Effects of Polarization Fields and Surface Charge Layers on p-Type Conductivity in In(Ga)N

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。技术：本项目旨在解决InGaN材料的两个关键问题。首先，晶格应变、成分、内部极化场、表面极性、缺陷和掺杂如何影响InGaN中的p型电导率？第二，是什么原因导致了InN的本征表面电子层？在基于接触的电测量中，该层模糊了体自由电荷载流子的特性，在极端情况下隐藏了p型电导率。本项目的实验方法包括分析InGaN薄膜的自发场和压电场、表面取向、组成、表面缺陷和掺杂的变化。它采用了一种新开发的光学霍尔效应技术，该技术允许非接触、非侵入性的电荷载流子分析，并解决了目前在InGaN上p电导率研究中的挑战。该项目的成功也可能为解决InAs表面电荷的开放性问题打开一扇门。非技术：该项目涉及材料科学主题领域的基础研究问题，具有高技术相关性。该项目的成功预计将对光电子学、固态照明和太阳能电池的进一步发展产生影响。该项目为研究生和博士后提供培训。PI和他的学生参加了在内布拉斯加州偏远地区太阳能使用的教育推广活动。PI还活跃于专业学会，并在科学会议上组织了几次关于椭偏仪的专题讨论会。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Technical: This project seeks to solve two key issues of InGaN materials. First, how do lattice strain, composition, internal polarization fields, surface polarity, defect, and dopant incorporation influence p-type conductivity in InGaN? Second, what is the cause of the intrinsic surface electron layer in InN? This layer obscures the bulk free charge carrier properties in contact-based electrical measurements, in the extreme case concealing p-type conductivity. The experimental approach of this project comprises InGaN thin film analysis with variation of spontaneous and piezoelectric fields, surface orientation, composition, surface defects, and dopant incorporation. It employs a newly developed optical Hall-effect technique, which permits noncontact, noninvasive charge carrier profiling and tackles the present challenges in p-conductivity research on InGaN. The success of the project may also open a door to answer the open questions about the surface charges in InAs.Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance. The success of the project is expected to have impacts on the further advancement of optoelectronics, solid state lighting, and solar cells. The project provides training of graduate and postdoctoral students. The PI and his students participate in education outreach activities for solar energy use in remote areas of Nebraska. The PI is also active in the professional societies and organizes several symposia on ellipsometry in scientific conferences.