Far infrared heterodyne detectors

The characteristics of far infrared detectors are reviewed. Three detectors, the InSb hot electron bolometer, the GaAs Schottky diode and the Josephson point contact junction, have been incorporated as mixers into sensitive heterodyne systems. The performances of existing heterodyne receivers/radiometers are described and compared. Other applications of submillimeter heterodyne techniques are discussed.Supported in part by the U. S. Army Research Office and the Department of the Air Force.     

4H-SiC MOSFET的温度特性研究

对4HSiCMOSFET的器件结构和温度特性进行了研究,总结了器件的结构参数对特性的影响,比较了不同温度下的输出特性以及饱和漏电流、阈值电压、跨导、导通电阻与温度的变化关系,模拟结果表明4HSiCMOSFET具有优异的温度特性,在800K下可以正常工作 关键词： 4H-SiC MOSFET     

纳米尺度MOSFET过剩噪声的定性分析

最近实验表明纳米尺度MOSFET中的过剩噪声主要为散粒噪声,而此前研究认为MOSFET中不存在散粒噪声,短沟道MOSFET中的过剩噪声为热噪声. 本文基于器件电流模型分析散粒噪声取代热噪声成为过剩噪声主要成分的转变条件,根据该条件对纳米尺度MOSFET噪声特性的预测与文献报道的实验现象、模拟结果以及介观散粒噪声相关结论相符合. 关键词： 散粒噪声 过剩噪声 纳米尺度MOSFET     

MOSFET scaling into the 10 nm regime

Scaling limits of the double-gate MOSFET structure are explored. Because short-channel effects can be adequately controlled by thinning the silicon body, the eventual scaling limit will be determined by the ability to control off-state leakage due to quantum mechanical tunneling and thermionic emission between the source and drain. Depending on threshold voltage and the source/drain doping profile, this will restrict gate length scaling to 5–11 nm. As power supplies are scaled down, maintaining on-state drive current may become difficult due to threshold voltage limitations. Series resistance becomes important as the body thickness is reduced, but intrinsic device performance may still be improved.     

Modern trends in the development of position sensitive neutron detectors for condensed matter research

Different types of neutron scattering experiment for the study of condensed matter properties pose specific and often contradictory requirements for detector characteristics. There is no single type of detector which satisfies all the criteria. Therefore, compromise is inevitable and some of the characteristics are trade off in favour of others. Present report gives an overview of detector systems presently operating at the leading neutron scattering facilities as well as some development work around the globe.      

Performance improvements of ultraviolet/infrared dual-band detectors

Results are reported on dual-band detectors based on a GaN/AlGaN structure operating in both the ultraviolet–midinfrared (UV–MIR) and ultraviolet–farinfrared (UV–FIR) regions. The UV detection is due to an interband process, while the MIR/FIR detection is from free carrier absorption in the emitter/contact followed by internal photoemission over the barrier at the GaN/AlGaN interface. The UV detection, which was observed from 300 K to 4.2 K, has a threshold of 360 nm with a peak responsivity of 0.6 mA/W at 300 K. The detector shows a free carrier IR response in the 3–7 μm range up to 120 K, and an impurity response around 54 μm up to 30 K. A response in the range 7–13 μm, which is tentatively assigned to transitions from C impurities and N vacancies in the barrier region, was also observed. It should also be possible to develop a detector operating in the UV–visible–IR regions by choosing the appropriate material system. A dual-band detector design, which allows not only to measure the two components of the photocurrent generated by UV and IR radiation simultaneously but also to optimize the UV and IR responses independently, is proposed.     

Competitive technologies of third generation infrared photon detectors

Hitherto, two families of multielement infrared (IR) detectors are used for principal military and civilian infrared applications; one is used for scanning systems (first generation) and the other is used for staring systems (second generation). Third generation systems are being developed nowadays. In the common understanding, third generation IR systems provide enhanced capabilities like larger number of pixels, higher frame rates, better thermal resolution as well as multicolour functionality and other on-chip functions. In the paper, issues associated with the development and exploitation of materials used in fabrication of third generation infrared photon detectors are discussed. In this class of detectors two main competitors, HgCdTe photodiodes and quantum well IR photoconductors (QWIPs) are considered. The performance figures of merit of state-of-the-art HgCdTe and QWIP focal plane arrays (FPAs) are similar because the main limitations come from the readout circuits. However, the metallurgical issues of the epitaxial layers such as uniformity and number of defected elements are the serious problems in the case of long wavelength infrared (LWIR) and very LWIR (VLWIR) HgCdTe FPAs. It is predicted that superlattice based InAs/GaInSb system grown on GaSb substrate seems to be an attractive to HgCdTe with good spatial uniformity and an ability to span cutoff wavelength from 3 to 25 μm.     

