Thursday, July 31, 2008

UCSD EDS & LEOS Chapters Host Distinguished Lecture

Fluorine Plasma Ion Implantation (Treatment) Technology: a New Dimension in GaN Device Processing

Professor Kevin J. Chen - Department of Electronic and Computer Engineering. The Hong Kong University of Science and Technology

Wide-bandgap gallium nitride (GaN) and related compound semiconductor materials possess attractive characteristics including high breakdown voltage, high polarization-induced carrier density and high electron saturation velocity. Rapid progress has been made in material growth and device processing technologies during the last decade. Meanwhile, there remain technical challenges to overcome. For example, unlike the silicon MOSFET technology, in which the devices' threshold voltage can be locally adjusted in the processing stage by ion implantation, the threshold voltage of AlGaN/GaN high electron mobility transistors (HEMTs) is mainly determined in the material growth stage and exhibit negative values. Recently, a robust approach to modulating the local potential and carrier concentration in AlGaN/GaN HEMTs was developed based on a post-epitaxy fluorine plasma ion implantation (or treatment) technology. The most significant development based on this technology is the demonstration of self-aligned enhancement-mode AlGaN/GaN HEMTs with low on-resistance.

In this talk, Dr. Chen will give a comprehensive overview of the fluorine plasma ion implantation technology. Underlying physical mechanisms will be discussed, together with detailed dc and RF device characteristics. Examples of extending this technology to improve the performance of power transistors as well as power rectifiers will be shown. The reliability issues related to the fluorine plasma ion implantation will be discussed based on results from stress test and molecular dynamics simulation.


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