掩埋异质结激光器的Mesa制备工艺

掩埋异质结结构的半导体激光器具有阈值低、光束质量好的优点。台面(Mesa)制作是掩埋结激光器加工过程中的一步关键工艺,采用传统的全湿法腐蚀工艺制作台面,3英寸圆片内腐蚀深度和器件输出功率水平差异较大。而采用干法刻蚀加湿法腐蚀工艺技术,制备出的台面表面光滑、侧壁连续,腐蚀深度差异为6%,最终器件输出功率水平的差异仅为2%。利用该掩埋结技术制备的1 550 nm大功率激光器均匀性有了较大提升,900μm腔长单管的阈值电流约12 mA,300 mA工作电流时功率输出100 mW。

Mesa沟槽终端耦合U型平面结的雪崩型SiC-TVS器件研究

瞬态电压抑制器(Transient Voltage Suppressor,TVS)作为常用的防护型器件具有吸收功率高、响应速度快等特点。目前,雪崩型SiC-TVS器件尚缺乏合理的终端设计,以常用N型衬底为基础的外延P+N-N+/Mesa结构SiC-TVS器件在反偏P+/N-结边缘处易形成负斜角边缘结构,导致器件因边缘电场集中而提前击穿,严重影响器件的工作可靠性。本文基于Sentaurus TCAD数值仿真,研究了一种雪崩型SiC-TVS器件结构,该结构采用离子注入形成大曲率半径的U型平面PN结,并将其边缘与Mesa沟槽终端顶点在器件上表面以距离x进行耦合设计,使器件表面形成正斜角终端,有效地避免了边缘电场集中效应。同时x的选取具有一定余量,在工艺上较易实现。最后利用该结构仿真得到了响应时间约5.3ns、钳位因子达到1.01的雪崩型SiC-TVS器件,仿真结果表明新型耦合结构器件对异常瞬态浪涌信号表现出良好的抑制效果。

基于VLPE技术的碲镉汞p-on-n双层异质结材料与器件研究进展

本文对比分析了碲镉汞p-on-n器件四种制备方式的优劣,其中,VLPE(Vertical Liquid Phase Epitaxy)技术具有原位As掺杂与高激活率的技术优势,是制备高性能p-on-n双层异质结器件的重要方式。针对该技术,从材料生长、器件工艺和器件性能方面回顾了国内外研究进展,讨论了国内外差距,明确了制约该技术发展的关键问题和技术难点,并提出了解决思路。最后,展望了VLPE技术pon-n异质结器件的发展趋势。

Investigation on Breakdown Characteristics of Various Surface Terminal Structures for GaN-Based Vertical P-i-N Diodes

GaN-based vertical P-i-N diode with mesa edge terminal structure due to electric field crowding effect, the breakdown voltage of the device is significantly reduced. This work investigates three terminal structures, including deeply etched, bevel, and stepped-mesas terminal structures, to suppress electric field crowding effects at the device and junction edges. Deeply-etched mesa terminal yields a breakdown voltage of 1205 V, i.e., 89% of the ideal voltage. The bevel-mesa terminal achieves about 89% of the ideal breakdown voltage, while the step-mesa terminal is less effective in mitigating electric field crowding, at about 32% of the ideal voltage. This work can provide an important reference for the design of high-power, high-voltage GaN-based P-i-N power devices, finding a terminal protection structure suitable for GaNPiN diodes to further enhance the breakdown performance of the device and to unleash the full potential of GaN semiconductor materials.

WindML中Mesa的应用

研究了在WindML3.0中应用Mesa来改进嵌入式图形界面显示效果的方法。针对实际产生的问题进行了简要的分析,提出了相应的解决方法,达到了预期的效果。

Autumn Daily Characteristics of Land Surface Heat and Water Exchange over the Loess Plateau Mesa in China

