Technical: This project aims for greater understanding of acceptor dopant behavior in ZnO. The investigation includes: (i) Implantation of p-type dopants into ZnO thin films and nanowires followed by annealing; both uniform p-nanowires and longitudinal p-n junctions will be studied. (ii) Measurement of electrical transport and optical emission properties to establish dopant ionization levels and activation efficiency. Electrical properties of undoped ZnO implanted with the most likely successful dopant candidates, based on size and stability arguments ( N, P and As), as a function of both implant temperature and post-anneal temperature will be obtained from Hall and electrochemical CV measurements. Diffusion properties will be assessed from SIMS measurements on the same samples to establish the most appropriate choice for implant doping of ZnO. Specific areas to be investigated are : 1. implantation of N, P or As acceptor species into insulating ZnO films grown with low compensation levels on sapphire substrates; 2. in some cases co-implantation of O will be used to maintain stoichiometry and reduce formation of O vacancies; 3. the activation energy of dopant activation will be obtained from time and temperature dependence of sheet carrier concentrations; 4. the redistribution of implanted dopants will be measured by SIMS profiling; 5. formation of p-n junctions by implantation of acceptors into lightly doped n-ZnO films and characterization of the junction properties (breakdown voltage, temperature coefficient of breakdown); 6. Te co-doping of group-V doped ZnO; 7. creation of p-type ZnO nanowires by acceptor implantation into insulating or lightly n-type wires, followed by annealing. Transport properties of wires will enable determination of differences in activation behavior in films versus wires and thus to quantify the effects of surface - related phenomena on dopant activation.
The project addresses basic research issues in electronics/photonics materials science with high technological relevance, and is expected to provide important opportunities for student training. Understanding the doping behavior and properties of p-type ZnO will assist in developing this material for UV photonics and transparent electronics technology. It will expose graduate and undergraduate students to a range of fundamental materials science phenomena as well as device issues, and to a variety of experimental techniques. The U. FL has a Student Science Training Program which brings in a select group of 10th and llth grade students to do research in science and engineering. Two such students will be hosted as part of this project. The PI will also present a lecture on ZnO to a Teacher Research Update Experience program during the summer and will collaborate with teachers to translate research experiences into modules which can be taken back to middle and high schools.
