GaN和AlxGa1-xN/CaN异质结的高温性质

通过高温Hall测量研究了GaN和AlxGa1-xN/GaN异质结从室温到500℃高温下的输运性质.实验发现GaN背景载流子浓度随着温度的升高而升高,载流子浓度变化的幅度和GaN的位错密度存在正比关系,持续光电导的跃迁幅度和GaN的位错密度也存在正比关系,说明位错相关的深施主或者陷阱对GaN在高温下的背景浓度有很大影响.实验发现AlxGa1-xN/GaN异质结中二维电子气的浓度在室温到250℃的范围内随着温度的升高而下降,然后随着温度的升高开始增加.前者主要是由于随着温度的升高,AlxGa1-xN/GaN异质结的导带不连续减小引起的,后者主要是由GaN层背景载流子浓度增加导致的.通过求解自洽的薛定谔和泊松方程得到的二维电子气浓度的温度关系和实验结果一致.     

GaN和AlxGa1-xN/CaN异质结的高温性质

通过高温Hall测量研究了GaN和AlxGa1-xN/GaN异质结从室温到500℃高温下的输运性质.实验发现GaN背景载流子浓度随着温度的升高而升高,载流子浓度变化的幅度和GaN的位错密度存在正比关系,持续光电导的跃迁幅度和GaN的位错密度也存在正比关系,说明位错相关的深施主或者陷阱对GaN在高温下的背景浓度有很大影响.实验发现AlxGa1-xN/GaN异质结中二维电子气的浓度在室温到250℃的范围内随着温度的升高而下降,然后随着温度的升高开始增加.前者主要是由于随着温度的升高,AlxGa1-xN/GaN异质结的导带不连续减小引起的,后者主要是由GaN层背景载流子浓度增加导致的.通过求解自洽的薛定谔和泊松方程得到的二维电子气浓度的温度关系和实验结果一致.     

GaN基材料和器件的质子辐照效应北大核心CSCD

由于综合性能优势,GaN基功率器件更适合于卫星电子系统等空间设备中射频功率放大模块的发展需求。因此,GaN基器件及材料的辐照效应研究显得尤为重要。通过对GaN基材料和器件进行质子辐照研究,可以发现,低注量辐照增加了GaN材料的载流子浓度和迁移率,降低了材料的串联电阻。此外,辐照增加了GaN的张应力,引起了材料表面形貌恶化,而对位错密度影响甚小。对于GaN基高电子迁移率晶体管(HEMT)器件,辐照发生在较高注量下,器件参数才发生较为明显的退化,而且阈值电压变化最为显著,分析认为,高注量辐照时,辐照感生受主缺陷造成的二维电子气(2DEG)浓度降低是上述器件退化的主要原因。     

AlGaN/GaN和AlGaN SBD的温度特性研究

研究了AlGaN/GaN异质结构上的肖特基接触的基本原理及载流子的高温输运特性.将AlGaN/GaN异质结SBD和AlGaN SBD,在27～250℃进行实验比较.发现随着温度上升,AlGaN SBD的势垒高度下降,理想因子增加,其影响因素包括热电子发射、场发射、隧穿效应及复合电流效应等机制.而AlGaN/GaN异质结SBD由于受到压电极化场和2DEG和的影响,其势垒高度和理想因子随温度的变化趋势与AlGaNSBD相反.实验结果还显示,AlGaN/GaN异质结SBD的反向电流随着温度的上升,呈现先增大后减小的趋势.     

Si/Si_(1-x)Ge_x HEMT异质结层的结构与二维电子气密度的关系

从晶格匹配及能带阶跃角度讨论了设计一个 n沟 Si/Si1-x Gex HEMT异质结层的原理及方法 ,对 K.Ismail器件进行了分析和计算 ,所得 2 DEG的 ns与实验结果基本相符 ,并利用该设计理论对 K. Ismail器件的异质结结构进行了优化改进 ,提高了器件 2 DEG的 ns。     

质子辐照对场板AlGaN／GaN HEMT器件电特性的影响

分别采用3MeV和10MeV的质子对GaN基HEMT（High Electron Mobility Transistor）器件进行辐照。实验发现：低注量辐照引起了体材料载流子浓度增加,高注量辐照引起了HEMT器件漏电流下降,跨导减小,阈值电压显著退化的结果。通过分析发现辐射感生受主缺陷引起的2DEG浓度降低是上述器件退化的主要原因。此外基于实验结果,采用辐射感生受主缺陷退化模型仿真并计算了HEMT器件主要参数随受主浓度的退化规律,仿真结果与实验结果有较好的一致性。本文实验结果也表明场板结构和SiN钝化层有效地阻止了电子陷落在表面态中,屏蔽了绝大部分的辐照损伤,是很有效的辐射加固手段。     

Si／Si1—xGexHEMT异质结层的结构与二维电子气密度的关系

从晶格匹配及能带阶跃角度讨论了设计一个n沟Si/Si1-xGexHEMT异质结层的原理及方法,对K.Ismail器件进行了分析和计算,所得2DEG的ns与实验结果基本相符,并利用该设计理论对K.Ismail器件的异质结结构进行了优化改进,提高了器件2DEG的n。     

辐照对IGBT特性的影响

阐述了中子辐照对ＩＧＢＴ特性的影响，给出了器件在中子辐射注量高达１０＾１３ｎ／ｃｍ＾２时的实验结果。实验发现，随着中子注量的增加，开关时间缩短，阈值电压漂移。对于所研究的注量范围，所观察的效应是由于ＩＧＢＴ少子寿命减少造成的，而不是由于有效掺杂浓度变化所致。     

电子辐照对GaAs HBT残余电压与饱和电压的影响

研究了GaAs HBT高能电子(～1MeV)辐照的总剂量效应。结果表明,电子辐照后GaAs HBT的基极电流增大,辐照损伤程度随辐照总剂量增加而增加,这和其他研究观察到的现象相同。所不同的是,实验中发现随辐照剂量增大器件集电极饱和电压、残余电压均增大。因此认为,高能电子辐照造成的位移损伤在GaAs HBT集电区和BC结内诱生的大量复合中心使集电极串联电阻增大,以及BE、BC结内形成的复合中心俘获结内载流子使载流子浓度降低造成BE、BC结自建电势差下降是集电极饱和电压和残余电压增加的主要原因。     

Analysis of PTCDA/ITO Surface and Interface Using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy

在低温和强磁场下,通过磁输运测量研究了不同Al组分调制掺杂AlxGa1-xN/GaN异质结二维电子气(2DEG)的磁电阻振荡现象.观察到低Al组分异质结中的2DEG有较低的浓度和较高的迁移率.     

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.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

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.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

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.     

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.