新型四配位硅基材料的结构与性质

硅基半导体已广泛用于光电转化和现代通信等不同领域,新型硅基材料的发展,有助于应对功能材料在现代科技领域面临的挑战.本文主要介绍本课题组近年来在新型四配位硅基材料领域中的理论设计与计算模拟,包括新型四面体硅基材料和平面四配位硅基二维单层材料.基于Si(C≡C)_4结构单元,设计了一系列类金刚石结构的宽带隙半导体材料,预测了它们的结构、光电及力学性质,分析了平面四配位硅的成键特征及其稳定化策略,探讨了含平面四配位硅的二维单层材料在锂离子电池和CO_2活化转化中的应用.     

硅基Ⅳ族材料外延生长及其发光和探测器件研究进展

硅基光电集成回路是信息时代最具影响力的核心技术之一,由硅基光源、光电探测器、光调制器等模块组成.硅材料是微电子集成电路的基石,然而在光电集成方面却遇到了瓶颈.首先,由于硅是间接带隙材料,其发光效率极低,因此难以应用于硅基高效光源的研制.其次,硅在近红外通讯波段吸收系数很低,因此在近红外光电探测器的应用中具有较大的局限性.然而,研究者发现,通过能带工程将硅与其他Ⅳ族材料相融合不仅可以有效提高直接带高效发光效率,同时能使材料在近红外波段具有较高的吸收系数.因此,以Ⅳ族材料为基础,与硅工艺兼容的硅基光电集成回路引起了研究者的广泛关注.本文综述了课题组在硅基材料外延生长及其发光和探测器件方面的研究进展.介绍了硅基Ⅳ族材料Ge,SiGe/Ge异质结和量子阱材料的外延生长技术,以及硅基GeSn量子点发光材料的制备新方法.基于硅基Ⅳ族异质结构材料,发展调制金属与半导体接触势垒高度新机理,研制了多种结构的光电探测器.设计并制备了与互补金属氧化物半导体(Complementary Metal Oxide Semiconductor,CMOS)结构兼容的横向异质结以及双有源区垂直共振腔型两种结构硅基电致发光器件,有效提升器件的发光性能,并观察到应变锗发光增益现象.     

多孔硅的研究及其应用

多孔硅是一种新型的纳米半导体光电材料,室温下具有优异的光电特性,易与现有硅技术兼容,极有可能实现硅基光电器件等多个领域的应用。本文简明的论述了多孔硅的光电特性之后,又简单介绍了多孔硅在生物科学、照明材料及太阳能电池等多个领域内的应用进展情况,并对其发展前景作了展望。     

紫外LED研究进展

 氮化物紫外LED的发光波长覆盖210~400 nm的紫外波段,可广泛应用于工业、环境、医疗和生化探测等领域。近年来紫外LED的技术水平发展迅速,器件性能不断提升。由于高Al组分AlGaN材料的固有特性,目前深紫外LED的外量子效率和功率效率仍有大量提升空间。综述了近年来AlGaN基紫外LED的研究进展,阐述了限制其性能的AlGaN外延质量、高Al组分AlGaN材料的掺杂效率、紫外LED量子结构、紫外LED光提取效率及可靠性等核心难题以及取得的重要研究进展。预计到2025年,深紫外LED的量产单芯片光输出功率可突破瓦级,功率效率有望提升至20%以上,寿命达到万小时级别。     

杭州士兰明芯科技有限公司

杭州士兰明芯科技有限公司是一家设计、制造高亮度GaN基发光二极管LED芯片的光电半导体公司。     

图书推介

正LED光源及其设施园艺应用刘文科,杨其长,魏灵玲著。中国农业科学技术出版社,2012年11月第1版,定价:50.00元。该书系统总结了LED光源及其在设施园艺生产中应用的国内外最新研究成果,阐述了LED半导体光源在设施园艺中应用的光电优势与光质生物学基础,以及设施园艺专用LED光源装置与灯具研发的国际进展,是国内外首部有关半导体LED光源在设施园艺中应用的著作。全书共8章内容,分别介绍了LED结构、发LED     

量子阱器件的发展及其应用

随着半导体量子阱材料的发展，量子阱器件广泛应用于各种领域。本文主要介绍量子阱的基本原理，重点从量子阱材料．量子阱激光器、量子阱虹外探测器、量子阱LED、量子阱光集成器件等方面介绍量子阱理论在光电器件方面的发展及其应用。     

高Al组分AlGaN基紫外LED结构材料

采用金属有机物气相外延(MOVPE)技术在c面蓝宝石衬底上,引入脉冲原子层外延技术,制备了一系列表面平整度较高的高Al组分AlGaN基异质结构外延片.并采用电子束金属蒸镀技术及优化热退火方法,获得了良好的欧姆接触电极,进一步将外延片制备成LED管芯.通过对量子结构有源层量子阱混晶组分的设计和调整,掌握并实现了主波长260～330 nm紫外LED结构材料的制备.     

