GaN

1. Atom Probe Tomography of Lattice Matched AlInN/GaN Based HEMT StructuresPatrick Kung, University of Alabama Tuscaloosa, DMR 0907558 Atom Probe Tomography is an emerging and powerful technique for the nanoscale characterization of semiconductors, which has the unique ability to identify and locate the positions of individual atoms from a specimen with 3-D atomic resolution. This technique is ideally suited to the investigation of phase segregation or composition fluctuation phenomena in electronic and photonic materials, including in next generation lattice matched AlInN/GaN HEMT structures where these such phenomena may occur due to the diverse thermodynamics characteristics of constituent InN and AlN compounds. In this project, we have developed a deeper understanding of mechanisms underlying the APT of these materials and used this technique to confirm the behavior of indium within the AlInGaN material. AlInGaN GaN Typical 3D reconstruction of an AlInGaN/GaN HEMT structure from data collected during APT experiments (left). Iso-concentration surfaces for Al and In at various locations within the HEMT structure (right).

2. Outreach to Underrepresented GroupsPatrick Kung, University of Alabama Tuscaloosa, DMR 0907558 In the Fall 2011, a new first year graduate student (J. Waters) from HBCU Virginia State University joined this project. He is pursuing a Ph.D. in Materials Science with the PI, focused on semiconductor material characterization. Since joining, J. Waters has also been in outreach by engaging students at Sumter Central High School in West Alabama, which is part of the Alabama Black Belt. During the Summer 2012, a Hispanic American student (J. Martinez) experienced research within the PI’s laboratory. New graduate student J. Waters engaging students in West Alabama high schools.