The Loess Plateau, located in northern China, has a significant impact on the climate and ecosystem evolvement over the East Asian continent. In this paper, the preliminary autumn daily characteristics of land surface energy and water exchange over the Chinese Loess Plateau mesa region are evaluated by using data collected during the Loess Plateau land-atmosphere interaction pilot experiment （LOPEX04）, which was conducted from 25 August to 12 September 2004 near Pingliang city, Gansu Province of China. The experiment was carried out in a region with a typical landscape of the Chinese Loess Plateau, known as ＂loess mesa＂. The experiment＇s field land utilizations were cornfield and fallow farmland, with the fallow field later used for rotating winter wheat. The autumn daily characteristics of heat and water exchange evidently differed between the mesa cornfield and fallow, and the imbalance term of the surface energy was large. This is discussed in terms of sampling errors in the flux observations-footprint; energy storage terms of soil and vegetation layers; contribution from air advections; and low and high frequency loss of turbulent fluxes and instruments bias. Comparison of energy components between the mesa cornfield and the lowland cornfield did not reveal any obvious difference. Inadequacies of the field observation equipment and experimental design emerged during the study, and some new research topics have emerged from this pilot experiment for future investigation.

基于Linux和OpenGL/Mesa的数控铣削仿真系统的研究

介绍了在Linux下,利用Qt和OpenGL/Mesa,采用面向对象技术和模块化的设计方式,建立的数控铣削几何仿真的总体结构。阐述了各模块的功能,分析了仿真算法实现。通过验证,系统能检验NC程序是否正确和工艺的合理性,可以发现干涉、碰撞情况。此模型能实时地,交互地显示毛坯材料的去除过程,实现了零件加工的三维实体动态仿真。

Enhanced thermal stability of VCSEL array by thermoelectric analysis-based optimization of mesas distribution

The thermal stability of a vertical-cavity surface-emitting laser（VCSEL） array is enhanced by redesigning the mesa arrangement. Based on a thermoelectric coupling three-dimensional（3D） finite-element model, an optimized VCSEL array is designed. The effects of this optimization are studied experimentally. Power density characteristics of VCSEL arrays with different mesa configuration are obtained under different thermal stress in which the optimized device shows improved performance. Optimized device also shows better stability from measured spectra and calculated thermal resistances. The experimental results prove that our simulation model and optimization is instructive for VCSEL array design.

Numerical and experimental study of the mesa configuration in high-voltage 4H–SiC PiN rectifiers

The effect of the mesa configuration on the reverse breakdown characteristic of a SiC PiN rectifier for high-voltage applications is analyzed in this study.Three geometrical parameters,i.e.,mesa height,mesa angle and mesa bottom corner,are investigated by numerical simulation.The simulation results show that a deep mesa height,a small mesa angle and a smooth mesa bottom（without sub-trench） could contribute to a high breakdown voltage due to a smooth and uniform surface electric field distribution.Moreover,an optimized mesa structure without sub-trench（mesa height of 2.2 μm and mesa angle of 20°） is experimentally demonstrated.A maximum reverse blocking voltage of 4 kV and a forward voltage drop of 3.7 V at 100 A/cm^2 are obtained from the fabricated diode with a 30-μm thick N^- epi-layer,corresponding to 85% of the ideal parallel-plane value.The blocking characteristic as a function of the JTE dose is also discussed for the PiN rectifiers with and without interface charge.

利用Mesa4.0在VxWorks下实现雷达三维仿真界面

雷达仿真界面是显示雷达信息最直观的图形界面。本文针对以往雷达二维图形仿真界面存在俯仰角参数表示不直观、运动目标状态显示不准确、人机操作界面不友好等问题,以VxWorks实时多任务操作系统为应用平台,通过在WindML3.0应用Mesa4.0技术实现图形三维显示效果,创新性地设计实现了一套高稳定性、高可靠性和强实用性的雷达三维仿真界面,改进了以往二维图形显控界面的缺点,同时兼顾二维仿真界面显示,实现了二维和三维雷达仿真界面的完美兼容。

Association of Obesity and Kidney Function Decline among Non-Diabetic Adults with eGFR >60 ml/min/1.73m²: Results from the Multi-Ethnic Study of Atherosclerosis (MESA)

