非掺半绝缘InP材料的电子辐照缺陷研究

本文针对磷化铁(FeP_2)气氛下高温退火非掺杂半绝缘磷化铟(IP SI-InP)材料,应用正电子寿命谱及热激电流谱学技术,研究了该材料在电子辐照前后的缺陷情况.研究发现,该材料经电子辐照后缺陷浓度在增大,且形成了复合体的缺陷结构.电子辐照后的正电子湮没平均寿命增加了18 ps,对应的热激电流谱(TSC)也出现了相应的缺陷峰.本文还对缺陷的特性、影响材料的性能等进行了简要的论述.     

用正电子研究Ⅲ—Ⅴ族化合物半导体的缺陷谱

简要介绍了本科研组近年来用正电子湮没谱学研究Ⅲ－Ⅴ族化合物半导体缺陷的最新进展,包括原生样品中缺陷的种类、大小、电荷态、负离子缺陷、缺陷与杂质的相互作用、辐照以及形变引入的缺陷等,研究表明,在原生半导体材料中存在各种缺陷,经过辐照和璩 变化有单空位、双空位及孔洞形成;在重掺杂材料中,空位还补偿载流子,使载流子发生饱和。     

电子辐照前后的n型6H-SiC低温正电子捕获的研究

在20～300K低温范围内,通过对电子辐照前后n型6H SiC正电子湮灭寿命谱的测量,揭示了不同空位型缺陷之间的正电子捕获的竞争.建立了一种用于解释正电子寿命谱测量结果的模型,该模型中费米能级位置的改变可影响缺陷的电离以及正电子在缺陷位置的被捕获.根据模型拟合正电子寿命谱数据后得到:在原生的SiC中,正电子最可能被碳空位和碳的双空位所捕获,经估算其浓度分别为1.1×1017cm-3和3.0×1016cm-3;在辐照后的SiC中,正电子最可能被碳的双空位,硅空位或硅空位的杂合态所捕获,经估算其浓度分别为9.8×1016cm-3和5.4×1016cm-3.     

6H-SiC γ辐照的正电子研究

用正电子湮没寿命谱(PALS)方法对经过不同剂量γ辐照的n型6H-SiC内的缺陷进行研究.实验表明,辐照可以使样品内部产生单空位缺陷Vc.对实验中得到的寿命谱的变化进行分析发现,低剂量的γ辐照对n型6H-SiC有类似退火效应的作用.这些研究结果可以为n型6H-SiC的生产及其可能的应用提供有效的参考价值.     

基非掺杂与掺Te的GaSb薄膜 的缺陷结构对比分析

在GaAs单晶衬底上用分子束外延技术,采用相同工艺生长了非掺杂及掺Te的GaSb薄膜．以原子力显微镜、X射线衍射谱和正电子湮没谱技术对比分析了样品的结构及缺陷．研究表明,样品在掺Te后在界面处缺陷减少,外延生长较好．并分析其缺陷的产生机理．     

碲镉汞电子结构缺陷的正电子湮灭研究

碲镉汞(Hg_(1-x)Cd_xTe,或称MCT),是60年代问世的一种性能优良的红外探测材料,它的电性能在很大程度上取决于电子结构中的缺陷:自然缺陷(空穴、填隙原子、空位和络化物等);扩散缺陷(位错、晶粒边界、沉积、熔点物和非掺入的杂质等).键稳模型断言,在MCT中,a.缺陷的形成和动态特性是热激活的;b.Hg-Te键很弱,汞空位是主要的自然缺陷;c.大多数扩散缺陷是电激活的.但是,迄今不能清楚地说明缺陷形成的动态过程及其与材料电性能的关系.正电子湮没技术(PAT)对于研究原子尺度的缺陷极其敏感.本文以PAT为手段,研究MCT退火过程中,缺陷浓度与电阻率的关系,以及充分退火后MCT的电阻率与温度的关系.     

III—V族半导体光导开关

本文用由半导体激光器所产生的毫微秒和微微秒脉宽的激光脉冲驱动了由掺铁的磷化铟(Fe:InP)、掺铬的砷化镓(Cr:GaAs)和未掺杂的砷化镓(GsAs)光导开关,对上述三种材料的光导开关,通过实验和理论分析作了比较.     

正电子谱学技术在功能材料微结构表征中的应用

特殊功能材料是一些具有优良电学、磁学、学、热学、学、力学、化学、物医学功能,在各类高科技领域到泛应用.正电子湮没技术是一种对材料微结构特别有效探测技术,特别是对各种缺陷、空位和微孔尤为灵敏,通过正电子湮没寿命谱、多普勒展宽谱和慢正电子束技术,通过分析正电子湮没参数可以获材料从表面到内部缺陷分布信息和随外部物理和化学条件变化、引起微结构变化.本文选取几种特殊材料正电子湮没实验结果来分析材料内部微结构,表明正电子湮没谱学是一种独特研究微观结构方法.     

