不同结构的碲镉汞长波光伏探测器的暗电流研究

摘要对B^ 注入的n-on-p平面结和分子束外延(MBE)技术原位铟掺杂的n-on-p台面异质结的碲镉汞(HgCdTe)长波光伏探测器暗电流进行了对比分析．与n-on-p平面结器件相比，原位掺杂的n-on-p台面异质结器件得到较高的零偏动态阻抗一面积值(RoA)．通过与实验数据拟合，从理论上计算了这两种结构的器件在不同温度下的RoA和在不同偏压下的暗电流，得到一些相关的材料和器件性能参数．     

用阶梯状掺杂埋层对超浅结进行C-V剖面分析

研究了应用双边C-V法测量超浅结(如p+-n结)的掺杂分布。推导了在已知p+-n结的电容-电压(C-VR)关系、n区掺杂、以及热平衡下n区耗尽层宽度(xn0)的情况下计算p区掺杂浓度分布的公式。xn0是计算p区掺杂分布所需的一个关键参数,通过将n区掺杂设计成阶梯状,可实现对xn0的精确提取。用Medici对具有相同的阶梯状掺杂n区的p+-n和n-肖特基结进行器件仿真可得其C-VR关系。运用常规C-V法,由肖特基结的C-VR关系可提取出n区掺杂浓度。实现了对xn0的精确提取,其精度达1.8nm。基于精确的xn0,运用双边C-V法提取的p+区的掺杂浓度分布与Medici仿真结果非常吻合。     

The redundancy of source coding with a fidelity criterion. 1. Knownstatistics

The problem of redundancy of source coding with respect to a fidelity criterion is considered. For any fixed rate R>0 and any memoryless source with finite source and reproduction alphabets and a common distribution p, the nth-order distortion redundancy D_n(R) of fixed-rate coding is defined as the minimum of the difference between the expected distortion per symbol of any block code with length n and rate R and the distortion rate function d(p,R) of the source p. It is demonstrated that for sufficiently large n, D_n(R) is equal to -(∂/∂R)d(p,R) ln n/2n+o(ln n/n), where (∂/∂R)d(p,R) is the partial derivative of d(p,R) evaluated at R and assumed to exist. For any fixed distortion level d>0 and any memoryless source p, the nth-order rate redundancy R_n(d) of coding at fixed distortion level d (or by using d-semifaithful codes) is defined as the minimum of the difference between the expected rate per symbol of any d-semifaithful code of length n and the rate-distortion function R(p,d) of p evaluated at d. It is proved that for sufficiently large n, R_n(d) is upper-bounded by ln n/n+o(ln n/n) and lower-bounded by In n/2n+o(In n/n). As a by-product, the lower bound of R_n(d) derived in this paper gives a positive answer to a conjecture proposed by Yu and Speed (1993)     

Silicon solar cells produced by corona discharge

A technique for producing p-n junction silicon solar cells has been developed involving the use of a continuous gaseous discharge operating in the corona mode. The process is applicable to the production of p on n or n on p structures. Detailed results are presented for a BF₃ discharge, producing p on n cells, along with preliminary results using a PF₅ discharge, resulting in n on p cells. Efficiencies of over 8% were obtained on single crystal Si p on n cells, and of over 3% for a heavily-defected polycrystalline at AMl without anti-reflective coatings. Fill factors as high as 0.76 were obtained. Analysis of these cells include ion microprobe mass analysis and anodic stripping for concentration profiles, and capacitance-vol tage and current-voltage measurements for electrical characterization. This work was performed under the auspices of the U.S. Energy Research and Development Administration under contract number W-7504-ENG-48.     

