Epitaxial Growth and Properties of New Group IV Semiconductor Alloys

9503210本研究旨在对一类含TiN的第四类半导体合金的合成、结构和电子结构进行最终评估。将探索新的合金合成方法，以克服生长均一的单晶锡基第四族半导体合金的热力学和动力学限制。有两种类型的外延异质结构令人感兴趣：一种是在厚层应变消除层或薄的共格应变层中生长的二元合金，相对于硅具有大的失配；另一种是原子尺寸差异能够实现局部应变补偿和相对于硅的低失配。首先，在局域密度近似下进行电子结构计算，以确定哪些结构是稳定的，并得到应变和非应变锡基合金的能带结构。来自电子结构计算的信息将被用来构造力场，用于使用高能束流对锡的掺入进行分子动力学模拟。单晶合金薄膜的电子和光学性质(例如光学能隙、载流子迁移率和载流子浓度)的测量将与计算的电子和光学性质进行比较。这个计划将是对一类新材料的首次全面研究，这种材料的电子性质可能导致在硅衬底上集成新的功能异质结电子和光电材料和器件。由于硅集成电路技术的普及性及其巨大的经济重要性，拟议方案的技术影响可能非常大。该项目的一个重要特点是在材料研究的基础和技术领域对学生进行培训。***

9503210 Atwater This research aims at a definitive assessment of the synthesis, structure and electronic structure of a class of Group IV semiconductor alloys containing tin. New approaches to alloy synthesis will be explored to overcome thermodynamic and kinetic limits to growth of homogeneous, single-crystal, Sn-based group IV semiconductor alloys. Two types of epitaxial heterostructures are of interest: Binary alloys with large misfit relative to silicon grown either in thick strain-relieved layers or thin, coherently strained layers; and alloys where atomic size differences enable local strain compensation and low misfit relative to silicon. First principles electronic structure calculations in the local density approximation will be performed to enable determination of which structures are stable and to obtain energy band structures of strained and unstrained Sn-based alloys. Information from the electronic structure calculations will be used to construct force fields for molecular dynamics simulations of Sn incorporation using energetic beams. Measurements of electronic and optical properties (e.g. optical energy gap, carrier mobilities and carrier concentrations) of single crystal alloy films will be compared to calculated electronic and optical properties. %%% This program will be the first comprehensive investigation of a new class of materials whose electronic properties may result in the integration of new functional heterojunction electronic and optoelectronic materials and devices on silicon substrates. Because of the pervasiveness of silicon integrated circuit technology and its enormous economic importance, the technological impact of the proposed program is potentially very large. An important feature of the program is the training of students in a fundamentally and technologically significant area of materials research. ***