交换关联对半导体超晶格等离激元色散关系的影响

本文用优化的局域密度泛函近似所给出的介电矩阵计算了GaAs-Al_xGa_(1-x)As超晶格中等离激元色散关系,得到了对无规相近似的重要修正.     

基于人工表面等离激元周期调制的漏波天线设计

基于超薄波纹金属条带结构,利用人工表面等离激元的周期调制原理,设计出辐射波束角度及数量均可设计的漏波天线.首先,分析了不同周期下人工表面等离激元单元结构的色散特性;其次,介绍了周期调制的原理,即通过将调制周期从亚波长尺寸不断增大到波长尺寸,人工表面等离激元将经历从高效传输到截止,然后到定向漏波乃至多波束辐射的过程;再次...     

单层原子的厚度对等离激元色散关系的修正北大核心CSCD

基于自由电子气体模型,利用线性响应理论结合格林函数方法求解了单层原子体系的等离激元频率,得出了可适用于高电子密度短波情形的等离激元色散关系的解析解。研究结果表明:原子层的厚度会降低等离激元的频率,原子层越厚,等离激元频率越小,这种变小在波矢越大时表现得越明显。当单层原子的厚度趋于零时,其等离激元的色散关系趋近于纯二维等离激元的色散关系。此外,在单层原子体系等离激元频率的一阶近似中,发现长波近似下等离激元频率的相对修正与波矢以及原子层的厚度都呈线性关系。     

石墨烯/光子晶体混合结构的可调谐表面等离激元自准直

文章探究了中红外波段表面等离激元在石墨烯/光子晶体混合结构传输的自准直现象。在石墨烯的硅基底上设计了二维周期圆形空气孔结构,该结构能够实现表面等离激元光子晶体的特性。运用平面波展开法计算石墨烯表面等离激元光子晶体的能带,并计算出等频线。从该结构的等频线可以获得自准直的频率。我们进一步应用有限时域差分方法计算自准直频率在结构中的传输,可观察到该频率下石墨烯上的表面等离激元电场在通过该结构时出现自准直现象。在基底参数不变情况下,通过调节石墨烯的费米能,来改变等离激元光子晶体的能带,从而调节等离激元自准直频率。文章提出的基于石墨烯的等离激元自准直器件,有望应用于未来集成等离激元器件之间的连接。     

基于结构诱导人工表面等离激元的宽带低耦合电路北大核心CSCD

实现超宽带传输和超高集成度设计是微波和太赫兹电路发展的终极目标。针对以上目标,本文提出了结构诱导人工表面等离激元的概念。基于此设计并验证了具有超高局附性和超小传输常数的结构诱导人工表面等离激元电路结构,打破了传统人工表面等离激元电路对传输常数和衰减常数的限制。理论分析和数值验证表明,相较于经典人工表面等离激元,具备优异的场局附性和传输特性的结构诱导人工表面等离激元具有明显的弱色散和低耦合特性,在电路设计中可以有效减少宽带信号传输的色散失真,同时提高布线密度。     

外电场下不对称阶梯型量子阱的等离激元特性

我们研究了Al Ga As/Ga As不对称阶梯形量子阱中准二维电子气的集体激发色散关系随电场的变化特性。发现正向电场会使子带间等离激元模变短甚至消失,反向电场会使子带间等离激元模变变长。该子带间集体激发模波矢的有效大小取决于最低两能级的波函数交叠程度。这些特性可能有利于研究基于电场效应的阶梯形量子阱结构的器件。     

等离激元太阳能电池概述

贵金属纳米粒子的表面等离激元共振峰附近的光散射可以有效的增强薄膜太阳能电池光吸收效率.基于等离激元方法设计的太阳能电池可以很大程度上增强光吸收,并且减少太阳能电池的光吸收层厚度从而减小体积.本文针对等离激元增强太阳能电池性能的原理进行介绍,并且对其未来发展趋势进行了展望.     

基于人工表面等离激元的天线研究进展

人工表面等离激元是在人工电磁媒质与传统材料界面激发的一种亚波长表面电磁模式, 具有波长短、场局域增强、色散可调等新奇的电磁特性, 在小型化微波器件、隐身材料与隐身结构、天线/天线罩等领域具有重要应用前景.文章综述了人工表面等离激元在天线中的应用研究进展, 包括基于混合模式耦合、相位梯度超表面解耦、周期结构解耦等原理的端射天线、多波束天线、频扫天线, 为新型天线的研发与应用提供技术支撑.     

