Engineering Research Grant: X-ray Diffractometer

我们正在申请资金购买x射线衍射仪，用于我们的化合物半导体材料和器件的研究。我们选择了一个紧凑的台式模型，这是专门为化合物半导体的表征设计的。该衍射仪将使我们能够精确测量在二元合金衬底上生长的外延层的晶格常数，并评估外延层的质量。许多正在进行的研究项目将受益于获得x射线衍射仪。我们对应变层和异质外延的实验研究主要依靠光学和电学表征技术。为了进行彻底的研究，必须更多地注意材料的结构性能。对于许多器件的研究项目来说，为了某些特定的应用，需要生长出完美的晶格匹配异质结。x射线衍射仪将为我们提供有关失配量的确切信息，以便可以对生长参数进行非常精细的调整，以获得晶格匹配。为了研究各种III-V材料体系的不同应变效应，还需要精确测量失配。此外，了解异质结构中的合金成分对于器件的优化以及器件性能与结构参数的关联具有重要意义。x射线衍射测量是测定层状结构中合金成分最直接的方法。我们开发了有机金属化学气相沉积技术，为我们的材料和设备研究项目培养高质量的III-V结构。添加双晶x射线衍射仪无疑将加强这些计划，并为进一步发展提供关键步骤。

We are requesting funding for the purchase of an X-ray diffractometer for our compound semiconductor materials and devices research. We chose a compact bench top model which is specifically designed for the characterization of compound semiconductors. This diffractometer will allow us to make precise measurements of the lattice constants of grown epitaxial layers on binary alloy substrates and assess the quality of the epi-layers. Many of the on-going research programs will benefit from the acquisition of the X-ray diffractometer. Our experimental studies on strained-layers and hetero-epitaxy have mainly relied on optical and electrical characterization techniques. In order to pursue a thorough investigation more attention must be paid to the structural properties of the materials. For a number of the device research programs, it is necessary to grow perfectly lattice-matched hetero-junctions for some specific applications. The X-ray diffractometer will provide us with information on the exact amount of mismatch so that very fine adjustments can be made in the growth parameters to obtain lattice matching. Accurate measure of the mismatch is also required for the study of different strain effects in various III-V material systems. Furthermore, knowledge of the alloy compositions in the heterostructures is important in optimization of the devices and correlation of the device performance to the structural parameters. X-ray diffraction measurement is the most direct means of determining the alloy compositions in layered structures. We have developed organometallic chemical vapor deposition techniques to grown high quality III-V structures for our material and device research programs. Addition of a double-crystal X-ray diffractometer will undoubtedly enhance these programs and provide crucial steps for further advancement.