Growth and Properties of III-VI Heterostructures

本项目的重点是III-VI基半导体的异质外延生长，以及这类材料的相关结构、电子和光学性质。该研究旨在阐明III-VI薄膜生长的机理，并将III-VI薄膜生长技术和材料表征发展到这些材料可以用于光电子应用的阶段。基于III-VI材料的界面化合物将用于控制III-VI和更标准的电子材料的异质外延，包括使用它们来促进层状和岛状纳米结构的形成。通过在Si、GaAs和CaF2等衬底上使用薄膜来解决与块状III-VI材料相关的问题，这些材料的机械和热性能较差。这一新一代材料的发展需要关于控制其电子、光学和结构特性的相互作用约束的新的基础知识。本项目致力于通过对普通电子材料和III-VI基材料之间异质界面形成的研究来阐明这些限制因素的作用。主要目标是：建立一个基于纳米级异质外延生长过程的实验和理论框架，以优化III-VI异质结的结构、电子和光学性质；开发III-VI界面化合物来控制半导体纳米结构的形成；评估III-VI基异质结的结构、电子和光学性质，为其在新的光电子学应用中的可行性提供依据。方法是集中在两个方面：(I)GaxSey、AlxSey及其合金在Si(111)、Si(100)、GaAs(100)和CaF2(111)上的成核、生长和性质，以及(Ii)使用所得到的薄膜作为衬底a)层状和孤岛生长GaAsSe和b)GaxSey-AlxSey超晶格。我们将利用原位扫描探针显微镜、超高真空转移光电子能谱和近边X射线吸收以及非原位高分辨电子显微镜和能量损失谱来研究生长动力学、形貌和量子点的性质。将使用光电子光谱和衍射、电子衍射、离子散射光谱和光学光谱(光热、反射-透射、光致发光和拉曼散射)来探索面积平均特性。%该项目解决具有高潜在技术相关性的材料科学主题领域的基础研究问题。这项研究将在基础水平上为电子/光子器件的新方面贡献基本的材料科学知识。从研究中获得的基本知识和理解将有助于提高先进器件和电路的性能和稳定性，为设计和生产改进的材料和材料组合提供基本的认识和基础。该计划的一个重要特点是通过在一个具有根本意义和技术意义的领域对学生进行培训，将研究和教育结合起来。

This project focuses on heteroepitaxial growth of III-VI based semiconductors and on interrelated structural, electronic, and optical properties of this class of materials. The research seeks to elucidate mechanisms of III-VI thin film growth, and to develop III-VI growth technology and materials characterization to the stage where these materials may be utilized for optoelectronic applications. Interface compounds based on III-VI materials will be used to control heteroepitaxy of both III-VI and more standard electronic materials, including their use to promote both laminar and islanded nanostructure formation. Problems associated with bulk III-VI materials, poor mechanical and thermal properties, are being addressed through use of thin films on substrates such as Si, GaAs and CaF2 . Development of this new generation of materials requires new, basic knowledge about the interacting constraints that control their electronic, optical and structural properties. This project strives to elucidate the role of these constraints through studies of heterointerface formation between common electronic materials and III-VI based materials. Primary goals are: to establish an experimental and theoretical framework based on nanoscale heteroepitaxial growth processes to optimize structural, electronic and optical properties of III-VI heterostructures; to exploit III-VI interface compounds to control semiconductor nanostructure formation; to evaluate structural, electronic, and optical properties of III-VI-based heterostructures for feasibility in novel optoelectronic applications. The approach is to concentrate in two areas: (i ) nucleation, growth and properties of GaxSey, AlxSey , and their alloys on Si(111), Si(100), GaAs(100), and CaF2 (111), and (ii) use of the resultant thin films as substrates for a) laminar and islanded growth of GaAs and ZnSe and b) GaxSey - Alx Sey superlattices. Growth kinetics, morphologies and quantum dot properties will be studied with nanoscale resolution using in situ scanning probe microscopy, UHV-transfer photoelectron spectroscopy and near-edge x-ray absorption, and ex situ high resolution transmission electron microscopy and energy loss spectroscopy. Area-averaged properties will be probed using photoelectron spectroscopy and diffraction, electron diffraction, ion scattering spectroscopy, and optical spectroscopies (photothermal, reflection-transmission, photoluminescence, and Raman scattering).%%%The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new aspects of electronic/photonic devices. The basic knowledge and understanding gained from the research is expected to contribute to improving the perform-ance and stability of advanced devices and circuits by providing a fundamental understanding and a basis for designing and producing improved materials, and materials combinations. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area.***