Ⅲ-Ⅴ族半导体材料组成光子晶体能态密度特性

应用平面波展开法研究Ⅲ-Ⅴ族半导体材料组成光子晶体能态密度特性,得到填充率f随品格半径a之间的变化对应的能态密度分布,当f=0．2a时归一化频率存在最大光子带隙。通过比较化合物半导体材料为AIP、AJAs、AISb和GaP构成二维方形光子晶体得出GaP有较宽的光子禁带,随着填充率的增加光子晶体带隙增加。研究结果为光子晶体器件的研究提供理论依据。     

Optical reflectometry elucidates layer thicknesses

Following on from his earlier articles in III-Vs Review's characterization series, on the applications of X-ray diffraction and photoluminescence, Chris Moore here turns his attention to spectrally resolved optical reflectrometry. Data interpretation relies on sophisticated analysis techniques but their automation yields a powerful tool for the routine characterization of compound semiconductor devices such as VCSELs.     

First Principles Study on Electronic Structure and Optical Properties of Ternary Semiconductor InxAl1 –xP Alloys

Semiconductors - The elastic, electronic and optical properties of the indium doped AlP, have been investigated by the first-principle calculations within the framework of the density functional...     

Theoretical calculations of Debye length,built-in potential and depletion layer width versus dopant density in a heavily doped p-n junction diode

Theoretical calculations of Debye length, built-in potential, depletion layer width and capacitance as a function of dopant density in a heavily doped p-n junction diode are described in this paper. The heavy doping effects such as carrier degeneracy, dopant density-dependent dielectric constant and bandgap narrowing are accounted for by using the empirical approximation for the reduced Fermi-energy given by[1] and the dopant density dependent dielectric constant given by[2], as well as the bandgap narrowing model proposed by[3]. The results show that: (1) bandgap narrowing and carrier degeneracy have important effects on the junction built-in potential; (2) carrier degeneracy and dopant density-dependent dielectric constant are important to Debye length for the abrupt junction case, and (3) the dopant density-dependent dielectric constant is a key parameter which strongly affects the values of depletion layer width and depletion capacitance. These findings are important for modeling of heavily doped p-n junction devices in the VLSI applications.     

在ICE设备上进行低材料灰化技术(英文)

为满足半导体产品的高性能化,Low-k穴低导电雪材料正被使用于层间绝缘膜,但是Low-k材料在灰化穴Ashing雪过程中由于高温及氧自由基穴O-radical雪的作用而引起材质变化导致导电率上升的问题的发生。为解决这个问题,在ICE设备上开发了灰化Low-k周边的低温处理工艺。Low-k导电率变化系在Low-k表面生成高导电率氧化层所致,所以为减少导电率变化须选择合适的离子源生成尽可能薄的氧化层是非常重要的且已被证明。在这里,Low-k灰化时导电率变化的机理,改善效果及相关运用作个介绍。     

Modification of Drude model on the free carrier property of IV-VI compound semiconductor in magnetic field

A general analytical expression is reported for the Drude model's dielectric function of free carrier in multi-valley IV-VI compound semiconductor in the magnetic field. The modifications of the energy band non-parabolicity and free carrier re-population are introduced to the dielectric function in combination with the $\vec k \cdot \vec P$ model. The difference of the dielectric function between the modified Drude model and the classical Drude model is demonstrated by the calculation for the typical IV-VI compound semiconductor material PbTe.     

Optical and mechanical properties of C,Si, Ge,and 3C–SiC determined by first-principles theory using Heyd–Scuseria–Ernzerhof functional

