PRISM/PCCM SEMINAR SERIES SPRING 2018: Patrick Lenahan, Pennsylvania State University

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Wed, Feb 14, 2018, 12:00 pm to 1:00 pm

calendar imageA New Approach to Magnetic Resonance at Heterointerfaces: Spin Dependent Charge Pumping in 4H-SiC MOSFETs

Abstract: Although 4H SiC MOSFETs have great promise in high power and high temperature applications, their great promise is limited by the presence of a defective silicon carbide-silicon dioxide interface region. We have utilized a new electron paramagnetic resonance (EPR) apprach to explore the defect structure at these SiC- oxide interfaces in fully processed transistors: multi-field and RF frequency spin dependent charge pumping.

Conventional electron paramagnetic resonance (EPR) offers unrivalled analytical power for the identification of point defects in semiconductors and insulators. Unfortunately, the sensitivity of conventional EPR measurements is, at best, about ten billion total defects. This sensitivity is inadequate for measurements in most devices of technological significance. A second limitation of conventional EPR in device physics studies is that it is sensitive to all paramagnetic defects within structure under study. EPR detection via electrically detected magnetic resonance (EDMR) can overcome both of these limitations. It provides a sensitivity typically at least ten million times higher than that of conventional EPR and is also exclusively sensitive to defect centers which impact the electronic behavior of the devices.

EDMR studies nearly always utilize spin dependent recombination (SDR). SDR is quite sensitive to deep level defects but, in studies of heterointerfaces such as the SiC/SiO2 boundary, defects throughout the entire interface bandgap can be important. In this study, we utilize a new EDMR apprach to invesitgate the silicon carbide-silicon dioxide interface: multi-magentic field and RF frequency spin dependant charge pumping (SDCP).

SDCP allows quite sensitive EDMR measurements of interface defects with levels throughout nearly the entire interface bandgap. The SDCP sensitivity is very nearly magnetic field and frequency independent and is typically more sensitive than SDR. The enhanced sensitivity as well as the field and frequency independence alows us to make measurements at resonance frequencies as high as 16 GHz and as low as 85 MHz. The multi-field and frequency measurements yield information about the relative contributions of hyperfine and spin orbit interactions and thereby aid in defect identification. In this presentation I will briefly review the physics involved in SDCP and discuss the defects which we observe via SDCP. In addition, I will briefly outline the close connection between low frequency SDCP and a near zero field non- resonant response in charge pumping currents. The near zero field response may one day provide a remarkably simple tool for the study of interface defect structure.

Bio: Patrick Lenahan earned his PhD from the university of Illinois in 1979. After completing the PhD., he had the great fortune of spending a brief post doc with Walter C. Johnson of Princeton University’s department of electrical engineering. In 1980, he joined Sandia National Laboratories in Albequerque, New Mexico. Since 1985, he has been with the Pennsylvania State University, where he is Distinguished Professor of Engineering Science and Mechanics and Co-chair of the Inter-College Program in Materials Science and Engineering. Patrick’s research interests have involved application of a variety of electron paramagetic resonance (EPR_ techniques to electronic materials physics problems. He is a fellow of the IEEE.

All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.

Bowen Hall Auditorium 222