Research and Fabrication of 4H-SiC Ultraviolet p-i-n Photodiodes and Linear Array

碳化硅（SiC）材料作为高温、高频以及大功率电子器件制备的理想半导体材料，近年来越来越受到世界各国的广泛关注。由于4H-SiC材料的宽带隙（~3.26eV），用其制备的紫外光电探测器将具有可见盲/日盲特性，并且在高温条件下4H-SiC光电探测器的暗电流也比传统硅基探测器要低几个数量级。因此，4H-SiC材料被认为是制备紫外光电探测器的首选材料，所制备的紫外光电探测器可在极端条件下应用于生化检测、可燃性气体尾焰探测、臭氧层监测、短波通讯以及导弹羽烟的紫外辐射探测等领域。对于p-i-n结构4H-SiC紫外光电二极管，由于其较小的结电容和较大的并联电阻，使得器件在低电压工作时具有较低的噪声、较快的响...As a promising semiconductor material for high temperature, high frequency, and high power devices, silicon carbide (SiC) has received more remarkable attentions now. Due to the wide bandgap of 4H-SiC (~ 3.26 eV), photodetectors utilising this material should have the advantage of a good visible-blind/solar-blind performance and a very low dark current which can be many orders of magnitude lower t...学位：理学博士院系专业：物理与机电工程学院物理学系_凝聚态物理学号：B20042402

同位素稀释电感耦合等离子体质谱测定环境和生物样品中的镉

建立电感耦合等离子体质谱(ICP-MS)测定镉同位素比值的方法,应用同位素稀释电感耦合等离子体质谱(Id-ICP-MS)对环境和生物样品茶叶、湖沉积物和人发标准物质中的镉进行测定研究.对电感耦合等离子体质谱(ICP-MS)的工作条件和参数进行了最优化.讨论了多原子离子和同量异位素对镉同位素比值的影响,通过天然镉标准溶液对质量歧视进行了校正,并优化同位素稀释剂的加入量.将该方法应用于茶叶、人发和沉积物标准物质的测定

Photoluminescence of Multilayer InAs Quantum Dots

采用MBE设备生长了多层InAs/GaAs量子点结构,测量了其变温光致发光谱和时间分辨光致发光谱。结果表明多层量子点结构有利于减小发光峰的半高宽,并且可以提高发光峰半高宽和发光寿命的温度稳定性。实验发现,加InGaAs盖层后,量子点发光峰的半高宽进一步减小,最小达到23.6 meV,并且发光峰出现红移。原因可能在于InGaAs盖层减小了InAs岛所受的应力,阻止了In组分的偏析,提高了InAs量子点尺寸分布的均匀性和质量,导致载流子在不同量子点中的迁移效应减弱。Multilayer InAs/GaAs quantum dots structures were grown by molecular-beam epitaxy(MBE).The steady-state and time-resolved photoluminescence of the samples were measured at various temperatures.Results showed that multilayer structures could not only narrow the photoluminescence FWHM(full width at the half maximum) but enhance the stability of the photoluminescence lifetime and FWHM.As for the quantum dots with InGaAs cap layer,the photoluminescent spectra became narrower(the narrowest FWHM was only 23.6meV) and the photoluminescent wavelength became longer.The possible reason for the above phenomena was that the InGaAs cap layer could both release the strains in InAs islands and inhibit segregation of In components,resulting in the weaker migration among different quantum dots

Study on the Distributions of Lead and Cadmium in Rats by ICP-MS with Stable Isotope Tracer

采用稳定同位素示踪技术研究重金属元素铅、镉在大鼠体内的分布,通过对大鼠进行浓缩同位素206Pb、112Cd灌喂,解剖取其肝、肾、睾丸和心脏等脏器,通过相应的化学处理,用电感耦合等离子体质谱(ICP-MS)测量铅、镉元素在各个脏器中的含量及其同位素组成变化。根据同位素比值的变化研究Pb、Cd在各脏器中的分布、蓄积规律和各脏器对引入的浓缩同位素利用率。结果发现:重金属Pb和Cd蓄积的最主要场所是肝和肾,其次是睾丸和心脏,而在脑中的积累最少。在肝和肾中Cd的同位素利用率为0.0488%、0.0154%,Pb的同位素利用率为0.0101%、0.0078%,远高于其它脏器。与传统的方法相比较,该法具有更接近慢性中毒、危害性小,能将重金属来源分为天然来源和人为引入等特点。The distributions of lead and cadmium in rats were studied using stable isotope tracer technique.The rats were fed with enriched stable isotope 206Pb and 112Cd,then the liver,kidney,testicle and heart were eviscerated.After chemical treatment,the contents of lead and cadmium and their isotope ratios in each viscera were determined by ICP-MS.Experimental results showed that lead and cadmium accumulated mostly in liver and kidney,next in testicle and heart,and least in brain.The utilization rates of cadmium and lead isotopes in liver were 0.048 8% and 0.010 1%,respectively,and in kidney 0.015 4% and 0.007 8%,respectively.Compared with the traditional methods,the present method can differentiate the origins of lead and cadmium.福建省重大科技项目资助课题(2003Y005-04,2003Y003