基于RSA算法的扩展算法

RSA的安全性是依据大整数分解的困难性而设计的。RSA公开密钥加密体制中n为2个大素数的乘积,即针对n=pq（p,q为大素数）的大整数分解,这里介绍了RSA算法的扩展算法的加密和解密原理,即针对n=p1,p2,…,pr（p1,p2,…,pr为大素数）的大整数分解。通过扩展素因子的个数达到RSA算法的安全性。比较RSA算法,扩展的RSA算法不仅可用于数据加密解密,也可用于数字签名。利用扩展的RSA算法实现数字签名也具有较高的安全性和可靠性。     

The redundancy of source coding with a fidelity criterion .II.Coding at a fixed rate level with unknown statistics

The redundancy problem of universal lossy source coding at a fixed rate level is considered. Under some condition on the single-letter distortion measure, which implies that the cardinality K of the reproduction alphabet is not greater than the cardinality J of the source alphabet, it is shown that the redundancy of universally coding memoryless sources p by nth-order block codes of rate R goes like |(∂/∂R)d(p,R)|Kln n/2n+o(ln n/n) for all memoryless sources p except a set whose volume goes to 0 as the block length n goes to infinity, where d(p,R) denotes the distortion rate function of p. Specifically, for any sequence {C_n}_n=1^∞ of block codes, where C_n is an nth-order block code at the fixed rate R, and any ϵ>0, the redundancy D_n(C _n,p) of C_n for p is greater than or equal to |(∂/∂R)d(p,R)|(K-ϵ)ln n/2n for all p satisfying some regular conditions except a set whose volume goes to 0 as n→∞. On the other hand, there exists a sequence {C_n}_n=1^∞ of block codes at the rate R such that for any p satisfying some regular conditions, the super limit of D_n(C_n,p)|(ln n/n) is less than or equal to |(∂/∂R)d(p,R)|K/2     

A Large Magnetoresistance Effect in p–n Junction Devices by the Space‐Charge Effect

The finding of an extremely large magnetoresistance effect on silicon based p–n junction with vertical geometry over a wide range of temperatures and magnetic fields is reported. A 2500% magnetoresistance ratio of the Si p–n junction is observed at room temperature with a magnetic field of 5 T and the applied bias voltage of only 6 V, while a magnetoresistance ratio of 25 000% is achieved at 100 K. The current‐voltage (I–V) behaviors under various external magnetic fields obey an exponential relationship, and the magnetoresistance effect is significantly enhanced by both contributions of the electric field inhomogeneity and carrier concentrations variation. Theoretical analysis using classical p–n junction transport equation is adapted to describe the I–V curves of the p–n junction at different magnetic fields and reveals that the large magnetoresistance effect origins from a change of space‐charge region in the p–n junction induced by external magnetic field. The results indicate that the conventional p–n junction is proposed to be used as a multifunctional material based on the interplay between electronic and magnetic response, which is significant for future magneto‐electronics in the semiconductor industry.     

n-CdTe Schottky势垒薄膜太阳能电池中嵌入p型层对其势垒高度影响的计算机模拟

通过求解Ｐｏｉｓｓｏｎ方程，对热平衡态金属：ｐ－ｎ－ＣｄＴｅＳｃｈｏｔｋｙ势垒薄膜太阳能电池进行计算机数值模拟。嵌入的ｐ型层增大传统金属：ｎ－ＣｄＴｅ结的有效Ｓｃｈｏｔｋｙ势垒高度与ｐ型层厚度、掺杂浓度以及ｎ－ＣｄＴｅ本底电阻率有依赖关系。最后讨论嵌入ｐ型层增强ＣｄＴｅＳｃｈｏｔｋｙ势垒太阳能电池对光生载流子的收集作用。     

半导体硅片的p-n结和铜沉积行为的电化学研究

分别采用电化学直流极化和交流阻抗技术,通过控制光照和溶液化学组分,研究了半导体硅片/氢氟酸体系的电化学特性和半导体性能.对p(100)和n(100)两种硅片的研究结果均表明,有光照条件下硅/氢氟酸界面上的电化学反应很容易发生且起着主导作用,而黑暗条件下硅片则处于消耗期,电化学反应难于发生,因而其半导体性能起着重要的作用.当溶液中有微量铜存在时,硅/溶液界面上的电化学反应将被加速.通过单独研究两种硅片的电化学行为,讨论了半导体硅片在氢氟酸溶液中形成的p-n接点行为,并通过考察溶液中的铜离子浓度、光照条件和沉积时间对铜在硅片上的沉积行为的     