等离激元增强金硅肖特基结近红外光电探测器进展

表面等离激元共振衰减诱导热电子,因其能量高、分布窄、打破半导体禁带宽度限制等特点被广泛应用于拓展半导体光电转换的响应光谱,如拓展宽禁带半导体的响应光谱至可见光波段,拓展硅的响应波段至近红外。此外,还可以通过调节表面等离激元结构调控响应光谱和实现偏振探测,在实现硅基近红外光电探测领域具有重要的应用价值。从表面等离激元以及表面等离激元内光电效应的机理出发,综述了表面等离激元热电子原理在实现硅基近红外光电探测方面的研究进展,并总结了表面等离激元结构的形貌,尺寸、分布等因素对热电子的产生（外量子效率）和注入效率（内量子效率）的影响。最后展望了基于表面等离激元结构的硅基肖特基结近红外光电探测的研究方向。     

表面等离激元纳米结构增效的光电探测器进展（特邀）

光电探测器作为航空航天、深空探测和环境监测等领域的核心器件之一,具有重要的科学研究和实用价值。表面等离激元具有可突破光学衍射极限、实现纳米聚焦的性质,为光电探测器的性能提升提供了全新的技术手段,是近年来光电探测增效研究领域的热点之一。文中围绕表面等离激元纳米结构增效的光电探测器研究展开综述,首先介绍了各类表面等离激元纳米结构的物理特性,主要包括局域表面等离激元结构和传导型的表面等离极化激元结构,以及由表面等离激元金属和半导体材料构成的异质结构;然后重点从探测器性能、探测原理和工艺方法等角度,介绍了等离激元纳米结构增强的光电探测器的研究进展;最后对表面等离激元纳米结构增效的光电探测器及其在未来面临的挑战进行了总结和展望。     

Proposal of a Microwave-Driven Semiconductor Superlattice Oscillator for Generation of THz Radiation

We present the proposal of a microwave-driven semiconductor superlattice oscillator. We show that the interplay of a microwave pump field with a synchronous harmonic field can make a semiconductor superlattice to a gain medium for the harmonic field. Placing the superlattice in a resonator for the harmonic field allows the operation of an oscillator. The gain mechanism is based on Bloch oscillations of miniband electrons. The gain is mediated either by the interaction of the high-frequency field with the single electrons or with space charge domains or with both. The microwave-driven superlattice oscillator should be suitable for generation of coherent radiation up to several THz.     

半导体/超晶格分布布拉格反射镜(DBR) 的分子束外延生长

用分子束外延技术(MBE)生长了以GaAs/AlAs超晶格替代AlxGa1-xAs所形成的P型半导体/超晶格分布布拉格反射镜(DBR)．此分布布拉格反射镜的反射谱中心波长为850nm．由实验表明,19个周期的反射镜获得了高达99％以上的高反射率．与此同时,采取自行设计的二次钨丝掩膜质子注入法制成15μm×15μm的正方形电流注入区,以此测定P型反射镜的串联电阻,克服了湿化学腐蚀法中腐蚀深度不易控制及侧面同时被腐蚀的缺点,实验得出此P型反射镜的串联电阻仅为50Ω左右．在生长过程中,发现在只含一个铝源的分子束外延生长系统中,生长这种半导体/超晶格反射镜相对其他半导体/半导体反射镜要节省很多外延生长时间,因此较适合应用于多层结构的光电器件中．     

Resonance and absorption band in the classical magnetoactive semiconductor-insulator superlattice

Electromagnetic wave propagation in the classical semiconductor-dielectric superlattice is investigated in the limit of wavelengths, exceeding the lattice spatial period. The resonance and absorption band have been experimentally discovered in a frequency range below the semiconductor plasma frequency in the presence of the dc magnetic field normal to the wave vector and the lattice periodicity direction.     

