蓝宝石衬底AlGaN/GaN HFET功率特性

通过台面隔离与注入隔离结合的方法,解决了由于GaN外延材料缓冲层质量差造成的AlGaN/GaN HFET击穿电压低的问题.通过优化的500℃/50s栅退火条件,改善Ni-AlGaN/GaN二极管特性,理想因子和势垒高度分别优化到1.5和0.87eV.通过改进AlGaN/GaN HFET制备工艺,得到提高器件输出功率的优化工艺,采用这一工艺制备的蓝宝石衬底总栅宽为1mm,器件在频率为8GHz时输出功率达到4.57W,功率附加效率为55.1%.     

AlGaN/GaN异质结场效应晶体管的阈值电压

利用AlGaN/GaN异质结场效应晶体管(AlGaN/GaN HFET)栅结构的电容-电压(C-V)特性确定AlGaN/GaN HFET的阈值电压.通过对模拟计算得到的AlGaN/GaN HFET电流-电压(I-V)特性曲线与测试得到的AlGaN/GaN HFET曲线比较分析,证实了依据AlGaN/GaN HFET栅结构的C-V特性曲线的微分极值点确定阈值电压是一种切实可行的方法.     

AlGaN/GaN异质结场效应晶体管的阈值电压

利用AlGaN/GaN异质结场效应晶体管(AlGaN/GaN HFET)栅结构的电容-电压(C-V)特性确定AlGaN/GaN HFET的阈值电压.通过对模拟计算得到的AlGaN/GaN HFET电流-电压(I-V)特性曲线与测试得到的AlGaN/GaN HFET曲线比较分析,证实了依据AlGaN/GaN HFET栅结构的C-V特性曲线的微分极值点确定阈值电压是一种切实可行的方法.     

跨导为325mS/mm的AlGaN/GaN HFET器件

报道了使用国产GaN外延材料（蓝宝石衬底）的AlGaN/GaN HFET器件的制备以及室温下器件的性能. 器件栅采用场板结构,其中栅长为0.3μm,场板长为0.37μm,源漏间距为3μm. 器件的饱和电流密度为0.572A/mm,最大漏电流密度为0.921A/mm,最大跨导为325mS/mm,由S参数外推出截止频率和最高振荡频率分别为27.9GHz和33.1GHz.     

跨导为325mS/mm的AlGaN/GaN HFET器件

报道了使用国产GaN外延材料(蓝宝石衬底)的AlGaN/GaN HFET器件的制备以及室温下器件的性能.器件栅采用场板结构,其中栅长为0.3μm,场板长为0.37μm,源漏间距为3μm.器件的饱和电流密度为0.572A/mm,最大漏电流密度为0.921A/mm,最大跨导为325mS/mm,由S参数外推出截止频率和最高振荡频率分别为27.9GHz和33.1GHz.     

采用PECVD方法制作SiO2绝缘层的AlGaN/GaN MOS-HFET器件

为了进一步减小栅漏电,提高击穿电压,将MOS结构的优点引入ALGaN／GaN HEMT器件中,研制并分析了新型的基于AlGaN／GaN的MOS—HFET结构。采用等离子增强气相化学沉积（PECVD）的方法生长了50nm的SiO2作为栅绝缘层,新型的AlGaN／GaN MOS—HFET器件栅长1μm,栅宽80μm,测得最大饱和输出电流为784mA／mm,最大跨导为44．25ms／mm,最高栅偏压＋6V。     

GaN基HFET电力电子器件的研究

作为第三代宽禁带半导体器件,GaN基HFET功率器件具耐高压、高频、导通电阻小等优良特性,在电力电子器件方面也具有卓越的优势。概述了基于电力电子方面应用的AlGaN/GaN HFET功率器件的研究进展。从器件的结构入手,介绍了AlGaN/GaN HEMT的研究现状,从栅材料的选取以及栅介质层的结构对器件性能的影响着手,对AlGaN/GaN MIS-HFET的研究进行了详细的介绍。分析了场板改善器件击穿特性的原理以及各种场板结构AlGaN/GaNHFET器件的研究进展。论述了实现增强型器件不同的方法。阐述了GaN基HFET功率器件在材料、器件结构、稳定性、工艺等方面所面临的挑战。最后探讨了GaN基HFET功率器件未来的发展趋势。     

凹栅AlGaN/GaN HFET

研究了总栅宽为100μm栅凹槽结构的AlGaN/GaN HFET,采用相同的外延材料,凹槽栅结构器件与平面栅结构器件比较其饱和电流变化小,跨导由260.3mS/mm增加到314.8mS/mm,n由2.3减小到1.7,栅极漏电减小一个数量级.在频率为8GHz时,负载牵引系统测试显示,当工作电压增加到40V,输出功率密度达到11.74W/mm.     

具有低欧姆接触电阻的高性能AlGaN/GaN HEMT器件研制

研究了AlGaN/GaN HEMT器件Ti/Al/Ti/Au四层金属结构欧姆接触的形成过程.通过系统研究退火条件获得了较低的欧姆接触电阻,实现了10-7Ω·cm2的欧姆接触率,并在此基础上对AlGaN/GaN HEMT欧姆接触形成机理进行了深入讨论.通过器件工艺的优化,研制了高性能的AlGaN/GaN HEMT器件.栅宽40μm的器件跨导达到250mS/mm,fT达到70GHz;栅宽0.8mm的功率器件电流密度达到1.07A/mm(Vg=0.5V),Vds=30V时,8GHz工作频率下(在片测试)器件的输出功率为32.5dBm(1.6W),输出功率密度达到2.14W/mm,功率增益为12.7dB.     

具有低欧姆接触电阻的高性能AlGaN/GaN HEMT器件研制

研究了AlGaN/GaN HEMT器件Ti/Al/Ti/Au四层金属结构欧姆接触的形成过程.通过系统研究退火条件获得了较低的欧姆接触电阻,实现了10-7Ω·cm2的欧姆接触率,并在此基础上对AlGaN/GaN HEMT欧姆接触形成机理进行了深入讨论.通过器件工艺的优化,研制了高性能的AlGaN/GaN HEMT器件.栅宽40μm的器件跨导达到250mS/mm,fT达到70GHz;栅宽0.8mm的功率器件电流密度达到1.07A/mm(Vg=0.5V),Vds=30V时,8GHz工作频率下(在片测试)器件的输出功率为32.5dBm(1.6W),输出功率密度达到2.14W/mm,功率增益为12.7dB.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.