AFLP analysis of arbuscular mycorrhizal fungi in roots of Prunus mume

第一作者: 蔡邦平，博士，副研究员。主要研究方向: 园林植物与观赏园艺、植物菌根。电话: 0592--2039576 Email : cbangping@ 163.com 地址: 361003 福建省厦门市思明区虎园路25 号厦门市园林植物园。[中文文摘]为了解决梅根系共生的丛枝菌根(AM)真菌难以应用形态学鉴定的问题,以巢式PCR的AFLP方法研究梅根系AM真菌DNA多态性。试验采集梅花期的根系样品,应用改良CTAB法提取总DNA,经纯化处理后,应用巢式PCR扩增根系AM真菌基因片段,进行AFLP分析。结果表明,18个梅品种的30个根系样品中,仅有8个样品经巢式PCR后获得纯化的DNA片段,占试验样品数的26.7%;8个样品共得到指纹图谱带24条,各样品平均多态性位点数为3.0个,Nei’s基因多样性为0.4097±0.0848,Shannon信息指数为0.5968±0.0955;利用Nei’s遗传相似性系数聚类,梅品种根系内AMF基因组DNA的聚类类别与梅"品种群"这一分类级别无相关性。该试验为植物根系共生AM真菌DNA多态性研究提供了一种简便的技术。[英文文摘]DNA polymorphism of arbuscular mycorrhizal fungi (AMF) was analyzed through the method of DNA amplification by nested PCR based on AFLP marker,in order to solve the difficulty of identifying the species of AMF associated with mei flowers (Prunus mume Sieb.et Zucc.).A total of 30 root samples from 18 mei cultivars were collected in the flowering phase from Wuhan Mei Garden as experimental materials.The results show that the purified DNA can be extracted only from eight root samples that account for 26.7% of total root samples.Totally 24 polymorphic loci were obtained from eight sample roots，averaging 3. 0 loci for each sample.The average genetic identity was 0. 409 7 ±0. 084 8，and the Shannon information index was 0. 596 8 ± 0. 095 5． The clustered groups of AMF DNA by AFLP marker from different cultivars were not identical with cultivar groups of P.mume.The results indicate that the AFLP marker technology is a brief and effective method to study the DNA polymorphism for the AMF in the roots of a plant．教育部科学技术研究重点项目(104034);; 国家自然科学基金项目(30670047);; 厦门市科技计划项目(3502Z20072010、3502Z20112004

Research and Analysis on Absorption Coefficient of 4H-SiC at Ultraviolet Wavelength

基于已报道的4H-SIC材料在紫外波段(325—390nM)吸收系数的测定,结合经验公式,采用外推和多项式拟合方法分析4H-SIC材料在200—400nM紫外波段的吸收系数,并得到4H-SIC材料的吸收系数与波长的关系式。对4H-SIC吸收系数的分析研究将作为4H-SIC光电探测器结构设计的一个重要依据。Based on the previous reports on the absorption coefficients of 4H-SiC at 325—390nm,the extrapolation and polynomial fitting methods for analysis of the absorption coefficients of 4H-SiC at 200—400nm was established.And the relationship between the absorption coefficient and the wavelength was obtained.福建省自然科学基金项目资助(No.2009J05151);厦门市科技计划项目(No.350z20031076)资

