Nitride-based, nanostructured, light-emitting devices

氮化物纳米结构发光器件

• 批准号: 5403294
• 负责人: Professor Dr. Detlef Hommel
• 金额: --
• 依托单位: Wroclawskie Centrum Badan EIT+ Sp. z o.o.
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2003
• 资助国家: 德国
• 起止时间: 2002-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5403294?language=en
• 关键词: Nitride; based; nanostructured; light; emitting

Nearly all of the projects depend to a significant extent on the availability of a FIB, either directly or indirectly via expected experimental results. If such a possibility for the nanofabrication of structures and the preparation of samples for analytical investigations is given, the expectation of novel experimental results will be justified, which also influence theoretical projects and modelling. Quantum dots are a central topic of the research group. The required structures for single QD studies can be prepared without undue delay and in sufficient numbers only if the FIB is available locally in Bremen. The same holds for TEM sample preparation, which is a basic requirement for a successful realization of the intended devices. The FIB will be fully exploited with regard to the large number of projects directly depending on this equipment. A focussed ion beam system is needed not only to write patterns, but also to enable the preparation of accurately specified areas for TEM investigations. In advanced systems taking into consideration here, the Ga-ion beam is not only used for patterning, but the surface can be imaged by the same beam with high resolution in a nearly non-destructive manner before, during and after processing. This is well possible for nitrides being a rather resistive material which contrasts, e.g., to the case of II-VI semiconductors where ion damage would occur unavoidably. Detailed arguments 1. Mesa etching is a precondition for the investigation of single quantum dots. The understanding of the energy transfer into the dots is a basic requirement for modelling the microscopic processes which determine quantum-dot lasing. The µ-PL spectroscopy efforts in project I-2 directly depend on the availability of mesa structures. 2. In order to achieve a three-dimensional confinement of the optical wave inside a semiconductor microcavity, micropillars with large height-to-diameter aspect ratios have to be prepared. The required precision for this task is only provided by a FIB. These taylored structures are needed for the optimization of device performance and fundamental studies of light-matter interaction. 3. The FIB technique greatly expedites the preparation of specimens for TEM, thus reducing the feed-back time for the optimization of the processing parameters. This will be of great benefit especially for the laser projects I-1 and I-2, as well as for the structural characterizations in II-1 and 11-2. 4. An essential requirement for the TEM investigations is the ability to prepare thin areas of a specimen from accurately specified sample positions, e. g. interfaces of quantum wells or quantum dots. This is difficult to achieve by conventional ion milling. In a "state of art" FIB, the secondary ions can be used to image the specimen and continuously monitor the preparation process without additional damage at least for nitridebased compounds. 5. Through injection of gases close to the point of impingement of the ion beam, it is possible either to enhance the etch rate or deposit layers onto the specimen surface, depending on the gas, the beam intensity and the scanning parameters. 6. The ability to vary the beam current over several orders of magnitude is a special feature of the FIB apparatus, allowing for a final thinning down to less than 100 nm over areas as large as 20 µm or even more. Such thin foils with nearly parallel surfaces and hence a large electron-transparent area allow for the determination of the density of lattice defects with a much greater statistical significance than is attainable with conventional ion milled specimens. The relevance for all device projects is evident. 7. In contrast to all other TEM preparation methods, FIB processing makes it possible to produce thin films with a known thickness. The examination of series of specimens with different thicknesses will be of great value for the determination of strain-relaxation effects. In addition, the specimen thickness must be known for image simulation.

几乎所有的项目都在很大程度上依赖于FIB的可用性，直接或间接地通过预期的实验结果。如果这种可能性的纳米结构和样品的制备分析研究是给定的，新的实验结果的期望将是合理的，这也影响理论项目和建模。量子点是该研究小组的中心课题。只有当FIB在不莱梅当地可用时，才能在没有不当延迟的情况下制备足够数量的单QD研究所需结构。这同样适用于TEM样品制备，这是成功实现预期器件的基本要求。FIB将在直接依赖于该设备的大量项目中得到充分利用。聚焦离子束系统不仅需要写入图案，而且还能够为TEM研究准备精确指定的区域。在这里考虑的先进系统中，Ga离子束不仅用于图案化，而且可以在加工之前、期间和之后以几乎非破坏性的方式通过相同的束以高分辨率对表面进行成像。这很可能是因为氮化物是一种相当电阻性的材料，对于II-VI族半导体的情况，其中离子损伤将不可避免地发生。 详细参数1.梅萨刻蚀是研究单量子点的前提。理解量子点的能量转移是模拟决定量子点激光的微观过程的基本要求。项目I-2中的µ-PL光谱工作直接取决于梅萨结构的可用性。2.为了实现光波在半导体微腔内的三维限制，必须制备具有大的高度与直径的纵横比的微柱。此任务所需的精度仅由FIB提供。这些泰勒结构是优化器件性能和光-物质相互作用基础研究所需要的。3. FIB技术大大加快了TEM样品的制备，从而减少了优化工艺参数的反馈时间。这对于激光项目I-1和I-2以及II-1和II-2中的结构表征将特别有益。4. TEM研究的一个基本要求是能够从精确指定的样品位置制备样品的薄区域，例如，G.量子威尔斯或量子点的界面。这很难通过常规的离子铣削来实现。在“最先进的”FIB中，二次离子可用于对样品成像并连续监测制备过程，而不会对至少氮化物基化合物造成额外损害。5.通过在离子束的撞击点附近注入气体，可以根据气体、束强度和扫描参数来提高蚀刻速率或在试样表面上存款层。6.在几个数量级上改变束流的能力是FIB设备的一个特殊功能，允许在20 μm甚至更大的区域上最终减薄到小于100 nm。这样的薄箔几乎平行的表面，因此一个大的电子透明区域允许的晶格缺陷的密度的测定具有更大的统计意义比传统的离子研磨试样可达到的。与所有器械项目的相关性是显而易见的。7.与所有其他TEM制备方法相比，FIB工艺可以生产已知厚度的薄膜。不同厚度的一系列试样的检验对于确定应变松弛效应具有重要价值。此外，为了图像模拟，必须知道试样厚度。