Growth and Properties of III-VI Based Heterostructures

这个项目的重点是III-VI基半导体的异质外延生长以及相关的结构和光学性质。III-VI材料包括两个主要类别：层状材料，如GaSe和InSe，以及立方体材料，如Ga2Se3和In2Se3，它们正在作为不同材料异质外延的原型系统进行研究，并可能成为电子或光电器件的新材料。这两类III-VI材料在光学范围内都有带隙，并且与更传统的电子材料具有化学相容性。III-VI半导体的结构使其具有高度的各向异性输运、力学和光学性质以及大的非线性磁化率。具体目标是：通过分子束外延（MBE）确定GaSe、Ga2Se3及其相关材料的生长机制；确定底物相互作用和表面键特性在控制GaxSey化合物成核和生长中的作用；建立实验和理论框架，以确定适当的生长条件，以获得III-VI材料的最佳结构、电子和光学特性；通过分析这些材料的基本结构、电子和光学性质，评估其用于新型光电应用的可行性。该方法主要集中于GaSe和Ga2Se3在Si、GaAs、CaF2和A1203上的成核和生长，以及所得薄膜的性能。结合原位和非原位实验探针，包括光电子能谱和衍射、电子衍射、光谱学、原子力显微镜和高分辨率透射电子显微镜，结合生长过程的动力学建模。离子在衬底中的作用、表面钝化程度以及与覆盖层的固有晶格不匹配将在四种材料中有所不同。该项目涉及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。该研究将为电子/光子器件的新领域提供基础材料科学知识。现在有了实验工具，可以在原子水平上观察基本的表面过程，这些过程一旦得到更好的理解，就会促进基础科学和技术的进步。从研究中获得的基本知识和理解预计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理解和基础。该计划的一个重要特点是通过培养学生在一个基础和技术上重要的领域的研究和教育的整合。＊＊＊

9801302 Olmstead This project focuses on the heteroepitaxial growth of III-VI based semiconductors and on interrelated structural and optical properties. The III-VI materials comprise two principal classes: layered materials, such as GaSe and InSe, and cubic materials such as Ga2Se3 and In2Se3, which are being investigated as prototype systems for heteroepitaxy of dissimilar materials and as possible novel materials for electronic or optoelectronic devices. Both classes of III-VI materials have bandgaps in the optical range and chemical compatibility with more traditional electronic materials. The structure of III-VI semiconductors gives them highly anisotropic transport, mechanical and optical properties and large non-linear susceptibilities. Specific goals are: to determine growth mechanisms for GaSe, Ga2Se3 and related materials by molecular beam epitaxy (MBE); to determine the role of substrate interactions and surface bond character in controlling the nucleation and growth of GaxSey compounds; to establish an experimental and theoretical framework for determining the appropriate growth conditions to obtain optimal structural, electronic and optical properties in III-VI materials; to evaluate the feasibility of using these materials for novel opto-electronic applications through analysis of fundamental structural, electronic and optical properties. The approach is to concentrate on the nucleation and growth of GaSe and Ga2Se3 on Si, GaAs, CaF2 and A1203, and on the properties of the resultant thin films. A combination of in situ and ex situ experimental probes including photoelectron spectroscopy and diffraction, electron diffraction, optical spectroscopy, atomic force microscopy, and high resolution transmission electron microscopy in combination with kinetic modeling of the growth process will be employed. The role of ionicity in the substrate, the degree of surface passivation, and the inherent lattice mismatch with the overlayer will be varied among t he four materials. %%% 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. Experimental tools are now available to allow atomic level observation of elementary surface processes which when better understood allow advances in fundamental science and technology. The basic knowledge and understanding gained from the research is expected to contribute to improving the performance 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. ***