CdSe核辐射探测器的噪声与漏电流

对具有金属-半导体-金属(MSM)结构的CdSe探测器的噪声进行了实验观测,并对探测器中光生载流子的输运过程进行了分析,结果表明探测器的噪声是由从正极注入的空穴电流引起的.因此只有改变正极接触,才能有效地阻止空穴注入,从而消除探测器噪声.     

CdSe核辐射探测器中的MIS接触电极

对MIS(金属-绝缘体-半导体)接触电极的特性进行了系统的分析和实验观察.结果表明,负极的电子可以通过表面能级和热激发注入到Cd Se晶片中,且晶片表面的电子能级密度越高,电子注入就越快,探测器的漏电流也越大.对探测器进行适当的热处理,可以降低表面能级密度,从而抑制电子注入,降低探测器的漏电流,改善探测器的能量分辨率.     

CdSe核辐射探测器中的MIS接触电极

对MIS(金属-绝缘体-半导体)接触电极的特性进行了系统的分析和实验观察.结果表明,负极的电子可以通过表面能级和热激发注入到CdSe晶片中,且晶片表面的电子能级密度越高,电子注入就越快,探测器的漏电流也越大.对探测器进行适当的热处理,可以降低表面能级密度,从而抑制电子注入,降低探测器的漏电流,改善探测器的能量分辨率.     

光电探测器的电噪声及其应用

电噪声检测方法正在成为一种无损的电子器件可靠性表征手段,而人们对其在光电探测器方面应用的研究还较少.本文在总结光电探测器电噪声类型及产生机理的基础上,分析了光电探测器与电噪声相关的各项性能参数.电噪声不仅是影响光电探测器性能的重要物理量,而且与光电探测器材料缺陷、界面缺陷及深能级陷阱存在相关性.构造的适当噪声参量可以表征光电探测器中的上述缺陷.与电噪声相关的缺陷往往是导致器件失效的因素,借鉴电噪声用于金属-氧化物-半导体场效应晶体管质量和可靠性表征的方法,本文提出了电噪声在表征光电探测器质量和可靠性方面的应用.     

焦平面输入电路研究

在混合式焦平面阵列中,探测器和读出电路的耦合通过输入级电路实现。为分析输入电路对探测器-放大器系统性能的影响,用分立元件设计制作了一个三级的前置放大器并进行了模拟实验,实验表明放大器输入级噪声是造成探测器信噪比下降的主要因素,应用中应该选用具有特定噪声性能的放大器与探测器匹配。研究了焦平面中常用的直接注入(DI)和电容反馈放大电路(CTIA)与探测器耦合时在噪声、输入阻抗、工作点匹配等方面应具备的条件。提出了临界输入阻抗的概念,实验表明,当电路的输入阻抗低于此临界值时(对于GaN p?蛳i?蛳n 光伏探测器来说约为106 Ω),焦平面才能获得较高的注入效率。     

MSM光电探测器特性二维数值模拟

为了解释在InGaAs金属-半导体-金属光电探测器(MSM—PD)内光产生载流子的行为及器件内电场分布,本文用有限元法数值求解了含复合项的二维泊松方程、电流连续方程及电荷俘获速率方程。得到了InGaAs MSM光电探测器的电流—电压特性及器件内电场和载流子分布。模拟结果解释了实验观察到的雪崩击穿现象,并表明电子电流比空穴电流提前饱和。     

利用新型的空穴注入层材料提高有机发光器件性能

研究使用新材料2-TNATA作空穴注入层制备OLED,发现空穴注入层厚度的最佳参数为35 nm,器件的发光光谱随空穴注入层厚度并不发生显著变化,微腔作用对发光光谱的影响基本可以忽略.并将2-TNATA作为空穴注入层的器件同CuPc制作的器件进行了对比,发现使用2-TNATA能获得更佳的器件性能.     

MSM光探测器直流特性的二维分析

基于有限差分方法对金属-半导体-金属(MSM)光探测器进行了二维分析,得到有明确物理意义的模拟曲线和结论,并结合模拟结果对MSM光探测器的光电直流特性进行了分析.全部模拟工作都是基于半导体物理的基本微分方程完成的,这对于未来优化设计探测器的性能和结构有很大的意义.     

