Electron Paramagnetic Resonance and Solid-State Electronics: New Techniques

Abstract: The physical mechanisms involved in semiconductor device issues cannot be fully understood without definitive identification of the point defects involved.  Conventional electron paramagnetic resonance (EPR) offers unrivalled analytical power in the identification of point defects in semiconductors and insulators.  Unfortunately, the sensitivity limit of conventional EPR is roughly ten billion defects, far more defects than one will find in virtually any technologically meaningful device. The contributions from conventional EPR are thus enormously limited by low sensitivity.  An additional significant shortcoming of conventional EPR in device physics studies is its inability to directly link the physical structure and electronic properties of point defects. These limitations are overcome by two EPR related techniques: electrically detected magnetic resonance (EDMR) and near zero field magnetoresistance (NZFMR).

EDMR has all the analytical power of conventional EPR; NZFMR has at least some of it. Both offer sensitivities ten to one hundred million times greater than that of conventional EPR. Both can be combined with many purely electronic device characterization tools such as MOS charge pumping and DCIV measurements, deep level transient spectroscopy, simple pn junction diode recombination current measurements, and trap assisted tunneling currents in thin dielectric films. EDMR and NZFMR have been applied to both conventional silicon-based devices as well as   SiC MOSFETs and diodes, multiple varieties of GaN based devices, and low dielectric constant thin films. Because the EDMR and NZFMR measurements are made directly through currents in real devices, the link between defect chemistry and electronic properties is direct and convincing.

Bio: Patrick Lenahan is Distinguished Professor of Engineering Science and Mechanics and Co-Chair of the Inter-College Graduate Program in Materials Science and Engineering at Pennsylvania State University. He earned his B.S. degree from the University of Notre Dame and his Ph.D. from the University of Illinois at Urbana–Champaign. He did a post-doc at Princeton University. Following the post-doc, in 1980, he joined Sandia National Laboratories, Albuquerque, NM, where he served as a member of the technical staff for five years. Since 1985 he has been with Pennsylvania State University. Patrick and his students have investigated materials physics problems in systems including the interfaces of Si and SiC with silicon dioxide, hafnium oxides, silicon nitrides, as well as multiple GaN and SiC devices and a variety of low-dielectric constant materials. The work has focused upon developing a fundamental understanding of the role of point defects in the operation of solid-state electronic devices. In recent years, his group has worked to develop various electrically detected magnetic resonance techniques to explore the structure and electronic properties of point defects in fully processed devices. A focus of his group’s recent work has been the development of a new electron spin-based technique called near zero filed magnetoresistance spectroscopy. The work has resulted in approximately 220 journal articles, about 50 conference proceedings articles, about 300 conference presentations, and 5 patents. Patrick has been technical program chairman and general program chairman for the IEEE IIRW and has also served on the technical program committee of several other conferences including the IEEE SISC, the IEEE NSREC, the Rocky Mountain Conference on Magnetic Resonance and, for most of the last twenty years, he has served either as an invited or elected organizer of the MRS Electronic Materials Conference. He is a fellow of the IEEE.