Is the Future of Electronics Spintronics

Dr. Ian Ferguson
Professor, Electrical and Computer Engineering, Georgia Tech

Date: Friday, March 14, 2008 at 1:00 PM
Room: PARB 239

Abstract

Recent predictions of room temperature ferromagnetism in transition metal doped wide bandgap semiconductors such as GaN have spawned a great interest for their use in the field of semiconductor-based spintronics. Spintronic devices differ from traditional electronics in that they are based on the electron spin instead of its charge. Both improved processing and efficiency within existing devices, as well as novel functionalities such as reconfigurable logic, nonvolatile chip-based memory, and a solid state quantum computing may be possible within magnetic semiconductor systems. If these devices can be implemented at room temperature, they will advance the state of the art in spintronics and create a new technological revolution similar to the invention of the transistor. Dilute magnetic semiconductors (DMS), which consist of semiconductors doped with rare earth or transition metals to provide magnetic functionality, have been suggested to be a suitable platform for spintronics due to their inherent similarity and compatibility with the existing III-V material technological base. A number of novel features have been demonstrated in Ga1-xMnxAs, such as spin-polarized luminescence from light emitting diodes. Unfortunately the Curie temperature of Ga1-xMnxAs is much less that room temperature, making it unsuitable for practical room temperature spintronics. Attention for room temperature spintronics has thus turned to the wide bandgap nitrides and oxides based on theoretical predictions of room temperature ferromagnetism in this system using a mean field approximation to the Zener model for carrier-mediated ferromagnetism. Reports of room temperature ferromagnetism in these materials are complicated by disparate crystalline quality and phase purity in these materials, as well as conflicting theoretical predictions as to the nature of ferromagnetic behavior in this system. It is not well understood whether the ferromagnetism derives from an intrinsic material property or from nanoscaled cluster distributions in the system. A complete understanding of these materials, and ultimately intelligent design of spintronic devices, will require an exploration of the relationship between the processing techniques, resulting transition metal atom configuration, defects, and electronic compensation as related to the structure, magnetic, and magneto-optical properties of this material. In this presentation, we will review the current theoretical and experimental status of the transition metal doped nitrides and discuss their suitability for future spintronic applications. A comparison of the predominant theoretical models and predictions for ferromagnetism in the nitrides will be compared with the available literature for Ga1-xMnxN and GaN doped with other tradition metals produced by a variety of techniques, including molecular beam epitaxy, ion implantation, and metalorganic chemical vapor deposition. In particular, the correlation of the structural, optical, and magnetic behavior will be analyzed in relation to theories of ferromagnetism in these materials. A summary of the preliminary spintronic device work based on the Ga1-xMnxN materials system will also be reviewed.

Presenter Bio

Ian T. Ferguson is a Professor in the School of Electrical and Computer Engineering at Georgia Institute of Technology (Georgia Tech) and Director for the Focused Research Center Next Generation Lighting. His research focuses on the area of wide band-gap materials and devices (emitters, detectors and electronics) using GaN and ZnO and developing these materials for illumination and spintronic applications. He has over 220 refereed publications, six book chapters, edited ten conference proceedings, two books and multiple patents. He teaches undergraduate, graduate and short courses on solid state lighting and illumination engineering and will publish a book on ‘Solid State Illumination and Illumination Engineering’ in 2007. He founded the International Conference on Solid State Lighting which is now in its eighth year and recently completed the Festival of Lights USA.