High performance trench MOS barrier Schottky diode with high-k gate oxide

A novel trench MOS barrier Schottky diode(TMBS) device with a high-k material introduced into the gate insulator is reported, which is named high-k TMBS. By simulation with Medici, it is found that the high-k TMBS can have 19.8% lower leakage current while maintaining the same breakdown voltage and forward turn-on voltage compared with the conventional regular trench TMBS.     

Control of high-k/germanium interface properties through selection of high-k materials and suppression of GeO volatilization

Two approaches to control high-k/Ge interface qualities were investigated. The first approach was using high-k materials that are intimate with Ge. These Ge-intimate high-k materials should have moderate reactivity with Ge to form an amorphized interface that will reduce the interface defects and will suppress the GeO desorption at the interface. The second approach was modifying the annealing processes by using a cap layer to block GeO out-diffusion. We found that Si works as the cap layer very efficiently. By combining those two approaches, we achieved fairly good high-k/Ge metal-insulator-semiconductor (MIS) characteristics with LaYO₃ as the Ge-intimate high-k material, and a NiSi_X electrode as the cap layer. These results provide us an important guide for controlling the high-k/Ge interface properties.     

Study on a low loss, low voltage, polarization-independent EO modulator based LPG

In this paper, a new type of high-speed EO modulator is presented. It is a multi-cladding structure with LPG written in the core, and polymer with high EO coefficient is fabricated as the outer layer. A special material with ultra-negative temperature coefficient is used for the temperature compensation. This modulator is polarization independent, it can be coupled with the optical fiber very easily and can work steadily with low voltage, high speed, is temperature insensitive, and its cost is low. To our knowledge, this is the first time a modulator has been designed with such a simple and effective structure.     

CVD-derived Hf-based High-k Gate Dielectrics

Hf-based high-k gate dielectric has been recently highlighted as the most promising high-k dielectrics for the next-generation CMOS devices with high performance due to its excellent thermal stability and relatively high dielectric constant. This article provides a comprehensive view of the state-of-the-art research activities in advanced Hf-based high-k gate dielectrics grown by chemical-vapor-deposition-based method, including metal-organic-chemical-vapor-deposition (MOCVD), atomic-layer-chemical-vapor-deposition (ALCVD), and plasma-enhanced- chemical-vapor-deposition (PECVD), in CMOS device. We begin with a survey of methods developed for generating Hf-based high-k gate dielectrics. After that, most attention has been paid to the detailed discussion of the latest development of novel Hf-based high-k gate dielectrics grown by CVD. Finally, we conclude this review with the perspectives and outlook on the future developments in this area. This article explores the possible influences of research breakthroughs of Hf-based gate dielectrics on the current and future applications for nano-MOSFET devices.     

A threshold voltage model of short-channel fully-depleted recessed-source/drain(Re-S/D) SOI MOSFETs with high-k dielectric

In this paper, a surface potential based threshold voltage model of fully-depleted(FD) recessed-source/drain(Re-S/D)silicon-on-insulator(SOI) metal-oxide semiconductor field-effect transistor(MOSFET) is presented while considering the effects of high-k gate-dielectric material induced fringing-field. The two-dimensional(2D) Poisson's equation is solved in a channel region in order to obtain the surface potential under the assumption of the parabolic potential profile in the transverse direction of the channel with appropriate boundary conditions. The accuracy of the model is verified by comparing the model's results with the 2D simulation results from ATLAS over a wide range of channel lengths and other parameters,including the dielectric constant of gate-dielectric material.     

Implementation of nanoscale circuits using dual metal gate engineered nanowire MOSFET with high-k dielectrics for low power applications

This work covers the impact of dual metal gate engineered Junctionless MOSFET with various high-k dielectric in Nanoscale circuits for low power applications. Due to gate engineering in junctionless MOSFET, graded potential is obtained and results in higher electron velocity of about 31% for HfO₂ than SiO₂ in the channel region, which in turn improves the carrier transport efficiency. The simulation is done using sentaurus TCAD, ON current, OFF current, I_ON/I_OFF ratio, DIBL, gain, transconductance and transconductance generation factor parameters are analysed. When using HfO₂, DIBL shows a reduction of 61.5% over SiO₂. The transconductance and transconductance generation factor shows an improvement of 44% and 35% respectively. The gain and output resistance also shows considerable improvement with high-k dielectrics. Using this device, inverter circuit is implemented with different high-k dielectric material and delay have been decreased by 4% with HfO₂ when compared to SiO₂. In addition, a significant reduction in power dissipation of the inverter circuit is obtained with high-k dielectric Dual Metal Surround Gate Junctionless Transistor than SiO₂ based device. From the analysis, it is found that HfO₂ will be a better alternative for the future nanoscale device.     

