This NIRT proposal focuses on the preparation of ordered arrays of nanodots and nanowires and incorporating them into device structures. This is a critical problem in nanometer-scale science of semiconductors. The NIRT research will build on our ability to grow quantum heterostructures with layer thickness down to a few atomic layers and to prepare ordered nanostructured templates. The two approaches will be combined to form structures and devices ordered on the nanometer scale in three dimensions. The research will include self-assembly of alumina masks, with pore sizes as small as 10 nm, on semiconductor substrates and deposition of semiconductor dots and nanowires into these pores using selective epitaxy. By either removing the alumina template or leaving it in place, we will have produced an array of identical semiconductor quantum dots. These will be compared with dots produced by epitaxial self-assembly. We will apply knowledge gained from these experiments to prepare ultraviolet light emitting devices based on the AlN/AlGaN heterostructures. These techniques will also be applied to the formation of nanowires of dilute magnetic semiconductors and to investigate spin transport and device applications of the (Ga, Mn)N and (In,Mn)N systems. Equally important, results of this research will be used to inject nanoscience into current courses, producing new laboratory based courses, and to educate science and engineering graduate students in this important area. Intellectual Merit: This proposal addresses fundamental problems that need to be solved in order to produce useful ultraviolet optoelectronic and spin-based devices. Advanced growth methods will be developed to produce nanoarrays of technologically important semiconductors. Devices will be fabricated out of these nanoarrays and their properties explored. There are several reasons to study three-dimensional quantum structures based on GaN and related compounds: 1. Quantum dots have higher radiative efficiency than two-dimensional layers, thus providing better device performance. Superior spin transport is expected in nanowires of dilute semiconductors. 2. Ordered nanostructures - devices grown with vertical (heterostructure) and lateral (nanodot) control will allow us to engineer properties on a quantum level, resulting in new device functionalities. 3. Further miniaturization of device structures requires better understanding of the self-assembly processes and finer control over nanodot and nanowire quality. Broader Impact: The assembly of nanostructured semiconductors into nanoscale devices will enable new applications in electronics, spintronics, and photonics. At the same time, preparation of such devices challenges our understanding of fundamental limits of size and scalability that determine electrical and optical properties of nanostructures. New approaches to research and education are needed to meet this challenge. Under this NIRT proposal the research plan will be closely integrated with educational activities. Specific steps that will be taken towards this goal include involvement of graduate and undergraduate students in advanced interdisciplinary research. Their participation will develop critical technical, team, and leadership abilities. New components of classroom and laboratory courses will be produced based on nanofabrication, attracting students from diverse backgrounds into research.
