常,能够满足使用要求。     

Shockley–Read–Hall Lifetime Study and Implication in HgCdTe Photodiodes for IR Detection

The Shockley–Read–Hall (SRH) mechanism might be a limiting factor of an infrared (IR) photodiode's dark current. This limitation is twofold. SRH generation might occur in the depletion region of the photodiode. In that case, the corresponding current is usually limiting the low-temperature dark current. Moreover, SRH generation might also occur in the diffusion volume, close to the space charge region, resulting in an increase of the diffusion dark current, usually limiting the high-temperature behavior of the photodiode. Hence, the determination of the SRH lifetime of IR materials is of first importance and has to be measured (or at least estimated) to define upcoming trends in future high-performance IR detectors. During the last few years, a lot of papers have been published about SRH lifetime in III–V materials (InSb, superlattices, InAsSb) and a few other communications have been more focused on comparing different material systems including III–V and II–VI materials. Those latter communications proposed very long SRH lifetimes (longer than ms) for HgCdTe, instead of the classical 10–100 μs usually admitted until now. This paper aims at investigating this SRH lifetime in HgCdTe based on experimental measurements carried out at the Laboratoire d’électronique des technologies de l’information (LETI) on HgCdTe grown in-house. Direct lifetime measurement (photoconductive or photoluminescence decay) as well as indirect estimations from photodiode dark currents are discussed in order to clarify this question of SRH lifetime and its consequences in upcoming advanced IR detection structures. In the end, it appeared that except for p/n extrinsic heterojunctions (for which the narrow gap depleted volume is not well known), most of the devices tested seemed limited by SRH lifetimes in the 10–100-μs range.     

Improved design for the scanning thermal imager based on 576 × 6 long-wavelength infrared detector

通过对长波576×6扫描型热像仪的扫描器组件摆扫频率、探测器配置、AD采样速率、信号处理速度以及图像数据的隔行和插值处理等的改进,提高热像仪的帧频至25 Hz,使之转为标准热像仪,以满足一般红外跟踪观察系统的要求.     

576×6长波红外探测器成像系统设计

设计了一个应用于线阵扫描型长波红外焦平面阵列的实时成像系统。系统中的适配电路为探测器提供工作环境,并对图像信号进行缓冲和电平变换。模拟视频信号的采集使用了高精度流水线ADC。数字信号处理电路实现了非均匀性校正,图像数据排序,坏像元补偿,直方图均衡和视频信号输出控制。结果表明该设计方法合理可行。     

32×32甚长波红外HgCdTe焦平面器件

甚长波红外波段富含大气湿度、CO2含量及云层结构和温度轮廓等大量信息,是大气遥感的重要组成部分。设计了一种3232甚长波红外焦平面阵列,采用在ZnCdTe衬底上液相外延生长的As掺杂p型材料上进行B+离子注入形成光敏元,通过铟柱倒焊技术和带有改进型背景抑制结构的读出电路互联,制成截止波长达到14 m的焦平面器件。该红外焦平面器件像元面积为60 m60 m,工作温度在50 K温度下。测试结果显示:读出电路性能良好,焦平面黑体响应率达到1。35107V/W,峰值探测率为2。571010 cmHz1/2/W,响应率非均匀性约为45%,盲元率小于12%。     

10 μm 1 280 × 1 024 HgCdTe中波红外焦平面阵列探测性能提升

对像元尺寸为10 μm的1280×1024碲镉汞（HgCdTe）中波红外焦平面阵列的制备技术和性能进行了研究。通过B⁺注入制备小尺寸n-on-p平面结;采用高平整度HgCdTe外延材料和高精度的倒焊互连技术,实现高的电学连通率;采用多段温度填胶固化和边缘刻蚀工艺减轻HgCdTe器件和读出集成电路（ROICs）之间的热失配,从而降低焦平面器件失效率。在85 K焦平面工作温度下,研制探测器的光谱响应范围为3.67 μm至4.88 μm,有效像元率高达99.95%,并且探测器组件像元的平均噪声等效温差（NETD）和暗电流密度的平均值分别小于16 mK和2.1×10^-8 A/cm²。与像元尺寸为15 μm的探测器相比,10 μm的1280×1024中波红外探测器可获取更加精细的图像,具有更远的识别距离。目前,该技术已成功转移到浙江珏芯微电子有限公司（ZJM）的HgCdTe红外探测器产线。     

基于长波576×6扫描型热像仪的改进设计

通过对长波576×6扫描型热像仪的扫描器组件摆扫频率、探测器配置、AD采样速率、信号处理速度以及图像数据的隔行和插值处理等的改进,提高热像仪的帧频至25 Hz,使之转为标准热像仪,以满足一般红外跟踪观察系统的要求。     

Silicon Deep Etching Techniques for MEMS Devices

Silicon deep etching technique is the key tabrication step in the development of MEMS. The mask selectivity and the lateral etching control are the two primary factors that decide the result of deep etching process. These two factors are studied in this paper. The experimental results show that the higher selectivity can be gotten when F- gas is used as etching gas and A1 is introduced as mask layer. The lateral etching problems can be solved by adjusting the etching condition, such as increasing the RF power, changing the gas composition and flow volume of etching machine.     