Optical modulator based on negative refractive material

Using negative refractive material slow-wave waveguide, a compact and integrated optical modulator is proposed for the first time to our knowledge. The slow group velocities of light, which are readily achievable in negative refractive material waveguide, can dramatically increase the induced phase shifts caused by small changes in the refractive index. Modulation operation with a 40 μm long negative refractive material slow-wave waveguide of a Mach–Zehnder interferometer (MZI) structure was demonstrated by using finite-element method. The size of the novel optical modulator is 100 times shorter than that of the conventional lithium niobate MZI optical modulator.     

A two-dimensional threshold voltage analytical model for metal-gate/high-k/SiO₂ /Si stacked MOSFETs

In this paper the influences of the metal-gate and high-k/SiO 2 /Si stacked structure on the metal-oxide-semiconductor field-effect transistor(MOSFET) are investigated.The flat-band voltage is revised by considering the influences of stacked structure and metal-semiconductor work function fluctuation.The two-dimensional Poisson’s equation of potential distribution is presented.A threshold voltage analytical model for metal-gate/high-k/SiO 2 /Si stacked MOSFETs is developed by solving these Poisson’s equations using the boundary conditions.The model is verified by a two-dimensional device simulator,which provides the basic design guidance for metal-gate/high-k/SiO 2 /Si stacked MOSFETs.     

Electrical and material characterization of tantalum pentoxide (Ta2O5) charge trapping layer memory

In this experiment, tantalum pentoxide (Ta₂O₅) was used in a metal/oxide/high-k Ta₂O₅/oxide/silicon (MOHOS) novel nanocrystal memory as a trapping layer. Post-annealing treatment, which can passivate defects and improve the material quality of the high-k dielectric, was applied to optimize device performance for a better memory window and faster P/E (program/erase) cycle. Material and electrical characterization techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and electrical measurements were performed to analyze the device under different annealing conditions. The Ta₂O₅ charge trapping layer memory annealed at 900 °C had a higher window of 3.3 V in the current-voltage (C-V) hysteresis loop, and a higher charge retention capability than the samples prepared under various annealing conditions. These higher levels were due to the higher probability of deep-level charge trapping and lower leakage current.     

Influence of ultra-thin TiN thickness(1.4 nm and 2.4 nm) on positive bias temperature instability(PBTI)of high-k/metal gate nMOSFETs with gate-last process

The positive bias temperature instability(PBTI) degradations of high-k/metal gate(HK/MG) n MOSFETs with thin Ti N capping layers(1.4 nm and 2.4 nm) are systemically investigated. In this paper, the trap energy distribution in gate stack during PBTI stress is extracted by using ramped recovery stress, and the temperature dependences of PBTI(90?C,125?C, 160?C) are studied and activation energy(Ea) values(0.13 e V and 0.15 e V) are extracted. Although the equivalent oxide thickness(EOT) values of two Ti N thickness values are almost similar(0.85 nm and 0.87 nm), the 2.4-nm Ti N one(thicker Ti N capping layer) shows better PBTI reliability(13.41% at 0.9 V, 90?C, 1000 s). This is due to the better interfacial layer/high-k(IL/HK) interface, and HK bulk states exhibited through extracting activation energy and trap energy distribution in the high-k layer.     

Low-V(pi) electro-optic modulator with a high-microbeta chromophore and a constant-bias field

A low half-wave voltage V(pi) of 1.57 V was obtained with a 2-cm-long birefringent polymer waveguide modulator at a wavelength of 1.3 microm by use of a modulator design with a constant-bias electric field and a high-microbeta chromophore. The design allows the maximum achievable electro-optic coefficient of the material to be utilized. This electro-optic coefficient can be more than twice as high as the residue value that is used by conventional modulator designs, after fast partial relaxation following poling.     

Development of spatial light modulators with nonlinear organic materials

An electrically addressable spatial light modulator is designed using nonlinear organic materials for optical information processing and display. One candidates for spatial light modulator (SLM) material is a nonlinear organic polymer of poly-methyl-methacrylate doped with disperse red 1. The measured electrooptic coefficient r₃₃ is 2.9 pm/V at the wavelength of 633 nm. Resonator structure for a material is discussed with the goal of increasing electrooptic effects for SLM applications.     

Study on Control of Bias Point Drifting in Optical Fiber CATV Externally Modulated Transmitters

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Analytical model, analysis and parameter optimization of a super linear electro-optic modulator (SFDR > 130 dB)

An analytical model of a super linear optical modulator with high spurious-free-dynamic-range (SFDR > 130 dB) is presented and analyzed. The linear modulator is referred to as IMPACC which stands for Interferometric Modulator with Phase-modulating And Cavity-modulating Components. The modulator is based on a unique combination of a RF-driven phase-modulator (PM) and a ring resonator (RR) within a Mach-Zehnder interferometer (MZI) configuration. Our analysis shows that our design can achieve SFDR values which are ~ 20 dB higher than the standard MZI modulator and 3-5 dB from the Ring Assisted Mach-Zehnder Interferometer (RAMZI) modulator. Both PM and RR in the IMPACC are simultaneously driven by a RF signal of the same frequency, but not necessarily the same amplitudes. The analytical model shows that the combination of these two optical elements, with the proper choice of RF-driving and device parameters, can lead to four important and compelling consequences. First, it offers a wholistic and elegant model in which the standard MZI modulator and the RAMZI modulator are just special cases of IMPACC. Second, the model offers an excellent parameter optimization methodology for fast parameter (internal and/or external) selection and performance evaluation. Third, it provides additional degree of control through the introduction of an external control parameter, the RF power split ratio (F). Lastly, it demonstrates one unique feature of IMPACC such as adaptive SFDR characteristics, where manufacturing tolerances in the transmission coefficient (τ) of the RR can be compensated with proper adjustments of the external parameter of the power split ratio (F).     

