GaN基材料生长及其在光电器件领域的应用

GaN具有禁带宽度大、热导率高、电子饱和漂移速度大和介电常数小等特点，在高亮度发光二极管、短波长激光二极管、高性能紫外探测器的高温、高频、大功率半导体器件等领域有着广泛的应用前景。介绍了GaN基半导体材料的制备方法，异质结构以及在光电子和微电子器件领域的应用，并讨论了今后的发展趋势。     

我国利用氮化镓器件从事核应用研究取得系列成果

氮化镓(GaN)是一种III/V直接带隙半导体,作为第三代半导体材料的代表,随着其生长工艺的不断发展完善,现已广泛应用于光电器件领域,如激光器(LD)、发光二极管(LED)、高电子迁移率晶体管(HEMT)等。GaN基材料的良好抗辐射性能和环境稳定性,使得其在核探测领域具有很好的应用前景,在新型核电池领域也具有巨大的应用潜     

GaN纳米线材料的特性和制备技术

GaN是一种具有优越热稳定性和化学性质的宽禁带半导体材料，这种材料及相关器件可以工作在高温、高辐射等恶劣环境中，并可用于大功率微波器件．最近几年，由于GaN蓝光二极管的成功研制，使GaN成为了化合物半导体领域中最热门的研究课题．简要介绍了GaN纳米线材料的制备技术；综述了GaN纳米线材料的制备结果和特性．用CVD法研制的GaN纳米线的直径已经达到5～12nm，长度达到几百个微米．纳米线具有GaN的六方纤锌矿结构，其PL谱具有宽的发射峰，谱峰中心在420nm．GaN纳米线已经在肖特基二极管的研制中得到应用．     

高附加值产品助推信息产业发展

电子信息材料是指在微电子、光电子技术和新型元器件基础产品领域中所用的材料,主要包括单晶硅为代表的半导体微电子材料;激光晶体为代表的光电子材料;介质陶瓷和热敏陶瓷为代表的电子陶瓷材料;钕铁硼永磁材料为代表的磁性材料;光纤通信材料;磁存储和光盘存储为主的数据存储材料;压电晶体与薄膜材料;贮氢材料和锂离子嵌入材料为代表的绿色电池材料等。这些基础材料及其产品支撑着通信、计算机、信息家电与网络技术等现代信息产业发展。近年来,电子信息材料总体发展趋势向着大尺寸、高均匀性、高完整性,及薄膜化、多功能化和集成化方向发展。当前的研究热点和技术前沿包括柔性晶体管、光子晶体、SiC、GaN、ZnSe等宽带半导体材料为代表的第三代半导体材料、有机显示材料及各种纳米电子材料等。     

消息报道

苏州纳米所利用氮化镓器件从事核应用研究取得系列成果氮化镓(GaN)是一种III/V直接带隙半导体,作为第三代半导体材料的代表,随着其生长工艺的不断发展完善,现已广泛应用于光电器件领域,如激光器(LD)、发光二极管(LED)、高电子迁移率晶体管(HEMT)等。GaN基材料的良好抗辐射性能和环境稳定性,使得其在核探测领域具有很好的应用前景,在新型核电池领域也具有巨大的应用潜力。因为GaN辐生伏特效应核电池     

第三代半导体或将引发又一次照明革命

事件：继硅（si）引导的第一代半导体和砷化镓（GaAs）引导的第二代半导体后，以碳化硅（SiC）、氮化镓（GaN）、氧化锌（ZnO）、金刚石、氮化铝（AlN）为代表的第三代半导体材料闪亮登场并已逐步发展壮大。与第一、二代半导体材料相比，第三代半导体材料具有更宽的禁带宽度，高的击穿电场、高的热导率、高的电子饱和速率和更高的抗辐射能力，因而更适合制作高温、高频、抗辐射及大功率器件。此外，第三代半导体材料由于具有发光效率高、频率高等特点，因而在一些蓝、绿、紫光的发光二极管、半导体激光器等方面有着广泛的应用。从目前第三代半导体材料和器件的研究来看，较为成熟的是碳化硅SiC和GaN半导体材料，而Zn0、金刚石和A1N等宽禁带半导体材料的研究尚属起步阶段。     

采用金属镓层氮化技术在石英衬底上生长多晶GaN

随着多晶GaN材料发光研究的不断深入，大面积、价格低廉的多晶GaN基光电器件的研制已成为工业生产中一个重要的研究领域。石英玻璃以其自身特有的优势，成为生长多晶GaN材料的较为理想的衬底。本采用一种新的金属镓层氮化技术，使用无定形石英作衬底，在常压下制备出多晶GaN。经分析测试表明，生长出的多晶GaN为六方结构且质量较好，并观察到针状的表面结构。     