576×6红外焦平面阵列驱动电路的设计与实现

介绍了576×6红外焦平面阵列驱动电路的工作原理和重要作用,提出了基于 MSP430单片机和FPGA硬件平台的驱动电路设计新思路,着重解决了如何在满足驱动能力的前提下提高直流偏置电压精度的问题,并给出了详细的实现方法.     

2048×2048 HgCdTe红外焦平面杜瓦冷头热应力有限元分析

利用有限元方法对2048×2048(15 μm)红外焦平面杜瓦冷头的原始结构以及加入的平衡层结构进行了分析.在陶瓷基板下方增加膨胀系数较小的平衡层,对探测器芯片变形及热应力有一定的缓解作用.通过增大AlN平衡层上表面的直径,减小了芯片中心以外的翘曲范围,缓解了应力过于集中的问题.当直径超过芯片对角长度时,最大热应力骤减,最终趋于稳定;芯片变形量随之迅速减小.在直径为36 mm时,达到最小值(6.86 μm);随后缓慢增加并趋于稳定.当AlN平衡层的直径超过芯片对角长度后,AlN平衡层的厚度对芯片变形的影响开始减小.通过加入AlN平衡层能够有效改善大面阵焦平面探测器芯片的变形及热应力,同时通过调节AlN平衡层的结构,可进一步优化探测器杜瓦组件的可靠性.     

4×128元HgCdTe红外焦平面TDI CCD信号处理器件

采用三相埋沟结构，设计并研制成功用于高背景下红外探测器的高灵敏度4×128元TDICCD信号处理器件。器件转移效率99．99％，动态范围60dB，时钟频率10MHz。文章详细阐述该器件的工作原理、结构设计和制作工艺。     

Fabrication of high-performance large-format MWIR focal plane arrays from MBE-grown HgCdTe on 4″ silicon substrates

We have developed the capability to grow HgCdTe mid-wave infrared radiation double-layer heterojunctions (MWIR DLHJs) on 4″ Si wafers by molecular beam epitaxy (MBE), and fabricate devices from these wafers that are comparable to those produced by mature technologies. Test data show that the detectors, which range in cutoff wavelength over 4–7 μm, are comparable to the trendline performance of liquid phase epitaxy (LPE)-grown material. The spectral characteristics are similar, with a slight decrease in quantum efficiency attributable to the Si substrate. With respect to R₀A, the HgCdTe/Si devices are closer to the theoretical radiative-limit than LPE-grown detectors. Known defect densities in the material have been correlated to device performance through a simple model. Slight 1/f noise increases were measured in comparison to the LPE material, but the observed levels are not sufficient to significantly degrade focal plane array (FPA) performance. In addition to discrete detectors, two FPA formats were fabricated. 128×128 FPAs show MWIR sensitivity comparable to mature InSb technology, with pixel operability values in excess of 99%. A 640×480 FPA further demonstrates the high-sensitivity and high-operability capabilities of this material.     

Dewar for 12.5 μm long linear HgCdTe IRFPA

256×2碲镉汞焦平面模块由2个256×1元芯片和2个光伏信号硅读出电路模块平行对称组成,并分别与2个不同波段的微型滤光片以架桥式结构直接耦合后封装在全金属微型杜瓦内,形成了长波256×2长线列碲镉汞红外探测器件组件.基本解决了256×2焦平面杜瓦组件的关键技术,即高精度的组装技术、器件在冷平台上的热失配设计技术和高可靠性封装技术.对抑制杂散光、降低背景辐射、提高组件的可靠性等方面采取了一系列措施,使研制的碲镉汞焦平面器件获得了良好的性能,并进行了一系列空间适应性实验,实验前后的组件性能未发生明显变化,满足工程化应用的要求.     

Calculation Model for Current-voltage Relation of Silicon Quantum-dots-based Nano-memory

Based on the capacitive coupling formalism, an analytic model for calculating the drain currents of the quantum-dots floating-gate memory cell is proposed. Using this model, one can calculate numerically the drain currents of linear, saturation and subthreshold regions of the device with/without charges stored on the floating dots. The read operation process of an n-channel Si quantum-dots floating-gate nano-memory cell is discussed after calculating the drain currents versus the drain to source voltages and control gate voltages in both high and low threshold states respectively.     

HgCdTe Growth on 6 cm × 6 cm CdZnTe Substrates for Large-Format Dual-Band Infrared Focal-Plane Arrays

This paper describes molecular-beam epitaxy growth of mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) dual-band device structures on large-area (6 cm × 6 cm) CdZnTe substrates. Wafer-level composition and defect mapping techniques were used to investigate the limiting mechanisms in improving the cutoff wavelength (λ _c) uniformity and reducing the defect density. Structural quality of epitaxial layers was monitored using etch pit density (EPD) measurements at various depths in the epitaxial layers. Finally, 640 × 480, 20-μm-pixel-pitch dual-band focal-plane arrays (FPAs) were fabricated to demonstrate the overall maturity of growth and fabrication processes of epitaxial layers. The MWIR/LWIR dual-band layers, at optimized growth conditions, show a λ _c variation of ±0.15 μm across a 6 cm × 6 cm CdZnTe substrate, a uniform low macrodefect density with an average of 1000 cm⁻², and an average EPD of 1.5 × 10⁵ cm⁻². FPAs fabricated using these layers show band 1 (MWIR) noise equivalent temperature difference (NETD) operability of 99.94% and band 2 (LWIR) NETD operability of 99.2%, which are among the highest reported to date.