Background: Obesity is associated with higher end-stage renal disease incidence, but associations with earlier forms of kidney disease remain incompletely characterized. Methods: We studied the association of body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR) with rapid kidney function decline and incident chronic kidney disease in 4573 non-diabetic adults with eGFR ≥ 60 ml/min/1.73m2 at baseline from longitudinal Multi-Ethnic Study of Atherosclerosis cohort. Kidney function was estimated by creatinine and cystatin C. Multivariate analysis was adjusted for age, race, baseline eGFR, and hypertension. Results: Mean age was 60 years old, BMI 28 kg/m2, baseline eGFRCr 82 and eGFRCys 95 ml/min/1.73m2. Over 5 years of follow up, 25% experienced rapid decline in renal function by eGFRCr and 22% by eGFRCys. Incident chronic kidney disease (CKD) developed in 3.3% by eGFRCys, 11% by eGFRCr, and 2.4% by both makers. Compared to persons with BMI 25, overweight (BMI 25 - 30) persons had the?lowest risk of rapid decline by eGFRCr (0.84, 0.71 - 0.99). In contrast, higher BMI categories were associated with stepwise higher odds of rapid decline by eGFRCys, but remained significant only when BMI ≥ 35 kg/m2 (1.87, 1.41 - 2.48). Associations of BMI with incident CKD were insignificant after adjustment. Large WC and WHR were associated with increased risk of rapid decline only by eGFRCys, and of incident CKD only when defined by both filtration markers. Conclusions: Obesity may be a risk factor for kidney function decline, but associations vary by filtration marker used.

Optoelectronic Properties of GaN-Based Light-Emitting Diodes with Different Mesa Structures

GaN/InGaN lighting-emitting diodes with different mesa structures are studied. The current-voltage characteristics, light output power, luminous efficiency, and peak wavelength of the GaN/InGaN lighting-emitting diodes with different mesa patterns are compared. It shows that the current-voltage characteristics of the chips with more mesa areas are im- proved greatly by reducing the current crowding. With higher injection current the light output powers of GaN-based LED with more mesa areas are enhanced. And the chips with more P-electrode area have a smaller red shift and a little bit blue shift due to the reduction of the current crowding.

绿山软件MESA在地震采集生产中的应用

绿山软件MESA是一款适于安装在地震仪器中的高分辨率三维地震勘探设计以及近地面折射静校正量分析的软件。在阿尔及利亚07-HRM-3D项目三维地震勘探采集工区中,针对公路交通发达、油气管网纵横密布、高大山体较多、整个工区地形复杂的特点,如何实现在野外组织生产、在现场施工中不丢漏炮、如何准确地确定收线桩号以及针对整束测线地形地况的把握,都对仪器现场操作人员提出了很高的要求,而绿山软件能够在实际生产中给予帮助。施工中,我们利用绿山软件结合野外现场实际情况形成了一整套监控及组织野外采集生产的方法。

Superjunction nanoscale partially narrow mesa IGBT towards superior performance

We present a detailed study of a superjunction （S J） nanoscale partially narrow mesa （PNM） insulated gate bipolar transistor （IGBT） structure. This structure is created by combining the nanoscale PNM structure and the SJ structure together. It demonstrates an ultra-low saturation voltage （Vce（sat）） and low turn-off loss （Eoff） while maintaining other device parameters. Compared with the conventional 1.2 kV trench IGBT, our simulation result shows that the gce（sat） of this structure decreases to 0.94 V, which is close to the theoretical limit of 1.2 kV IGBT, Meanwhile, the fall time decreases from 109.7 ns to 12 ns and the Eoff is down to only 37% of that of the conventional structure. The superior tradeoff characteristic between Vce（sat） and Eoff is presented owing to the nanometer level mesa width and SJ structure. Moreover, the short circuit degeneration phenomenon in the very narrow mesa structure due to the collector-induced barriers lowering （CIBL） effect is not observed in this structure. Thus, enough short circuit ability can be achieved by using wide, floating P-well technique. Based on these structure advantages, the SJ-PNM-IGBT with nanoscale mesa width indicates a potentially superior overall performance towards the IGBT parameter limit.

基于Mesa的ABM仿真

ABM仿真是当前复杂系统研究的重要方法之一,现有ABM仿真工具建模语言具有局限性。Mesa是具有Python开发的ABM仿真框架,不仅具有传统ABM仿真工具的优势,而且可以充分利用Python语言在数据统计分析、挖掘和可视化等方面的强大功能。通过示例展示Mesa的强大功能,为ABM仿真研究提供一个新的选择和入门途径。

Mesa Diaphragm-Based Fabry-Perot Optical MEMS Pressure Sensor

An optical micro electron mechanical system （MEMS） pressure sensor with a mesa membrane is presented. The operating principle of the MEMS pressure sensor is expatiated by the Fabry-Perot （F-P） interference and the relation between deflection and pressure is analyzed. Both the mechanical model of the mesa structure diaphragm and the signal averaging effect is validated by simulation, which declares that the mesa structure diaphragm is superior to the planar one on the parallelism and can reduce the signal averaging effect. Experimental results demonstrate that the mesa structure sensor has a reasonable linearity and sensitivity.