A study of p-type Ohmic contact for 4H-SiC avalanche photodetector

对4H-SiC雪崩光电探测器的Ti/Al/Au p型欧姆接触进行了详细的研究。通过线性传输线模型(LTLM)测得经930℃退火后欧姆接触的最小比接触电阻为5.4×10~(-4)Ωcm~2。分别用扫描电子显微镜(SEM)、俄歇电子能谱(AES)、X射线光电子能谱(XPS)和X射线衍射谱(XRD)对退火前后的表面形貌、金属之间以及金-半接触界面之间相互反应及扩散情况进行测试与分析,发现了影响欧姆接触性能的主要原冈。对采用此欧姆接触制备的4H-SiC雪崩光电探测器进行测试,发现器件的击穿电压约为-55 V,此时其p型电极处的电压降仅为0.82 mV,可以满足4H-SiC雪崩光电探测器在高压下工作的需要。The p-type Ohmic contact of Ti/Al/Au multiple metal alloy for 4H-SiC avalanche photodetector(APD)was investigated and the lowest specific contact resistance of 5.4×10~(-4)Ωcm~2 was achieved by the linear transmission line method(LTLM).The scanning elec- tron microscope(SEM),Auger electron spectroscopy(AES),X-ray photoelectron spectroscopy (XPS)and Panalytical X'pert PRO X-ray diffraction(XRD)were measured to analyze the contact morphology,chemical composition and the phase formation of the samples before and after annealing.In addition,the electrical properties of 4H-SiC APDs with the same p-type Ohmic contact were also measured.Near the breakdown voltage of about-55 V,the voltage descent at p electrode was as low as 0.82 mV,which showed that the Ohmic contact can satisfy the requirement of 4H-SiC APD

Separate Absorption and Multiplication 4H-SiC Ultraviolet Avalanche Photodetector

设计和制备了吸收层和倍增层分开的4H-SiC穿通型雪崩紫外光电探测器.设计器件的倍增层和吸收层厚度分别为0.25和1μm.采用multiplejunctionter mination extension(MJTE)方法减少器件的电流集边效应和器件表面电场.对器件的暗电流、光电流和光谱响应进行了测量.器件在55V的低击穿电压下获得了一个高的增益(>104);穿通前器件暗电流约为10pA数量级;0V偏压下器件光谱响应的紫外可见比大于103.光谱响应的峰值波长随反向偏压的增大而向短波方向移动,在击穿电压附近光谱响应的峰值波长移到210nm,此波长远远小于在0V时的响应峰值.结果显示器件在紫外光探测中具有优良的性能.A 4H-SiC avalanche photodetector(APD)with separate absorption and multiplication layers was designed and fabricated.The thicknesses of the absorption and multiplication epilayers were designed as 0.25 and 1μm,respectively.A multiple junction termination extension(MJTE)was used to eliminate the electric field crowding effect at the edge and to reduce the surface electric field.Dark current,photocurrent,and spectral responsivity were measured.High gain(>104)was achieved at a low breakdown voltage,and the dark current was on the order of about 10pA before device was punched through.The ratio of responsivity at 260nm to that at 380nm was higher than 103.A new phenomenon was observed in its spectral responsivity.The response wavelength peak shifted to shorter wavelength as the reverse bias was increased.Near breakdown voltage the peak of the response wavelength was located at 210nm,which was shorter than that at 0V.These results show that the samples have good performance for ultraviolet detection

High-performance 4H-SiC-based ultraviolet p-i-n photodetector

A high-performance 4H-SiC p-i-n photodetector for visible-blind ultraviolet (UV) applications has been designed and fabricated. The electrical and optical characteristics were measured at room temperature. The photodetector suffered from significant dark current of 2.5 pA/mm(2) at reverse bias of 5 V, and the UV light photocurrent was larger than four orders of magnitude higher than the dark current. The built-in potential and the unintentional i-layer doping concentration were obtained from capacitance-voltage (C-V) measurements. The spectral peak responsivity of the detector reached 0.13 A/W at a wavelength of 270 nm, corresponding to a maximum external quantum efficiency of similar to 61%. And the ratio of responsivity at 270 nm to that at 380 nm was > 10(3). The characteristics imply that the photodetector has a great improved ultraviolet-visible rejection ratio which is needed for ultraviolet signal detection

Effect of the intrinsic layer thickness on the spectral performance of p-i-n structure 4H-SIC ultraviolet photodetector

Conference Name:2011 International Conference on Remote Sensing, Environment and Transportation Engineering, RSETE 2011. Conference Address: Nanjing, China. Time:June 24, 2011 - June 26, 2011.Nanjing University of Information Science and Technology; Peking University; Fudan University; Tsinghua University; Jilin UniversityThe absorption coefficients of 4H-SiC at 200-400 nm were obtained by extrapolation and polynomial fitting methods. Considering the effect of different junction-depth on the spectral performance, the continuity equations of photogenerated minority carrier were used to theoretically calculate the responsivity of p+-n-(i)-n-n+ structure 4H-SiC ultraviolet photodetector (PD) and to find out the effect of the intrinsic layer thickness on the spectral performance. The theoretical analyses can be applied to the practical design of p-i-n structure 4H-SiC PDs. ? 2011 IEEE