航天用氮化镓材料的研究进展

氮化镓(GaN)材料由于具有优良的电学特性而受到了广泛的关注,有望在航天工程中获得重要应用。本文首先对GaN材料的特性进行了简要阐述,进而对基于GaN的高电子迁移率晶体管(AlGaN/GaN HEMTs)、空间太阳能电池、紫外探测器等的研究和应用现状进行了梳理及分析,最后从新型GaN器件的开发、空间环境适应性评价、GaN器件的加固等角度给出了航天器用GaN材料及器件的发展方向和建议。     

三菱化学宣布将优先投资白色LED及车载锂电池材料两大领域

据报道,三菱化学日前召开了经营方针说明会,宣布今后将优先投资白色LED及车载锂离子充电电池材料两大领域。白色LED领域包括GaN(氮化镓)底板及荧光体等材料、以及照明器具及液晶电视用     

介孔材料制备及研究进展

介孔材料是一类孔径分布在1．5～50nm之间的多孔材料，具有比表面积大，孔隙率高，孔径分布窄，孔排布有序的特点，在催化、分离等领域具有广阔的应用前景。综述了介孔材料近些年在制备、应用、机理等方面的最新进展与前景展望。     

Electrically pumped waveguide lasing from ZnO nanowires

Ultraviolet semiconductor lasers are widely used for applications in photonics, information storage, biology and medical therapeutics. Although the performance of gallium nitride ultraviolet lasers has improved significantly over the past decade, demand for lower costs, higher powers and shorter wavelengths has motivated interest in zinc oxide (ZnO), which has a wide direct bandgap and a large exciton binding energy. ZnO-based random lasing has been demonstrated with both optical and electrical pumping, but random lasers suffer from reduced output powers, unstable emission spectra and beam divergence. Here, we demonstrate electrically pumped Fabry-Perot type waveguide lasing from laser diodes that consist of Sb-doped p-type ZnO nanowires and n-type ZnO thin films. The diodes exhibit highly stable lasing at room temperature, and can be modelled with finite-difference time-domain methods.     

Micromachined optical concentrators for IR negative luminescent devices

Negative luminescent (NL) devices, which to an IR observer appear colder than they actually are, have a wide range of possible applications, including use as thermal radiation shields in IR cameras, and as IR sources in gas-sensing systems. For many of these applications a large area (>1 cm²) device which displays as large as possible apparent temperature range is required. However, under reverse bias, significant currents are required to reduce the carrier concentrations to the levels needed for maximum possible absorption. We have therefore used a novel micromachining technique to fabricate integrated optical concentrators in InSb/InAlSb and HgCdTe NL devices. Smaller area diodes can then be used to achieve the same absorption (e.g. for InSb an area reduction of 16 is possible) and the required currents are thus reduced. To fabricate the concentrators, spherical resist masks are first produced, which are ～10 μm high and ～53 μm wide, by resist reflow at 120°C. Inductively coupled plasma (ICP) etching is then used to etch alternately the resist mask and the semiconductor, with oxygen and methane/hydrogen respectively, producing concentrators with almost parabolic profiles. Currently, the concentrators are typically 30 μm high, with a top diameter of ～15 μm. Continuing optimization of the process to reach the theoretical limits of optical gain is described.     

Gate‐Controlled BP–WSe2 Heterojunction Diode for Logic Rectifiers and Logic Optoelectronics

p–n junctions play an important role in modern semiconductor electronics and optoelectronics, and field‐effect transistors are often used for logic circuits. Here, gate‐controlled logic rectifiers and logic optoelectronic devices based on stacked black phosphorus (BP) and tungsten diselenide (WSe₂) heterojunctions are reported. The gate‐tunable ambipolar charge carriers in BP and WSe₂ enable a flexible, dynamic, and wide modulation on the heterojunctions as isotype (p–p and n–n) and anisotype (p–n) diodes, which exhibit disparate rectifying and photovoltaic properties. Based on such characteristics, it is demonstrated that BP–WSe₂ heterojunction diodes can be developed for high‐performance logic rectifiers and logic optoelectronic devices. Logic optoelectronic devices can convert a light signal to an electric one by applied gate voltages. This work should be helpful to expand the applications of 2D crystals.     

用于光子器件的ZnO薄膜的分子束外延生长

近年 来，由于蓝绿发光二极管和激光二极管的发展，宽禁带ＩＩＩ－Ｖ族氮化行和ＺｎＳｅ基ＩＩ－ＶＩ族半导体材料成为举世瞩目的研究热点之一，取得这些进展的重要原因是材料质量的不断改善以及创新性的掺杂方法的引入。氧化锌（ＺｎＯ）是具有特殊性质的宽禁囊直接带隙ＩＩ－ＶＩ族半导体材料，具有在半导体材料中最高的激子束缚能（６０ｍｅＶ），将是另一种重要的商用光子器件材料。本文将描述高质量氧化锌单晶薄膜的等离子分子     

Layer-by-layer assembly of multicolored semiconductor quantum dots towards efficient blue, green, red and full color optical films