随机层厚分布的半导体超晶格光荧光对温度的依赖关系

本文提出热激活辐射过程和Berthelot-型的非辐射复合过程互相竞争的简单模型解释无序半导体超晶格的光荧光随温度变化行为,预言了当温度升高荧光衰变时间在某一温度附近快速下降;获得了高温时较大无序度的半导体超晶格比较小无序度的半导体超晶格荧光强,在低温时情况相反;且荧光峰随温度变化存在一个最大值。理论结果与实验观察到的无序半导体超晶格荧光行为一致。     

计算二维半导体体系电子能带的ATM(英文)

It is pointed out that in terms of the asymptotic transfer method (ATM) suggested by us, the electron subbands and wavefunctions can be solved consistently for both type-I and type-Ⅱ semiconductor multi-quantum-well systems in which the bandedges of conduction bands and valence bands are not flat (oblique lines or curves). As illustrative examples,we performed a self-consistent calculation of electron subbands and wavefunctions of a Ga1-xAlxAs sawtooth superlattice taking account of the variation of the effective mass of electrons with the concentration of Al. We also finished a calculation of electron subbands of type-Ⅱ semiconductor multi-quantum-well systems when an electric field was applied along the growth axis. It is shown that for type-Ⅱ semiconductor multi-quantum-well systems the application of an electric field also results in a strong localization of the eigenstates.     

Hybrid and effective satellites for studying superlattices

Observation of new synchrotron X-ray scattering processes in semiconductor superlattice structures are reported. They are analogous to the three-beam diffraction in single crystal; however, the basic difference is that in these new processes superlattice-satellite reflections came to play. They give rise to effective-satellite reflections (superlattice–superlattice coupling) and hybrid-satellite reflections (substrate–superlattice coupling). These sort of reflections are features that depend on the rotation of the sample around the surface-normal direction, i.e. an azimuthal or φ rotation. Their positions in φ are very sensitive to the in-plane projection of the reciprocal space, but while the effective-satellite reflections are sensitive to the superlattice parameters, the positions of the hybrid-satellite reflections depend mostly on the substrate ones. The selective sensitivity of these two sort of reflections is the physical fact that can be used as a new tool for studying superlattices.     

Design of quantum-dot lasers with an indirect bandgap short-period Superlattice for reducing the linewidth enhancement factor

A novel gain medium consisting of direct bandgap semiconductor quantum dots (QDs) embedded in a short-period superlattice of indirect bandgap as barrier material is proposed to produce QD lasers with extremely small linewidth enhancement factor /spl alpha/. Our analysis has shown that at least one order-of-magnitude reduction in /spl alpha/ can be achieved at room temperature compared to that of similar QDs embedded in direct-bandgap barriers, making low chirp, narrow linewidth semiconductor lasers feasible.     

Radiative tunneling recombination and luminescence of trapezoidal δ-doped superlattices

Radiative recombination is investigated in the authors’ previously proposed δ-doped superlattice, which can be grown from one of several well-known single-crystal semiconductors of the type InSb, InAs, or GaAs. The energy diagram of the superlattice consists of alternating trapezoidal n-type and p-type potential wells for electrons and holes. An equation for the radiative recombination rate is derived for such a trapezoidal superlattice, and it is shown that, owing to the spatial separation of electrons and holes, the radiative lifetime can attain values of the order of 1 ms, and that it depends weakly on the temperature. This result is attributable to the fact that radiative recombination in a trapezoidal superlattice is governed by optical tunneling transitions of electrons from states near the bottom of the n-type wells to states near the bottom of the p-type wells. An expression is obtained for the luminescence spectrum of the superlattice, where the spectral maximum corresponds to a photon energy much smaller than the width of the semiconductor band gap and can be situated in the far-infrared range. It is noted that such a trapezoidal superlattice can be an efficient converter of thermal radiation into very long-wavelength radiation. Fiz. Tekh. Poluprovodn. 33, 101–105 (January 1999)     

超晶格半导体材料的光磁电效应(I)

从Shockley-read统计出发，引入载流子寿命与浓度的相关性，描述了超晶格半导体载流子的输运特征，将载流子的输运方程化为二阶非线性方程，并用双参数摄动法找到了方程的一般解.在二阶近似下，计算了半导体材料的短路电流和光导电流，进一步揭示了大信号情况下光磁电效应的非线性特征.     

Figurate superlattices in the classical problem of signal filtering against the noise background on the basis of a cellular nonlinear network

A new type of multilayer semiconductor structures (figurate superlattices) that can be used in construction of resonant-tunneling diode components has been proposed and investigated. The superlattice advantages over structures with standard nonlinear current-voltage characteristics are discussed as applied to the classical filtering problem on the basis of a cellular nonlinear network. It is demonstrated that the absolutely new, so-called fractal cellular nonlinear networks can be developed.