Localized States, Chemical Reactions, and Charge Transport at ZnO Surfaces and Interfaces

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

Technical. This project addresses fundamental aspects of surface and interface properties of ZnO The approach encompasses: (a) controlled growth of state-of-the-art ZnO, (b) characterization of surface, subsurface, and bulk properties using a complement of electronic, optical, and surface science techniques, (c) analysis of systematic variations with growth, surface treatment, and met-allization to quantify and identify defect and doping mechanisms, and (d) systematic feedback of these results to further refine both growth and metallization processes. Objectives include: (a) quantify and identify ZnO near-surface donors and acceptors, (b) describe the thermionic emis-sion, tunneling, and defect-assisted hopping contributions to charge transport within ZnO sur-faces and interfaces; (c) develop a self-consistent charge transport model for carrier concentra-tions within ZnO surfaces and Schottky barrier formation across ZnO-metal interfaces that ac-counts for the depth-resolved cathodoluminescence spectroscopy, deep level transient spectros-copy, capacitance-voltage, and current-voltage measurements quantitatively; (d) use this model to predict surface and metal-interface transport properties of ZnO; and (e) establish the utility of this model to other compound semiconductors. The ability to detect and analyze localized elec-tronic state properties at surfaces, interfaces and their extension into the semiconductor bulk on a nanometer scale is expected to reveal interplay between native point defects, impurities, and chemical reactions that substantially alter the conventional picture of the semiconductor space charge region. This project provides a new basis for predicting interface electronic properties that paves the way for controlling ZnO opto- and microelectronic contacts. Non-Technical. The project addresses fundamental research issues in a topical area of elec-tronic/photonic materials science having technological relevance. Understanding and controlling charge transport at ZnO surfaces and interfaces will enable electronic applications with benefits such as UV light-emitting diodes and laser diodes for energy-efficient white lighting and high capacity DVDs, and transparent transistors for displays. This project will also expand research experiences to women and minority university undergraduates and women from local high schools, the latter involving students from Columbus School for Girls in summer research on the OSU campus. OSU?s College of Engineering and Women in Engineering programs will augment this project with funding and programs, respectively. The project provides students with impor-tant opportunities for hands-on laboratory experience, a chance to do publishable research, and a glimpse of the excitement and opportunities in scientific research.