P沟道和N沟道MOS场效应管的辐照实验研究

通过对P沟道MOS场效应管IRF9530和N沟道MOS场效应管IRF540N的X射线和钴源γ射线的辐照对比研究,发现两种场效应管阈值电压变化随吸收剂量近似成一阶指数衰减关系。产生这种现象的原因是场效应管氧化物中的空间俘获电荷与吸收剂量近似成线性变化,对阈值电压变化和吸收剂量有近似线性的改变;而界面态对空间电荷有补偿作用,其对阈值电压的改变与吸收剂量有近似成二次方的关系。     

Geometry of etched charged particle tracks in crystalline detectors

Studies on the shape of etched fission tracks in crystalline detectors show that the track geometry carries valuable information on the crystal structure of the detector involved. The geometry of the etched tracks in crystalline detectors is a prism formed of certain crystal planes. In mica detectors, for given etching conditions the type and number of the planes depend on the incident angle and the extent of the radiation damage along the track. In a single track the type of crystal planes forming the track prism may change along the track resulting in dramatic variations of the track geometry at certain depth of focus.     

Role of guard rings in improving the performance of silicon detectors

BARC has developed large-area silicon detectors in collaboration with BEL to be used in the pre-shower detector of the CMS experiment at CERN. The use of floating guard rings (FGR) in improving breakdown voltage and reducing leakage current of silicon detectors is well-known. In the present work, it has been demonstrated that FGRs can also be used to improve the spectroscopic response of silicon detectors. The results have been confirmed by carrying outα-particle (≈5 MeV) andγ-ray (60 keV) spectroscopies with the FGR floating or biased and the underlying physics aspect behind the change in spectra is explained. Although reduction in leakage current after biasing one of the guard rings has been reported earlier, the role of a guard ring in improving the spectroscopic response is reported for the first time. Results of TCAD simulations for silicon detectors with the guard ring under different biasing conditions have been presented. Low yield in producing large-area silicon detectors makes them very costly. However, with one of the FGRs biased even a detector having large surface leakage current can be used to give the same response as a very good detector. This makes the use of large-area silicon detectors very economical as the yield would be very high (>90%).     

Analytical analysis of surface potential for grooved-gate MOSFET

The improvement of the characteristics of grooved-gate MOSFETs compared to the planar devices is attributed to the corner effect of the surface potential along the channel. In this paper we propose an analytical model of the surface potential distribution based on the solution of two-dimensional Poisson equation in cylindrical coordinates utilizing the cylinder approximation and the structure parameters such as the concave corner $\theta _0 $. The relationship between the minimum surface potential and the structure parameters is theoretically analysed. Results confirm that the bigger the concave corner, the more obvious the corner effect. The corner effect increases the threshold voltage of the grooved-gate MOSFETs, so the better is the short channel effect (SCE) immunity.     

Study of the neutron field with etched track detectors in radiobiological experiments

Low dose cell culture irradiation experiments have been carried out at the filtered beam of Budapest Research Reactor for several years. The aim of the present study is to provide along with the macroscopically determinable “dose”, more detailed information on the components of the radiation affecting the cells. For this purpose CR-39 detectors with several types of radiator and absorber materials were mounted in different geometrical arrangements on the walls of the cell holder flasks and irradiated under the same conditions as those of the cells. With these detectors individual particles can be investigated using an image analyser and the effect of thermal, intermediate and fast neutrons hitting the cells, the protons induced by neutrons in the wall of the flasks, backscattered by the medium and by the surroundings can be studied. The methods, results of the measurements and dose calculations will be presented.     

新型CZT半导体X射线和g射线探测器研制与应用展望

CdZnTe(CZT)半导体是一种性能优异的室温X射线和γ射线探测材料,在环境监测、医学诊断、工业无损检测、安全检查、空间科学等众多领域有广泛的应用前景。文章简要介绍了CZT探测器的基本工作原理和性能评价指标,阐述了CZT晶体物理性能对CZT探测器性能的影响规律和CZT探测器的模拟与设计方法。CZT半导体探测器的应用与发展前景广阔,为此需要重点开展高质量、低成本的CZT晶体生长研究,CZT探测器的设计与制备以及辐射探测整机系统的设计与开发。     

Research into accelerator driven systems using particle track detectors

In the interaction of relativistic protons with heavy and extended targets such as lead, large number of neutrons is produced in the course of the so-called spallation process. These neutrons can be used to drive a sub-critical nuclear assembly for energy generation and/or for the transmutation of the long-lived nuclear waste isotopes to environmentally safer nuclear species. Such nuclear assemblies are referred to as accelerator driven systems (ADS).