La0.67Sr0.33MnO3体系的Mn位铁掺杂效应

采用固相反应方法制备了名义成分为La0.67Sr0.33Mn1-xFexO3(0≤x≤0.20)的系列样品.通过对La0.67Sr0.33MnO3系列样品的XRD曲线、R—T曲线的测量,研究了Fe掺杂对样品磁电性质的影响.室温下利用正电子湮没技术对样品进行了研究,根据正电子寿命谱参数的变化情况讨论了掺杂样品中缺陷及电子结构的变化.实验结果显示,该系列样品可以忽略氧空位缺陷的影响,样品中位错、微空洞和晶界等缺陷的存在、铁磁与反铁磁作用的相互竞争及样品内部电子局域化所形成的极化行为等因素导致了样品性质的变化.     

高能球磨Fe-TiN间界面反应及磁性

利用X射线衍射(XRD)结合穆斯堡尔谱和宏观磁性测量研究了高能球磨Fe TiN体系的界面反应机制及界面磁性.结果表明：通过高能球磨，部分Fe原子扩散到TiN晶粒中形成顺磁相TiN(Fe)，Fe原子的扩散溶解随球磨时间增加而饱和.同时，部分TiN在球磨过程中分解成Ti和N并溶入Fe晶格形成铁磁性的Fe(Ti，N)固溶体.Ti和N原子溶入后使样品饱和磁化强度产生变化.随固溶量的增加，饱和磁化强度先增大后减小.     

InP晶体材料中的杂质

本文给出了ＩｎＰ材料（１００）和（１１１）晶面的质谱分析结果，并对（１００）晶面做了光荧光分析．研究表明沾污主要来自硅     

MOCVD生长的InP外延层的输运及发光特性

使用ＭＯＣＶＤ生长技术，在ｎ型及半绝缘衬底上生长了ＩｎＰ外延层，通过对迁移率和低温光致发光，光反射谱的分析，得出了样品纯度与有关生长条件的关系。比较两种不同衬底上外延层的光荧光谱，发现杂质ｓ在ＩｎＰ外延层中的扩散是不容忽视的。     

Undoped semi-insulating indium phosphide (InP) and its applications

During the past several years, the research and de-velopment of InP material has made great progress due to serving as the substrate for most optoelectronic devices operating at the communications wavelength of 1.31 and 1.55 mm. At present, InP has become an important semi-conductor material together with Si and GaAs. When compared to GaAs, InP has higher electron velocity, higher radiation hardness and better heat-conducting property. The advantage of InP crystal material allows higher f…     

Undoped semi-insulating indium phosphide (InP) and its applications

During the past several years, the research and development of InP material has made great progress due to serving as the substrate for most optoelectronic devices operating at the communications wavelength of 1.31 and 1.55 μm. At present, InP has become an important semiconductor material together with Si and GaAs. When compared to GaAs, InP has higher electron velocity, higher radiation hardness and better heat-conducting property. The advantage of InP crystal material allows higher frequency operation and lower power requirements. Therefore, InP is widely being used for the manufacture of microwave devices, high-frequency devices and optoelectronic integrated circuits (OEICs) which are indispensable for wireless technology, satellite communications^[1—3]. Although n-type and p-type InP can meet actual needs, semi-insulating InP substrates remain to be improved due to their poor uniformity and consistency. For this reason, several possible approaches have been reported to the preparation of SI InP by wafer annealing under different conditions^[4—9].     

基于 In$_{{\bf 1}-x}$Ga$_{x}$P 梯度合金核无镉量子点的制备及 LED 应用

低毒性磷化铟量子点(indium phosphide quantum dot, InP QD)作为最有可能取代有毒重金属镉基量子点的材料, 已经在下一代商业显示和照明领域中显示出巨大潜力. 然而, 合成具有高荧光量子产率(photoluminescence quantum yield, PL QY)的InP QD 仍然具有挑战性. 因此, 提出了以乙酰丙酮镓作为镓源, 在高温下通过乙酰丙酮基对表面配体的活化作用, 生成具有梯度合金核的 In$_{1-x}$Ga$_{x}$P/ZnSe/ZnS 量子点, 有效解决了原有的 InP 与 ZnSe 之间晶格失配的问题; 同时减少核壳界面缺陷, 使量子点的荧光量子产率高达 82%, 所制备量子点发光二极管(quantum dot light-emitting diode, QLED)的外量子效率(external quantum efficiency, EQE)达到 3.1%. 相比传统的 InP/ZnSe/ZnS 结构量子点, In$_{1-x}$Ga$_{x}$P/ZnSe/ZnS 量子点荧光量子产率提高了 25%, 器件的外量子效率提高了近一倍. 该方案为解决 InP 量子点荧光量子产率低、发光器件性能差等问题提供了新的思路.     