Accurately calculating the band gap and electronic state density distribution of crystals is significant in determining optical properties. First-principles calculations were based on the projector-augmented-wave method with the Perdew–Burke–Ernzerhof generalized gradient approximation functional, pure density functional theory (DFT) and Heyd–Scuseria–Ernzerhof (HSE) hybrid functional. Such calculations account for the lattice parameters, electronic structure, optical properties, and mechanical properties of materials, which include the diamond-C and zinc blende structure of Si, Ge, and 3C–SiC in this study. The results obtained with HSE calculations is more accurate than that of the pure DFT calculations, and consistent with previous experimental values. The band structure and density of states of Si, Ge, and 3C–SiC indicate that these materials are indirect band gap materials. Based on HSE calculation, the band gap of Si and 3C–SiC is in accordance with previous experimental values. The imaginary part of the analytical dielectric function, the refractive index, and the adsorption coefficient also matches previous experimental values. A corresponding relationship exists among the peak of the imaginary part of the analytical dielectric function, the refractive index, and the adsorption coefficient. The optical properties have a direct relationship with the distribution of the crystal band gap and electronic state density. The materials exhibit brittleness. Although 3C–SiC is not as hard and stiff as diamond, it is a better semiconductor than Si and Ge. The mechanical anisotropy of the four materials is inconspicuous. The anisotropy of diamond-C in terms of its Young's modulus is extremely inconspicuous.     

Challenges of integration of high-κ dielectric with III–V materials (Invited Paper)

This paper gives a brief overview of some of the challenges and approaches of integration of high dielectric constant (high-κ) dielectrics with compound semiconductor materials for future high performance low power logic applications. Reviewed themes include interface passivation layer, atomic layer deposition self-cleaning effects and characterization of dielectric/III–V interfaces.     

Organozinc Compounds as Effective Dielectric Modification Layers for Polymer Field‐Effect Transistors

The interface between the organic semiconductor and dielectric plays an important role in determining the device performance of organic field‐effect transistors (OFETs). Although self‐assembled monolayers (SAMs) made from organosilanes have been widely used for dielectric modification to improve the device performance of OFETs, they suffer from incontinuous and lack uniform coverage of the dielectric layer. Here, it is reported that by introduction of a solution‐processed organozinc compound as a dielectric modification layer between the dielectric and the silane SAM, improved surface morphology and reduced surface polarity can be achieved. The organozinc compound originates from the reaction between diethylzinc and the cyclohexanone solvent, which leads to formation of zinc carboxylates. Being annealed at different temperatures, organozinc compound exists in various forms in the solid films. With organozinc modification, p‐type polymer FETs show a high charge carrier mobility that is about two‐fold larger than a control device that does not contain the organozinc compound, both for devices with a positive threshold voltage and for those with a negative one. After organozinc compound modification, the threshold voltage of polymer FETs can either be altered to approach zero or remain unchanged depending on positive or negative threshold voltage they have.     

Fabrication of polymer blend composites based on [PVA-PVP](1−x):(Ag2S)x (0.01 ≤ x ≤ 0.03) with small optical band gaps: Structural and optical properties

In this paper composite materials, based on polymer blends of polyvinyl alcohol (PVA): polyvinyl pyrrolidone (PVP) with small optical band gap, has been studied. Silver sulfide (Ag₂S) semiconductor particles have been synthesized in PVA:PVP blend host polymer, using in situ method. X-ray diffraction (XRD) analyses and Fourier transform infrared (FTIR) spectroscopy for the composite samples were carried out. From the XRD pattern, distinguishable crystalline peaks caused by the Ag₂S semiconductor particles were observed. From the result of FTIR spectroscopy, the intensity of the FTIR bands were shifted and increased, revealing the occurrence of interactions between the PVA:PVP blend system and Ag₂S particles. The composite samples were found to exhibit absorption spectra that cover UV–visible to near infrared regions. The absorption edge was found to be 5 eV for pure PVA:PVP system and shifted to 1.15 eV for incorporated PVA:PVP with 3 M of Ag₂S. The refractive index was also evaluated for the samples and observed to be increased from 1.15 to 1.52 as doping increased to the highest. A linear relationship between the refractive index and the filler fraction has been reported. Theoretical discussion of optical dielectric loss, which is a crucial parameter for the band gap estimation, was given. The achieved results reveal that spectra of the optical dielectric loss (ɛ_i) can be used to study the band gap structure and Tauc's model can be important in determining the types of electronic transition. The optical band gap was found to decrease from 5.2 eV for the pure PVA:PVP to 1.1 eV for doped PVA:PVP with 3 M of Ag₂S. Such reduction can be associated with the increase of optical dielectric constant. Finally, the correlation between optical dielectric constant and density of states was discussed.     