一种新型电吸收调制激光器的优化设计

针对传统选择性区域生长叠层双有源区电吸收调制激光器(SAG-DSAL-EML)在高频调制环境下的响应速度问题以及改善其远场发散角特性,文章提出利用掺铁掩埋技术对电吸收调制激光器(EML)结构进行优化,设计了InGaAsP/InP材料1310 nm掺铁掩埋结构的SAG-DSAL-EML并制作样本芯片,新型SAG-DSAL-EML有源区变为台面结构,并在其两层外延生长掺铁InP层。同时,利用先进激光二极管模拟器(ALDS)软件和高频结构仿真(HFSS)软件对所设计掺铁掩埋结构的EML和调制器进行数值及仿真分析,结果表明,与传统多量子阱结构相比,SAG-DSAL-EML阈值电流减少了13%;与传统脊波导结构相比,掺铁掩埋结构的侧向限制能力提高52%,激光远场横纵角度之差降低了40%,具有更小的远场发散角;与传统PNPN掩埋结构相比,掺铁掩埋结构的调制器在-3 dB的响应带宽提高了约24%。对样本芯片进行测试,试验表明,SAG-DSAL-EML的阈值电流为14.5 mA,边模抑制比(SMSR)为45.64 dB,70 mA注入电流下,电吸收调制器-3 dB的响应带宽为43 GHz,满足高速激光通信的基本要求。

A change of phenolic acids content in poplar leaves induced by methyl sali-cylate and methyl jasmonate

The contents of seven different phenolic acids such as gallic acid, catechinic acid, pyrocatechol, caffeic acid, coumaric acid, ferulic acid and benzoic acid in the poplar leaves （Populus Simonii×Populus Pyramibalis c.v and Populus deltoids） suffocated by Methyl jasmonate （MeJA） and Methyl salicylate （MeSA） were monitored for analyzing their functions in interplant communications by using high-pressure liquid chromatography （HPLC）.The results showed that the contents of phenolic acids had obviously difference in leaves exposed to either MeSA or MeJA.When P.deltoides leaves exposed to MeJA or MeSA, the level of gallic acid, coumaric acid, caffeic acid, ferulic acid and benzoic acid was increased, gallic acid in leaves treated with MeJA comes to a peak at 24 h while to a peak at 12-d having leaves treated with MeSA.When P.Simonii ×P.Pyramibalis c.v leaves were exposed to MeJA or MeSA, the level of gallic acid, pyrocatechol and ferulic acid was increased; The catechinic acid and benzoic acid had a little drop; The caffeic acid and coumaric acid were undetected in both suffocated and control leaves.This changed pattern indicated that MeJA and MeSA can act as airborne signals to induce defense response of plants.

垂直扩展台面结构螺栓连接建模方法

螺栓连接是工程上广泛应用的一种紧固连接方式,为了快速、准确评估采用螺栓连接的垂直扩展台面的性能指标,从而缩短研发周期和减少研发成本,本文针对目前常用的一体化、刚性单元连接、梁单元连接和实体螺栓连接模型,基于苏州苏试试验集团股份有限公司某扩展台面,采用Lanczos法求解模态振型和模态频率。以实测一阶垂向共振频率为参照,对比4种垂直扩展台面螺栓连接模型的精确性,确定一种适用于垂直扩展台面的最优螺栓连接模型。最终结果表明,采用梁单元连接模型求解的一阶垂向共振频率与实测一阶垂向共振频率的误差最小,求解效率较高。

新型结构压电石英晶片去耦效应的研究

针对中低频光刻工艺的小型化压电石英晶片,为解决双台面(BI-MESA)型压电石英晶片的寄生耦合振动的影响,以及封装过程中点胶区域对振动区域的力频效应影响导致温-频特性的阻抗跳动。提出一种带有沟槽的BI-MESA型AT切压电石英晶体谐振器,并通过有限元仿真谐响应分析方法,给出其振动幅-频分布情况和势能分布情况。仿真分析比较发现,晶体表面沟槽的设计可有效抑制振动传播到点胶区域产生力-频效应的影响,改善BI-MESA谐振器的振动特性。