Interface models and processing technologies for surface passivation and interface control in III-V semiconductor nanoelectronics

Interface models and processing technologies are reviewed for successful establishment of surface passivation, interface control and MIS gate stack formation in III-V nanoelectronics. First, basic considerations on successful surface passivation and interface control are given, including review of interface models for the band alignment at interfaces, and effects of interface states in nanoscale devices. Then, a brief review is given on currently available surface passivation technologies for III-V materials, including the Si interface control layer (ICL)-based passivation scheme by the authors’ group. The Si-ICL technique has been successfully applied to surface passivation of nanowires and to formation of a HfO₂ high-k dielectric/GaAs interfaces with low values of the interface state density.     

储存环相干谐波自由电子激光器新光学速调管工作状态分析

 合肥国家同步辐射实验室（NSRL）正在开展储存环相干谐波自由电子激光研究，为了在较高电子束能量下进行实验、且具有较高的相干辐射强度，光学速调管从原来的对称结构改造为非对称结构。分析了相干谐波实验中各参数之间的关系，及对相干谐波辐射的影响，并给出了两种工作状态下的最佳工作参数。     

Numerical and analytical investigations for the SOI LDMOS with alternated high-k dielectric and step doped silicon pillars

This paper presents a new silicon-on-insulator(SOI) lateral-double-diffused metal-oxide-semiconductor transistor(LDMOST) device with alternated high-k dielectric and step doped silicon pillars(HKSD device). Due to the modulation of step doping technology and high-k dielectric on the electric field and doped profile of each zone, the HKSD device shows a greater performance. The analytical models of the potential, electric field, optimal breakdown voltage, and optimal doped profile are derived. The analytical results and the simulated results are basically consistent, which confirms the proposed model suitable for the HKSD device. The potential and electric field modulation mechanism are investigated based on the simulation and analytical models. Furthermore, the influence of the parameters on the breakdown voltage(BV) and specific on-resistance(R_on,sp) are obtained. The results indicate that the HKSD device has a higher BV and lower R_on,sp compared to the SD device and HK device.     

Thermal stability of HfO2/Si（001） films prepared by electron beam evaporation in ultrahigh vacuum using atomic oxygen

HfO2 films on silicon substrates have been prepared by electron beam evaporation in ultrahigh vacuum using atomic oxygen.Synchrotron radiation photon-electron spectroscopy was used to investigate the thermal stability of HfO2 films under an ultrahigh vacuum environment.At the temperature of 750℃,HfO2 films begin to decompose.After being further annealed at 850℃ for 3 min,HfO2 films decomposes completely,partially to form Hf-silicide and partially to form gaseous HfO.Two chemical reactions are responsible for this decomposition process.A small amount of Hf-silicide,which is formed at the very beginning of growth,may result in the films grown subsequently to be loosened,and thereby leads to a relatively low decomposition temperature.     

Harmonic and Intermodulation Performance of Fabry-Perot Intensity Modulator

Abstract

In this article, a mathematical model for the transfer function of the Fabry-Perot intensity modulator is presented. The model, basically a cosine-series function, can be used to obtain closed-form expressions for the amplitudes of the harmonic and intermodulation products of the Fabry-Perot intensity modulator driven by a multi-frequency radio frequency voltage. The special case of a Fabry-Perot intensity modulator driven by an equal-amplitude two-frequency radio frequency voltage is considered in detail, and the results are compared, whenever possible, with previously published experimental and numerically obtained results.     

Sensitivity improvement of broadband electro-optic polymer-based optical phase modulator using 1D and 2D photonic crystal structures

This Letter introduces the design and simulation of a microstrip-line-based electro-optic(EO) polymer optical phase modulator(PM) that is further enhanced by the addition of photonic crystal(PhC) structures that are in close proximity to the optical core. The slow-wave PhC structure is designed for two different material configurations and placed in the modulator as a superstrate to the optical core; simulation results are depicted for both1 D and 2D PhC structures. The PM characteristics are modeled using a combination of the finite element method and the optical beam propagation method in both the RF and optical domains, respectively.The phase-shift simulation results show a factor of 1.7 increase in an effective EO coefficient(120 pm/V) while maintaining a broadband bandwidth of 40 GHz.