Monolithic Semiconductor Waveguide Device Concept for Picosecond Pulse Amplification, Isolation, and Spectral Shaping

In this paper, a waveguide device concept, named IRIS, is presented. The device consists of a monolithic array of concatenated semiconductor optical amplifiers and saturable absorbers. We have theoretically investigated picosecond pulse transmission through these devices. The parameters used in the simulation are representative for InP-InGaAsP bulk gain material, operating in the 1550-nm region. Operated as an optical amplifier for picosecond pulses, the simulation results show increased pulse peak amplification and decreased temporal broadening of the pulses for the IRIS devices as compared to a semiconductor optical amplifier of equivalent length. Used as a nonlinear element to increase the optical bandwidth of a picosecond pulse, the spectra obtained with IRIS devices show an increased broadening and smoothness as compared to a semiconductor optical amplifier. Finally the feasibility for using the IRIS device as an optical isolator is shown. It is operated in a regime where the device is transparent for a picosecond pulse train, while it is absorbent for lower power reflections.     

Ⅲ-Ⅴ族半导体材料组成光子晶体能态密度特性

基于平面波展开法,以Ⅲ-Ⅴ族半导体材料AIP、AIAs、AISb和GaP构成二维方形格子光子晶体,并对其光子晶体能态密度特性进行了数值模拟。结果表明,Ⅲ-Ⅴ族半导体材料构成二维方形格子光子晶体具有较好的光子带隙,形成的最大带隙随介电常数差值的增大而增大,f=0.2a时归一化频率达到最大光子带隙,AISb具有较宽的光子禁带。该研究结果为光子晶体器件的研究提供理论依据。     

A Review on Dielectric Breakdown in Thin Dielectrics: Silicon Dioxide,High‐k,and Layered Dielectrics

Thin dielectric films are essential components of most micro‐ and nanoelectronic devices, and they have played a key role in the huge development that the semiconductor industry has experienced during the last 50 years. Guaranteeing the reliability of thin dielectric films has become more challenging, in light of strong demand from the market for improved performance in electronic devices. The degradation and breakdown of thin dielectrics under normal device operation has an enormous technological importance and thus it is widely investigated in traditional dielectrics (e.g., SiO₂, HfO₂, and Al₂O₃), and it should be further investigated in novel dielectric materials that might be used in future devices (e.g., layered dielectrics). Understanding not only the physical phenomena behind dielectric breakdown but also its statistics is crucial to ensure the reliability of modern and future electronic devices, and it can also be cleverly used for other applications, such as the fabrication of new‐concept resistive switching devices (e.g., nonvolatile memories and electronic synapses). Here, the fundamentals of the dielectric breakdown phenomenon in traditional and future thin dielectrics are revised. The physical phenomena that trigger the onset, structural damage, breakdown statistics, device reliability, technological implications, and perspectives are described.     

A Novel Bondpad report process for III-V semiconductor devices using full HSQ properties

This paper reports on an easy and quick planarization and passivation technique of III-V compound semiconductor compatible with nanoscale devices. Vertical etching requires good sidewalls passivation to reduce drastically the leakage current and to obtain a good planarization of the devices for metal connection. This novel technique offers the capability to planarize all the different compounds in the entire wafer independently of the height of the structure to be connected. This method uses the HSQ properties (fluidity, solidification to silica film by using O₂ plasma treatment, negative tone e-beam lithography resist, low-k dielectric, etc.) to planarize and to passivate all the devices at once. We applied this quick and easy method to InP digital optical switches. We demonstrated photonic switches with high yield (>90%), high breakdown voltage (>30 V), low ohmic contact resistance (8 Ω) and a low leakage current (21 pA/μm² for 5 V reversed bias).     

