ZnO is a leading candidate for the next generation of electronics, stemming from the recent introduction of blue light emitters and high power field-effect transistors based on GaN, and the realization that ZnO is a fundamentally better material for these applications. That is, ZnO is cheaper, less toxic, easier to grow, more efficient as an emitter, and faster as a transistor. Perhaps the most near-term commercial application will be solid-state lighting, which is forecast to dominate the artificial lighting industry by 2025, and at an annual cost savings of $125 Billion. However, ZnO as a material is not ready for such applications. It cannot be easily made "p-type," which is a necessary step in the fabrication of a light emitting p-n homojunction. Secondly, it is difficult to form Schottky barriers, which are required for field-effect transistors. Thirdly, its surface and interface properties are difficult to control, largely because of the polar nature of the surface. These problems must be addressed and solved before ZnO will be a commercially viable material. In view of this, this GOALI (Grant Opportunity for Academic Liaison with Industry) project addresses the key issues determining advances in ZnO materials science and electronics. The approach encompasses: (a) controlled growth of state-of-the-art ZnO provided by the industrial partner, (b) characterization of bulk and interface properties by the academic partners using a complement of electronic, optical, and surface science techniques, (c) analysis of systematic growth variations to isolate pivotal defect and doping mechanisms, and (d) synergistic feedback of these results to further refine the growth process. The objectives and intellectual merit for the project are to: (1) understand the complex relationships between growth, processing, intrinsic defects and extrinsic doping in both the bulk and at the interface and (2) use these findings to create ZnO single crystal films and bulk wafers that expand the range of optoelectronic applications by enabling full control of doping, interface states and barrier formation. This GOALI project aims to address these issues in the most direct approach possible, by linking key physical properties with systematic variations in growth. The interdisciplinary GOALI team consists of researchers who combine complementary and unique expertise in single crystal growth, characterization, and modeling with a shared interest to explore and exploit the relationships between growth, electronic and structural properties, and interface properties of wide band gap semiconductors. Core activities include: (1) developing crystal growth techniques that identify and control electrically-active defects; (2) establishing growth principles that facilitate the incorporation and activation of p-type dopants; (3) creating interface characterization techniques that provide key electronic, chemical, and structural information on ZnO formed under different controlled growth conditions; and (4) exploring the role of pre-growth surface chemistry in defect and interface state formation at ZnO homoepitaxial junctions. Non-Technical. The broader impacts of this GOALI collaboration include yearly personnel exchanges that place graduate research students, undergraduates, and university personnel in direct contact with industrial scientists at ZN Technology in closely coordinated activities. These exchanges will provide opportunities to broaden students' education by providing exposure to industrial researchers both within academia and a high technology industry environment, as well as access to advanced crystal growth and characterization equipment. The collaboration also provides summer research experiences relevant to industry for promising local high school students in Columbus and Dayton, especially women at the Columbus School for Girls, as well as students via a strongly affiliated Air Force Research Laboratory summer program. .