CdS基半导体纳米材料的研究进展

CdS基半导体纳米材料由于具有良好的光电性能成为人们关注的宽禁带半导体之一,被广泛应用在多功能生物成像、生物医学、光催化、太阳能电池、光电探测和磁光领域.本文综述了近年来CdS基半导体纳米材料的研究进展,从CdS的晶体结构、不同形貌的材料制备方法和应用方面做了重点阐述.     

新型铅卤基钙钛矿材料及其应用

铅卤基钙钛矿材料因其优异的光电转化效率、可调禁带宽度、较高载流子迁移率、较大光吸收系数等突出性能,在太阳能电池、发光器件和光电探测等领域获得广泛关注。介绍了铅卤基钙钛矿薄膜、量子点和单晶的制备和相关物理性能,总结了其在太阳能电池、发光二极管(LED)、光电探测器等领域的最新研究进展,讨论了目前存在的问题及未来发展前景。     

功率LED芯片键合材料对器件热特性影响的分析与仿真

针对倒装型功率发光二极管器件,描述了功率LED器件的热阻特性,对不同芯片键合材料的功率LED热阻进行了分析,并运用AN SY S软件对3类典型芯片键合材料封装的功率LED热特性进行了仿真。仿真结果表明:采用功率芯片键合材料提高了功率LED的散热特性、降低器件PN结温,而采用普通热沉粘接胶作为芯片键合材料的功率LED的PN结温则较高,因此普通热沉粘接胶不适合用作功率LED的芯片键合材料。     

The application of the microstructured metallic grating to light emission extraction

Microstructured metallic gratings can be used to enhance the light emission efficiency of LEDs,and the spectral radiation properties of the LEDs vary with the different metallic materials used,leading to variation of the light emission enhancement at the same wavelength for different metallic grating materials.In this paper,the finite difference time domain(FDTD) method has been used to investigate the light emission extraction enhancement of LEDs in which gratings with different metallic materials have been applied.Through analysis of the permittivity of the metals and the quality factors of the surface plasmons(SPs),we concluded that the larger the plasma frequency obtained for the metallic interband transition,then the more suitable the metals are for light emission extraction of photons with relatively short wavelengths.This is because of the abundance of free electrons in the metals with large plasma frequencies.We also found that the wavelength-dependent trends of the extraction enhancement resulting from the scattering mechanism for different metallic materials are similar to each other.For SP-induced enhancement,either the enhancement peak position or the peak value changes significantly with the different metals.     

Recent progress in ZnO-based heterojunction ultraviolet light-emitting devices

Wide bandgap(3.37 eV)and high excitonbinding energy of ZnO(60 meV)make it a promising candidate for ultraviolet light-emitting diodes(LEDs)and low-threshold lasing diodes(LDs).However,the difficulty in producing stable and reproducible high-quality p-type ZnO has hindered the development of ZnO p–n homojunction LEDs.An alternative strategy for achieving ZnO electroluminescence is to fabricate heterojunction devices by employing other available p-type materials(such as p-GaN)or building new device structures.In this article,we will briefly review the recent progress in ZnO LEDs/LDs based on p–n heterostructures and metal–insulatorsemiconductor heterostructures.Some methods to improve device efficiency are also introduced in detail,including the introduction of Ag localized surface plasmons and single-crystalline nanowires into ZnO LEDs/LDs.     

Nitride semiconductors free of electrostatic fields for efficient white light-emitting diodes

Compact solid-state lamps based on light-emitting diodes (LEDs) are of current technological interest as an alternative to conventional light bulbs. The brightest LEDs available so far emit red light and exhibit higher luminous efficiency than fluorescent lamps. If this luminous efficiency could be transferred to white LEDs, power consumption would be dramatically reduced, with great economic and ecological consequences. But the luminous efficiency of existing white LEDs is still very low, owing to the presence of electrostatic fields within the active layers. These fields are generated by the spontaneous and piezoelectric polarization along the [0001] axis of hexagonal group-III nitrides--the commonly used materials for light generation. Unfortunately, as this crystallographic orientation corresponds to the natural growth direction of these materials deposited on currently available substrates. Here we demonstrate that the epitaxial growth of GaN/(Al,Ga)N on tetragonal LiAlO2 in a non-polar direction allows the fabrication of structures free of electrostatic fields, resulting in an improved quantum efficiency. We expect that this approach will pave the way towards highly efficient white LEDs.     