Multicolored semiconductor quantum dots have shown great promise for construction of miniaturized light-emitting diodes with compact size, low weight and cost, and high luminescent efficiency. The unique size-dependent luminescent property of quantum dots offers the feasibility of constructing single-color or full-color output light-emitting diodes with one type of material. In this paper, we have demonstrated the facile fabrication of blue-, green-, red-?and full-color-emitting semiconductor quantum dot optical films via a layer-by-layer assembly technique. The optical films were constructed by alternative deposition of different colored quantum dots with a series of oppositely charged species, in particular, the new use of cationic starch on glass substrates. Semiconductor ZnSe quantum dots exhibiting blue emission were deposited for fabrication of blue-emitting optical films, while semiconductor CdTe quantum dots with green and red emission were utilized for construction of green-?and red-emitting optical films. The assembly of integrated blue, green and red semiconductor quantum dots resulted in full-color-emitting optical films. The luminescent optical films showed very bright emitting colors under UV irradiation, and displayed dense, smooth and efficient luminous features, showing brighter luminescence in comparison with their corresponding quantum dot aqueous colloid solutions. The assembled optical films provide the prospect of miniaturized light-emitting-diode applications.     

InP Quantum Dots: Synthesis and Lighting Applications

InP quantum dots (QDs) are typical III–V group semiconductor nanocrystals that feature large excitonic Bohr radius and high carrier mobility. The merits of InP QDs include large absorption coefficient, broad color tunability, and low toxicity, which render them promising alternatives to classic Cd/Pb‐based QDs for applications in practical settings. Over the past two decades, the advances in wet‐chemistry methods have enabled the synthesis of small‐sized colloidal InP QDs with the assistance of organic ligands. By proper selection of synthetic protocols and precursor materials coupled with surface passivation, the QYs of InP QDs are pushed to near unity with modest color purity. The state‐of‐the‐art InP QDs with appealing optical and electronic properties have excelled in many applications with the potential for commercialization. This work focuses on the recent development of wet‐chemistry protocols and various precursor materials for the synthesis and surface modification of InP QDs. Current methods for constructing light‐emitting diodes using novel InP‐based QDs are also summarized.     

AlGaN/GaN-based diodes and gateless HEMTs for gas and chemical sensing

The characteristics of Pt/GaN Schottky diodes and Sc/sub 2/O/sub 3//AlGaN/GaN metal-oxide semiconductor (MOS) diodes as hydrogen and ethylene gas sensors and of gateless AlGaN/GaN high-electron mobility transistors (HEMTs) as polar liquid sensors are reported. At 25/spl deg/C, a change in forward current of /spl sim/6 mA at a bias of 2 V was obtained in the MOS diodes in response to a change in ambient from pure N/sub 2/ to 10% H/sub 2// 90% N/sub 2/. This is approximately double the change in forward current obtained in Pt/GaN Schottky diodes measured under the same conditions. The mechanism appears to be formation of a dipole layer at the oxide/GaN interface that screens some of the piezo-induced channel charge. The MOS-diode response time is limited by the mass transport of gas into the test chamber and not by the diffusion of atomic hydrogen through the metal/oxide stack, even at 25/spl deg/C. Gateless AlGaN/GaN HEMT structures exhibit large changes in source-drain current upon exposing the gate region to various polar liquids, including block co-polymer solutions. The polar nature of some of these polymer chains lead to a change of surface charges in gate region on the HEMT, producing a change in surface potential at the semiconductor/liquid interface. The nitride sensors appear to be promising for a wide range of chemicals, combustion gases and liquids.     

Stepwise current oscillations in tunnel and high-frequency semiconductor diodes

The response of tunnel and high-frequency diodes to an external harmonic signal of large amplitude has been studied. Stepwise current oscillations have been found on the current-voltage characteristics measured at a direct current when an external high-frequency signal is imposed simultaneously on the sample. The frequency of these oscillations decreases with increasing frequency of the external signal. Analogs of the appearance of stepwise current oscillations in semiconductor and other systems are indicated.     

Two-dimensional CdS nanosheet-based TFT and LED nanodevices

Semiconductor nanosheets have several unique applications in electronic and optoelectronic nanodevices. We have successfully synthesized single-crystalline n-type CdS nanosheets via a chemical vapor deposition (CVD) method in a Cd-enriched ambient. The as-synthesized nanosheets are typically 40-100 nm thick, 10-300 μm wide, and up to several millimeters long. Using the nanosheets, we fabricated for the first time (to our knowledge), nano thin-film transistors (nano-TFTs) based on individual CdS nanosheets. A typical unit of such nanosheet TFTs has a high on-off ratio (～1.7 ×10(9)) and peak transconductance (～14.1μS), which to our knowledge are the best values reported so far for semiconductor nano-TFTs. In addition, we fabricated n-CdS nanosheet/p(+)-Si heterojunction light emitting diodes (LEDs) with a top electrode structure. This structure, where the n-type electrode is directly above the junction, has the advantage of a large active region and injection current favorable for high-efficiency electroluminescence (EL) and lasing. Room-temperature spectra of the LEDs consist of only an intense CdS band-edge emission peak (～507.7 nm) with a full width at half-maximum of about 14 nm.