This project addresses controlled n-type and p-type doping of (Zn,Mg)O for wide bandgap elec-tronics. The approach includes the synthesis and properties of carrier-doped (Zn,Mg)O crystalline thin films with a focus on understanding the formation of acceptor and donor states in epitaxial (Zn,Mg)O thin films. The alloy compositions of interest include the Zn-rich region for which the phase-pure wurtzite structure can be realized, as well as the Mg-rich region where the rock-salt structure is obtained. The objective is to understand the role of dopant species, complex forma-tion, and growth conditions on the incorporation of activated dopants. Activities will include the study of doping using two complementary epitaxial film-growth techniques. First, anion doping with group V acceptors (primarily N) will be investigated using molecular beam epitaxy. Specific theoretical predictions have been made regarding the effectiveness of single nitrogen versus multi-nitrogen bearing molecules as the delivery species for nitrogen doping. The role of Zn in-terstitials, oxygen vacancies, and/or hydrogen complexes in forming compensating shallow donor levels imposes the need to simultaneously consider the role of in situ and post-growth processing conditions. Second, pulsed-laser deposition will be used to investigate both acceptor doping and donor doping of (Zn,Mg)O. The donor dopant will be a group III element (Ga) substituted on the cation site. For acceptor doping using pulsed laser deposition, the primary focus will be on phos-phorus doping, as recent results suggest p-type behavior in heavily P-doped ZnO surfaces. It has also been predicted that co-doping with certain donor impurities may lead to a lowering of the acceptor levels due to the formation of acceptor-donor-acceptor complexes. As a secondary op-tion to p-type doping, co-doping approaches will be considered, with the focus on determining whether deep acceptor levels can be shifted to lower energies via the formation of acceptor-donor-acceptor complexes. Temperature-dependent Hall, Seebeck, C-V, and resistivity meas-urements will be used to determine conduction mechanisms, carrier type, and doping. Low tem-perature photoluminescence and admittance spectroscopy will be used to determine the location of the acceptor level for a given dopant. X-ray diffraction will used to characterize film crystal-linity. .%%% This project addresses basic research issues in a topical area of materials science with significant technological relevance, and places emphasis on the integration of research and education. Pro-ject activities will include developing a tutorial on Electronic Oxide Physics and Materials to be delivered as part of the Graduate Student Seminar Series in both Materials Science and Physics. It will be presented on an annual basis either by the PI or the graduate students involved in the re-search. The presentation materials will be posted on a designated website, thus providing access for researchers and students outside the University of Florida. In order to enhance the exposure of undergraduate students to oxide electronics, and research in general, the research project will in-corporate undergraduates through an existing Senior Research Thesis program. Each year, a fourth-year Materials Science and Engineering undergraduate student will be recruited to select an oxide electronics-related project as his or her Senior Thesis research topic. Persons from un-der-represented groups (women, minorities) will be particularly encouraged to participate. ***