高性能宽频带碲镉汞探测器

本文研究77°K工作的8～14微米碲镉汞探测器的响应率与探测器噪声的频率关系。结果表明,这些参数具有同样的频率关系与拐角频率。对D_λ~*～5×10~(10)厘米~(1/2)瓦~(-1)的探测器,实验得出f~*值≥10兆赫。同时看出,结果与假定空穴和电子寿命相等的简单光电导理论一致。     

薄栅氧化层相关击穿电荷

栅氧化层厚度的减薄要求深入研究薄栅介质的击穿和退化之间的关系 .利用衬底热空穴注入技术分别控制注入到薄栅氧化层中的热电子和空穴量 ,对相关击穿电荷进行了测试和研究 .结果表明薄栅氧化层击穿的限制因素依赖于注入热电子量和空穴量的平衡 .提出薄栅氧化层的击穿是在注入的热电子和空穴的共同作用下发生的新观点 .建立了 Si O2 介质击穿的物理模型并给出了理论分析     

Effect of anode material on high-field-induced hole current in SiO2 layer of metal-oxide-semiconductor field-effect transistor

The effects of three anode materials: polysilicon (semiconductor), aluminium and gold (metals) on hole currents in oxide layers of MOSFET's are presented for both thin (19 nm) and the thick (78 nm) oxide layers. Similar anode material effects were observed in both the thin and the thick oxide layers. The results suggest that anode hole generation plays the same role for both the thin and the thick oxide layers in our experiment. The larger the anode electron barrier height, the larger the hole current generation efficiency. The observable anode material effect decreases with increase of oxide electric field. When the oxide electric field is larger than 10 MV/cm, the observable anode material effect disappears. Our results show that the anode hole generation is the dominant mechanism on both the thin and thick oxide layers for oxide electric fields smaller than 10 MV/cm. For oxide electric fields larger than 10 MV/cm, further analysis is needed to identify the dominant mechanism of high-field-induced oxide hole currents     

前栅极冷阴极器件中单根纳米线表面电场分布研究

利用静电场理论,对带栅极纳米线场发射冷阴极器件模型进行电场计算,在此基础上,进一步对器件几何参数以及电压对纳米线顶端表面电场的影响做了理论分析。结果表明,在纳米线低于栅极的情况下,纳米线顶端表面电场强度比其他点更强,随着离纳米线顶端距离的增加,电场急剧下降;栅孔半径、阴极与栅极距离的减小以及纳米线长度的增加,均使纳米线顶端表面电场大大增强,而栅极与阳极间距变化对顶端表面电场的作用很微弱;另外,纳米线顶端表面电场随栅极和阳极电压的增加而大幅度增强,尤其栅极电压的变化对纳米线顶端表面电场的影响更大。     

Avalanche-initiated space-charge oscillations

Physical mechanisms are proposed for avalanche oscillations in n⁺-n-n⁺semiconductor structures. A linearized analysis is proposed for these mechanisms, the results of which agree well with the results of a large-signal computer simulation. The oscillation mechanism is dependent upon a large excess electron concentration that is present at high current levels in the n region of an n⁺-n-n⁺structure. This electron concentration causes a net negative space charge in the n region, which in turn causes the electric field to be nonuniform, peaking at the anode n⁺contact. At sufficiently high current densities, an avalanche zone will form at the anode contact. The resultant carrier generation in this zone creates a hole domain of density sufficient to quench the avalanche. This hole domain then travels across the n region under the influence of the field. The positive space charge of the hole domain depresses the field sufficiently to prevent avalanche from recurring at the anode until the domain has extracted at the cathode. The field variation during this cycle causes transit-time terminal voltage oscillations. It is shown how, under proper conditions, a steady-state plasma region may be established over a substantial portion of the device length. This plasma region will cause the device to exhibit a negative differential resistance, and will also support relaxation oscillations at a frequency comparable to the reciprocal of its extraction time.     

A Monte Carlo investigation of multiplication noise in thin p+-i-n+ GaAs avalanche photodiodes

A Monte Carlo (MC) model has been used to estimate the excess noise factor in thin p⁺-i-n⁺ GaAs avalanche photodiodes (APD's). Multiplication initiated both by pure electron and hole injection is studied for different lengths of multiplication region and for a range of electric fields. In each ease a reduction in excess noise factor is observed as the multiplication length decreases, in good agreement with recent experimental measurements. This low noise behavior results from the higher operating electric field needed in short devices, which causes the probability distribution function for both electron and hole ionization path lengths to change from the conventionally assumed exponential shape and to exhibit a strong dead space effect. In turn this reduces the probability of higher order ionization events and narrows the probability distribution for multiplication. In addition, our simulations suggest that fur a given overall multiplication, electron initiated multiplication in short devices has inherently reduced noise, despite the higher feedback from hole ionization, compared to long devices     