Smart in-plane switching of nanowires embedded liquid crystal matrix

Ultra-thin, high yield semiconductor CdS nanowires (NW's) have been successfully fabricated by the conventional hydrothermal method using ethylenediamine (EDA). This novel hydrothermal approach deals with solvent and ligands exchange process by surfactant injection into solution-phase route, at a fixed holding time and temperature. It is found to be crucial to fabricate large distribution of uniform CdS-NW's width varies up to 7–10 nm. With these extended in thermotropic liquid crystals (e.g. Pimelic acid with undecyloxy benzoic acid; PA+11BAO) matrix producing skein-worm like nanostructures. Liquid crystals (LC) constitute a fascinating class of soft condensed matter characterized by the counter intuitive combination of nanomaterials fluidity and long-range order. Comprehensive graphical response behaviours are performed to investigate dielectric relaxations and phase variance optical switching through this novel nanocomposite device. Moreover, smart electro-optic switching approach is quite promising as well as applicable to other nanomaterials also, and it utilizes the currently mature high contrast liquid crystal switching. This article emerges capacitance vs. voltage hysteresis in a Preisach model fitting analysis. The remarkable signature of a reversal and bi-stable DC switching is also realized in the induced smectic binary composite system upon the application of an appropriate electric field. Electrical and optical tuning interaction of the composites may allow for engineering of practical applications in novel switchable devices.     

High permittivity dielectrics for poly(3-alkylthiophene) field-effect transistor devices

In an attempt to disentangle the effects of permittivity and surface energy of the gate insulator (expressed by its dielectric constant k and water contact angle, respectively) on the performance of organic field-effect transistors (FETs), we fabricated top- and bottom-gate FET architectures with poly(3-alkylthiophenes) (P3ATs) of different side-chain lengths, using a range of gate dielectrics. We find that this class of semiconductor, including the short butyl-(C₄-) substituted derivative, is significantly less susceptible to the often detrimental effects that high-k dielectrics can have on the performance of many organic FETs. For bottom gate devices we identify the surface energy of the gate dielectric to predominantly dictate the device mobility.     

Rare-earth-enabled universal solders for microelectromechanical systems and optical packaging

In packaging of microelectromechanical systems (MEMS), optical, and electronic devices, there is a need to directly bond a wide variety of inorganic materials, such as oxides, nitrides, and semiconductors. Such applications involve hermetic-sealing components, three-dimensional MEMS assembly components as well as active semiconductor or optical components, dielectric layers, diffusion barriers, waveguides, and heat sinks. These materials are known to be very difficult to wet and bond with low melting-point solders. New Sn-Ag- or Au-Sn-based universal solders doped with a small amount of rare-earth (RE) elements have been developed, which now allow direct and powerful bonding onto the surfaces of various MEMS, optical, or electronic device materials. The microstructure, interface properties, and mechanical behavior of the bonds as well as the potential packaging applications of these new solder materials for MEMS and optical fiber devices are described. Various packaging-related structural, thermal, or electrical issues in MEMS are also discussed.     

一种新型半导体材料的电子结构和光学特性：石墨烯一氧化物：

本文首次基于密度泛函理论研究了石墨烯一氧化物一种新型半导体材料的电子结构和光学特性。计算表明石墨烯一氧化物是直接带隙为0.95ev的半导体。通过绘制态密度和分波态密度研究了该材料的能带结构。除此之外,本文给出了该材料的光学特性,这对于材料在光电子器件的潜在应用有着一定的意义。     

半导体激光器光场分析程序的算法研究

本文利用有效介电常数法和等效传输线法两种技巧,导出了一种半导体激光器光场结构分析的计算机程序的算法,并给出了相应的该算法的程序框图.     

具有谐振腔的弯折光子晶体波导特性研究

为了研究基于光子晶体波导的高性能滤波器,采用调节谐振腔结构和优化耦合结构等方法,基于耦合模理论,在正方格光子晶体中设计了3种光子晶体弯折波导,并进行了理论分析和仿真验证,利用时域有限差分法取得了3种波导在S波段及C波段上的工作特性数据。结果表明,3种波导在不同波段表现出良好的带阻或带通特性,且其结构截止传输波长和通带传输波长随整体介质柱相对介电常数增加向长波方向移动,介电常数ε_r每增加0.3,截止传输波长和通带传输波长均增加6nm左右。这一结果对微型光传感器、微型光通信器件、集成光路等方面的设计都是有帮助的。