4H-SiC npn双极型晶体管的研制

采用国产的4H-SiC外延材料和自行开发的SiC双极晶体管的工艺技术,实现了4H-SiC npn双极晶体管特性。为避免二次外延或高温离子p+注入等操作,外延形成n+/p+/p/n-结构材料,然后根据版图设计进行相应的刻蚀,形成双台面结构。为保证p型基区能实现良好的欧姆接触,外延时在n+层和p层中间插入适当高掺杂的p+层外延,但也使双极晶体管发射效率降低,电流放大系数降低。为提高器件的击穿电压,在尽量实现低损伤刻蚀时,采用牺牲氧化等技术减少表面损伤及粗糙度,避免表面态及尖端电场集中,并利用SiC能形成稳定氧化层的优势来形成钝化保护。器件的集电结反向击穿电压达200 V,集电结在100 V下的反向截止漏电流小于0.05 mA,共发射极电流放大系数约为3。     

外延层厚度对垂直结构6H-SiC光导开关特性影响的研究

设计了新颖的具有垂直结构的6H-SiC光导开关。首先采用离子注入工艺在半绝缘6H-SiC衬底两侧生成一层p+离子注入层,然后利用外延工艺在其中的一侧生长一层n+外延层,并将此侧定义为开关的阴极。利用二维半导体器件仿真软件,研究了n+外延层厚度对6H-SiC光导开关特性的影响。结果表明,增加外延层厚度可以提高开关的击穿电压;而开关的导通电流,首先随着n+外延层厚度的增加而减小,在n+外延层厚度为5?m达到最小值,随后随着厚度的增加,导通电流增加。     

Negative current-mirror using n?p?n transistors

The interconnection of an operational amplifier and an n?p?n transistor array facilitates the design of a negative-current mirror that avoids the use of p?n?p devices. For an input current in the range 1 ?A?1 mA, current transfer ratios that differ from unity by less than 0.3% are achievable. The incremental output resistance is inversely related to the operating current, and exceeds 10 M? at 1 mA.     

C.W. oscillation with p+-p-n+ silicon IMPATT diodes in 200 GHz and 300 GHz bands

Submillimetre-wave silicon single-drift-region IMPATT diodes with a p+?p?n+ structure have been fabricated by ion implantation. C.W. output powers of 7.5 mW at 285 GHz and 78 mW at 185 GHz were obtained. The maximum c.w. oscillation frequency observed was 394 GHz.     

Lower bounds for the divergence of orientational estimators

This paper is concerned with the properties of estimators in O(n,p),the n×p orthogonal matrices. It is shown that it is natural to introduce the notion of a parallel estimator where the expected value of the estimator must lie in normal space (orthogonal complement of tangent space) of O(n,p) at the true value. An appropriate measure of variance, referred to as divergence, is introduced for a parallel estimator and a Cramer-Rao (CR) type bound is then established for the divergence. The well-known Fisher-von Mises matrix distribution is often used to model random behavior on O(n,p) and depends on parameters Θ∈O(n,p) and H a p×p symmetric matrix. The bound for this distribution is calculated for the case n=p=3 and the divergence of the maximum-likelihood estimator (MLE) of Θ is estimated by simulation. The bound is shown to be tight over a wide range of H     

Degradation of silicon bipolar junction transistors at high forwardcurrent densities

The physical degradation mechanisms of silicon bipolar function transistors at high forward current densities were delineated quantitatively using three n/p/p and one p/n/p state-of-the-art submicron polysilicon-emitter transistor technologies. The increase of the operating current gain and decrease of emitter series resistance from million-ampere per square centimeter stress current are related to hydrogenation of the electronic traps at the metal-silicide/polycrystalline-Si and polycrystalline-Si/crystalline-Si emitter contact interfaces. A demonstration of the 10-year operation Time-to-Failure extrapolation methodology is also presented     

The spatial variation of the charged gold concentration in silicon p-n step junctions

