Technical. The project aims for fundamental understanding of the MOVPE (metallo-organic vapor phase expitaxy) epitaxial growth of Al1-xInxN compound semiconductors, by focusing on two primary aspects. The objective of one aspect is to demonstrate material quality and composition control through the use of a novel MOVPE reactor whose growth chamber has the ability to be reconfigured in-situ. Characterization of structural, optical and electrical properties will be an integral part of these studies. The objective of a second focus area is to investigate phase segregation phenomena in Al1-xInxN using a Local Electrode Atom Probe (LEAP), an instrumental tool enabling the identification of individual atoms and their location in a three-dimensional microstructure with near atomic resolution. Design of experiments and correlation between growth conditions and the resulting material properties are expected to yield greater fundamental understanding of material synthesis mechanisms. Non-Technical. The project addresses fundamental research issues in a topical area of electronic/photonic materials science having technological relevance. Societal benefits of the proposed research on AlInN materials can be very broad since the specific materials being studied could support applications such as all-weather radar, surveillance, reconnaissance, high speed wireless telecommunications and automotive radar for collision warning sensors. Students will acquire fundamental research and education skills as part of this project. Additionally, the scientific concepts underlying this project will be integrated into new courses that the PI and Co-PI are developing at both undergraduate and graduate levels. In order to broaden the participation from under-represented groups, the proposed activity will benefit from an HBCU Workshop at U. AL to reach science faculty members and educators from HBCUs, as well as a project entitled, "Broadening Participation Research Initiation Grants in Engineering" (BRIGE) program. Out-reach activities to local schools and general public will be carried out in conjunction with existing activities within the U. AL Center for Materials for Information Technology (MINT).
AlInN is a promising electronic material which has the potential to enable more reliable transistors that can operate at higher frequency, higher power and higher temperature. Intellectual merit: In this project, the growth of these semiconductor materials by metalorganic vapor phase epitaxy was investigated, along with the study of atom probe tomography, which was an emerging technique for characterizing the properties of materials at the nanometer scale, with the unique ability to identify and map the positions of individual atoms with three-dimensional atomic resolution. The fundamental mechanisms underlying the atom probe tomography of GaN and AlInN based semiconductors were studied, which helped establish proper conditions for reliable analysis of atom probe data by minimizing artifacts. Field ion microscopy of GaN was successfully demonstrated and investigated to yield deeper knowledge of field ion emission of GaN based materials. Voltage-mode atom probe was also successfully demonstrated and its fundamental differences compared with commonly used laser-assisted atom probe. The properties of AlInN based transistor structures were analyzed, including especially buried interfaces, and correlated with their other properties. Broader impact: Atom probe tomography was successfully used to investigate the structural characteristics of other electronic and photonic materials, such as ZnO and GaAs/AlGaAs nanowires. Outreach to Historically Black Colleges and Universities faculty and teachers was carried out in the form of lecture presentations and laboratory visits. Seven undergraduate students (1 female, 3 minorities), and three high school interns (1 female, 2 minorities) were mentored and participated on this project. Outreach activities at local high schools with a predominantly underrepresented minority population, including Sumter Central High School in West Alabama and Martin Luther King Elementary School in Tuscaloosa, were carried out in the form of regular seminars and demonstration experiments.