光激瞬态电流谱方法中激发光强度等因素对结果的影响

本文讨论了用光激瞬态电流谱测量半绝缘材料中深能级时,所加电压的极性、光强的变化等因素对结果的影响。对Martin等人提出的判断陷阱类型的方法进行了分析,在此基础上提出了一种新的方法。并给出了由光强变化而引起的能级位置的测量误差的修正方法。     

La3+和Ni2+掺杂二氧化钛纳米粉体的制备与光催化性能

采用溶胶 凝胶法分别制备了未掺杂、La³⁺和Ni²⁺单掺与共掺的TiO₂粉末,通过XRD、SEM、UV-visible吸收等对样品的晶型、微观形貌、光吸收和对亚甲基蓝的光降解特征进行了考察。结果表明,La³⁺和Ni²⁺的掺杂抑制了TiO₂的相变和晶粒的增长,纯TiO₂的粒径主要分布为20～30nm,掺杂La³⁺和Ni²⁺后样品的晶粒尺寸在9～20nm之间。掺杂后各样品在紫外和可见光区的吸收能力均有不同程度地增强。与未掺杂TiO₂的吸收带边相比,La³⁺掺杂TiO₂的吸收带边蓝移,Ni²⁺掺杂和共掺TiO₂的吸收带边分别红移了约40和35nm。La³⁺单掺和La³⁺-Ni²⁺共掺促进了光生电子-空穴对的分离,从而提高了光催化降解亚甲基蓝的活性。     

Defects in NTD InP probed by positron annihilation spectroscopy

Two samples of high purity InP extracted from the same wafer were examined by positron annihilation spectrum analysis after having been, processed by means of thermal Neutron Transmutation Doping (NTD). Compared with the as grown sample with an average positron lifetime of 246 ps at 300 K, the high dose doped one has an average lifetime of 251 ps and the lower dose doped one 248 ps measured under the same condition, indicating that some defects have been introduced in the NTD process. Annealing experimental results show a steady decrease in the average lifetime with increasing annealing temperature up to 550°C. And a peak in lifetime curve around 500°C was observed which may be attributed to defects related structure conversion. Temperature experiments conducted on the low dose doped sample from 150K to 290 K suggest the existence of vacancy-impurity complex which have given rise to an abnormal reduction of average lifetime with increasing temperature. Also a n-type InP sample (A61) was irradiated with thermal neutrons in another reactor and the lifetime results display an increase of 15 ps. Furthermore, to study epithermal neutron irradiation effects on InP, measurements were performed on an n-type InP sample (N119) along with one p-type sample (P118) after having been irradiated with high fluence of epithermal neutrons. The former has an average lifetime of 262 ps and the latter 247 ps after irradiation. The results prove that on some occassion epithermal neutrons can produce sizable defects in InP. Foundation item: Supported by the Science Foundation of Hubei Province (203980532) Biography: WEN Xiang-e (1976-), male, Master candidate, Research direction; majar research interest is defects in semiconductor materials using positron annihilation spectroscopy.     

Different effects of substrates on the morphologies of single-walled carbon nanotubes

In this work, different effects of substrates on the morphologies of single-walled carbon nanotubes （SWNTs） are studied. SWNTs were produced by floating catalytic chemical vapor deposition using CH4 as carbon source gas and Ar as carrier gas. Then the SWNTs were deposited on lithography-patterned different substrates. The as-grown SWNTs at the boundaries between SiO2 and metal were characterized by scanning electron microscopy, atomic force spectroscopy and Raman spectroscopy. It is found that SWNTs deposited on low-conductivity substrates trend to have curved morphologies and some of them form rings, while SWNTs deposited on metal sub- strates remain straight and orientated. The mechanism of these effects was also discussed, which is closely related to the thermal conductivities and the principle of energy dissipation.     

Preparation and optical properties of composite thin films with embedded InP nanoparticles

InP nanoparticles embedded in SiO₂ thin films were prepared by radio-frequency magnetron co-sputtering. We analyzed the structure and growth behavior of the composite films under different preparation conditions. X-ray diffraction and Raman spectroscopy analyses indicate that InP nanoparticles have a polycrystalline structure. The average size of InP nanoparticles is in the range of 3–10 nm. The broadening and red shift of the Raman peaks were observed, which can be interpreted by the phonon confinement model. Optical transmission spectra indicate that the optical absorption edges of the films can be modulated in the visible light range. The marked blue shift of the absorption edge with respect to that of bulk InP is explained by the quantum confinement effect. The theoretical values of the blue shift predicted by the effective mass approximation model are different from the experimental results for the InP-SiO₂ system. Analyses indicate that the exciton effective mass of the InP nanoparticles is not constant and is inverse relative to the particles radius, which may be the main reason that results in the discrepancy between the theoretical and the experimental result. We discussed the possible transition of the direct band gap to the indirect band gap for InP nanoparticles embedded in SiO₂ thin films.