LED器件热管理分析方法及其应用

发光二极管(LEDs)是三明治结构的半导体材料。LED芯片是产生光和热量的核心功能器件,但累积的热量会严重影响LED的光学性能。因此,热管理在LED的封装和应用中十分重要。综述了一些现有的热故障。为了有助于进一步理解热管理,介绍了LED封装、热阻网络系统以及传热强化技术,以及通过降低热阻来实现有效温度控制的方法。     

Ⅲ—Ⅴ氮化物与蓝光LEDs(Ⅰ)

回顾了Ⅲ—Ⅴ氮化物材料和GaN-based蓝光LED的研究状况及近期的重大进展,分成两部分先后在本刊发表,首先简要地概述了GaN及其有关化合物的晶体生长技术,较为详细地讨论了衬底选择和外延层的晶体结构。     

白光LED用量子点玻璃的制备方法及应用研究进展

白光LED用量子点玻璃不但具有量子点高荧光效率、发光波长可调和较窄的发射波长等新颖的光学特性,而且量子点的热稳定性差和水氧抵抗性差的问题也很好的得到了解决,可以有效的避免封装材料黄化老化、发光不均匀和出现光斑等传统封装白光LED出现的问题。综述了白光LED用量子点玻璃的制备方法及其在LED的应用,并对白光LED用量子点玻璃的荧光效率和无铅、无镉量子点玻璃的研制提出了进一步展望。     

Growth of nanowire superlattice structures for nanoscale photonics and electronics

The assembly of semiconductor nanowires and carbon nanotubes into nanoscale devices and circuits could enable diverse applications in nanoelectronics and photonics. Individual semiconducting nanowires have already been configured as field-effect transistors, photodetectors and bio/chemical sensors. More sophisticated light-emitting diodes (LEDs) and complementary and diode logic devices have been realized using both n- and p-type semiconducting nanowires or nanotubes. The n- and p-type materials have been incorporated in these latter devices either by crossing p- and n-type nanowires or by lithographically defining distinct p- and n-type regions in nanotubes, although both strategies limit device complexity. In the planar semiconductor industry, intricate n- and p-type and more generally compositionally modulated (that is, superlattice) structures are used to enable versatile electronic and photonic functions. Here we demonstrate the synthesis of semiconductor nanowire superlattices from group III-V and group IV materials. (The superlattices are created within the nanowires by repeated modulation of the vapour-phase semiconductor reactants during growth of the wires.) Compositionally modulated superlattices consisting of 2 to 21 layers of GaAs and GaP have been prepared. Furthermore, n-Si/p-Si and n-InP/p-InP modulation doped nanowires have been synthesized. Single-nanowire photoluminescence, electrical transport and electroluminescence measurements show the unique photonic and electronic properties of these nanowire superlattices, and suggest potential applications ranging from nano-barcodes to polarized nanoscale LEDs.     

An aluminium nitride light-emitting diode with a wavelength of 210 nanometres

Compact high-efficiency ultraviolet solid-state light sources--such as light-emitting diodes (LEDs) and laser diodes--are of considerable technological interest as alternatives to large, toxic, low-efficiency gas lasers and mercury lamps. Microelectronic fabrication technologies and the environmental sciences both require light sources with shorter emission wavelengths: the former for improved resolution in photolithography and the latter for sensors that can detect minute hazardous particles. In addition, ultraviolet solid-state light sources are also attracting attention for potential applications in high-density optical data storage, biomedical research, water and air purification, and sterilization. Wide-bandgap materials, such as diamond and III-V nitride semiconductors (GaN, AlGaN and AlN; refs 3-10), are potential materials for ultraviolet LEDs and laser diodes, but suffer from difficulties in controlling electrical conduction. Here we report the successful control of both n-type and p-type doping in aluminium nitride (AlN), which has a very wide direct bandgap of 6 eV. This doping strategy allows us to develop an AlN PIN (p-type/intrinsic/n-type) homojunction LED with an emission wavelength of 210 nm, which is the shortest reported to date for any kind of LED. The emission is attributed to an exciton transition, and represents an important step towards achieving exciton-related light-emitting devices as well as replacing gas light sources with solid-state light sources.