The spatial variations of the three charged gold states in the transition region of silicon p+n and n+p step junctions are calculated. The exact solution is obtained at thermal equilibrium. Under reverse applied bias, exact solution is not possible and approximate solutions using staircased charge distributions are obtained. Under reverse bias, most of the gold atoms in the transition region are in the negative or acceptor charge state for both p+n and n+p junctions. This is due to the dominance of the hole emission process at the neutral gold centers over all other electron and hole emission processes of the three charge states at 300°K. Since the shallow-level impurities in these two types of junctions are of opposite charge and the deep-level gold impurity is mainly in the negative charge state, quite different electrical behaviors are expected from these two junction types. In work to be described elsewhere, some of these differences have been demonstrated experimentally, such as the breakdown voltage and the impedance, and quantitatively correlated with theory using the spatial variations obtained in this paper.     

Microwave Si avalanche diode with nearly-abrupt-type junction

Microwave Si avalanche diodes with a nearly-abupt-type junction have been made. The maximum output power so far obtained in CW operation is 1.1 watts at 12 GHz with an efficiency of 7.7 percent. The maximum efficiency observed is 8.0 percent. The improved performance over the previously reportedp nu nstructure, for which the best result was 250 mW at 12 GHz with an efficiency of 2.8 percent results from a reduction in length of the avalanche region in the abrupt junction. In the previously reportedp nu ndiode the efficiency is still sharply increasing at the burnout point, while in the present diode the efficiency is nearly saturated at the burn-out point. The advantages and disadvantages of using different polarity of the diode (p on n or n on p) and different material (Ge) are given. Small-signal theory was used to analyze device operation.     

Characterization of spiral inductors with patterned floating structures

The impact of two different types of floating patterns on spiral inductors was investigated. Both patterned trench isolation with a floating p/n junction and floating metal poles were implemented underneath reference spiral inductors. All three types of inductors have an identical spiral geometry. Combination of patterned trench isolation with a floating p/n junction increases maximum quality factor (Q/sub max/) by 17% compared to the reference inductors. The floating metal poles enable adjustment of the frequency at Q/sub max/ (f/sub max/) without hampering the Q/sub max/. A ladder-type lump-element model was employed to analyze inductor performance after it was demonstrated to precisely capture behavior of all three inductors. Enhancement of the quality factor due to patterned trench isolation with a floating p/n junction was found to result from an increment of effective resistivity in substrates. Reduction of the frequency f/sub max/ due to the floating metal poles was caused by increasing effective coupling capacitance between the spiral inductors and substrate.     

Improved germanium avalanche photodiodes

New kinds of germanium avalanche photodiodes with n+-n-p and p+-n structures were devised for improved excess noise and high quantum efficiency performance. Multiplication noise, quantum efficiency, and pulse response were studied and compared with those of the conventional n+-p structure diode. Multiplication noise of the new type of diodes were measured in the wavelength range between 0.63 and 1.52 μm. The effective ionization coefficient ratio of the p+-n diode was lower than unity at a wavelength longer than 1.1 μm and 0.6-0.7 at 1.52 μm, and that of the n+-n-p diode was 0.6-0.7 in the whole sensitive wavelength region. Response times were evaluated by using a mode-locked Nd:YAG laser beam and a frequency bandwidth wider than 1 GHz was estimated. Receiving optical power levels were compared with each other using parameters measured in this study.     

Optimization of n/i and i/p buffer layers in n-i-p hydrogenated microcrystalline silicon solar cells

Hydrogenated microcrystalline silicon (μc-Si:H) intrinsic films and solar cells with n-i-p configuration were prepared by plasma enhanced chemical vapor deposition (PECVD). The influence of n/i and i/p buffer layerson the μc-Si:H cell performance was studied in detail. The experimental results demonstrated that the efficiency is much improved when there is a higher crystallinity at n/i interface and an optimized a-Si:H buffer layer at i/p interface. By combining the above methods, the performance ofμc-Si:H single-junction and a-Si:H/μc-Si:H tandemsolar ceils has been significantly improved.