一种背栅极冷阴极器件中纳米线表面电场的分析

利用静电场理论计算了背栅极冷阴极器件的纳米线附近电场,给出电场分布的表示式及J-V曲线,并分析了几何参数对纳米线顶端表面电场的影响.结果表明,纳米线顶端表面产生巨大的电场,随着离纳米线顶端表面距离的增大,电场迅速下降;纳米线突出栅孔的长度(L-d1)越大,纳米线半径r0、栅孔半径R以及栅极与阳极间距d2越小,则纳米线顶端表面电场越强,而d2较大时d2对表面电场的影响很弱;纳米线顶端边缘电流密度J随着阳极与栅极电压的增加而指数增大.     

基于计算机仿真的ZnO场致发射显示器的研究

在Spindt结构仿真方法的基础上,将四针状纳米ZnO近似处理成尖锥结构,采用C语言程序编程,求解电位、电场分布、电子运动轨迹及发射电流密度。通过计算机模拟仿真,分析了栅极孔径、栅极电压以及阳极电压等对显示器性能的影响。在理论优化设计指导下,采用丝网印刷制作带孔的介质层,用电泳方法在阴极电极上沉积ZnO发射体,制成孔状金属栅三极结构显示屏。测试了显示器的电子发射调制性能,实验表明采用计算机仿真设计的三极结构ZnO场致发射显示器具有良好的场致发射性能。     

Avalanche noise characteristics of thin GaAs structures withdistributed carrier generation [APDs]

It is known that both pure electron and pure hole injection into thin GaAs multiplication regions gives rise to avalanche multiplication with noise lower than predicted by the local noise model. In this paper, it is shown that the noise from multiplication initiated by carriers generated throughout a 0.1 μm avalanche region is also lower than predicted by the local model but higher than that obtained with pure injection of either carrier type. This behavior is due to the effects of nonlocal ionization brought about by the dead space; the minimum distance a carrier has to travel in the electric field to initiate an ionization event     

Two-dimensional Braille readers based on electrorheological fluid valves controlled by electric field

Holes filled with electrorheological fluids (ERF) are used to form the Braille symbols or a relief in array manipulators. Matrix of holes is made from the fabric-based copper laminate. Voltage applied to upper and lower coppered surfaces of the plate, creates electric field, which controls ERF viscosity. Three methods to form a relief are investigated: (a) using an elastic membrane, covering the holes; (b) dielectric pins moving in the holes; and (c) metallic pins moving in the holes. Electric field in a hole of the matrix is calculated as the electric field in a hole of the plane capacitor. When voltage upon electrodes is kept uniform, the mean electric field in the electrorheological fluid with metallic pins becomes 1.7, with dielectric pins mean electric field being 1.25 times stronger than in the electrorheological fluid with the membrane. In the case of metallic pins, the mean electric field near the electrodes is considerably stronger than in the case of dielectric pins. In the points situated not further than 0.25 of the hole height in the direction of the hole axis, the mean electric field is 3 times stronger than in the hole without the pin. The controlling voltage can be decreased using multilayer copper laminate valves, composed of some fabric-based plates in the opposite directions of the electric field in the neighboring plates.     

Noise transport in the crossed-field diode

The present work treats the transport of noise, originating at a thermionic cathode, across a planar crossed-field diode. A multivelocity Monte Carlo analysis is used to simulate thermionic emission by using random numbers to generate electron emission times and velocities. Trajectories for many charges are followed through the diode space by means of a high-speed digital computer. Measurements performed on a planar triode model for the crossed-field diode show that the anode noise current increases rapidly near the critical magnetic field, at which the stream just grazes the anode. The theory agrees well with these experimental findings. The Monte Carlo study predicts the increase of both the normal anode velocity fluctuations and the spread of the velocity distribution with magnetic field. This is caused mainly by the "geometrical" spreading of the initial velocity distribution. The crossed-field potential minimum exhibits no instabilities in the planar model. The noise current smoothing at low frequencies in ordinary streams is predicted for moderate fields but disappears near the critical field.     

Effect of an anode hole on electron avalanches in methane at high pressure

Measurements of the growth and size distribution of electron avalanches have been made in methane gas, over a pressure range from a few torr to 14 atm absolute, which show that field distortion due to a hole in the anode influences the growth of avalanches occurring at high gas pressures and at values of electrode separation ? 0.5 cm. The degree of influence depends on the size of the anode hole and on the value of E/p0.