Knowledge of the neutron yield in the spallation process and an understanding of the behaviour of these neutrons in the desired sub-critical assembly are the most important and determining factors in the design and operation of these systems. Many parameters related to the neutronics of an ADS can be studied qualitatively as well as quantitatively using solid-state nuclear track detectors (SSNTD). In some circumstances SSNTDs provide the best and the most logical detector option for these investigations.

In this paper applications of the SSNTDs into research related to ADS are discussed and some experimental and theoretical results presented.     

超导探测器与太赫兹天文应用

太赫兹频段(0.1—10 THz)占有宇宙空间近一半的光子能量,特别适合观测早期遥远天体、正在形成冷暗天体,以及被尘埃遮掩天体,且具有非常丰富的分子、原子及离子谱线,是其他频段不可替代的宇宙观测窗口。近四十年来,低温超导探测器技术得到快速发展,在天文学领域率先实现应用并取得系列有显著影响的研究成果,如黑洞成像、原行星盘精细结构观测以及近邻宇宙水分子刻画和宇宙最先诞生的电离氢化氦离子探测等。文章将主要介绍4种国际主流太赫兹超导探测器(即超导隧道结(SIS)混频器、超导热电子(HEB)混频器、超导相变边缘(TES)探测器和超导动态电感(KID)探测器)的研究进展、应用突破和未来发展趋势。     

Study of a 4H-SiC epitaxial n-channel MOSFET

Epitaxial channel metal-oxide semiconductor field-effect transistors (MOSFETs) have been proposed as one possible way to avoid the problem of low inversion layers in traditional MOSFETs. This paper presents an equation of maximum depletion width modified which is more accurate than the original equation. A 4H--SiC epitaxial n-channel MOSFET using two-dimensional simulator ISE is simulated. Optimized structure would be realized based on the simulated results for increasing channel mobility.     

超短沟道MOSFET电势的二维半解析模型

本文根据超短沟道MOSFET的工作原理, 在绝缘栅和空间电荷区引入两个矩形源, 提出了亚阈值下电势二维分布的定解问题. 通过半解析法和谱方法相结合, 首次得到了该定解问题的二维半解析解, 解的结果是一个特殊函数, 为无穷级数表达式. 该模型的优点是避免了数值分析时的方程离散化, 表达式不含适配参数、运算量小、精度与数值解的精度相同, 可直接用于电路模拟程序. 文中计算了沟道长度是45—22 nm的MOSFET电势、表面势和阈值电压. 结果表明, 新模型与Medici数值分析结果相同. 关键词： 半解析法 电势 阈值电压 MOSFET     

An improvement to computational efficiency of the drain current model for double-gate MOSFET

As a connection between the process and the circuit design, the device model is greatly desired for emerging devices, such as the double-gate MOSFET. Time efficiency is one of the most important requirements for device modeling. In this paper, an improvement to the computational efficiency of the drain current model for double-gate MOSFETs is extended, and different calculation methods are compared and discussed. The results show that the calculation speed of the improved model is substantially enhanced. A two-dimensional device simulation is performed to verify the improved model. Furthermore, the model is implemented into the HSPICE circuit simulator in Verilog-A for practical application.     

Tight-binding study of quantum transport in nanoscale GaAs Schottky MOSFET

This paper explores the band structure effect to elucidate the feasibility of an ultra-scaled GaAs Schottky MOSFET (SBFET) in a nanoscale regime. We have employed a 20-band sp3d5s* tight-binding (TB) approach to compute E K dispersion. The considerable difference between the extracted effective masses from the TB approach and bulk values implies that quantum confinement affects the device performance. Beside high injection velocity, the ultra-scaled GaAs SBFET suffers from a low conduction band DOS in the Γ valley that results in serious degradation of the gate capacitance. Quantum confinement also results in an increment of the effective Schottky barrier height (SBH). Enhanced Schottky barriers form a double barrier potential well along the channel that leads to resonant tunneling and alters the normal operation of the SBFET. Major factors that may lead to resonant tunneling are investigated. Resonant tunneling occurs at low temperatures and low drain voltages, and gradually diminishes as the channel thickness and the gate length scale down. Accordingly, the GaAs (100) SBFET has poor ballistic performance in nanoscale regime.     

阵列探测器的像点亚像素定位精度

本文研究阵列探测器的像点亚像素定位精度与内插算法及像斑大小的关系，文中提出一种校正算法误差、提高定位精度的方法。上述分析和论述通过实验证明是正确的。