Nanoscale Properties of Wide-Band Gap Semiconductor Surfaces

宽带隙半导体表面的纳米级特性

• 批准号: 0503748
• 负责人: Randall Feenstra
• 金额: --
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2009-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0503748&HistoricalAwards=false
• 关键词: Nanoscale; Properties; Wide; Band; Gap

This project aims to advance fundamental knowledge of structures and transport properties of semiconductor surfaces, the former with respect to greater understanding and optimization of growth of GaN and other III-nitrides, in particular, and the latter as exploration of an area with potential impact on nanoscale electronic devices. The structural and electronic properties of wide-band-gap semiconductor surfaces will be studied with a combination of atomic-scale microscopic and spectroscopic probes. Bilayer-thick metallic Ga layers that naturally terminate GaN will be studied by low-energy electron diffraction (LEED) at temperatures of about 750 C. The morphology and coverage of these layers will be observed as a function of incident Ga flux. The behavior of alternate terminating layers such as indium will also be investigated. Similar experiments will be performed for AlN. The electronic states of terminating layers on GaN will also be investigated by scanning tunneling spectroscopy (STS). The surface electronic structure will be probed with STS measurements on in-situ prepared GaN surfaces, comparing clean surfaces to ones that have been exposed to oxygen or other adsorbates. High- dynamic-range STS measurements, using carefully prepared (metallic) probe-tips, will be used to observe evolution of surface state-density as a function of exposure. LEEM observation will be used to observe overall morphological effects of adsorbates. Transport properties of surface electronic bands will be studied by STS, including measurements over a wide range of tunnel currents and at temperatures from 300 K down to 7 K. The observation of spectral shifts, as a function of current, will be used to deduce transport parameters of surface bands. Spectral shifts will be compared with those expected from a 3-dimensional solution of Poisson's equation for the tip-semiconductor geometry. Inclusion of electrostatic effects in the theory arising from surface accumulation or depletion of charge due to limited transport in the semiconductor is expected to permit identification and evaluation of limiting transport mechanisms. %%% The project addresses basic research issues in a topical area of materials science with high technological relevance. Experimental tools are now available which allow atomic level observation of elementary surface processes which when better understood allow advances in fundamental science and technology. Broader impact of the work lies in its application to semiconductor thin film growth (for nitrides) and for its potential in future nanoscale electronics. 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. ***

该项目旨在推进半导体表面结构和输运性质的基本知识，前者是对GaN和其他iii -氮化物生长的更好理解和优化，特别是，后者是对纳米级电子器件潜在影响领域的探索。本文将结合原子尺度的显微探针和光谱探针来研究宽带隙半导体表面的结构和电子特性。采用低能电子衍射（LEED）技术，在750℃左右的温度下研究自然终止GaN的双层厚金属Ga层。这些层的形貌和覆盖范围将被观察为入射Ga通量的函数。交替终止层（如铟）的行为也将被研究。将对AlN进行类似的实验。利用扫描隧道光谱（STS）研究了氮化镓上终端层的电子态。表面电子结构将通过STS测量在原位制备的GaN表面进行探测，将清洁表面与暴露于氧气或其他吸附剂的表面进行比较。高动态范围STS测量，使用精心准备的（金属）探针头，将用于观察表面状态密度作为暴露函数的演变。LEEM观察将用于观察吸附物的整体形态效应。STS将研究表面电子带的输运特性，包括在宽范围的隧道电流和从300 K到7 K的温度下的测量。光谱位移的观测，作为电流的函数，将用于推断表面波段的输运参数。谱移将与尖端半导体几何的泊松方程的三维解所期望的谱移进行比较。由于半导体中的有限输运而引起的表面积聚或电荷耗尽引起的静电效应被纳入理论，预计将允许识别和评估限制输运机制。该项目涉及材料科学中具有高技术相关性的主题领域的基础研究问题。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，如果更好地理解这些过程，就可以促进基础科学和技术的进步。这项工作更广泛的影响在于它在半导体薄膜生长（氮化物）方面的应用，以及它在未来纳米级电子学方面的潜力。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。＊＊＊